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Performance of natural‐fiber–plastic composites under stress for outdoor applications: Effect of moisture, temperature, and ultraviolet light exposure

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Abstract

The effects of moisture, temperature, and ultraviolet (UV) light on performance of natural-fiber–plastic composites (NFPC) were assessed. We conducted short-term tests in the laboratory and long-term tests under natural exposure and measured changes in mechanical properties and color in samples of the composite. Chemical changes of the composite's materials were measured by X-ray photoelectron spectroscopy to elucidate the mechanisms of chemical transformations on the material surface. Relative humidity highly affected the modulus of rupture (MOR) and the modulus of elasticity (MOE), and had a greater effect than temperature and UV exposure on performance of the composite. The lightness of the composite was increased by the UV effect in the short- and the long-term tests. The X-ray photoelectron spectroscopy (XPS) analysis suggested that the composite was protected by the UV absorber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2570–2577, 2006

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... The use of WPC as building products has resulted in concern about the durability of these products when exposed to outdoor environments [1,2,3,4]. Outdoor durability may include thermal stability, moisture resistance, fungal resistance, and ultraviolet (UV) stability [3,5]. UV exposure for example can cause the composites to undergo photodegradation leading to undesirable effects, including a loss in mechanical properties and surface quality, i.e. surface micro-cracking and color change. ...
... Other options include pre-treatment of the wood component to reduce its hydrophilic character [14] and ensuring good interfacial bonding within the composite [6]. There are many reports available on the literature on the effects of weathering on WPCs with respect to changes in appearance [1, 3, 11-13, 16, 18], surface chemistry [1,2,4,5,13,15,18] and mechanical properties [1-3, 11, 12, 17, 18]. Reports too are available on the effect of weathering cycle [11], manufacturing methods [1,5,11,13] as well as the use of photo-stabilizers [3,18] on the weathering characteristics of WPCs. ...
... There are many reports available on the literature on the effects of weathering on WPCs with respect to changes in appearance [1, 3, 11-13, 16, 18], surface chemistry [1,2,4,5,13,15,18] and mechanical properties [1-3, 11, 12, 17, 18]. Reports too are available on the effect of weathering cycle [11], manufacturing methods [1,5,11,13] as well as the use of photo-stabilizers [3,18] on the weathering characteristics of WPCs. Most of these works, however, were conducted based on laboratory studies by using appropriate accelerated weathering chambers. ...
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Natural weathering of recycled high-density polyethylene (HDPE)/wood flour (WF) composites (with and without photo-stabilizers; hindered amine light stabilizer (HALS) or ultraviolet absorber (UVA) or both photo-stabilizers) was carried out according to ASTM 1435. Initial changes in surface morphology and chemistry, color as well as flexural properties of the composites after several weathering periods were determined and compared. Scanning electron microscopy (SEM) showed that weathered samples experienced greater surface damage than the un-weathered samples. Formation of carbonyl and terminal vinyl groups at the composite surfaces were confirmed with Fourier transform infrared (FTIR) spectroscopy. The composites also lightened and experienced several changes in the flexural properties. Addition of HALS or UVA or both photo-stabilizers delayed and minimized the adverse effects of natural weathering on HDPE/WF composite. Stabilized HDPE/WF composite with UVA showed the best protection in the loss of flexural modulus. Combination of HALS and UVA did not produce a synergistic effect to protect HDPE/WF composite from undergoing some changes in the properties as a result of natural weathering. 1.0 INTRODUCTION Wood-plastic composites (WPCs) are now being marketed for various applications such as building products, automotive and packaging materials. As building products WPCs are used for applications like decking, fencing, siding, window frames and roofing tiles. The use of WPC as building products has resulted in concern about the durability of these products when exposed to outdoor environments [1, 2, 3, 4]. Outdoor durability may include thermal stability, moisture resistance, fungal resistance, and ultraviolet (UV) stability [3, 5]. UV exposure for example can cause the composites to undergo photo-degradation leading to undesirable effects, including a loss in mechanical properties and surface quality, i.e. surface micro-cracking and color change. WPCs readily absorb moisture due to the hydrophilic character of the wood component. Water absorption in WPCs can lead to build up of moisture in the wood fibre cell wall that would result in fibre swelling leading to micro-cracks in the polymer matrix. This would lead to greater penetration of water molecules within the composite structures. Another effect of fibre swelling is dimensional instability of the composites. Moisture build up can also occur at the wood-polymer interface. Degradation in the mechanical properties of WPCs has been reported in the literature and this has been attributed to degradation of wood-polymer interfacial quality as a result of water absorption [6, 7, 8]. Although both UV radiation and moisture can degrade WPCs, exposure to the combination of UV radiation and moisture has been found to result in more detrimental effects to WPCs than the exposure to UV radiation alone [9].
... It was found that long-term exposed of the composites to elevated conditions affected the mechanical properties. Solar irradiance (UV component of the sunlight), relative humidity and temperature are the causal agents of this deterioration of natural fiber of impregnated samples (Lopez et al. 2006). The increase in the mechanical properties due to the chemical modification has been reported by several researchers. ...
... This might be because of the lower degree of crystallinity of OPS nanoparticles which leaded to higher water absorption of the sample. The reduced degree of water absorption due to the replacement of the hydroxyl groups with carbon atoms in the PF chains has also been reported by several researchers (Lopez et al. 2006;Abdul Khalil et al. 2010b). Abdul Khalil et al. (2010b) found an interesting result that the highest water absorption because of the presence of more hydroxyl groups in the parenchyma tissue that enabled more hydrogen bonding formation. ...
... Previous studies of the weathering of benzoylation of wood showed that benzoylation treatment reduced the formation of free radicals in wood when exposed to UV light, possibly because the benzoyl groups in wood absorbed UV light or scavenged free radicals (Esteves et al. 2008). The effects of water on OPTL weathering was also recognized as one of the principle causes of weathering by changing the dimension resulting cracks and checks formation and undergo degradation (Lopez et al. 2006). However, PF-NPI reduced the water uptake by OPTL during weathering and thus, reduced the degradation. ...
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In this study, a green composite was produced from Oil Palm Trunk Lumber (OPTL) by impregnating oil palm shell (OPS) nanoparticles with formaldehyde resin. The changes of physical, mechanical and morphological properties of the OPS nanoparticles impregnated OPTL as a result of natural weathering was investigated. The OPS fibres were ground with a ball-mill for producing nanoparticles before being mixed with the phenol formaldehyde (PF) resin at a concentration of 1, 3, 5 and 10% w/w basis and impregnated into the OPTL by vacuum-pressure method. The treated OPTL samples were exposed to natural weathering for the period of 6 and 12 months in West Java, Indonesia according to ASTM D1435-99 standard. Physical and mechanical tests were done for analyzing the changes in phenol formaldehyde-nanoparticles impregnated (PF-NPI) OPTL. FT-IR and SEM studies were done to analyze the morphological changes. The results showed that both exposure time of weathering and concentration of PF-NPI had significant impact on physical and mechanical properties of OPTL. The longer exposure of samples to weathering condition reduced the wave numbers during FT-IR test. However, all these physical, mechanical and morphological changes were significant when compared with the untreated samples or only PF impregnated samples. Thus, it can be concluded that PF-NP impregnation into OPTL improved the resistance against natural weathering and would pave the ground for improved products from OPTL for outdoor conditions.
... Weathering causes color changes in WPC that are both undesirable and irreversible (Clemons and Stark 2009;Fabiyi et al. 2008). Water soaking is an important type of weathering test that is useful in determining the durable nature of a thermoplastic composite (Lopez et al. 2006;Clemons and Stark 2009;Zabihzadeh 2010a;Segerholm et al. 2012). Weathering causes PE-composites to undergo chemical reactions such as breakdown of lignins into water-soluble products, forming chromophoric functional groups such as carboxylic acids, quinones, and hydroperoxy radicals (Fabiyi et al. 2008). ...
... These color changes are associated with chemical and physical alterations occurring from the composites in response to the presence of water. Mechanical properties of WPC after exposure to environmental stress of water soaking have been measured by others to assess the potential commercial value of a composite (Thwe and Liao 2002;Lopez et al. 2006;Clemons and Stark 2009;Kord 2011;Zabihzadeh 2010a,b). Flexural properties (MOR and MOE) have been shown to decrease when LPC are weathered (Thwe and Liao, 2002;Lopez et al. 2006;Clemons and Stark 2009). ...
... Mechanical properties of WPC after exposure to environmental stress of water soaking have been measured by others to assess the potential commercial value of a composite (Thwe and Liao 2002;Lopez et al. 2006;Clemons and Stark 2009;Kord 2011;Zabihzadeh 2010a,b). Flexural properties (MOR and MOE) have been shown to decrease when LPC are weathered (Thwe and Liao, 2002;Lopez et al. 2006;Clemons and Stark 2009). In this work, the Type V tensile bars that were not soaked and Type V bars that were soaked in water for 672 hours were tested for TS and YM, as shown in (Table 5). ...
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Dried Distillers Grain with Solubles (DDGS) was evaluated as a bio-based fiber reinforcement. Composites of high density polyethylene (HDPE) composed of 25% by weight DDGS and either 0% or 5% by weight of maleated polyethylene (MAPE) were produced by twin screw compounding and injection molding. An improved DDGS bio-filler was produced by solvent treating DDGS (STDDGS). Injection-molded test specimens were evaluated for their tensile, flexural, impact, and thermal properties. Composite blends composed of STDDGS were superior to their DDSG counterparts. Composites made with STDDGS and MAPE had significantly improved tensile and flexural properties compared to neat HDPE. Impact strength of all composites was similar and lower than neat HDPE. Soaking of tensile bars of the various PE-DDGS blends in distilled water for 28 days altered their physical, color, and mechanical properties. Differential scanning calorimetery and thermogravimetric analysis were conducted on neat HDPE and DDGS composites to evaluate their thermal properties.
... Other investigators have reported that inclusion of maleated olefins with the composite blend considerably reduces water absorption when using bio-fillers such as poplar wood, loblolly pine wood, sisal fiber, or wheat straw. [34][35][36][37][38] Particle size of PW in composite blends did influence weight gain ( Figure 4). Composite blends composed of smaller particles (PP-#200PW-MAPP and PP-25BGPW-MAPP) exhibited less weight gain than composites that contained larger particles (PP-#40PW-MAPP and PP-#60PW-MAPP) (Figure 4). ...
... The response of a biocomposites to water soaking is related closely to the chemical and lignocellulosic anatomical properties of the bio-filler employed. [34][35][36][37][38] Employment of filler such as STDDGS results in a much larger increase in weight gain compared to employing PW filler (Figure 4). DDGS fillers contain more protein and less cellulose/lignin material than the PW fillers which maybe the reason for their higher absorbance rates (Figure 4). ...
... Environmental stresses such as water soaking may cause changes in the mechanical properties to occur which needs to be measured in order to assess the potential commercial value of a composite. 37,38 Flexural properties have been reported to decrease when LPC are weathered. 18,37,38 The mechanical properties of composites as well as neat PP and PP-MAPP may be affected by water soaking (Figure 5). ...
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Studies aimed at improving the tensile, flexural, impact, thermal, and physical characteristics of wood-plastic composites composed of Paulownia wood flour derived from 36-month-old trees blended with polypropylene were conducted. Composites of 25% and 40% w/w of Paulownia wood were produced by twin-screw compounding and injection molding. Composites containing 0-10% by weight of maleated polypropylene were evaluated and an optimum maleated polypropylene concentration determined, i.e., 5%. The particle size distribution of Paulownia wood filler is shown to have an effect on the tensile and flexural properties of the composites. Novel combination composites of dried distiller's grain with solubles mixed with Paulownia wood (up to 40% w/w) were produced and their properties evaluated. Depending on the composite tested, soaking composites for 872 h alters mechanical properties and causes weight gain.
... This effect was mainly observed for the native polymer materials, with PP and BioPE showing an increase of 3 and 5% to 856 ± 6 and 898 ± 8 kg/m 3 , respectively, after hygrothermal and UV aging. This could result from oxidation reactions of the polymer, occurring through free radicals and catalyzed by UV radiation and heat [31]. The increase in density for the fiber-filled composites was negligible, which further reveals that moisture absorption by the lignocellulosic fibers was insignificant. ...
... At the same time, the flexural modulus was found to increase after climatic aging of the biocomposites, illustrating rigidification of the composites. This phenomenon has also been reported for date palm fiber/PP composites and may be explained through photo-and/or thermo-oxidation of the PP/PE polymer, resulting in chain scissions and thus, a reduced molecular weight, and in the formation of carbonyl groups [31,32]. While the reduced chain length results in slightly more rigid materials, it is detrimental in terms of mechanical strength. ...
... However, as interfacial adhesion plays a crucial role in mechanical performance, the reinforcing effect of aging may be attributed to a stronger fiber/matrix interaction owing to the newly formed carbonyl groups. Furthermore, crosslinking reactions between the reactive matrix polymer and the lignin fraction may occur, contributing to a strong adhesion and an improvement of the mechanical strength properties [7,31]. ...
Article
In this study, coriander straw fiber was effectively incorporated as a reinforcing filler in polypropylene and biobased low-density polyethylene composite materials through twin-screw extrusion compounding and injection molding. Maleic anhydride-grafted copolymers were added as a coupling agent and effectively provided fiber/matrix compatibilization. With a significant reinforcing effect, resulting in a 50% increase in the flexural and tensile strength (from 19 to 28 MPa and from 12 to 17 MPa, respectively, for polypropylene composites) as compared to the native polymer, coriander straw allowed the production of 40% filled thermoplastic biocomposites with adequate mechanical properties comparable to those of commercial wood fibers, excellent durability in terms of UV and hygrothermal weathering and high potential for recycling. At the same time, such coriander biocomposites show a favorable cost structure, with 28% reduction of the granule cost as compared to wood fiber composites.
... It is believed that most of the weight reduction in the composite materials after UV exposure occur mainly in the dominantly epoxy-based matrix and less in the CFs [23]. However, the CF (surface layer) could manifest a color fade [24]. The chemical properties of the composites after UV exposure could lose the adhesive forces that connect the CF layers with the surrounding resin. ...
... In general, there is a slight decrease in stress and also in strain from the baseline condition. This type of mechanical property change is similar to the heat effect on the mechanical properties of the CFRP [24]. The stress-strain values express the typical behavior of the CFRP under axial loading regime. ...
... Figures 14 and 15 show the surface roughness changes by increasing exposure time. The increase in surface roughness can be attributed to changes in the dominantly epoxy-based matrix due to exposure to sunlight that causes the formation of new cracks or expansion of initial surface defects [24]. It is believed also that the deterioration may extend to the interface region between the epoxy and the CF and could lead to more dislocation and interlamination crack initiation in the matrix. ...
Article
It is clear that modern carbon fiber (CF) manufacturing methods will go beyond luxurious or limited-use of CF products toward a vast and unlimited commercial evolution of CF uses in multiple engineering applications. This expansion of the unlimited use of CF will be a major challenge for researchers to provide in-depth information to define the mechanical properties of CF products and the extent to which these properties are affected by various environmental factors. Therefore, defining the carbon fiber-reinforced polymer (CFRP) properties under different loading and environmental conditions is critical for extreme operating conditions. Sunlight, heat, and humidity have become a research focus to explore the impact of these parameters on the morphological and mechanical characteristics of the CFRP. This article investigates the influence of sunlight expressed in terms of UltraViolet (UV) light on the morphological and mechanical properties of two different layups of CFRP through tensile testing. The fracture modes were classified based on the ASTM standards to categorize the changes of CFRP with respect to the duration of UV exposure. Furthermore, the observed weight reduction of the exposed CFRP is related to the changes in the mechanical properties. The outcomes show that there is a reduction in tensile strength to approximately 18% for the 45° layup setting and 21% for the 90° layup setting by increasing the UV exposure time to 160 hr. Moreover, the fracture mode was also affected by the UV exposure time, showing more tendency of explosive catastrophic fracture in the center of the specimen at various places, which is known as XMV fracture mode according to ASTM standards.
... Additionally, studies have shown that WPCs can suffer physical and mechanical deterioration when exposed to outdoor conditions and there is a necessity for more thorough research of the moisture dynamics of these materials because of its direct impact on WPC durability [4]. Some of the factors affecting WPC performance are directly or indirectly related to moisture, stress levels, biodeterioration, photodegradation or a combination of these agents [5]. ...
... 3 Short-term accelerated tests have shown that bending strength and the modulus of elasticity are more affected by exposure to high environment relative humidity (93%), than by temperature (23 to 40 ºC) or UV exposure (0.85 mW/cm 2 ) [5]. The study used commercial extruded profiles composed of a HDPE matrix and natural flour. ...
... The study used commercial extruded profiles composed of a HDPE matrix and natural flour. Regarding the modulus of elasticity, an average decrease of 34% was observed due to an exposure of 93% relative humidity condition in an environment of 23 ºC and without exposure to UV radiation [5]. ...
Article
Wood plastic composites (WPCs) are being increasingly used as alternatives to wooden decks. In the present study, it was verified the potential loss of stiffness of WPC deck boards as a result of moisture intake. It was also assessed the importance of moisture intake in the fulfilment of serviceability limit states. For these purposes, three different types of commercial WPC decks were studied, with high (WPCH), medium (WPCM) and low (WPCL) expected mechanical performance. Different experimental designs were followed to simulate full exposure to outdoor conditions and the effect of possible internal stress due to differential shrinkage and the swelling behaviour of fibres and the matrix. The results indicate a high loss of bending modulus of elasticity due to water absorption (between 40 and 50%) and shrinkage/swelling movements (between 22 and 29%). This level of stiffness loss has a direct impact on ensuring the compliance to the serviceability limit states. A strong negative linear relationship between water absorption and the loss of bending stiffness was established, which can be a helpful tool to assist manufacturers in defining the application rules and ensuring the expected service life of their products. http://www.sciencedirect.com/science/article/pii/S026412751630497X
... Absorption of water by composites is a crucial factor in determination of the ability of bio-composite to be commercially utilized (Zabihzadeh 2010a,b). Water soaking of bio-composites simulates a severe environmental stress that may cause changes in the mechanical properties to occur; such effects need to be determined in order to assess the potential commercial value of a composite (Thwe and Liao 2002;Lopez et al. 2006;Clemons and Stark 2009;Kord 2011;Zabihzadeh 2010a,b). For example, flexural properties have been reported to decrease when bio-composites are weathered (Thwe and Liao 2002;Lopez et al. 2006;Clemons and Stark 2009). ...
... Water soaking of bio-composites simulates a severe environmental stress that may cause changes in the mechanical properties to occur; such effects need to be determined in order to assess the potential commercial value of a composite (Thwe and Liao 2002;Lopez et al. 2006;Clemons and Stark 2009;Kord 2011;Zabihzadeh 2010a,b). For example, flexural properties have been reported to decrease when bio-composites are weathered (Thwe and Liao 2002;Lopez et al. 2006;Clemons and Stark 2009). The mechanical properties of Type V tensile bars that were soaked and not soaked for 872 h are shown in Fig. 5. Fig. 5. Mechanical properties of original (unsoaked) and soaked composites. ...
Article
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Columbian coffee trees are subject to frequent replacement plantings due to disease and local climate changes, which makes them an ideal source of wood fibers for wood plastic composites (WPC). Composites of polypropylene (PP) consisting of 25% and 40% by weight of coffee wood flour (CF) and 0% or 5% by weight of maleated PP (MAPP) were produced by twin screw compounding and injection molding. Composites containing MAPP had significantly improved tensile and flexural properties compared to neat PP or composites without MAPP. Excellent mechanical properties were obtained with CF relative to conventional wood fillers. IZOD impact resistances of CF composites were significantly lower than neat PP although WPC containing MAPP were superior to WPC without MAPP. Bio-based fiber composites made by mixing CF in equal portions with other fiber sources were evaluated to determine the compatibility of using CF with other sources of filler materials. Soaking of tensile bars of the various CF blends in distilled water for 35 days may alter their mechanical properties and result in weight gain. Differential scanning calorimetry and thermogravimetric analysis were conducted on the neat PP and biocomposites to evaluate their thermal properties as they relate to potential degradation during conventional thermoplastic resin processing.
... WPCs is promoted by their exposure to humidity, elevated temperatures, and UV radiation [4][5][6][7]. The outdoor application of WPCs usually results in a severe loss in its aesthetic appearance and mechanical properties [8][9][10]. ...
... This is explained by the scission of polymer chains, resulting in surface cracks and embrittlement. The number of chain scissions increases with exposure time, leading to shorter polymer chains, and degradation of all mechanical properties [4][5][6][7][8]. Likewise, the scission of chains lowers the molecular weight of polymer [11][12][13]. ...
Article
The effects of weathering on the physical and mechanical properties of polypropylene (PP)/wood flour (WF) composites with and without nanoclay were investigated. The composites were placed in a xenon-arc weatherometer chamber, and then their color changes, flexural strength (MOR) and modulus (MOE), and water uptake were evaluated during 1800 h of their accelerated weathering. The study showed that the water uptake and thickness swelling of the composite increased and their MOR and MOE decreased with weathering time, but the addition of nanoclay diminished these effects.
... Exposure tests of WPCs have been conducted in Asia (Taib et al. 2010, Darabi et al. 2012, Zhao et al. 2012, Chaochanchaikul et al. 2013, Ebe and Sekino 2015, Australia (Li 2000), Europe (Oberdorfer and Golser 2005, Butylina et al. 2012a, 2012b, Kallakas et al. 2015, and North America and Hawaii (Verhey et al. 2003, Anon. 2005, Lopez et al. 2006, Schauwecker et al. 2006, Manning and Ascherl 2007, Gnatowski 2009, Ibach et al. 2013, Fabiyi and McDonald 2014. Most of these exposure tests were carried out for a limited period of time, usually not exceeding one year, and only on the rare occasion were the tested composites left in the field for extended periods of 3-10 years. ...
... Basidiomycete fungi were not detected. WA in WPCs was also found by other researchers to be a major cause of decreased flexural properties in laboratory and field exposure experiments (Clemons and Ibach 2002, Lopez et al. 2006, Ibach et al. 2007, Gnatowski 2009, Morrell et al. 2009, Machado et al. 2016. Commercial and experimental WPC boards with wood content of 50-65% exposed near Hilo and Vancouver (BC, Canada) had a significant amount of WA (Manning andAscherl 2007, Gnatowski 2009). ...
Article
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The flexural properties of wood–plastic composite (WPC) deck boards exposed to 9.5 years of environmental decay in Hilo, Hawaii, were compared to samples exposed to moisture and decay fungi for 12 weeks in the laboratory, to establish a correlation between sample flexural properties and calculated void volume. Specimens were tested for flexural strength and modulus, both wet and dry, at 23°C and 52°C. Some specimens degenerated to only 15% of original flexural strength. UV radiation had no impact on flexural properties of field-exposed boards; loss occurred mainly on the side opposite to the sun-exposed surface. The mechanism of the aging process on colonization of WPC by fungi was examined and is consistent with development of slow crack growth in the polyethylene matrix combined with wood decay by fungi. Wood particle decay, moisture, and elevated temperature were the major factors causing composite degradation, indicated by accumulation of voids and a severe decrease in flexural properties. To simulate long-term field impact (including decay) on WPC flexural properties in the laboratory, conditioning of specimens in hot water for an extended period of time is required. Exposure to water (70°C/5 days) was adequate for simulating long-term composite exposure in Hawaii of 4 × 15 × 86 mm³ specimens.
... On the other side, ATH appeared to decrease the hygroscopicity of WPCs and increase the hydrolytic stability of the composites as compared to APP. When the composites are used as load bearing structures in furniture, automotive, or building industries, their flexural strength (MOR) and flexural modulus (MOE) are the critical performance metrics [49]. Figure 2 shows that the incorporation of 30 wt % APP significantly decreased the MOR of the composites from (72.6 ± 0.4) MPa to (63.7 ± 1.8) MPa (≈12% average decrease), likely due to the poor APP/matrix compatibility, and increased the MOE from (2.8 ± 0.1) GPa to (3.5 ± 0.1) GPa (≈26% average increase) due to the intrinsic high MOE of APP. ...
... The MOR and MOE values were not significantly affected by the APP to ATH mass ratio (see WPC/APP-20/ATH-10, WPC/APP-15/ATH-15, WPC/APP-10/ATH-20 in Figure 2). When the composites are used as load bearing structures in furniture, automotive, or building industries, their flexural strength (MOR) and flexural modulus (MOE) are the critical performance metrics [49]. Figure 2 shows that the incorporation of 30 wt % APP significantly decreased the MOR of the composites from (72.6 ± 0.4) MPa to (63.7 ± 1.8) MPa (≈12% average decrease), likely due to the poor APP/matrix compatibility, and increased the MOE from (2.8 ± 0.1) GPa to (3.5 ± 0.1) GPa (≈26% average increase) due to the intrinsic high MOE of APP. ...
Article
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Two halogen-free inorganic flame retardants, ammonium polyphosphate (APP) and aluminum hydroxide (ATH) were added to wood-flour/polypropylene composites (WPCs) at different APP to ATH mass ratios (APP/ATH ratios), with a constant total loading of 30 wt % (30% by mass). Water soaking tests indicated a low hygroscopicity and/or solubility of ATH as compared to APP. Mechanical property tests showed that the flexural properties were not significantly affected by the APP/ATH ratio, while the impact strength appeared to increase with the increasing ATH/APP ratio. Cone calorimetry indicated that APP appeared to be more effective than ATH in reducing the peak of heat release rate (PHRR). However, when compared to the neat WPCs, total smoke release decreased with the addition of ATH but increased with the addition of APP. Noticeably, WPCs containing the combination of 20 wt % APP and 10 wt % ATH (WPC/APP-20/ATH-10) showed the lowest PHRR and total heat release in all of the formulations. WPCs combustion residues were analyzed by scanning electron microscopy, laser Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Thermogravimetric analysis coupled with FTIR spectroscopy was used to identify the organic volatiles that were produced during the thermal decomposition of WPCs. WPC/APP-20/ATH-10 showed the most compact carbonaceous residue with the highest degree of graphitization.
... Loss of flexural modulus was observed after natural weathering due to micro-cracks on the WPC surfaces that degraded stress resistance. Lopez et al. [14] studied the effects of humidity, temperature, and ultraviolet light exposure on the performance of natural fiber and plastic composites. High humidity was the main determinant of loss of flexural properties. ...
... On the other hand, at lower plastic contents, for example in WPCs with 40 wt% plastic content, the incomplete encapsulation of wood flour in the plastic matrix gave poorer resistance to natural weathering: the loss of mechanical properties was higher. The results are in good agreement with Te-Hsin et al. and Lopez et al., who reported that WPCs with 40 wt% plastic content showed the largest losses of physical and mechanical properties after natural weathering, whereas with more than 50 wt% plastic content they had improved resistance to natural weathering [12,14]. Additionally, during exposure to natural weathering, the ultraviolet radiation causes decrease of crystallinity in the plastic matrix, because the polymer chains are lacerated causing fractures [25,26]. ...
Article
The influences of plastic matrix on mechanical properties (flexural and tensile properties) of wood-plastic composites (WPCs) were investigated. WPCs were prepared with five types of plastic as the matrix phase, namely high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS). Rubberwood flour was used as reinforcing filler. Additionally, maleic anhydride, UV-stabilizer, and paraffin wax were used as coupling agent, ultraviolet stabilizer and lubricant, respectively. The WPCs were produced in two stages: mixing in an internal mixer, and compression molding. WPCs from PS and PP exhibited higher mechanical properties whereas LDPE, HDPE, and PVC gave lower values. In particular LDPE gave consistently the poorest mechanical properties to WPCs. Moreover, the WPCs with PS and PP had the smallest losses of mechanical properties from natural weathering, while LDPE would again be the poorest choice in this respect. These results indicate that WPCs from PP and PS are the best alternatives for applications requiring resistance to natural weathering (exposure to ultraviolet and humidity) or with high mechanical loading (stresses).
... Because of increasing environmental consciousness, over the last few decades researchers have been looking for the environment-friendly materials and the alternative to synthetic fibre reinforced polymer composites. In recent years, natural fibre-reinforced polymer composites (NFRPCs) have attracted the attention of the research community worldwide [1][2][3][4][5][6][7]; as because they have already been proven to be the alternatives to the conventional non-renewable and non-biodegradable materials, such as glass, carbon, kevlar, aramid etc. reinforced composites in various engineering applications. Natural fibres exhibit many advantageous properties which promote the replacement of synthetic fibres in polymer composites. ...
... The use of natural fibres in composite materials, however, presents a few drawbacks due to some characteristics of the fibres such as quality variations, high moisture uptake, poor compatibility with hydrophobic polymer matrix and low thermal stability [4][5][6][7]. Natural fibres are hydrophilic in nature as they are derived from lignocellulose, which contain hydroxyl groups. These fibres, therefore, are inherently incompatible with hydrophobic thermoplastic matrix. ...
Article
The utilization of natural fibres as reinforcement in polymer composites has been increased significantly for their lightweight, low cost, high specific strength, modulus and biodegradable characteristic. In this present work, the mechanical properties of randomly distributed short coir-fibre-reinforced polypropylene (PP) composites have been studied as a function of fibre loading. In order to improve the composite’s mechanical properties, raw coir fibres were treated with 1% alkali (NaOH) solution. Both raw and alkali treated coir-fibre-reinforced PP composites were prepared with different fibre loadings (10, 15, 20, 25, 30 and 35 wt%) using a double roller open mixer machine and injection molding machine. The mechanical properties, such as tensile strength (TS), tensile modulus (TM), flexural strength (FS) and flexural modulus (FM) were investigated for the prepared composites. The alkali treated coir-fibre-reinforced PP composites showed better results in mechanical properties compared to untreated composites. Finally, the optical microscopic studies were carried out on fractured surfaces of the tensile test specimens, which indicated weak interfacial bonding between the fibre and the polymer.
... 7,19,74 Water soaking is an important weathering test and is useful in determining the durable nature of a thermoplastic composite. 7,64,71,76 Weathering (e.g., water soaking) causes HDPE-composites to undergo chemical reactions such as breakdown of lignins into water soluble products which form chromophoric functional groups such as carboxylic acids, quinones, and hydroperoxy radicals. 74 Figure 13.6 compares color values (L*, a* and b*) of the original composites to the soaked composites. ...
... Environmental stresses such as water soaking may cause changes in the mechanical properties to occur which needs to be determined in order to assess the potential commercial value of a composite. 7,64,70,73,76,79 For example, flexural properties have been reported to decrease when LPC are weathered. 7,71,72 The response of the mechanical properties of composites as well as neat HDPE and HDPE-MAPE by water soaking are presented in Table 13 (Table 13.4). ...
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There is a need to identify usable lignocellulosic materials that can be blended with thermoplastic resins to produced commercial lignocellulosic plastic composites (LPC) at lower costs with improved performance. The core objectives of this study are to: i) evaluate the use of dried distillers grain with solubles (DDGS) and Paulownia wood (PW) flour in high density polyethylene-composites (LPC); ii) assess the benefit of chemically modifying DDGS and PW flour through chemical extraction and modification (acetylation/malation); and iii) to evaluate the benefit of mixing DDGS with Pine wood (PINEW) in a hybrid LPC. Injection molded test specimens were evaluated for their tensile, flexural, impact, environmental durability (soaking responses), and thermal properties. All mechanical results from composites are compared to neat high-density polyethylene (HDPE) to determine their relative merits and drawbacks. HDPE composites composed of various percentage weights of fillers and either 0% or 5% by weight of maleate polyethylene (MAPE) were produced by twin screw compounding and injection molding. Chemical modification by acetylation and malation of DDGS and PW fillers prior to compounding was done to evaluate their potential in making an improved lignocellulosic material. Composite-DDGS/PINEW mixture blends composed of a majority of PINEW were superior to composites containing DDGS only. Composites containing MAPE
... Mechanical properties is one of the most important properties of wood-plastic composites [20], so the effect of xenon-arc exposure on these properties were tested and recorded in Fig. 2. Fig. 2a and b shows that the values for both flexural strength (MOR) and modulus (MOE) of BHTi composites were higher than those for BH composites, indicating that rutile nano-TiO 2 had played a role as reinforcing agent in the composites. The MOR and MOE of both BH and BHTi composites strongly decreased upon extended exposure time during xenon-arc weathering. ...
... The lifetime and applications of materials are determined by their susceptibility to degradation in a variety of environments and conditions. Durability is measured through performance and appearance (Lopez et al., 2006); failing in appearance and mechanical properties shortens the service life of the product. The durability of wood-polymer composites (WPCs) exposed to outdoor conditions is determined by their solar radiation and moisture resistance, thermal stability and fungal resistance (Stark and Gardner, 2008). ...
Article
Purpose – The purpose of this paper is to study the resistance of wood-polypropylene and wood-wollastonite-polypropylene composites containing pigments to natural weathering. Design/methodology/approach – Natural weathering of composites was conducted in Finnish climatic conditions for one year. The colour of the composites was determined with a spectrophotometer, the morphology of the composite surface was analysed by scanning electron microscopy (SEM), and the changes in the polymer structure in surface layer of the composites were analysed with differential scanning calorimetry (DSC). Charpy impact strength was determined with an impact tester. Findings – The pigments used in this study reduced the colour change of the composites exposed to outdoor weathering as compared with the un-coloured composite. The carbon black pigment was more effective than the iron oxide pigment. Moreover, only the carbon black pigment was found to reduce the degradation of the surface layer of the composites. The addition of the carbon black pigment had a positive effect on the dimensional stability of the composites in a water absorption test. Only the combination of the carbon black pigment and wollastonite resulted in a composite which was capable to retain its Charpy impact strength both after one year of outdoor weathering and cyclic treatment. Research limitations/implications – This study is a part of continuous research on the development of wood-polymer composites (WPUs) suitable for outdoor applications in Finnish climatic conditions. The first part of the study, which has been published earlier, showed the results of weathering of composites in accelerated tests in comparison with 1,000 hours outdoor exposure during summer time (June and July). Outdoor weathering limited to 1,000 hours cannot give an objective view on the weathering behaviour of composites in Finnish climatic conditions. The results of the current study were obtained from one-year outdoor exposure of composites. Originality/value – The wood-polypropylene composite made with the combination of the carbon black pigment and wollastonite can be recommended for outdoor applications. The study provides useful information on the resistance of wood-polypropylene composites to weathering in Finnish climatic conditions.
... However, both the reinforcement and matrix materials are hydrophilic, that is, they will absorb moisture when immersed in water or kept in a high humidity environment. Currently, the strength, tensile and impact energy absorption ability of all immersed biocomposites show reduced performance, and further exposure to moisture oftentimes leads to debonding of fiber from the matrix [7]- [9]. Soy-based and PLA resins also require food grade agricultural products such as soybeans and starch extracted from corn, which can and perhaps should be used to feed people and livestock instead. ...
Thesis
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A new approach to manufacture biocomposite sandwich structures from purely natural constituents and the corresponding analysis useful for process design are fully demonstrated in this thesis. The constituent materials include agricultural waste (agri-waste) bound together with fungal mycelium as core, natural textiles bound to the core surfaces with mycelium as reinforcement skins, and a bioresin, if needed, to stiffen and strengthen the skins for high performance applications. Based on a series of preliminary experiments, an optimized seven-step manufacturing approach is proposed including: (1) die cutting of skin reinforcement; (2) natural glue impregnation using a nip roller system to allow preforming of the skins; (3) forming/sterilizing of the preform skins with matched and heated molds to serve as integral tools; (4) filling the tools with agri-waste inoculated with mycelium vegetative tissue; (5) allowing the mycelium to grow and bind all constituents together; (6) convectively and conductively drying the workpiece to drive off water and inactive the mycelium; and (7) infusing skins with bioresin and allowing them to cure. Key aspects, process parameter effects and sensitivities and design models of the seven manufacturing steps were investigated and developed further. It was determined that the number of reinforcement plies should be maximized when cutting with steel rule dies to reduce the number of cutting defects. The resulting skin layups can be rapidly impregnated using a nip roller system with an starch-based glue that is continuously circulated, and an analytical model is available for designers to use. Forming, sterilizing and setting of the glue occur simultaneously using heated tooling coated with a ceramic-polymer composite where molding pressure and temperature play a key role. Integral tooling with preformed skins, although potentially offering significant manufacturing cost reductions, loses shape fidelity during the growth process in a high humidity environment. Conductive drying helps to bring the part back into shape conformance, although convective drying is still required to achieve the low moisture levels required by the industrial collaborator. Resin transfer molding with a soy-based bioresin is demonstrated to complete the process cycle. Finally, a manufacturing system model involving all seven steps is developed for system optimization purposes, and a case study to maximize profit is demonstrated.
... Even though the natural fibers are environmental friendly and are obtained from renewable resources variations in quality, dimensional instability, moisture absorbing tendency, debonding over time, low thermal stability are some of the problems which are related to the utilization of unmodified/raw fibers in the preparation of the composites. [23][24][25] In order to overcome these difficulties and to obtain diversity of material properties, hybrid composites have been conceived where two or more fibers are blended into a single matrix to form hybrid composites. [26] Studies prove that the hybridization of fibers show improved flexural, compressive, thermal and dynamic mechanical properties. ...
Article
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Increased environmental awareness and the need for recyclable, reusable, renewable materials have gained more predominance leading various researches towards development and usage of natural fibers. Effective utilization of available natural resources and waste management can lead to sustainable products by reducing the dependence on petroleum based fibers and matrix. In this paper, hybrid composites are developed by blending alkali treated rice straw fiber and chicken feather fibers using unsaturated polyester resin under different fiber matrix combinations and their tensile properties are studied. Results obtained shows increase in tensile strength and tensile modulus values of rice straw, chicken feather and hybrid fibers reinforced composites on fiber loading of more than 35%. The hybrid composites containing rice straw and chicken feather fibers show improved tensile properties than the individual fibers and the alkali treated fibers show better tensile properties compared to the untreated fibers. Fiber volume of more than 35% can be considered as potential reinforcements to achieve enhanced tensile properties.
... However, it was not apparent in PF-impregnated SC-CTL specimens. According to Lopez et al. (2005), exposure to natural sunlight, wetting and drying cycles, and exposure to the wind caused the samples to rub against each otheron the edges as well as the faces. However, deterioration on PF-impregnated SC-CTL is lower compared to the impregnated SC-CTL other, where the PF-impregnated SC-CTL surface minimally exposed (Fig. 2). ...
Article
The weathering resistance properties of short cycle coconut trunk lumber (SC-CTL) were evaluated in response to impregnation using kraft black liquor (BL) and black liquor/phenol formaldehyde (BL/PF) resin. Concentrations of 10, 15, 20, and 25% w/w kraft BL and PF resin with BL were impregnated into SC-CTL using a vacuum-pressure method. Natural weathering tests lasting 6 and 12 months were performed according to ASTM D1435 (1999). After the prescribed testing period, samples were analyzed for their morphological changes via FT-IR and SEM. Mechanical tests were conducted to analyze changes caused by natural weathering in impregnated SC-CTL. The results showed that BL with PF resin impregnation into SC-CTL improved the resistance against natural weathering. The SEM study confirmed that fungi could not colonize the treated samples. The results also suggested that addition of 20% BL in PF resin was sufficient to inhibit weathering. Thus, it was concluded that impregnation of PF resin with BL is a good method to improve the mechanical properties of SC-CTL.
... Commonly, fibers are dried before inclusion into the matrix [34,[39][40][41], but determination of the value of fiber drying in PHBV/natural fiber composites has not previously been assessed to the author's knowledge. ...
... Although natural fibers are obtained from renewable sources and the polymer composites based on them are environmentally friendly as compared to the SFRPCs, there are also some disadvantages, which are related to the utilization of unmodified/raw fibers in the preparation of the composites. These disadvantages are as quality variations, high moisture uptake and low thermal stability of the raw fibers [35][36][37] . ...
... As an outdoor application, a blade is daily exposed to solar radiation, (especially UV ray), temperature and moisture. These parameters define the durability of a material, which is measured by performance and appearance (Lopez, Sain, and Cooper 2006). ...
Thesis
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In the context of the global environmental challenges facing humankind, there is an increasing need to develop new environmentally friendly products and processes to minimise or avoid the use of polluting materials. Natural fibres have become attractive to researchers, due to their low cost, relatively good mechanical properties, high specific strength, non-abrasive, eco-friendly and bio-degradability characteristics. They are now being exploited in replacement of organic and synthetic fibres, such as glass, aramid and carbon in the composite material design. For the past two decades, several plants such as flax, sisal, cotton and coconut have been used by various industry groups such as Mercedes for the development of composite products. In this thesis, a structured six-stage approach has been developed to study the potential of using fibres from different endemic Pandanus leaves for the manufacture of a polyester composite. For each stage, experimental tests and measurement were carried out using well-calibrated devices. As a first stage, the mechanical and chemical characteristics of the Mascarene endemic Screwpine Pandanus (Pandanaceae) fibres have been studied according to several physiological properties of this species (tree maturity, leaf maturity, sunlight exposure, state of natural degradation of the leaf, position of a fibre along the leaf). This first study includes the selection of the species with the highest fibre tensile strength among the 21 existing in Mauritius, the optimisation of alkaline-treatment parameters (soaking time and NaOH concentration) of the fibres from the selected Pandanus species. The purpose of the alkaline-treatment is to increase the strength of the fibre and to improve its adhesion to the matrix. This study revealed that the best species having the highest tensile strength (TS) is the P. iceryi (251 ± 149 MPa) followed by P. utilis (153 ± 81 MPa). An optimum improvement of 23.2 and 36.2 % in the tensile strength compared to untreated fibres were obtained after 0.5 wt. % NaOH for 8 h and 0.5 wt. % NaOH for 14 h respectively for these two species. At the end of this part, a new method for predicting the fibre tensile strength has been developed through the correlation between FT-IR (specific IR peaks ratio relative to the cellulose crystallinity) results and the fibre tensile strength. In the rest of the study, the P. utilis was chosen because of its relatively high strength and its higher availability/abundance than P. iceryi. In the second stage, P. utilis treated fibres having the optimum tensile strength were converted into non-woven preformed fibre-mats. A method similar to the pulp alignment process, used in papermaking was used to orient the fibres randomly on the web. Hydroxyethylcellulose (HEC) was used such as a fibre-bonding agent. Then, the third stage consists to determine the interfacial shear stress (IFSS) improvement after alkaline-treatment, the effect of using HEC fibre-bonding agent and the fibre critical length using a single fibre pull-out test (fibre – polyester). The results have shown that HEC has no adverse influence on fibre strength and the alkaline-treatment followed by a coating of 2 wt. % of HEC increases the resistance of the shear-stress by 36 % compared to the untreated one (7.3 ± 1.9 and 4.6 ± 1.2 MPa respectively). Morphological properties such as inter-fibre void spacing, fibre orientation and fibre dispersion were compared to that of a commercial E-glass mat and the results showed a high similarity of these properties. During the fourth stage, non-woven fibre-mat composites at different volume fractions (0, 10.7, 21.6 and 32.4 % of fibres) were manufactured using the vacuum infusion process. After performing tensile and flexural tests (ASTM D638 and ASTM D790 respectively), the composite having the highest tensile and flexural strengths (32.4 % of fibre/matrix volume fraction for both tests) was chosen for the rest of the study. The results of the composite sample tests showed that the tensile and flexural strength increased at relatively low values of 10 and 16 % respectively compared to the unreinforced matrix. Both the tensile and flexural moduli significantly increase by 51 % and 70 % respectively. The optimal composite was chosen to manufacture a 550 mm Air-X 403 blade model using the vacuum infusion process. A flap wise static test to determine the load at normal operation, load at worst-case and load at failure was performed as per BN-EN 61 400-2: 2006 standard. The failure was achieved by applying a force of 105 N at a distance of 2/3 of the blade length from the blade root. This maximum force is more than enough to cover the normal operation (45.8 N) and the worst-case scenario (64.8 N). The blade flexural stiffness obtained using Macaulay's equation was 30.1 kN m2 knowing that this value is 53 kN m2 for a unidirectional E-glass / polyester blade composite according to the literature. Three replicated blades were tested to check the repeatability of the test and the blade and the result shows that the variation in the force and deflection at the failure of the blades were 4.5% and 9.5% respectively. The main part of the fifth stage consists of the development of a homogenised mathematical model of the optimum composite material using the finite element method (FEM). The model was used to predict the maximum theoretical value of the composite strength. Three homogenisation methods using ANSYS Mechanical APDL (ANSYS Parametric Design Language) were performed including the tensile curve fitting method, ANSYS Material Designer tool and direct analysis of a Representative Elementary Volume (REV). The latter takes into account the interfacial shear stress between fibre and matrix, and specific parameters (dynamic and static frictional coefficients) were obtained through a simulation of the pull-out test using ANSYS APDL. Fibre architecture of the REV was obtained by using an image reconstitution technique. Result of the pull-out simulation showed that dynamic friction and a ratio (static to dynamic frictional coefficient) of 0.1 and 9.5 respectively allowed to obtain the targeted IFSSs relative to the fibre bond-slip behaviour (relative error of 0.95 % and 6.7 % for the maximum shear stress and sliding stress respectively compared to the experimental result). The comparison of the three-homogenisation methods showed that the fitting method is the most suitable when optimising an application, the Material Designer tools when optimising the fibre architecture and volume fraction, and the direct REV when optimising the micromechanical parameters such as IFSS. The result of the simulation on a 3-D composite sample showed that the composite should have a maximum tensile strength of 72 MPa, i.e. 30.5 % more than that of the physical model. The reliability of the mathematic model was confirmed by the result of a flexural test. Generally, the correlation coefficient between the theoretical and the experimental curve obtained in this stage was R2 = 0.98. In the sixth stage, the homogenised material was used to model a 550 mm 3-D solid-blade in view of determining the maximum theoretical flap wise force, optimising the internal structure design of a skinned blade and proposing an optimal ratio blade skin-thickness to blade length. The simulation of the flap wise tested as per BN-EN 61 400 -2: 2006 standard revealed that the maximum force at failure should be twice that of the physical model (200 N and 105 N respectively. It was found that to resist a worst-case scenario; a non-solid blade model must have at least a skin-thickness of 1.75 mm. However, 1 mm of blade-skin-thickness will be sufficient when using a 3mm thick reinforcement flange. A material saving of 35.5 % compared to a solid-blade will be obtained in the latter case. The numerical model allows the prediction of the mechanical behaviour of the bio-based (fibre) composite for the specified application, thus reducing the need to perform several expensive physical tests. Based on the findings of the different experimental and theoretical models, it is concluded that P. utilis fibres can effectively be used as a reinforcing material in the polyester matrix for the manufacture of a small-scale WTB, promoting the use of green energy. It also offers an opportunity for the creation of a micro-enterprise. A critical analysis of the future work, perspective and possible improvement has been presented in the last chapter. Keywords: alkaline-treatment, ANSYS APDL, Hydroxyethylcellulose, interfacial shear stress, natural fibre polyester composite, non-woven mat, Pandanus utilis, pull-out test, Representative Elementary Volume, tensile strength, flexural strength, wind-turbine blade.
... NFCs are renewable, and possess numerous unique advantages over synthetic fibers, such as low cost, recyclability, low density, biodegradability, good thermal properties, high specific stiffness, minimal tool wear, and few health disorders [31À34]. Although NFCs are more eco-friendly compared to SFCs, they also have some limitations related to the utilization of raw fibers which have problems in quality, high moisture uptake, and low thermal stability that will cause a problem in the preparation of composites from these fibers [35,36]. ...
... In the literature, many cases are reported that features of the fiber-reinforced composite, such as surface chemistry, mechanical property, and appearance, are affected by weather. [7][8][9]14,15 HALS have been proven to be very effective in constraining photooxidation, but no significant effects on color stability have been shown. 16,17 In polyolefins, in addition to HALS, UVA is commonly used. ...
Article
In this work, various stabilizers have been introduced to prevent or delay degradation due to ultraviolet (UV) light exposure to prolong the service life of cotton fiber-reinforced composites. The effect of various additives like hindered amine light stabilizer, UV absorber (UVA), and antioxidant as photostabilizers of CF/low-density polyethylene (CF/LDPE) composites was compared. We showed how they influence to delay or eliminate the photodegradation of CF/LDPE subjected accelerated weathering. Surface analysis was performed by Fourier transform infrared spectroscopy and color measurements. The results showed us the insight of the photodegradation mechanism of weathered CF/LDPE composites undergoing photooxidative reactions which causes a loss surface quality such as micro-cracking and color change. Among the stabilizers, UVA was found to be the most effective to delay some color changes in long term.
... Some general degrading influences in the laminates are surface erosion, color fading, loss of weight, and mechanical characteristics that might reduce the final product's service. [23,24] Water absorption characteristic is another critical parameter employed when processing with the plant cellulose fiber composites. The features of water absorption capacity in plant cellulose fiber composites are affected by many parameters such as fiber orientation, fiber content, exposed surface area, temperature, hydrophilicity of single component, void content, and fiber permeability. ...
Article
In the present research, the physical, mechanical, and thermal characteristics of bio and synthetic basalt fabric epoxy composites reinforced with coir microparticles and TiC nanofillers under before and after exposure of accelerated weathering were investigated. All the bio and synthetic epoxy hybrid composites were exposed to humidity, elevated temperature, and ultraviolet radiation. It has been examined that both bio and synthetic epoxy composites exhibited reduced mechanical characteristics after the exposure of accelerated weathering when compared with before exposure. The wettability experiment was performed from the contact angle evaluation method and found that all the fabricated samples before and after the exposure of accelerated weathering have contact angle value lower than 90° that is assigned with the hydrophilic surface characteristics of the laminate. The water absorption capacity showed that all the bio and synthetic epoxy composites reacted for water absorption up to 45 days and then endured constant in both conditions. After the exposure of accelerated weathering, epoxy hybrid composites absorbed more water than before exposure. The chemical modifications possessed on the surface were evaluated from Fourier transform infrared spectra. The intensity of hydroxyl and carbonyl functional groups of bio and synthetic epoxy hybrid composites decreased compared with the original samples, which tends to decrement in tensile, flexural, and impact characteristics of the laminate. The production of more fracture lines on the cross-sectional surface of epoxy hybrid composites has been observed from scanning electron microscope micrographs after the exposure of accelerated weathering. The onset, end set, and glass transition temperature of bio and synthetic epoxy composites in the thermal examination were reduced after the disclosure of accelerated weathering for all fabricated specimens. The reason may be assigned to the weaker bonding between the coir microparticles and TiC nanofillers. The undesirable impact emerged from ultraviolet radiation, elevating the temperature and humidity. The test results showed that the accelerated weathering has negative impact on physicomechanical characteristics of bio/synthetic epoxy hybrid polymer composites. The overall thermal characteristics were not considerably affected with 570 h of the weathering exposure.
... It is mainly used to analyze the surface elements and valence states of samples [31]. In recent years, it has been widely used in chemical composition and valence bond analysis of WPCs [32,33]. Fig. 4 shows the XPS spectrum of the surface of WPCs after thermo-oxidative aging for different time. ...
... The highest water absorption resistance was recorded at minute filler size. The results were comparable to previous researchers (Zabihzabel, 2010;Kord, 2011;Lopez et al, 2006). This inference was ascertained due to high particles leads to large pores space for the composite to absorb water. ...
... The physical modification of a cellulosic natural fibre refers to the changing of the surface properties such as surface energy, polarity, surface area, cleanliness and wettability. Corona treatment [160,[221][222][223], plasma treatment [224][225][226], ultraviolet (UV) treatment [227][228][229][230], fibre beating [231][232][233] and heat treatment [234] are some of the remarkable techniques for physical modifications of fibre without hampering the chemical structure of fibres [235][236][237]. In the case of the corona, for plasma and UV treatment, fibre surface energy is changed using a high voltage at low temperature and atmospheric pressure [160]. ...
Article
Full-text available
The increasing global environmental concerns and awareness of renewable green resources is continuously expanding the demand for eco-friendly, sustainable and biodegradable natural fibre reinforced composites (NFRCs). Natural fibres already occupy an important place in the composite industry due to their excellent physicochemical and mechanical properties. Natural fibres are biodegradable, biocompatible, eco-friendly and created from renewable resources. Therefore, they are extensively used in place of expensive and non-renewable synthetic fibres, such as glass fibre, carbon fibre and aramid fibre, in many applications. Additionally, the NFRCs are used in automobile, aerospace, personal protective clothing, sports and medical industries as alternatives to the petroleum-based materials. To that end, in the last few decades numerous studies have been carried out on the natural fibre reinforced composites to address the problems associated with the reinforcement fibres, polymer matrix materials and composite fabrication techniques in particular. There are still some drawbacks to the natural fibre reinforced composites (NFRCs)-for example, poor interfacial adhesion between the fibre and the polymer matrix, and poor mechanical properties of the NFRCs due to the hydrophilic nature of the natural fibres. An up-to-date holistic review facilitates a clear understanding of the behaviour of the composites along with the constituent materials. This article intends to review the research carried out on the natural fibre reinforced composites over the last few decades. Furthermore, up-to-date encyclopaedic information about the properties of the NFRCs, major challenges and potential measures to overcome those challenges along with their prospective applications have been exclusively illustrated in this review work. Natural fibres are created from plant, animal and mineral-based sources. The plant-based cellulosic natural fibres are more economical than those of the animal-based fibres. Besides, these pose no health issues, unlike mineral-based fibres. Hence, in this review, the NFRCs fabricated with the plant-based cellulosic fibres are the main focus.
... The physical modification of a cellulosic natural fibre refers to the changing of the surface properties such as surface energy, polarity, surface area, cleanliness and wettability. Corona treatment [160,[221][222][223], plasma treatment [224][225][226], ultraviolet (UV) treatment [227][228][229][230], fibre beating [231][232][233] and heat treatment [234] are some of the remarkable techniques for physical modifications of fibre without hampering the chemical structure of fibres [235][236][237]. In the case of the corona, for plasma and UV treatment, fibre surface energy is changed using a high voltage at low temperature and atmospheric pressure [160]. ...
Article
Full-text available
The increasing global environmental concerns and awareness of renewable green resources is continuously expanding the demand for eco-friendly, sustainable and biodegradable natural fibre reinforced composites (NFRCs). Natural fibres already occupy an important place in the composite industry due to their excellent physicochemical and mechanical properties. Natural fibres are biodegradable, biocompatible, eco-friendly and created from renewable resources. Therefore, they are extensively used in place of expensive and non-renewable synthetic fibres, such as glass fibre, carbon fibre and aramid fibre, in many applications. Additionally, the NFRCs are used in automobile, aerospace, personal protective clothing, sports and medical industries as alternatives to the petroleum-based materials. To that end, in the last few decades numerous studies have been carried out on the natural fibre reinforced composites to address the problems associated with the reinforcement fibres, polymer matrix materials and composite fabrication techniques in particular. There are still some drawbacks to the natural fibre reinforced composites (NFRCs)—for example, poor interfacial adhesion between the fibre and the polymer matrix, and poor mechanical properties of the NFRCs due to the hydrophilic nature of the natural fibres. An up-to-date holistic review facilitates a clear understanding of the behaviour of the composites along with the constituent materials. This article intends to review the research carried out on the natural fibre reinforced composites over the last few decades. Furthermore, up-to-date encyclopaedic information about the properties of the NFRCs, major challenges and potential measures to overcome those challenges along with their prospective applications have been exclusively illustrated in this review work. Natural fibres are created from plant, animal and mineral-based sources. The plant-based cellulosic natural fibres are more economical than those of the animal-based fibres. Besides, these pose no health issues, unlike mineral-based fibres. Hence, in this review, the NFRCs fabricated with the plant-based cellulosic fibres are the main focus.
... Flexural strength (MOR) and flexural stiffness (MOE) showed a crucial role in the performance of WPCs in the cases of realistic using [52]. The MOR and MOE retention ratio of the specimens that exposed to three freeze-thaw cycles were shown in Fig. 6. ...
Article
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Using the lignocellulosic biomass materials to produce wood (wood fibers/natural fibers) plastic composites (WPCs) is one of the most environmentally friendly and economical ways to solve the residuals of biorefineries. In this study, tropical maize bagasse (TMB), sweet sorghum bagasse (SSB) and sugarcane bagasse (SCB), the solid residuals from bio-ethanol plants, were used as the reinforcement phase in the production of WPCs. The mechanical, thermal and accelerated weathering behaviors of WPCs were evaluated. The experimental results indicated that the TMB reinforced composites showed better mechanical properties, with tensile strength and flexural strength of 26.8 ± 3.4 and 46.1 ± 3.1 MPa, respectively. Moreover, the retention ratios of the rupture modulus and the elasticity modulus of the SSB reinforced composites were the highest among the three groups after multigelation and 2000 h of xenon lamp weathering, which were reached 84.9 ± 6.7 and 76.0 ± 4.4%, and 76.1 ± 4.7 and 69.4 ± 2.9%, respectively. The production of WPCs reinforced by solid residuals showed potential in connecting with the biorefinery plants.
... Durability in terms of environmental exposure is measured through the changes in mechanical performance, thermal, chemical, and the material appearances after experiencing a certain period of weathering test. Some commonest damaging effects in the composites are color fading, surface erosion, mechanical properties and weight losses which might shorten the service life of the product (Lopez et al., 2006). Water absorption property is another major factor that should be considered when dealing with NFPC. ...
Article
Full-text available
Non-woven kenaf fiber (KF) mat reinforced acrylic-based polyester resin composites were prepared by an impregnation process followed by compression molding. They were exposed to durability test of accelerated weathering and water absorption. Accelerated weathering test through UV irradiation caused modification in chemical, mechanical, surface appearance, and color change of the composites. Two competing reactions occurred throughout the exposure period, i.e., post-crosslinking and photo-oxidation process. FTIR analysis revealed that the former occurred at the early stage of exposure while the latter toward the end of the exposure, exhibited by an accentuated increase in carbonyl and vinyl index. The post-crosslinking process contributes to the improvement in flexural properties and thermal stability of the composites, whereas the oxidation process does not. SEM observation showed that the degradation by photo-oxidation resulted in the formation of voids and blisters on composite's sample. Water uptake of all composites was found to follow Fickian behavior. Good recoveries (exceeding 79%) of flexural properties were obtained upon re-drying. However, a significant reduction in flexural strength and modulus was obtained in the wet state condition. SEM observation revealed that full recovery was not possible because of the impairment of the—matrix interfacial region. Relatively higher flexural properties were exhibited by alkali-treated KF composites even after the durability test due to the improved strength and—matrix adhesion following the treatment.
... The highest water absorption resistance was recorded at minute filler size. The results were comparable to previous researchers (Zabihzabel, 2010;Kord, 2011;Lopez et al, 2006). This inference was ascertained due to high particles leads to large pores space for the composite to absorb water. ...
Article
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This research was aimed at optimizing the properties of avocado wood flour/high density polyethylene composite (AW/HDPE). The effect of particle size (P 1) and filler weight (P 2) on the tensile strength (Z TS), flexural strength (Z FS), impact strength (Z IM) and water absorption (Z W) properties of the composite was examined. The avocado wood flour (AW) was compounded into fine particles (100-20 mesh) at 5-25 % wt with high density polyethylene (HDPE) by injection molding. The optimization process was done using a quadratic function of central composite design to forecast the optimum size and filler weight on the propert ies of the composite. The optimum input variables were 80 mesh and 21.62 % for P 1 and P 2. The optimum output variables were 25.652 MPa, 55.168 MPa, 47.397 KJ/m 2 and 2.782 % for Z TS ,Z FS, Z IM and Z W , respectively. The error between the experiment and response surface methodology (RSM) model at optimum is less than 1%, which indicated a good prediction of the model. This shows that RSM model is appropriate for the optimization of avocado wood flour polymer composite. Natural filler should be considered as a suitable substitute to conventional non-metal compound use as filler in the production of avocado wood flour polymer composite for furniture application.fa
... It can also alter the material properties so that FRP becomes more vulnerable when subjected to other environmental aspects, such as moisture or temperature (Nguyen et al. 2012). The UV radiations can be avoided by using a FRP UV absorber (Lopez et al. 2006). Tuwair et al. (2016) conducted tensile and 4-point loading tests on GFRP laminates exposed to UV radiation according to ASTM G154 (ASTM 2016). ...
In the past two decades, fiber-reinforced polymer (FRP) materials have been increasingly used in civil engineering. Compared with its wide applications in the civil infrastructure system, the use of FRP in buildings is rather limited. One reason for this is that, unlike civil infrastructure, buildings have more stringent nonstructural performance requirements, including those for fire rating, smoke and toxicity, flame spread, water resistance, flood resistance, and so forth. Although numerous studies have been conducted on structural performances of FRP structures, limited studies are available on the nonstructural performance. This paper aims to identify the gap between building code requirements and the current state of research on FRP materials. The first section of this paper is devoted to a summary of the research findings on nonstructural performances. Based on codes and other specifications, the second section systematically examines the code requirements according to the FRP's target applications, such as load bearing members, interior finishes, exterior finishes, or roofings, and their corresponding standards. The next section evaluates the research findings from the first section against the requirements from building codes in the second section. Finally, the applicability, limitations, and future work for FRP materials to be used for building applications are provided in the last section. It can be concluded that, strengthwise, FRP can be used for building applications. Fire rating can be met with different insulate schemes, which vary from 0 to 3 h based on different applications. Exposed FRP needs to meet the requirements of smoke, toxicity, and flame spread. Adding fire-retardant fillers, such as alumina trihydrate (ATH), can enhance performances and meet the code requirements. Further studies on water resistance, weathering tests, flood resistance, combustion, and so forth, are needed. Most of the insulation materials are proprietary and expensive, which restricts their wider applications. It is advantageous to develop cost-effective fire protection systems. No study is available on unified modeling and design guidelines for fire rating, smoke, toxicity, and flame spread. There is a need to provide effective design methods to design these items based on their targeted applications, similar to the methods for structural design.
... In order to estimate the service life of WPCs, little research has been done under natural conditions to collect the actual response. [29][30][31] There is no information about accelerated weathering and decay resistance of heat-treated wood-filled composites. In this article, the main objective of the present study was to investigate heat-treated lignocellulosic filler on the surface characteristics and decay resistance of the wood flour/SMA composites. ...
Article
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The aim of this study was to investigate the effect of heat‐treated lignocellulosic filler on the surface characteristics and decay resistance of the wood flour/styrene maleic anhydride (SMA) composites. In this study, heat treatment was conducted at 212°C for 8 hours. Test specimens were prepared by injection molding at 220°C. Weathering tests were performed by cycles of UV‐light irradiation for 8 hours, water spray for 15 minutes, and then conditioning for 3.45 hours in an accelerated weathering test cycle chamber. Heat‐treated wood flour/SMA composites were evaluated for color changes, and attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy was used to analyze chemical changes on the sample surfaces. The wood decay tests were performed of white rot fungus, Trametes versicolor (L.: Fr.) Pilat was based on mini‐block specimens on 48% malt extract agar in petri dishes. The study showed that color changes occurred when heat‐treated filler rate is increased in this material. Therefore, materials in 10% filler rate show lower color changes than other variation. As a result of the FTIR analysis, the addition of wood filler into the SMA causes changes in the chemical structure. In addition, the increase in wood filler reduced the resistance to weathering. Decay results showed that thermally modified wood has lower mass loss caused by fungal attack than untreated wood material. The weight loss decreases with the increase in wood flour rate expect 10%T and 10%UT in all composites.
... The prolonged testing is necessary to determine the important properties of composites fabricated for outdoor applications since they can still be influenced by moisture uptake, fungal resistance, thermal stability, and ultraviolet (UV) stability. Therefore, it is essential to improve the lifespan of natural fiber composites according to their applications [23]. ...
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Photovoltaic module backsheets are characterized according to their thermal, optical, mechanical, and technical properties. This work introduces new fabricated backsheets for PV modules using polyvinylidene fluoride (PVDF) reinforced with short sugar palm fiber (SSPF) composites. The preparation of composites undergoes multiple phases of fabrication. Thermal, optical, and technical investigations of their properties were conducted. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, in-situ scanning probe microscopy (SPM), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and prolonged technical testing were accomplished to expansively understand the complex behavior of composites under various conditions. The optical properties of PV backsheets are critical components in determining the reflectance, absorbance, and transmittance of light. The PVDF–SSPF composites exhibited exceptional compatibility and thermal stability, further revealing a homogenous composite structure with enhanced interfacial bonding between the short fiber and polymer matrix.
... The reason for the degradation includes the changes in crystallinity of the matrix phase, oxidization of WPC surfaces and the interfacial strength degradation in WPCs [20,[23][24][25][26][27]. The effect of natural weathering on WPCs is reported in many studies [28][29][30] as fencing, decking, outdoor furniture, window parts, roofline products, door panels, etc. are frequently made by WPCs, are subjected to natural weathering [31][32][33]. The elastic modulus and the strength of wood fibers are roughly 40 times and 20 times higher than that of the polyethylene [34]. ...
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The present work reports the inclusion of different proportions of Mango/Sheesham/Mahogany/Babool dust to polypropylene for improving mechanical, wear behavior and biodegradability of wood-plastic composite (WPC). The wood dust (10%, 15%, 20% by weight) was mixed with polypropylene granules and WPCs were prepared using an injection molding technique. The mechanical, wear, and morphological characterizations of fabricated WPCs were carried out using standard ASTM methods, pin on disk apparatus, and scanning electron microscopy (SEM), respectively. Further, the biodegradability and resistance to natural weathering of WPCs were evaluated following ASTM D5338-11 and ASTM D1435-99, respectively. The WPCs consisting of Babool and Sheesham dust were having superior mechanical properties whereas the WPCs consisting of Mango and Mahogany were more wear resistant. It was found that increasing wood powder proportion results in higher Young’s modulus, lesser wear rate, and decreased stress at break. The WPCs made of Sheesham dust were least biodegradable. It was noticed that the biodegradability corresponds with resistance to natural weathering; more biodegradable WPCs were having the lesser resistance to natural weathering.
... Çìåíøåííÿ ê³ëüêîñò³ ã³äðîêñèëüíèõ ãðóï ó ñêëàä³ êîíîïëÿíî¿ êîñòðèö³, âèòðà÷åíèõ íà âçàº-ìîä³þ ç ôóíêö³éíèìè ãðóïàìè ñïîëó÷íîãî, çóìîâëþº ïîë³ïøåííÿ ¿õ ô³çèêî-õ³ì³÷íèõ âëàñòèâîñòåé çàâäÿêè çíèaeåííþ ã³äðîô³ëüíîñò³ ïîë³-Ðèñ. 5. ²×-ñïåêòð ïðåñîâàíîãî êîìïîçèòà íà ä³ëÿíö³ 3700-3000 ñì - ìåðíèõ êîìïîçèò³â, ÿêà, ÿê â³äîìî [10,15], º íàéâàaeëèâ³øîþ ïåðåøêîäîþ íà øëÿõó äî ¿õ øèðîêîãî ïðàêòè÷íîãî âèêîðèñòàííÿ. ...
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The interaction of the components both in the model systems and in the epoxy-urethane matrix, based on the polyisocyanate, epoxy resin ED-20 and sodium silicate, as well as in the filled composite based on the epoxy-urethane matrix was investigated by the FTIR spectroscopy method. It was shown that trimerization of isocyanate groups occurs during the formation of the epoxyurethane polymer matrix in the system simultaneously with the reaction of urethane formation at the interaction of isocyanate groups of polyisocyanate with hydroxyl groups, isocyanurate fragments being formed as additional cross-links units of a three-dimensional network. The influence of the temperature of the reaction medium on the course of chemical reactions of epoxy-urethane matrix formation was studied. On the basis of synthesized epoxy-urethane matrix, the polymer composite material containing hemp chaff as a fiber filler was prepared. Hemp chaff is a source of cellulose fiber suitable for strengthening of polymers and as rapidly renewable natural resource, which is characterized by cheapness, ease of working and recycling. The interaction between the functional groups of the epoxy-urethane matrix and hydroxyl groups of hemp chaff was shown. Almost complete conversion rates of isocyanate and epoxy groups in the pressed sample of the filled composite material was revealed. It was determined that the optimal temperature of polymer composite material forming is 160 ⁰ Ñ. © 2019 Ukrainian State University of Chemical Technology. All Rights Reserved.
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Natural fiber composites are playing an important role in present area of composites and among them plant fibers have a major role as a fiber reinforcement material. Thermal analysis has a crucial role and plays a significant factor in determining the materialistic properties of composites. In the present study, a vetiver fiber composite was prepared by a simple hand lay-up method. Tensile and flexural test was carried out. Thermal degradation analysis was performed with thermal gravimetric analyzer and the studies show that the fibers were treated with some more chemical treatments it would have added less thermal degradation and more mechanical properties.
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Chapter
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The growth in applications of natural fibre polymer composites (NFPCs) has increased the importance of understanding time-dependent viscoelastic properties such as creep resistance, stress relaxation, and fatigue, all of which are covered in this chapter. The fundamentals of measurement of these properties are discussed, and the use of short- and long-term prediction of creep resistance of the NFPCs to achieve adequate long-term performance is outlined. The effects of the interfacial interaction between natural fibres and polymers on fatigue and stress relaxation properties of the NFPCs are explored.
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In this study, there were two kinds of recycled polypropylene (RPP) packaging bags, RPP disposable packaging bags (RPP-DB) and RPP woven bags (RPP-WB), used as matrix reinforced with wheat straw fiber (WSF). The aim of this study was to investigate the relative degradation behavior of WSF/RPP composites with two RPP matrices under weathering conditions. The RPP packaging bags were blended with WSF by a two-roll mill mixer and then molded by a compression molding machine. The effects of accelerated weathering on the surface morphology, surface color, surface chemistry, thermal properties, and mechanical properties were evaluated after distinct periods; the total time of exposure of the composites in a QUV-accelerated weathering tester was 1,200 hours. The weathering degradation process of WS/RPP-DB was gradual from surface to interior, whereas the internal collapse aggravated the performance reduction of WS/RPP-WB. The weathering resulted in significant discoloration. The photobleaching of WS/RPP-DB was faster than of WS/RPP-WB. The Fouriertransform infrared spectrum suggested that the color change was closely related to the formation of carbonyl groups and degradation of lignin. After weathering, the thermal properties of WS/RPP-DB and WS/RPP-WB were both decreased. The flexural strength and modulus of WS/RPP strongly decreased with exposure time and was related to the surface crack of composites. The utilization of RPP packaging bags as matrix could be a good candidate of wood-plastic composites for applications in the future.
Chapter
The natural fiber-reinforced composites (NFCs) are used to make sustainable eco-friendly products with properties comparable to synthetic materials. However, NFCs are susceptible to aging-induced degradation in environmental conditions such as moisture and ultra violet (UV) exposure. Therefore, it is imperative to understand the aging phenomenon of NFCs and the mechanical properties degradation due to aging and UV exposure. This chapter provides an insight into the effects of aging and UV exposure on the mechanical properties of NFCs. The chapter consists of a comprehensive literature review, simplified procedure for aging and UV exposure tests, a case study and a finite element method (FEM) based model for studying the effect of aging and UV exposure on NFCs. It was evident that with an increase in UV exposure time, the mechanical properties deteriorate significantly as a result of matrix erosion, cracking, and photo-degradation. A further insight into the previous work of one of the authors was provided to understand aging in wood-plastic composites (WPCs). The wood-plastic composites (WPCs) experience a noticeable reduction in the tensile strength (TS), bending strength (BS) and wear resistance after weathering for 13 weeks. In the present work, the sugarcane dry leaves composites (SDLRPCs) also showed a reduction in the TS, BS, and Mode I plane strain fracture toughness (K1C) after 80 hours of UV exposure. The FEM-based micromechanical model was constituted to visualize the state of stress within the NFCs. It predicted that after UV exposure, the NFCs such as SDLRPCs have a higher tendency to undergo matrix shear yielding near the crack tip.
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The use of natural fibres as reinforcement material have become common in human applications. Many of them are used in composite materials especially in the polymer matrix composites. The use of natural fibres as reinforcement also provide alternative solution of usage instead of being a waste materials. In some applications, these natural reinforced polymer composites were used as the outer layer, making them exposed to ultra violet exposure, hence prone to UV radiation. This paper reviews the effect of UV radiation towards the mechanical properties of natural fibre reinforced polymer matrix composite material. The effect of chemical treatment towards the natural fibre is also investigated. One of the important features that was critically explored was the degradation of the composite materials. The influence of UV radiation on the degradation rate involve several parameters such as wavelength, intensity and exposure time. This review highlights the influence of these parameters in order to provide better solution for polymer matrix composite's development.
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The Young's modulus of multilayer films containing cellulose nanocrystals (CNCs) and polyethyleneimine (PEI) was measured using a buckling-based method and compared to analogous films containing nanofibrillated cellulose (NFC) and PEI [1]. For films 61 nm to 1.7 μm thick, the Young's modulus was constant but strongly dependent on relative humidity. Films were stiffer at lower relative humidities, with modulus values of 16 ± 5, 12 ± 1, and 3.5 ± 0.3 GPa at 30%, 42%, and 64% relative humidities, respectively. CNC/PEI films had larger elastic moduli than NFC/PEI films. Both types of nanocellulose multilayer films showed the same modulus dependence on relative humidity over the range studied. Results suggest that ambient water might have an even more pronounced role in nanocomposites than in traditional natural fiber-reinforced composites. This straightforward buckling-based method has quantified mechanical properties and provided a useful comparison between CNC and NFC films. Furthermore, it qualitatively assesses that the components in the composite film are highly compatible and that the hydrophilicity and hygroscopicity of cellulose and PEI combined do not allow for the full mechanical potential of crystalline cellulose nanoelements to be exploited. This work is one approach toward finding dependable methods to characterize nanocellulose, specifically cellulosic thin films, which is increasingly important as we extract nanocellulose from wood, plants, algae, bacteria, and animals and enter a new age of cellulose materials.
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In this research, the effect of fibre content, fibre size and alkali treatment to the impact resistance of the composite material have been investigated, The composite material employs oil palm fibre as the reinforcement material whereas the matrix used for the composite materials are polypropylene. The Oil Palm fibres are prepared for two conditions: alkali treated fibres and untreated fibres. The fibre sizes are varied in three sizes: 5mm, 7mm and 10mm. During the composite material preparation, the fibre contents also have been varied into 3 different percentages: 5%, 7% and 10%. The statistical approach is used to optimise the variation of specimen determined by using Taguchi method. The results were analyzed also by the Taguchi method and shows that the Oil Palm fibre content is significantly affect the impact resistance of the polymer matrix composite. However, the fibre size is moderately affecting the impact resistance, whereas the fibre treatment is insignificant to the impact resistance of the oil palm fibre reinforced polymer matrix composite.
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Modification of natural polymers like protein by graft co-polymerization is an important method to incorporate the desired properties into the backbone. Soy protein concentrate (SPC) was grafted with ethylmethacrylate (EMA) using ascorbic acid /potassium persulphate as redox initiator system under pressure. Different reaction parameters such as reaction time, reaction pressure, solvent amount, initiator ratio, pH and monomer concentration were optimized to get maximum graft yield (59.5%). The optimized reaction conditions were: reaction time; 150 min, reaction pressure; 7.5 psi, solvent; 150ml, AAc: KPS; 1:1.25, pH; 8, [EMA]; 1.99 X 10(-3) Mol L-1. The graft copolymer formed was characterized by FTIR, XRD and SEM techniques. The grafted protein was found to undergo physico-chemical changes on incorporation of polymer chains onto backbone through graft copolymerization which resulted in enhanced resistance towards moisture absorbance and acid-base attack. Thermal analysis showed higher final decomposition temperature of grafted protein as compared to that of ungrafted backbone.
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This work computationally predicts the onset of moisture-induced damage for different wood polymer composite (WPC) formulations using an experimentally validated micromechanical model. For model validation, the flexural mechanical properties of a commercially available WPC were experimentally obtained after exposure to either moisture or combined moisture and freezing conditions. As expected, exposure caused a loss in mechanical properties, which was primarily attributed moisture-induced damage and not further exacerbated by freezing. Once validated, the model was used to predict that the WPC would incur damage when placed in a commonplace 40–45 % relative humidity environment. This work demonstrates that computational simulations can be used to design moisture-resistant WPC formulations given specific environmental conditions (i.e., relative humidity, temperature) of the intended target application.
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Natural fiber-polymer composites are becoming increasingly important for load-bearing application due to their unique benefit of light weight and good mechanical performance. Polymers alone exhibit time dependent mechanical properties influenced by many environmental factors. More significantly, when natural fibres are present in the polymer matrices, the thermo-mechanical properties of such composites are changed by the environmental conditions and exhibit an internal and a global time dependent behavior. While durability analysis of the natural fibre-polymer composites is the main concern in real-life application, development of prediction methods is essential for evaluating their mechanical performance. Both temperature and moisture diffusion are known to influence the time dependent mechanical properties of polymer based composites; however, conventional analysis method considers the temperature factor only. Therefore, an evaluation technique is presented in this paper to describe the nonlinear viscoelastic behavior of natural fibre-polymer composites under concurrent temperature and moisture diffusion effects. Using an analogous approach to the TTSP, time-moisture superposition will be used to identify the moisture-dependent shift factors under an assumption that the effects of temperature and moisture can be decoupled and separately determined, and reassembled later on.
Chapter
Various chemimechanical refiner pulps (unbleached, peroxide-bleached and pre-yellowed) were irradiated with monochromatic light at selected wavelengths. The change in reflectance at 457 and 557 nm was monitored using UV-VIS reflectance spectroscopy and post-color values were calculated from the reflectance changes. Photoyellowing and photobleaching were observed. Unit yellowing was subsequently obtained using experimentally derived kinetic curves for the reflectance versus exposure dose at a certain wavelength. The action spectra for the photoyellowing were obtained by plotting the reciprocal of the exposure dose necessary to produce a certain change versus wavelength. A different set of action spectra for both photoyellowing and photobleaching was constructed by keeping the exposure time constant and plotting the ratio of the photoyellowing or photobleaching to the light intensity at a certain wavelength against wavelength. The action spectra obtained with the two methods are similar in shape, suggesting that the observed changes are linearly dependent on the light intensity. Photoyellowing was found to be most extensive with light of wavelength 310-320 nm. For strongly pre-yellowed pulp, photobleaching with a maximum effect at 430-450 nm was observed to be the major process on irradiation. The implications of the action spectra for the different pulps are discussed.
Chapter
Fifty years of research has shown that light-induced yellowing of mechanical and ultra-high yield pulps proceeds through a photooxidative discolouration of lignin in the fibre wall. At least four reaction pathways were identified: (1) direct absorption of uv light by conjugated phenolic groups to form the phenoxyl free-radical, (2) abstraction of phenolic hydroxyl hydrogen as a result of aromatic carbonyl triplet excitation to produce a ketyl and phenoxyl free-radical, (3) cleavage of non-phenolic phenacyl-α-O-arylethers to phenacyl-phenoxyl free radical pairs, and (4) abstraction of the benzylic hydrogen of the guaiacylglycerol-β-arylether group to form the ketyl free-radical which in turn undergoes cleavage of the β-O-4 aryl ether bond to produce an enol and phenoxy free radical. Alkoxyl and peroxyl free-radicals produced from the reaction of oxygen and lignin free-radicals react with the phenoxy free-radical formed to produce the quinonoid coloured chromophore.
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The wavelength sensitivity of low-density polyethylene (LDPE) films exposed to filtered xenon arc radiation was determined by the sharp cut filter technique based on the changes in IR absorption and tensile properties. The spectral sensitivity curves in terms of both changes in IR absorption of carbonyl and elongation at break had a similar trend, and the spectral region, responsible for PE photo-oxdation, was found to be in a rather wide range of approximately 260–420 nm. The activation spectra of PE at two different irradiation times based on the changes in IR absorption were also obtained. From the activation spectra it was shown that the most effective spectral region for causing PE photo-oxidation is in the range 330–360 nm. The results are discussed from the point of view of photo-oxidation mechanism.
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During recent years there has been increasing use of polymer-based materials, such as thermoplastics, thermosets and composites, as replacements for the traditional building materials. Although these polymers offer an impressive range of attractive properties, the effect of climatic conditions on the durability and performance of these materials is not fully understood. This paper briefly examines the effects of the UV radiation on the performance and properties of the polymer-based building products. The use of accelerated weathering techniques to assist in assessing the durability of building materials is also briefly discussed.
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Development of the wood-thermoplastic composite market has been hampered by a lack of data on durability and reluctance by homebuilders to utilize undemon­ strated products. This paper presents an overview of re- search at the Forest Products Laboratory to evaluate the durability performance of natural fiber-thermoplastic composites intended for use in roofing applications. An accelerated aging device was used to evaluate the effect of ultraviolet light exposure on the fading of various com­ posites as well as the effect of weathering on the degrada­ tion of engineering properties. The results indicate low variability in fading and mechanical properties.
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HCO radical at a concentration of about 1014 cm−3 is produced by monochromatic laser photolysis of H2CO with a 0.6 mJ frequency-doubled, flashlamp-pumped dye laser pulse. Intracavity dye laser spectroscopy quantitatively monitors HCO absorbance near 614 nm as a function of delay time between photolysis and probing pulses. Rate constants for HCO + O2 and HCO + NO are found to be 4.0 ± 0.8 × 10−12 and 1.45 ± 0.2 × 10−11 cm3 molecule−1 sec−1.
Article
Ultraviolet weathering performance of polyvinyl chloride (PVC) filled with different concentrations of wood flour was studied. Extruded PVC/wood-flour composite samples were subjected to cyclic ultraviolet lamps/condensation exposures and assessed over a total of 400 and 2600 hours. Each assessment consisted of DRIFTFTIR and XPS collections, contact angle measurement, color measurement, and tensile property testing. The experimental results indicated that wood flours are effective chromophore materials since their incorporation into a rigid PVC matrix accelerated the degradation of the polymeric matrix. Photodegradation converted unfilled PVC samples to a colored material of lower extensibility. Although composite samples exhibited greater discoloration than unfilled PVC samples, they retained all their original strength and stiffness properties even after 2600 hours of cyclic UV irradiation/condensation exposures.
Article
The wavelength sensitivity of polypropylene photooxidation was studied by using a cut-off filter technique. Both xenon arc lamp and sunlight were used as irradiation sources. Carbonyl absorption and tensile strength of samples were measured to determine the degradation degree. Activation spectra of polypropylene were obtained. Results showed that in the experimental period of the accelerated test, radiation with wavelength longer than 400 nm contributed little to the degradation. In the energy range of solar exposure, radiation with wavelength longer than 360 nm made negligible contribution to the degradation. In the activation spectra of the accelerated test, the most effective spectral region was 300–350 nm at the beginning. When the irradiation time surpassed 68 h, it was 335–360 nm. Compared with other wavelength regions, the degradation effect of radiation in the 335–360 nm spectral region rose fastest with the irradiation time in the accelerated photooxidation.
Article
The incompatibility of hydrophilic wood fiber and hydrophobic polymers is the main difficulty with wood thermoplastic polymer composites. To overcome this issue, many researchers suggest grafting polymer onto wood fiber for improving the interfacial adhesion during mixing. A systematic ESCA study of chemi-thermo-mechanical pulp (CTMP) grafted fiber has been performed to provide chemical information about surface composition modification. The material analyzed included initial CTMP fiber, the pure polymer i.e., poly(methyl methacrylate) (PMMA) as reference material, and grafted fiber at different polymer loadings. Interest is focused on the carbon and oxygen spectra. Samples at high polymer loading or high grafting level have an O/C, C1, C2, C4, O1, and O2 intensities much similar to those of the PMMA but a little different since some wood fiber sites have still not fixed the polymer. ESCA spectra provide information on about 1–5 nm depth. The ESCA technique allows the monitoring of grafting polymer onto wood fiber as a surface phenomenon.
Article
Long term degradations in weathering condition and in controlled environment conditions of different factors (ultraviolet light, oxidation and heat) were conducted for wood flake reinforced HDPE composites. An interaction of the mechanical recovery of the compressed wood cell structure and environmental stress cracks of HDPE plays an important role in the weathering degradation. Daily temperatures and sunshine times are believed be less crucial than rainfall and UV intensity. In controlled degradations, the oxidative degradation of the composite exposed to air was obvious but limited. After excluding the effect of dehydration the kinetic theory of the first order reactions could describe the thermal degradation of the composite, whose activation energy of 23.2 kJ/mol indicates an ease thermal degradation. UV exposure greatly promoted the environmental stress cracks of HDPE, but its impact on the composite was limited in the controlled dry condition.
Article
The use of wood-derived fillers by the thermoplastic industry has been growing, fueled in part by the use of wood-fiber–thermoplastic composites by the construction industry. As a result, the durability of wood-fiber–thermoplastic composites after ultraviolet exposure has become a concern. Samples of 100% high-density polyethylene (HDPE) and HDPE filled with 50% wood-flour (WF) were weathered in a xenon arc-type accelerated weathering apparatus for 2000 h. Changes in surface chemistry were studied using spectroscopic techniques. X-ray photoelectron spectroscopy (XPS) was used to verify the occurrence of surface oxidation. Fourier transform infrared (FTIR) spectroscopy was used to monitor the development of degradation products, such as carbonyl groups and vinyl groups, and to determine changes in HDPE crystallinity. The results indicate that surface oxidation occurred immediately after exposure for both the neat HDPE and WF/HDPE composites; the surface of the WF/HDPE composites was oxidized to a greater extent than that of the neat HDPE. This suggests that the addition of WF to the HDPE matrix results in more weather-related damage. The results also show that while neat HDPE may undergo crosslinking in the initial stages of accelerated weathering, WF may physically hinder the ability of HDPE to crosslink, resulting in the potential for HDPE chain scission to dominate in the initial weathering stage.
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