Fiber Reinforced Soy-Based Polyurethane Spray Foam Insulation. Part 1: Cell Morphologies
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Environmentally friendly polyurethane (PU) spray foam insulation was prepared by substituting petrochemical polyol with soy-based polyol. The effects of adding wood fiber and water on the cell morphologies were studied. Cell size increased with the presence of wood fiber, but it decreased with an increase of water (H2O). Still, shorter fiber decreased in foam density but increased in cell size and open cell content.
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... The morphology changes at higher fiber concentrations, and the fibers present good adhesion with the matrix. The fibers can improve the crosslink reaction, promoting higher porosity with smaller cell sizes, as shown in Table 2. 42,43 No loose fibers were found in the middle of empty cells confirm the good adhesion. 40 Good adhesion at higher concentrations of fiber can be associated with the more significant number of free hydroxyls available to interact with the active isocyanate groups and the hydrophilic character of PU and fibers. ...
... 43 The formation of hydrogen bonds forms urethane units, and the fibers participate in the formation of the porous structure. 41,42 The PU composite foams' open porosity plays a crucial role in numerous applications, such as sound absorption efficiency and removal of toxic compounds of gases. 43,44 The fibers reinforced in polyurethane do not exhibit preferential orientation either; however, they were more irregular, and a defective shape of cells with many cracks was observed. ...
... 40 Additionally, the fibers restrained the cell's expansion, which promoted a significant number of small cells with a thinner cell structure, commonly observed in PU composites. 41,42 Mechanical results: Compression tests Figure 5 shows the compressive stress-strain curves for PU and its composites. The curves presented three typical stages of deformation: initially, there is a linear behavior between stress and strain; then a plateau region where the deformation increases significantly without significant changes on stress; and finally, a region where the densification of foam occurs and the stress rises quickly until the fracture point. ...
This work prepared eco-friendly biocomposites of polyurethane (PU) and sheath palm residues, using castor oil as a polyol. PU composites filled with natural fibers were prepared at different loading rates: 0 to 20 wt.%. Results indicated that the sheath palm was hydrogen-bonded to PU chains and increased the foams' density. Pore size decreased with an increase in fiber content, from 256 to 116 µm. The fiber's addition improved the ductility of PU foams (compressive modulus from 4.74 to 0.26 MPa) and the foams' crystallinity index (from 5.4 to 15.4%). Compared to pristine PU, the composites showed high hydrophobicity (reaching 123° of contact angle for PU-15%) and thermal stability (T onset from 96 to 96.3°), and high density (from 41 to 60 kg.m ⁻³ ), making the developed composites an excellent option for environmental applications, such as oil removal and contaminant adsorption.
... This is in line with other research, which found that wood reinforcement with a fine grain size acts as a nucleation site in the foam. This creates more cells and subsequently more microvoids, thus reducing the properties of the resulting foams, such as density [16]. The specific surface area is very high for the finest particle size, which could induce a higher hydroxyl number, thus reducing the polyol and isocyanate interactions. ...
Incorporating biodegradable reinforcement, such as wood particles, into rigid polyurethane foams (RPUFs) is among the alternatives to reduce their environmental impact. This study aims to assess the effect of different wood particles as reinforcement in RPUFs. Reinforced rigid polyurethane foams are synthesized with milled wood particles of various forms and sizes and commercial polyol and isocyanate. The effect of fiber treatments and mechanical stirring on foams’ properties is also studied. Additional tests on polyisocyanurate foams (PIR) were undertaken to assess the effect of reinforcement on their properties. Mechanical properties are measured to investigate the impact of wood particle reinforcement on the foam. Confocal microscopy and Fourier-transform infrared spectroscopy (FTIR) showed the interaction between the wood fibers and the matrix. Despite the adhesion observed for some fibers, most of the cell walls of RPUFs were punctured by the rigid wood fibers, which explained the decrease in the compressive strength of the composites for manually mixed foams. Mechanical stirring proved to be an efficient method to enhance the reinforcement power of untreated fibers. RPUF foams’ properties showed similar changes when untreated wood flour was introduced to the formula, increasing compressive strength significantly.
... The authors are aware of several papers (Harikrishnan et al., 2006;Wang and Yang, 2020;Zhang et al., 2019) describing the synthesis of open-cell PUR foams with relatively high apparent densities (45-90 kg/m 3 ) for purposes other than insulation. Gu et al. (2011) and Khazabi et al. (2011) described the manufacture of a fiber-reinforced soyoil-based polyurethane foams with an apparent density >24.5 kg/m 3 and open cell content >85%. The thermal conductivity coefficient of the foams was not tested. ...
Used cooking oil is a widely available and inexpensive waste with a high application potential as a feedstock for the bio-based polyurethane production. Usually, bio-polyols from vegetable oils have higher viscosity and lower hydroxyl values compared to commercial petrochemical polyols, which limits their usefulness. This article reports on the development of open-cell polyurethane foam systems wherein 100% of the polyol components were bio-polyols obtained from used cooking oil. What is particularly considered is the effect of bio-polyol properties (molecular weight, viscosity and hydroxyl value) on the properties of the final open-cell polyurethane systems - apparent density, thermal conductivity coefficient, content of closed cells, mechanical strength, brittleness and short-term water absorption. It was found that the key step in the synthesis of bio-polyols designed for open-cell polyurethane foams is the epoxidation reaction. The epoxy value has a significant effect on the occurrence of side reactions (mainly oligomerization) during the oxirane ring-opening process determining the properties of bio-polyols. The resulting open-cell foams were characterized by apparent densities from 12.4 to 13.3 kg/m3, thermal conductivity coefficients from 36.6 to 38.2 mW/m∙K, and closed cell contents below 10%, which makes them comparable to commercial products. The results demonstrate that used cooking oil-based polyols can provide an alternative starting material for open-cell polyurethane foam production.
... Wood fibre based materials still have a high optimisation potential (Hobballah et al. 2018). The same is true for combination of lignocellulosic fibres with foams, but there is little literature referring to the topic in combi- nation with polyurethane foams ( Khazabi et al. 2011). No literature is available which considers 100% natural fibres foams as insulation materials. ...
X-ray tomography and densitometry (XRT and XRD) were applied to characterise wood fibre based insulation materials, which were produced by the foam forming technology. XRT is a high resolution approach with long measurement times of around 29 h, while XRD measurement needs only a few minutes. The determination of density distribution of boards in the thickness direction was the focus of this study. Both approaches visualised well the impact of raw materials and manufacturing processes on the structure of the panels. The density profiles were dependent on the pulp applied for panel production, and the processing conditions were also influential. Air flow resistance correlated with the maximum density measured inside the board. Both XRT and XRD revealed similar trends, which are useful for the characterisation of insulation materials.
... Moreover, for PUR/BSG20 and PUR/ BSG10/GTR10 samples more cells were broken comparing to PUR without fillers. Similar observations were described by Khazabi et al. (2011), which investigated the impact of wood fibers on morphology of soy-based polyurethane spray foam. On the other hand, the microstructure of PUR/GTR20 sample was similar to reference sample (average cell size for these samples: 200 μm), which indicates that application of GTR enhance formulation of smaller and more regular polyurethane cells. ...
In this work, brewers' spent grain (BSG) and ground tire rubber (GTR) waste fillers were applied as low-cost reinforcement phase in rigid polyurethane foam (PUR). PUR/BSG/GTR composites were prepared by a single step method, using polyglycerol as partial substitute of commercially available petrochemical polyols. Foaming parameters, chemical structure, dynamic mechanical properties, thermal stability, physico-mechanical properties and morphology of obtained composites were evaluated as function of BSG/GTR ratio (in range: 20/0; 15/5; 10/10; 5/15; 0/20 parts by weight – pbw). Modification of PUR/BSG composite foams with GTR accelerated foaming reactions, which resulted in decrease of rise time and tack free time. Higher content of GTR in PUR/ BSG/GTR composites significantly enhanced their physico-mechanical properties and thermal stability. Compressive strength of PUR modified with BSG/GTR in ratio 5/15 pbw was more than 50% higher than for PUR/BSG composite foam without GTR, which correspond to 37% increase of density. Additionally, it was observed that temperatures corresponded to a 2% and 5% weight loss were for 9 °C and 24 °C higher for composite with BSG/GTR hybrid filler than for pure polyurethane matrix. Presented results indicate better compatibility between polyurethane matrix and GTR than with BSG, confirmed also by ATR-FTIR, DMA, swelling behavior and SEM analysis. Conducted investigations showed that performance properties of poly-urethane/brewers' spent grain composite foams could be successfully tailored using GTR, which consequently extend their potential industrial applications.
Finding alternatives to fossil feedstocks is increasing in importance with the challenges of global warming, increasing oil prices and depleting fossil fuel reserves that we currently face. Today, plant oils are important renewable raw materials for the chemical industry and are heavily used for surfactants, cosmetic products and lubricants.
This book covers the green chemistry of products and intermediates synthesised from plant oils. Photo-initiated polymerisation and polymerization of vegetable oils in environmental media are covered as well as click reactions to chemically modify vegetable oils. Useful products from plant oils such as polymers, biomaterials, biofibres and lubricants, as well as their further applications, are described.
This book is a valuable resource for researchers in academia and industry, biomass producers and suppliers and manufacturers of end-products.
Polyurethane (PU) composite foams were successfully reinforced with different concentrations (1 wt%, 2 wt%, 5 wt%) of nutmeg filler. The effect of nutmeg filler concentration on mechanical, thermal, antimicrobial and anti-aging properties of PU composite foams was investigated. PU foams were examined by rheological behavior, processing parameters, cellular structure (Scanning Electron Microscopy analysis), mechanical properties (compression test, impact test, three-point bending test, impact strength), thermal properties (Thermogravimetric Analysis), viscoelastic behavior (Dynamic Mechanical Analysis) as well as selected application properties (thermal conductivity, flammability, apparent density, dimensional stability, surface hydrophobicity, water absorption, color characteristic). In order to Disc Diffusion Method, all PU composites were tested against selected bacteria (Escherichia coli and Staphylococcus aureus). Based on the results, it can be concluded that the addition of 1 wt% of nutmeg filler leads to PU composite foams with improved compression strength (e.g. improvement by ∼19%), higher flexural strength (e.g. increase of ∼11%), improved impact strength (e.g. increase of ∼32%) and comparable thermal conductivity (0.023–0.034 W m⁻¹ K⁻¹). Moreover, the incorporation of nutmeg filler has a positive effect on the fire resistance of PU materials. For example, the results from the cone calorimeter test showed that the incorporation of 5 wt% of nutmeg filler significantly reduced the peak of heat release rate (pHRR) by ca. 60% compared with that of unmodified PU foam. It has been also proved that nutmeg filler may act as a natural anti-aging compound of PU foams. The incorporation of nutmeg filler in each amount successfully improved the stabilization of PU composite foams. Based on the antibacterial results, it has been shown that the addition of nutmeg filler significantly improved the antibacterial properties of PU composite foams against both Gram-positive and Gram-negative bacteria.
The effects of filler loading and size of kenaf fibre on the mechanical properties of kenaf fibre-filled natural rubber latex foam (NRLF) have been studied. The NRLF was prepared by using the Dunlop method. The kenaf fibre was sieved to 97, 144 and 200 µm particle sizes and incorporated into the rubber vulcanizates at 0, 1, 3, 5 and 7 part per hundred rubber fibre contents. Increasing kenaf fibre loading in NRLF resulted in the reduction of tensile strength, elongation at break and recovery percentage but increased in modulus at 100% (M100), compression strength, compression set, hardness and foam density. At the same kenaf fibre loading, smaller size of kenaf fibre-filled NRLF showed higher tensile properties, compression strength, compression set and hardness. Scanning electron microscope demonstrated that as kenaf fibre loading and size increased, a larger pore size of NRLF was formed and this led to tensile strength, M100, compression strength and hardness.
This chapter introduces the science, various technologies used, and applications related to the use of biopolymers and biomaterials in the development of porous structures. The main focus is placed on the bio-based foams incorporated with cellulose fibres. The chapter reviews the composition of bio-based foams, processing methods, properties of these porous materials as well as performance and applications of the resulting foams. One section is dedicated to interesting platform for functionalization of cellulose fibres with layered double hydroxides (LDH). An engineering process for the in situ synthesis of Mg-Al LDH s with pulp fibres is pre sented as well. LDHs have a particularly interesting property that neither of the constituent precursors have in themselves. LDHs carry a net positive charge due to trivalent aluminium. To counter that charge build up there are intercalated anionic components in between its lamella. Cellulose fibres are naturally acidic facilitating electrostatic interaction with layer double hydroxide in neutral or alkaline medium. Therefore, the synthesis of LDHs, in situ, with cellulose fibres may bring additional benefit to the foam process in which the addition of additives such as flame retardants after the foam has been formed is difficult unless it is inherently part of the matrix.
Wood has played a major role throughout human history. Strong and versatile, the earliest humans used wood to make shelters, cook food, construct tools, build boats, and make weapons. Recently, scientists, politicians, and economists have renewed their interest in wood because of its unique properties, aesthetics, availability, abundance, and perhaps most important of all, its renewability. However, wood will not reach its highest use potential until we fully describe it, understand the mechanisms that control its performance properties, and, finally, are able to manipulate those properties to give us the desired performance we seek.
The Handbook of Wood Chemistry and Wood Composites analyzes the chemical composition and physical properties of wood cellulose and its response to natural processes of degradation. It describes safe and effective chemical modifications to strengthen wood against biological, chemical, and mechanical degradation without using toxic, leachable, or corrosive chemicals. Expert researchers provide insightful analyses of the types of chemical modifications applied to polymer cell walls in wood. They emphasize the mechanisms of reaction involved and resulting changes in performance properties including modifications that increase water repellency, fire retardancy, and resistance to ultraviolet light, heat, moisture, mold, and other biological organisms. The text also explores modifications that increase mechanical strength, such as lumen fill, monomer polymer penetration, and plasticization.
The Handbook of Wood Chemistry and Wood Composites concludes with the latest applications, such as adhesives, geotextiles, and sorbents, and future trends in the use of wood-based composites in terms of sustainable agriculture, biodegradability and recycling, and economics. Incorporating decades of teaching experience, the editor of this handbook is well-attuned to educational demands as well as industry standards and research trends.
Vegetable oils are excellent but very heterogeneous renewable raw materials for polyols and polyurethanes. This review discusses the specific nature of vegetable oils and the effect of their structures on the structure of polyols and polyurethanes. One section is dedicated to polyols for rigid and flexible foams and methods of their preparation such as direct oxidation of oils, epoxidation followed by ring opening, hydroformylation, ozonolysis, and transesterification. The next section deals with preparation and structure‐property relationships in polyurethanes from different groups of polyols, different isocyanates, and different degrees of crosslinking. The final section covers the environmental aspects of bio‐based polyurethanes, i.e., thermal stability, hydrolytic stability, and some aspects of biodegradability.
The contents of a report by the US Department of Agriculture on world trade in cotton released in August 1997 are summarized. World production and prices, imports, exports and stocks, and the textile industries of the USA, Colombia, France, Paraguay, Syria and Uzbekistan are discussed.
Epoxidized vegetable oils (EVO) have drawn much attention in recent years, especially in the polymer industry as they are economical, available, environmentally friendly, non-noxious and renewable. Vegetable oils can be transformed into useful polymerizable oxygenated monomers commonly by Prileshajev-epoxidation, catalytic epoxidation using acidic ion exchange resin, chemo-enzymatic epoxidation, or metal-catalyzed epoxidation. Among those epoxidation methods, chemo-enzymatic epoxidation has achieved considerable interest nowadays since this method is safe, environmentally friendly and conversion rate of epoxidation usually exceeds 90%. Bio-based epoxidized vegetable oils from renewable natural resources are potential green materials to partially substitute and toughen petrochemical-based polymers.
The standard conditions and equipment no longer adequately describe the insulation value of the products in the market place because of the elimination of CFCs from rigid polyurethane foam. As CFCs were replaced with more environmentally friendly HCFC, HFCs, carbon dioxide and hydrocarbons for foam expansion, the thermal efficiency of the insulation products produced with these blowing agents became confused and complex. This confusion arose due to the significantly differing boiling points of these blowing agents and the resulting dramatic changes of the partial pressure of the gases entrapped within the foam cell with respect to temperature. As a result, the k-factor of rigid polyurethane foams blown with HCFC-22 and HFC-134a are linear with respect to temperature, while foams blown with HCFC-141b, HFC-245fa and HFC-365mfc are not. The potential exists for one polyurethane foam system to provide a superior insulation material at an elevated temperature and not provide this at a reduced temperature. To obtain a more accurate insulation value, which would reflect the energy efficiency of the final product measurement of the insulation value of the rigid polyurethane foam under actual use temperature is important. This paper describes the k-factor of rigid polyurethane foams over a mean temperature range from 17°F to 75°F (-8°C to 24°C). Blowing agents which are liquid at room temperature, such as HCFC-141b, HFC-245fa, HFC-365mfc, n-pentane, c-pentane and iso-pentane, were evaluated. Gaseous blowing agents, such as HCFC-22 and HFC-134a, were also evaluated, as well as blends of liquid and gaseous blowing agents. The use of this technique allows the end consumer of rigid polyurethane foam systems to evaluate the energy efficiency of various systems dependent upon the actual use temperatures of the specific application. A more informed consumer can then make the appropriate system choice.
Most adhesives are polymeric adhesives and if made from renewable sources they will have low cost and biodegradability which are of importance. In view of these properties we synthesized polyurethane (PU) adhesives from three different polyester polyols, obtained by reacting a castor oil derivative and diols (glycols) with diisocyanate adducts, where different NCO/OH ratios were used to give various compositions. The polyols and PUs were characterized by FTIR spectroscopy. The effect of NCO/OH ratios, types of isocyanate adducts and chain length of glycols were studied, by determining wood-to-wood adhesion strength, i.e. by lap shear strength measurement. The change in lap shear strength after being placed in cold water, hot water, acid or alkali solutions was tested. Thermal stability of these PU adhesives was determined by thermogravimetric analysis.
A slab stock urethane foam cell ideally resembles an elongated pentagonal dodeca hedron. The faces are bounded by ribs, and membranes stretch across the ribs during the expansion of the foam. The normal formation of the foam does not result in the rupture of all the membranes. Data are presented showing that Air Flow values for flexible polyether and polyester foams are affected profoundly by the membrane population and, to a smaller extent, by density and cell geometry. It is also shown that within a given bun Air Flow values may vary with both position and orientation. Air Flow val ues also vary considerably between different foams. Because variation in Air Flow values is related to cell structure, it can be related to certain physical properties. Examples of this are given for ball rebound, compression load deflection, flex fatigue, and color shad ing. A quantitative definition of operating range based on Air Flow values is demon strated for tin catalyst concentration in a polyether foam. As a result of these findings Air Flow is recommended as a new parame ter for describing flexible urethane foam cell structure.
Theories of adhesion are based on adsorption and wetting, on diffusion, on donor/acceptor or electrostatic interactions and on simple mechanical interlocking of the adhesive into irregularities of its substrate. The principal contributions of recent work to these theories are outlined. Joint strength is also a matter of stress distribution and knowledge of this has been advanced both by formal mathematical methods and by the use of finite element analysis. The tack of adhesives is now better understood as involving the interaction of both bulk and surface properties with the rate of separation. Fracture mechanics has been applied to the investigation of the failure of structural adhesives in humid environments. The properties determining adhesive behaviour comprise Tg, solubility parameter, surface free energy, viscosity and the microstructure of the polymer. The latter, more recently explored, is examined in detail. The structure of the adhesives for use at high temperature and the changes in technology demanded by impending legislation conclude the review.
Density is an important parameter that influences the properties and performances of rigid polyurethane foam (PUF). Rigid PUF with different densities were prepared by varying the amount of distilled water as blowing agent. This investigation reports the mechanical, morphological, water absorption, thermal conductivity, and thermal behavior of rigid PUF varying with the density, which controls the foam architecture. The density of the PUF decreased from 116 to 42 kg/m3 with an increase in the amount of water from 0.1 to 3.0 parts per hundred polyol by weight (phr), respectively. It was found that the mechanical properties of the PUFs changed with the foam density. The results of water absorption of the PUFs showed that water absorption increased with decrease in density, due to increase in the cell size and decrease in the cell-wall thickness. The thermal conductivity measurements showed that the thermal conductivity decreased with increase in density. It was due to the decrease in cell size. The thermal analysis of the PUFs shows that the glass transition temperature increases with the decrease in foam density, but the thermal stability decreases with the decrease in foam density. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008