No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Rheological and thermal properties of exfoliated graphite nanoplatelets-filled impact modified polypropylene nanocomposites
Abstract
The objective of this research was to investigate the influence of exfoliated graphite nanoplatelets (xGnP) particle diameter, filler loading, and the addition of coupling agents on the rheological and thermal properties of xGnP-filled impact modified polypropylene (IMPP) nanocomposites. xGnP-filled IMPP composites were manufactured via melt mixing with and without the addition of polypropylene-graft-maleic anhydride (PP-g-MA). Particle diameter of xGnP had no significant effect on the melting (Tm) and crystallization (Tc) temperatures as well as degradation behavior of the composites. Storage modulus (E') of the composites increased with increasing xGnP percent at high filler loadings and the incorporation of xGnP did not significantly affect the glass transition temperature, but filler loading does have a significant effect on the magnitude of the tan delta max peak values. The shear storage modulus (G') of the composites with smaller diameter xGnP particles was lower than those of the composites with big diameter particle xGnP at lower frequencies. The higher the xGnP content of the composite, the higher the shear viscosity and the smaller particle diameter of xGnP results in lower viscosity values. Addition of a coupling agent decreased the melt viscosity of the xGnP-filled nanocomposites and caused a slight reduction in the shear-thinning behavior.
... Figure 3a shows the crystallization curves of all samples in the first cooling thermogram, and the shift toward higher temperatures in correspondence with the amount of xGnP depending on its nucleating agent role is evident. Crystallization temperature rose by about 5 • C in nanocomposites, and this could be attributed to the sufficient dispersion and distribution of nanoparticles, as reported in our previous study and others in the literature (Table 5) [33,41]. ...
... Figure 3a shows the crystallization curves of all samples in the first cooling thermogram, and the shift toward higher temperatures in correspondence with the amount of xGnP depending on its nucleating agent role is evident. Crystallization temperature rose by about 5 °C in nanocomposites, and this could be attributed to the sufficient dispersion and distribution of nanoparticles, as reported in our previous study and others in the literature (Table 5) [33,41]. Crystallization enthalpy was similar for all samples, as shown in Table 5. ...
... Platelets were prone to sliding over polymer chains rather than restricting mobility via network formation [45]. xGnP with a similar aspect ratio provided network formation polymer chains even in the absence of a coupling agent in the literature [41]. The orientations of platelets driven by melt flow and shear forces might restrict the network formation, and this supports the discussion of the morphological analysis and agrees with the literature. ...
Lightweighting is a challenge for the automotive industry, and foaming is a key technology used to address this problem. A new practical approach is studied to regulate the cell formation of copolymer polypropylene (co-PP) by utilizing graphene nanoplatelets (xGnP) as a process aid during foam injection molding. The approach was designed to enable process freedom to tune part performance by adjusting the amount of xGnP masterbatch. Two different levels of 1–2 wt % xGnP and 0.25–0.35 wt % supercritical fluid (SCF) were investigated. Prepared samples were compared with samples prepared by the traditional method (twin-screw extrusion followed by foam injection molding). The nanocomposite with 2 wt % xGnP comparatively showed about twofold reduction in cell size magnitude. Although the increment in SCF amount resulted in a 47% and 122% enhancement in flexural modulus and strength, respectively, and a 45% loss in Izod unnotched impact strength, the cell size was prone to increasing with regard to low melt strength as compared to neat foams. In conclusion, a 12% weight reduction fulfilled the desired performance parameters in terms of mechanical and sound insulation by utilizing 2 wt % xGnP as a process aid.
... Polypropylene (PP) is a thermoplastic polymer, which is commonly used in various industrial applications due to its advantageous properties at a reasonable price [1][2][3][4][5][6]. Due to high and ever-growing consumption, a significant amount of PP is found in the industrial and municipal wastes [7]. ...
The principal aim of this study is to investigate the utilization feasibility of waste materials, i.e., recycled Polypropylene (PP), and fly ash in the formulation of auto parts which are commonly designed based on PP. The typical formulation of auto parts consists of PP, elastomer, filler, and compatibilizer. Various recycled PP/virgin PP ratios were considered as the matrix of the composites. It is found that the increasing concentration of recycled PP in the composite leads to a reduction in mechanical properties, particularly ductility and impact strength. However, due to a lower viscosity at the presence of recycled PP, better dispersion of filler particles, observed by SEM analysis, leading to the improvement of tensile strength. Besides, the employment of recycled material lowers the percentage of crystallinity and melting temperature. It is deduced that the deployment of 20/80 to 40/60 ratios of recycled PP/virgin PP in the composites reasonably meets the requirements for auto parts with advantages in the environmental and economic aspects. Compared to the composites filled with talc, the ductility of fly ash-filled composites is higher. The simultaneous utilization of talc and fly ash as a hybrid system brings about higher ductility, but lowers impact strength compared to talc-filled samples. Using recycled PP mixed with fly ash provides advantages in cost reduction and sustainable and environment-friendly production.
... However, compared to F13E samples, the rate of slope mutation in F13H composites was higher. Similar findings was also reported by Kiziltas et al. [5]. It is worth noting that in EC100filled composites, the percolation threshold took place at merely 5 vol% GnP, which is due to the higher aspect ratio of EC100 GnP [28]. ...
This study aimed to evaluate the impacts of different polypropylene (PP) chain configurations, i.e., linear and branched form, on the rheological, mechanical, and electrical properties of PP-based, graphite nanoplates (GnP)-reinforced nanocomposites. The incorporation of GnP with different particle size gave us constructive information about the influences of filler's dimension on the abovementioned properties. A solid-state shear pulverization (SSSP) technique followed by conventional melt mixing was employed to get GnP-filled samples prepared for better filler dispersion. Due to higher interfacial surface area, the obtained mechanical properties from finer GnP (EC1500) were more satisfying. However, the electrical and rheological percolation thresholds (the formation of conductive pathways) took place at a lower content of larger GnP (EC100), which is mainly due to its higher aspect ratio compared to EC1500 GnP. Replacement of linear PP with branched one did not lead to conspicuous alterations in tensile modulus and strength. Based on rheological evaluations, however, the presence of side branches hindered the development of GnP sound network throughout PP matrix, so that in comparison to linear PP-based sample the augmentation of electrical conductivity of branched PP-based composites against filler loading demonstrated slower rates.
... A number of reports have been published on the rheological properties of polymer nanocomposites: polypropylene (PP) Gu et al., 2004;Lee et al., 2008;Jian et al., 2003;Kiziltas et al., 2018;Wang et al., 2018) poly(ethylene oxide)/ silica (Zhang and Archer, 2002), poly(ε-caprolatone)/clay (Lepoittevin et al., 2002), PSeclay (Zhao et al., 2005), polycarbonate (PC)/multiwalled carbon nanotubes (MWNTs) (Potschke et al., 2004), and HDPE/clay (Swain and Isayev, 2007), linear lowedensity polyethylene/clay (Swain and Isayev, 2007), epoxy/clay (Swain and Isayev, 2007), and PS/clay (Kim et al., 2002). ...
The current chapter is designed to provide a general introduction to rheology. This is accompanied by explaining various terms involved in rheology, different types of rheological response exhibited by various materials, and different sets of rheological geometries commonly used for various studies.
In this study, graphene nanoplatelets (GNP) (2%, 4%, 6% and 8% by wt.) were incorporated into PA610 matrix via melt compounding using a twin-screw extruder to compensate for the relatively lower mechanical and thermal properties of bio-based PA610 compared to petroleum-based polyamide. Thermogravimetric analysis showed a slight improvement in thermal stability which peaked for the formulation of 6% GNP. Shear-thinning behavior was more severe with the increase in GNP content. Significant improvement in tensile modulus was observed with increment up to 95% for composites with 8% GNP loading. 16% for Flexural modulus increased by16% and strength by 9.5% for 8% GNP composites. These results suggest GNP fillers can be used to enhance the mechanical and thermal properties of PA610 for automotive applications.
Elastomer nanocomposites have attracted tremendous attention in recent years owing to their exceptional mechanical, electrical, thermal, barrier and flame-retardant properties. Graphene has become a prevalent constituent in elastomer nanocomposites thanks to its superior stiffness and strength, as well as its potential to enhance multifunctional properties. In this study, sustainable thermoplastic elastomers based on recycled polypropylene (RPP) and renewable guayule latex, which has recently entered the commercial arena as an alternative natural rubber, were prepared with polypropylene-graft-maleic anhydride as a coupling agent. Graphene nanoplatelets (GnP) (2.5% to 10% by wt.) were added to enhance the mechanical (strength and modulus), thermal and flame retardant properties. With the addition of 10% GnP, the flexural modulus increased by a factor of 1.24, whereas tensile modulus increased by 76%. Scanning electron microscopy of the fractured surface of GnP reinforced nanocomposites showed a good correlation with the improvements in impact properties. Thermogravimetric analysis of composites with 10% GnP showed an increase in carbon residue at 600°C by a factor of 3.4 indicating improved thermal stability. Incorporation of GnP did not have a significant effect on the glass transition temperature range, however, the magnitude of storage modulus increased significantly. As expected, incorporation of GnP increased the shear viscosity, which decreased with shear rate exhibiting non-Newtonian behavior. These results indicate that GnP reinforced composites could be used in the next generation of automotive thermoplastic elastomer products such as cowl vent grills, wheel lips, rear bumper fascia, rocker panels and side moldings with certain improvements in mechanical, thermal and physical properties.
Carbon-based aerogels composites are a unique class of porous material with a numerous physicochemical features such as good porosity, low density, extraordinary surface area, and flexible surface chemistry. The viability of this porous material as gas sensor composite has been widely explored. The carbon-based aerogel has drawn significant attentions as an adsorption media for deletion of several environmental and human health-threatening pollutants and hazardous gases. Although, aerogel performance for environmental remediation are promising, some drawbacks of such aerogels such as intricate drying process, mechanically delicate structure, and processing cost have also taken into account and have been halted at a certain way in the studies.
Engineered nanomaterials (ENMs) and nanotechnology are revolutionising the world. Especially in the twenty-first century, it has gathered considerable interest from the society, academic world, researchers and the industrial sector. Nanotechnology is now an established scientific area that has undergone an exciting growth phase with a wide range of applications in different fields. Although the field of nanomaterials is mature and well established, the scale-up from research and development to commercialisation remains tedious due to the reliability and reproducibility of technology. To overcome the limitation, there is a need to standardise, validate and evaluate each stage of process development. Extensive research has been done at the institutional and investors level for the modernisation and smooth technology transfer. This chapter emphasises the significant progress, applications and challenges in nanotechnologies and ENMs. In the end, the application properties of this specific topic and future directions for research are discussed.
Glycerine treated nanofibrillated cellulose (GNFC) was prepared by mixing aqueous nanofibrillated cellulose (NFC) suspensions with glycerine. Styrene maleic anhydride (SMA) copolymer composites with different loadings of GNFC were prepared by melt compounding followed by injection molding. The incorporation of GNFC increased tensile and flexural modulus of elasticity of the composites. Thermogravimetric analysis showed that as GNFC loading increased, the thermal stability of the composites decreased marginally. The incorporation of GNFC into the SMA copolymer matrix resulted in higher elastic modulus (
G
′
) and shear viscosities than the neat SMA copolymer, especially at low frequencies. The orientation of rigid GNFC particles in the composites induced a strong shear thinning behavior with an increase in GNFC loading. The decrease in the slope of elastic modulus with increasing GNFC loading suggested that the microstructural changes of the polymer matrix can be attributed to the incorporation of GNFC. Scanning electron microscopy (SEM) images of fracture surfaces show areas of GNFC agglomerates in the SMA matrix.
Some of the significant trends and opportunities in the development of graphene-based polymer nanocomposites (GPNC) are discussed. Interest in graphene for use in nanocomposites has increased is due to its intrinsic properties. has been predicted that a single, defect-free graphene platelet can have an intrinsic tensile strength higher than that of any other material. Polymer chemists and materials scientists are incorporating graphene and its derivatives in polymer matrices to develop applications that work. A report suggests that the production of graphene nanoplatelets is expected to exceed 200 tons per year by 2013. The trend to produce graphene and graphene nanoplatelets in bulk quantities centers on chemical exfoliation of graphite. Another route to producing graphene in bulk quantities is through thermal expansion of graphite oxide.
The concept of nanostructured materials design is gaining widespread importance among the automotive industry. Although employment of nanotechnology in current and future automotives will go long way in solving energy crises, it is necessary to understand both the hazards associated with nanomaterials and the levels of exposure that are likely to occur. The existing knowledge in these areas is quite limited and it will be necessary in the near future. This paper highlights these key issues and goes a long way in pointing recent activities on environmental risks of nanomaterials. Some research directions are given and existing automotive opportunities and applications explored.
Exfoliated graphite nanoplatelets (xGnP)-filled impact-modified polypropylene (IMPP) composites were prepared at 2, 4, 6, and 8 wt % xGnP with and without the addition of a coupling agent and manufactured using melt mixing followed by injection molding. The coupling agent used in this study was polypropylene-graft-maleic anhydride (PP-g-MA). The nanoparticles used were xGnP with three different sizes: xGnP5 has an average thickness of 10 nm, and an average platelet diameter of 5 μm, whereas xGnP15 and xGnP25 have the same thickness but average diameters are 15 and 25 μm, respectively. Test results show that nanocomposites with smaller xGnP diameter exhibited better flexural and tensile properties for both neat and compatibilized composites. For composites containing a coupling agent, tensile and flexural modulus and strength increased with the addition of xGnP. In the case of neat composites, both tensile and flexural modulus and strength decreased at higher filler loading levels. Increasing xGnP loading resulted in reduction of elongation at break for both neat and composites containing coupling agent. Explanation of this brittle behavior in a nanoplatelet-filled IMPP is presented using scanning electron microscopy and transmission electron microscopy.
Polypropylene (PP)/graphite (G) hybrid nanocomposites have been prepared by melt mixing using maleated PP (PP-g-MA) and graphite oxide (GO) as compatibilizing agents. Melt mixing was achieved using a Gelimat, a high-speed thermo-kinetic mixer. The PP-g-MA and GO used as compatibilizers helped the dispersion of the graphite on a nano-scale and improved flexural properties but more significantly the impact strength of the material. TEM micrographs showed a partial exfoliation of the graphite in the PP/PP-g-MA/GO/G hybrid nanocomposites. SEM micrographs of etched nanocomposite samples showed a fine grain micron-sized structure, while pure PP was characterized by larger 3-dimensional spherulites. Non-isothermal crystallization kinetics of PP and PP/PP-g-MA/GO/G nanocomposites were investigated by differential scanning calorimetry (DSC). The crystallinity and crystallization temperature of the nanocomposites were higher than for neat PP. Using the Kissinger model, the activation energy of crystallization of the nanocomposites was determined to be lower than PP. Models by Ozawa and Liu et al. were used to analyze and describe the non-isothermal crystallization kinetics. Overall, results indicate that the type of nucleation, growth and geometry of PP crystals markedly change in the presence of nano-sized graphite particles.Keywords: Nanocomposites, Polypropylene, Graphite, Non-isothermal, Crystallization Kinetics
Particulate reinforced thermoplastic composites are designed to improve the properties and to lower the overall cost of engineering plastics. In this study the effects of adding mica with variable particle size on the mechanical, thermal, electrical and rheological properties of nylon-6 was investigated. Composites of nylon-6 with v arying concentrations (viz. 5 to 40 weights %) of mica were prepared by twin screw extrusion. The composite showed improved mechanical, thermal as well electrical properties on addition of filler. It is also observed that mechanical properties, electrical properties as well as thermal properties increases with decrease in particle size.
The effect of different interfacial interaction on the crystallization and melting behavior of PP/nano-CaCO3 composites was investigated using differential scanning calorimetry, X-ray diffraction and polarized optical microscope.
The results indicated that nano-CaCO3 acted as heterogeneous nuclei for PP crystallization. There existed a synergistic effect of heterogeneous nucleation between
nano-CaCO3 and compatibilizer for PP crystallization, which was proved by increasing the crystallization rate and decreasing the fold
surface free energy as well as favoring the formation of β-crystal of PP. However, this synergistic effect was dependent on
the interfacial interaction between PP and compatibilizer. The increased miscibility between compatibilizer and PP favored
this synergistic effect.
The effect of four nucleating agents on the crystallization of isotactic polypropylene (iPP) was studied by differential scanning
calorimetry (DSC) under isothermal and non-isothermal conditions. The nucleating agents are: carbon nanofibers (CNF), carbon
nanotubes (CNT), lithium benzoate and dimethyl-benzylidene sorbitol.
Avramișs model is used to analyze the isothermal crystallization kinetics of iPP.
Based on the increase in crystallization temperature (T
c) and the decrease in half-life time (τ½) for crystallization, the most efficient nucleating agents are the CNF and CNT, at concentrations as low as 0.001 mass%.
Sorbitol and lithium benzoate show to be less efficient, while the sorbitol needs to be present at concentrations above 0.05
mass% to even act as nucleating agent.
Currently there is great interest in graphene-based devices and applications. The main advantages of graphene include excellent conductive and mechanical properties. The applications of graphene cover a wide range of possibilities, from next-generation transistors to light-weight, high-strength composite materials. However, commercial use of graphene will depend on the development of an industrially-viable method of fabricating and handling graphene. The recent advances in manipulating graphene and patents will be reviewed with a focus on the progress of graphene nanoparticle synthesis and applications.
To assess the potential of biochar as filler for thermoplastic materials and to optimize its processing conditions, composites of polyamide 6 and biochar were produced by extrusion followed by injection moulding. Biochar was prepared by grinding and ball-milling, respectively before addition to the polymer. The different biochar treatments resulted in strong differences in the mean particle size as well as the particle size distribution. The size of the filler particle significantly influences the flow behaviour of the melt.
Exfoliated graphite nanoplatelets (xGnP)-filled impact modified polypropylene (IMPP) composites were prepared at 2, 4, 6, and 8 wt% xGnP with and without the addition of a coupling agent and manufactured using melt mixing followed by injection molding. The coupling agent used in this study was polypropylene-graft-maleic anhydride. The nanoparticles used were xGnP with three different sizes: xGnP5 has an average thickness of 10 nm, and an average platelet diameter of 5 μm, whereas xGnP15 and xGnP25 have the same thickness but average diameters are 15 and 25 μm, respectively. Test results show that nanocomposites with smaller xGnP diameter exhibited better impact properties for both neat and compatibilized composites. However, unnotched and notched impact strengths as well as fracture initiation resistance were dramatically deteriorated with the introduction of xGnP. Explanation of this brittle behavior in a nanoplatelet-filled IMPP is presented using melt flow index and transmission electron microscopy.
Melt rheology and crystallization behavior of polyamide 6 (PA 6) and microcrystalline cellulose (MCC) composites were systematically studied in this research. The incorporation of MCC into the PA 6 matrix resulted in higher complex viscosities (|η*|), storage modulus (G′), and shear viscosities than those of neat PA 6, especially at low frequencies. The orientation of rigid molecular chains in the composites introduced by the addition of MCC induced a strong shear thinning behavior with an increase in MCC loading. The non-isothermal crystallization kinetics of PA 6 and MCC composites were investigated by differential scanning calorimetry. The Avrami and Tobin model were applied to describe the process of non-isothermal crystallization and to determine the crystallization parameters of the composites. Analysis of the crystallization kinetics indicated that the Avrami (na) and Tobin exponent (nt) was altered by the MCC. It was also found that the Avrami and Tobin equations fit the empirical data well. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers
Polypropylene (PP)/exfoliated graphite nanoplatelet (xGnP) nanocomposites with various intrinsic aspect ratios of graphite nanoplatelets (GnPs; large and small in diameter) were prepared by a melt-mixing procedure. Transmission electron microscopy showed that all types of xGnP were well-dispersed in the polymer matrix. The effects of the dimensions and loading of the xGnPs on the morphology, mechanical reinforcement, and electrical properties of PP/xGnP were studied. A differential scanning calorimetry study of the PP/xGnP morphology indicated that all types of xGnP additives were heterogeneous nucleation sites for PP crystallization.
Tensile testing, DMA, and thermogravimetric analysis of PP/xGnPs with different types of GnP additives showed enhancements in their mechanical properties, heat resistance, and thermal stability compared to plain PP. We also found a significant increase in the conductivity of PP/xGnP. The PP/xGnP with a large diameter of GnPs demonstrated the lowest percolation threshold, equal to 4 vol % of the xGnP loading. The mechanical properties were estimated by means of micromechanical modeling. VC 2012 Wiley Periodicals,
Inc. J. Appl. Polym. Sci. 128: 1417–1424, 2013
The effect of clay dispersion on the crystallization behavior of isotactic polypropylene (iPP)-based nanocomposites is reported.
The T
m0 of the materials was calculated by the method proposed by Marand, the kinetics of crystallization was evaluated by the Avrami
analysis and also the Hoffman-Lauritzen theory of crystallization regimes was applied. Montmorillonite was found to depress
T
m0, to enhance the rate of crystallization and to ease the chain folding of macromolecules. These effects were magnified if
clay was exfoliated, rather than intercalated.
Wollastonite reinforced polypropylene (PP/CaSiO3) composites were prepared by melt extrusion. A silane coupling agent and a maleic anhydride grafted PP (PP-g-MA) were used to increase the interfacial adhesion between the filler and the matrix. The increased adhesion observed by scanning electron microscopy (SEM) resulted in improved mechanical properties. A model was applied to describe the relationship between the interfacial adhesion and tensile properties of PP/CaSiO3 composites. There is stronger interfacial adhesion between silane-treated CaSiO3 and polymer matrix containing PP-g-MA as a modifier. Results of dynamic mechanical thermal analysis (DMTA) showed that stronger interfacial adhesion led to higher storage modulus. The influence of CaSiO3 particles on the crystallization of PP was studied by using differential scanning calorimetry (DSC). The introduction of CaSiO3 particles does not affect the crystallization temperature and crystallinity of PP matrix significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Graphene is a true wonder material that promises much in a variety of applications that include electronic devices, supercapacitors, batteries, composites, flexible transparent displays and sensors. This review highlights the different methods available for the synthesis of graphene and discusses the viability and practicalities of using the materials produced via these methods for different graphene-based applications.
In this study, the main focus was on the effect of wood fiber (WF) content and particle size on the morphology and mechanical, thermal, and water-absorption properties of uncompatibilized and ethylene glycidyl methacrylate copolymer (EGMA) compatibilized ethylene vinyl acetate copolymer–WF composites. For uncompatibilized composites, the tensile strength decreased with increasing WF content, whereas for compatibilized composites, the tensile strength initially decreased, but it increased for composites containing more than 5% WF. Small-WF-particle-containing composites had higher tensile strengths than composites containing larger WF particles, both in the presence and absence of EGMA. WF particle size did not seem to have much influence on the degradation behavior of the composites, whereas water absorption by the composites seemed to be higher in composites with smaller particle sizes for both compatibilized and uncompatibilized composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3645–3654, 2007
Poly(propylene)‐clay nanocomposites and poly(propylene) containing conventional inorganic fillers such as calcium carbonate (CaCO 3 ) and glass fiber were used in a comparative study focusing on dimensional stability, structure, mechanical and thermal properties. Micro‐ and nanocomposites were prepared by melt blending in a twin‐screw extruder. The relative influence of each filler was observed from dimensional stability measurements and structural analysis by WAXD, TEM, and thermal and mechanical properties. At equal filler loadings, PP/clay nanocomposites exhibit an improvement in dimensional stability and were the only composites capable of reduced shrinkage in both in‐flow and cross‐flow directions. The flexural modulus of PP increased nearly 20% by compounding with 4% organoclay, as compared to a similar performance obtained by compounding with 10 wt.‐% of CaCO 3 or approximately 6 wt.‐% of glass fiber. The HDT and thermal stability of PP were enhanced by using nanoclay as filler.
magnified image
The rheological properties of silicone sealant filled with different calcium carbonate (CaCO3) particles varying in size were investigated. It is found that as particle size decreases, the dynamic storage modulus (G′) and shear viscosity (η) increase; whereas, the width of linear viscoelastic region decreases. At low shear rate, a modulus plateau appears and the shear thinning behavior becomes apparent. The reasons for these can be ascribed to the enhanced particle–particle interaction and formation of filler network structure. Moreover, results dealing with the buildup of network structure monitored by kinetic recovery experiments reveal that both the rate of recovery and magnitude of rheological parameters increase with decreasing particle size. This phenomenon is consistent with the data collected from creep and recovery measurements, indicating an enhanced elasticity and network structure. Furthermore, transmission electron microscopy (TEM) observation and mechanical properties tests for cured sealant samples were also carried out to provide an evidence for the discussion further. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Pristine multiwalled carbon nanotubes (P-MWNTs) were functionalized with 4-chlorobenzoic acid via “direct” Friedel-Crafts acylation in polyphosphoric acid (PPA)/phosphorous pentoxide (P2O5) medium. The resultant 4-chlorobenzoyl-functionalized MWNTs (F-MWNTs) were soluble in chlorinated solvents such as dichloromethane, chloroform, and carbon tetrachloride. A large scale of nylon 610/F-MWNT composite could be conveniently prepared by in situ interfacial polymerization of 1, 6-hexamethylenediamine (HMDA) in an aqueous phase, and sebacoyl chloride with F-MWNTs in an organic phase. Similarly, nylon 610/P-MWNT composite was also prepared for comparison. The state of F-MWNTs dispersion in nylon 610 matrix was distinctively better than that of P-MWNTs, which could be clearly discerned by both naked eye and scanning electron microcopy (SEM). As a result, the tensile strength of nylon 610/F-MWNT composite was 4.9-fold higher than that of nylon 610/P-MWNT composite. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6041–6050, 2008
Polyurethane-clay nanocomposite elastomers were synthesized using polyol-clay blends with different levels of dispersion, which affected the final elastomer microstructure. A PU-clay microcomposite elastomer containing partially dispersed clay showed poorer mechanical and similar fire properties to the unmodified polyurethane. More complete dispersion of the clay into the polyol led to an exfoliated structure in the final elastomer. This showed a higher modulus and kept a viscoelastic behavior to higher temperature than the pristine PU. The enhancement of mechanical and thermal properties in the nanocomposite elastomer can be attributed to the degree of clay exfoliation, and this also prevented dripping during the UL 94 fire test. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Shear and extensional flow properties of the melts of high-density polyethylene (HDPE)-maple composites were studied with capillary rheometry to understand the effects of the wood content, particle size, and maleated polyethylene (MAPE). The viscosity data were compared with the values for neat matrix resin for reference. The effects of commercial wood particle size grades were examined at 60% by weight of wood loading. It was found that both shear and extensional viscosities increase with wood content but the filler content dependence is not as significant as for suspensions of inorganic fillers at similar filler loadings. Commercial wood particle size grades were found to result in less change in viscosity than wood content. The Mooney analyses conducted on the lower branch of the capillary shear flow data revealed a significant contribution of wall slip and confirmed the presence of a yield stress at higher filler contents. The internal lubrication role of MAPE was also illustrated in detail through the changes in both shear and extensional flow. POLYM. ENG. SCI., 45:549–559, 2005. © 2005 Society of Plastics Engineers
Melt compounded PP/MWCNT (polypropylene/multi-walled carbon nanotube) composites were prepared by diluting highly concentrated masterbatch chips. Maleic anhydride grafted polypropylene (PP-g-MAH) was used as a compatibilizer to promote dispersion and interaction of MWCNTs. Rheological properties were investigated with respect to the MWCNT and compatibilizer loadings, and related to morphological and electrical properties. As the MWCNT loading was increased, shear viscosity and yield stress were increased at low shear rate region because of increased interaction between MWCNT particles. When the MWCNT loading was low, MWCNT dispersion was improved by the PP-g-MAH compatibilizer because MWCNTs were wetted sufficiently due to the presence of the compatibilizer. However, rheological and electrical properties of highly concentrated MWCNT composites with the compatibilizer were not improved compared with PP/MWCNT composites without the compatibilizer because the compatibilizer did not provide sufficient wrapping of MWCNT particles. Electrical and morphological properties of PP/MWCNT composites were correlated with the rheological properties in steady and dynamic oscillatory shear flows.
The main objective of this research was to investigate the effect on thermal properties of the addition of two different compatibilizing agents, maleic anhydride (MA)-grafted polypropylene (MAPP) and MA-grafted polyethylene (MAPE), to bio-flour-filled, Polypropylene (PP) and low-density polyethylene (LDPE) composites. The effect of two different types of MAPE polymer, MA-grafted high-density polyethylene (HDPE-MA) and MA-grafted linear LDPE (LLDPE-MA), was also examined. With increasing MAPP and MAPE content, the thermal stability, storage modulus (E), tan δ max peak temperature (glass transition temperature: T g) and loss modulus (E max) peak temperature (β relaxation) were slightly increased. The thermal stability, E and E of MAPE-treated composites were not significantly affected by the two different MAPE polymers. The melting temperature (T m) of the composites was not significantly changed but the crystallinity (X c) of MAPP-and MAPE-treated composites was slightly increased with increasing MAPP and MAPE content. This enhancement of thermal stability and properties could be attributed to an improvement in the interfacial adhesion and compatibility between the rice husk flour (RHF) and matrix due to the treatment of compatibilizing agent. Attenuated total reflectance (FTIR-ATR) analysis confirmed this result by demonstrating the changed chemical structures of the composites following MAPP and MAPE addition.
a b s t r a c t Nylon 6 (PA6) composites with different loadings of multi-walled carbon nanotubes (MWNT) were pre-pared by melt compounding technique. Melt rheological properties of PA6/MWNT composites were stud-ied in linear viscoelastic response regions. The incorporation of MWNT into PA6 matrix resulted in higher complex viscosities (|g * |), storage modulus (G 0), loss modulus (G 00), and lower loss factor (tan d) than those of neat PA6, especially in low frequency region. The orientation of rigid molecular chains in the compos-ites introduced by the addition of MWNT induced a strong shear thinning behavior and an increasing activation energy for the flow process. With the increase of MWNT loading, the composites experienced a transition from liquid-like to solid-like viscoelasticity. The decrease in the slope of the plot of log G 0 ver-sus log G 00 with increasing MWNT loading suggested the microstructural changes of the polymer matrix due to incorporation of MWNT. At low frequencies, nonterminal solid-like rheological behavior of PA6 composites were observed and attributed to the formation of the network-like structures of MWNT in the polymer composites.
The objective of this research was to investigate thermal stability and dynamic mechanical behavior of Exfoliated graphite nanoplatelets (xGnP™)-Linear Low-Density Poly Ethylene (LLDPE) nanocomposites with different xGnP loading content. The xGnP-LLDPE nanocomposites were fabricated by solution and melt mixing in various screw rotating systems such as co-, counter-, and modified-corotating. The storage modulus (E′) of the composites at the starting point of −50°C increased as xGnP contents increased. E′ of the nanocomposite with only 7 wt% of xGnP was 2.5 times higher than that of the control LLDPE. Thermal expansion and the coefficient of thermal expansion of xGnP-loaded composites were much lower than those of the control LLDPE in the range of 45–80°C (299.8 × 10−6/°C) and 85–100°C (365.3 × 10−6/°C). Thermal stability of the composites was also affected by xGnP dispersion in LLDPE matrix. The xGnP-LLDPE nanocomposites by counter-rotating screw system showed higher thermal stability than ones by co-rotating and modified-co-rotating system at 5 wt% and 12 wt% of xGnP. xGnP had a great effect on high thermal stability of xGnP-LLDPE composites to be applied as tube and film for electrical materials. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
The preparation of polypropylene (PP)/graphite nanocomposites by melt-mixing PP with different levels of graphite (G) and graphite oxide (GO) using maleated PP and GO as interface modifiers was investigated. Melt-mixing was achieved using a Gelimat, a high-speed thermo-kinetic mixer. Evidence of the nanoscale dispersion of graphite sheets within the PP were provided by wide-angle X-raty diffraction (WAXD) and supported by scanning electron microscopy (SEM). The high mechanical shear stresses generated by the Gelimat greatly reduced the ordering initially measured by WAXD between graphite sheets and sheet aggregates, indicating a dispersion of the graphite in the polymer to the extent that graphite particles could hardly be observed by SEM.
Polypropylene (PP)–microcrystalline cellulose (MCC) composites were prepared containing Poly(propylene-graft-maleic anhydride) (PP-g-MA) and MCC treated with silicone oil, stearic acid or alkyltitanate coupling agent to promote matrix–filler dispersion and compatability. Infrared spectroscopy confirmed surface treatment. MCC content and PP-g-MA increased PP thermal stability and crystallisation temperature (Tc), though reduced crystallinity due to cellulose II crystals. Tensile stress–strain analysis revealed increased modulus with MCC content, PP-g-MA, alkyltitanate and stearic acid. MCC and PP-g-MA reduced creep deformation and increased permanent strain. Storage modulus, loss modulus and glass transition temperature increased with MCC concentration due to effective interaction between PP and MCC.
A series of polyamide 1010 (PA1010 or nylon 1010) and multiwalled carbon nanotubes (MWNTs) composites were prepared by in situ polymerization of carboxylic acid-functionalized MWNTs (MWNT–COOH) and nylon monomer salts. Mechanical tensile tests and dynamic mechanical analysis (DMA) show that the Young modulus increases as the content of the nanotubes increases. Compared with pure PA1010, the Young's modulus and the storage modulus of MWNTs/PA1010 in situ composites are significantly improved by ca. 87.3% and 197% (at 0 °C), respectively, when the content of MWNTs is 30.0 wt%. The elongation at break of MWNTs/PA1010 composites decreases with increasing proportion of MWNTs. For the composites containing 1.0 wt% MWNTs, the Young modulus increases by ca. 27.4%, while the elongation at break only decreases by ca. 5.4% as compared with pure PA1010 prepared under the same experimental conditions. Compared with mechanical blending of MWNTs with pure PA1010, the in situ-prepared composites exhibit a much higher Young's modulus, indicating that the in situ polycondensation method improves mechanical strength of nanocomposites. Scanning electron microscopy (SEM) imaging showed that MWNTs on the fractured surfaces of the composites are uniformly dispersed and exhibit strong interfacial adhesion with the polymer matrix. Moreover, unique crystallization and melting behaviors for MWNTs/PA1010 in situ composites are observed using a combination of differential scanning calorimetry (DSC) and X-ray diffraction methods. It was shown that only the α-form crystals are observed in our MWNTs/PA1010 in situ composites. This result is quite different from PA1010/montmorillonite and PA6-clay composites, where both of α- and γ-form crystals were found.
Effect of different compatibilizers and magnesium hydroxide (MH) on morphology, thermal stability and mechanical properties of polypropylene (PP) composites were investigated in this study. Two different types of compatibilizers namely, polypropylene grafted-maleic anhydride (PP-g-MA) and ethylene–octene copolymer grafted-maleic anhydride (POE-g-MA) were used in this study. The results indicated that the degradation of PP/MH composites contained two steps: decomposition of MH and degradation of macromolecular. MH particles acting as physical barrier improved the thermal stability of PP, especially in oxygen. POE-g-MA enhanced it furthermore. Introduction of PP-g-MA or POE-g-MA to PP/MH composites resulted in considerable improvement in mechanical properties. The addition of PP-g-MA was most effective in increasing the tensile strength, while addition of POE-g-MA greatly increased the impact strength of PP/MH composites.Morphological investigation revealed that the improvement was attributed to the formation of encapsulation structure in these compatibilized PP/MH composites.
Master of Science in Mechanical Engineering
- C Chu
- Wunderlich
- Zhang
Development of polymer nanocomposites for automotive applications ”Master of Science in Mechanical Engineering Georgia Institute of
- C Chu
Retrieved from nanomarkets-the global market for graphene to
- Futuremarkets