Wood Filler Research Articles

Wood–polyethylene composites using ethylene–vinyl alcohol copolymer as adhesion promoter

Saw dust–reinforced linear low density polyethylene (LLDPE) (1:1) composites were prepared by using ethylene–vinyl alcohol copolymer (EVAL) as adhesion promoter to improve mechanical strength. To evaluate the optimum vinylalcohol (VA) content in EVAL, various EVAL samples containing different contents of VA were used. The tensile properties of saw dust–LLDPE composites were improved by using EVAL as adhesion promoter in place of ethylene–vinyl acetate copolymer (EVAc). The saw dust–LLDPE composites prepared with EVAL containing 15 mol% VA showed the maximum yield stress and modulus. The tensile stress increased with addition of EVAL up to 3 wt% on the wood filler, and then leveled off in the range of 3–10 wt%. However, the elongation was decreased with increasing VA content. Hydrogen bonding interaction between saw dust and EVAL was detected by FT-IR spectra. When EVAL consisting with 15 mol% VA was used, good adhesion between saw dust and LLDPE matrix was confirmed by SEM fractography.

Effect of Wood Flour Fillers on Density and Mechanical Properties of Polyurethane Foams

A comparison analysis has been undertaken to study the effect of different wood fillers on density and mechanical properties of two different types of commercial polyurethane (PUR) foams: low-density flexible foams and high-density rigid foams. The micro-fillers used were based on wood flour particles of size 70-250 microns (wood waste of furniture industry). The relationships between the filler size and content, density and various mechanical properties - compression test, compression force deflection test and modulus of elasticity have been studied. It was found that micro-fillers provide various effects depending on flexibility and density of PUR foams. For low-density flexible PUR foams, the density and mechanical properties increased for both types of fillers. However, for high-density rigid PUR foams these effects were just the opposite: the density and compression strengths decreased for both types of fillers. Explanation of the observed effects should take into consideration the chemical nature and physical structure of flexible and rigid PUR binders based on various types of polyol-isocyanate systems, as well as chemical and physical affiliation of cellulose based fillers with the matrices.

Graft copolymers of lignin as hydrophobic agents for plastic (wood‐filled) composites

AbstractPoly[lignin‐g‐(1‐phenylethylene)] graft copolymers synthesized by free‐radical, graft copolymerization on lignin and verified by fractionation, infrared spectroscopy, and solubility change possess macromolecular surface activity as indicated by their capacity to form stable emulsions between incompatible fluid phases, to adhesively bond to wood surfaces, and to change the contact angle of water on coated wood. The surface activity of the copolymer changes with its composition. As the weight percent lignin in the copolymerization reaction product increases beyond 20 wt %, the amount of the emulsion phase formed in a water–benzene mixture decreases. Maple wood flour could be solvent‐coated with a copolymer and both coated and uncoated maple flour could be extruded through a stranding plate into a wood‐filled composite with polystyrene. Physical property tests show that composite control samples are about 3% stiffer and less deformable than are the copolymer composites when dry and about 5 or more percent more deformable than are the copolymer composites when wet, showing that the copolymer coating increased the wet strength. The copolymer samples are always denser than are the controls. Copolymer coating on wood filler decreases the swelling in the composite, the partial molar volume of the imbibed water, and the dimensional change in the solid. These effects cause increase in the density of the copolymer composite upon imbibition of water. Coating the wood component of the composite with a copolymer creates a hydrophobic barrier that produces a decrease in water imbibition into the composite, which will not disappear in 20 or more years of water immersion. Expansion in water is highly dependent on the direction of extrusion. The length expands about 1%, the width expands about five times as much, and the thickness expands over 10 times as much as does the length. This differential expansion may be due to the 22% reduction in the width and a 71% reduction in the thickness of the melt as it passes through the die and the alignment of the long axis of the fiber with the direction of flow through the die. The reaction product is a thermoplastic solid stable below 200°C and thermoformable at between 150 and 180°C. Products which contain between 10 and 50 wt % lignin are heterogeneous solids. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1266–1276, 2003

Effectiveness of functionalized polyolefins as compatibilizers for polyethylene/wood flour composites

AbstractThe effects of various types of compatibilizers on the mechanical properties of high‐density polyethylene/wood flour (HDPE/WF) composite were investigated. Functionalized polyolefins such as maleated and acrylic acid grafted polyethylenes, maleated polypropylene (PPgMA) and styrene‐ethylene/butylene‐styrene triblock copolymer (SEBSgMA) were incorporated to reduce the interfacial tension between the polyethylene matrix and the wood filler. Among them, it was found that maleated linear low‐density polyethylene (LLDPEgMA) gave maximum tensile and impact strength of the composites, presumably because of better compatibility with the HDPE matrix. Similar but less enhanced improvements in the mechanical properties, depending on the compatibilizer loading, were seen for the SEBSgMA system. Whereas acrylic acid grafted high‐density polyethylene (HDPEgAA) and maleated polypropylene (PPgMA) only slightly improved tensile modulus and tensile strength; and they both increased with increasing loadings of compatibilizers. A scanning electron microscopic study was employed to reveal the interfacial region and confirm these findings. In addition, dynamical mechanical thermal measurements also revealed the interaction between filler and matrix, and FTIR spectroscopy was used to assign the chemical fixation and the various chemical species involved at the surface of the wood fillers before and after surface treatment.

Comparative study of maleated polyolefins as compatibilizers for polyethylene/wood flour composites

AbstractThe effects of various types of compatibilizers on the mechanical properties of high‐density polyethylene/wood flour composites were investigated. Functionalized polyolefins, including maleated polyethylenes, polypropylene, and styrene–ethylene/butylene–styrene copolymer, were incorporated to reduce the interfacial tension between the polyethylene matrix and wood filler. Of these, maleated linear low‐density and high‐density polyethylenes gave higher tensile and impact strengths for the composites, presumably because of their better compatibility with the high‐density polyethylene matrix. Similar but less enhanced improvements in the mechanical properties, depending on the compatibilizer loading, were seen for a maleated styrene–ethylene/butylene–styrene triblock copolymer, whereas maleated polypropylene only slightly improved the tensile modulus and tensile strength, which increased with increasing compatibilizer loadings. Scanning electron microscopy was used to reveal the interfacial region and confirm these findings. Dynamic mechanical thermal measurements showed the interaction between the filler and the matrix. Fourier transform infrared spectroscopy was used to assign the chemical fixation and the various chemical species involved on the surfaces of the fillers before and after surface treatment. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 487–496, 2003

Impact behavior of sawdust/recycled–PP composites

AbstractThe instrumented Izod and Charpy tests were performed on the sawdust–polypropylene (PP) composites to study the nature of impact resistance in the thermoplastic wood composites. The notched Izod strength was found to increase with filler content in composites containing the Maleic–anhydride–grafted PP (MAPP) additive. The Izod strength even exceeds that of the neat matrix resin at higher filler contents, indicating a methodology for applying the recycled PP and also for reinforcing the thermoplastics with wood powders. While the static tensile results show evidences for the reinforcing role of the wood filler, a fracture mechanics characterization through the Charpy impact tests effects of MAPP under the impact loading rates. The choice of MAPP as the additive was discussed accordingly for application of the sort of materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1420–1428, 2001

Twin Screw Compounding of PE-HD Wood Flour Composites

Abstract The compounding of wood flour filled polyethylene is discussed with reference to co-rotating twin-screw extruders from two manufacturers. An acrylic acid-grafted polyethylene (PE-HD-AA) copolymer was used as the compatibilizer in high density polyethylene wood flour (PE-HD/WF) composite system. Special consideration was given to the compounding of the heat- and shear-sensitive wood flour. The relevant screw configuration was found to consist of short mixing length with low intensity of shearing. A suitable combination of processing variables was necessary for limiting the thermal degradation of the wood filler, however, tensile properties of the composites were not affected much. Furthermore, the allowable range of processing temperature was limited, and there was an upper bound of rotating speed and a lower bound of throughput rate within which the darkening of wood filler in the composites was acceptable. The processing window was also experimentally constructed in terms of the degree of darkening of wood composites.

A FRACTURE MECHANICS STUDY OF POLYPROPYLENE–WOOD FLOURS BLENDS

Polypropylene/wood blends were prepared from various resins and wood flours through extrusion compounding and injection molding. It was observed that the notched Izod strength of the blends with a relatively brittle resin matrix exceeded that of the neat resin at higher filler loading when the compounds contained the maleic-anhydride-polypropylene (MAPP) copolymer. The Izod strength of the blends with a tough matrix increased with the content of the interfacial modifier MAPP and is higher in blends with coarser fillers. The fracture mechanics analyses of the instrumented drop-weight Charpy test results were then performed to sudy the nature of these increases in impact fracture resistance. It was found that both the fracture toughness Kc and the critical strain release energy Gc increase with filler content in blends containing MAPP. In blends without MAPP, however, Gc decreases slightly with filler content while Kc increases less significantly. The increases of Gc with MAPP and with increasing filler particle size were also observed for the blends with a tougher PP as matrix. It is thus the reinforcing role of cellulosic fibers of the wood flours that contribute positively to the impact resistance of the PP/wood blends. It was thus proposed that higher wood filler aspect ratio, stronger interface, and tough copolymer matrix is the better choice in designing the PP/wood compounds.

Collapse behaviour of plastic tubes filled with wood sawdust

The influence of foam-like wood filler on the mode of collapse and energy absorption performance of polyvinylchloride (PVC) tubes has been investigated under quasi-static loading conditions. The mode of collapse of axially crushed PVC tubes has been found to revert from regular three-lobe diamond mode to axisymmetric concertina mode at a certain wood-filling density. The energy absorption capacity of the PVC tubes is enhanced by wood compression as well as by extra stretching in the tube circumference due to shifting from multi-lobe to axisymmetric mode. The collapse of the PVC tubes has been analyzed considering multi-lobe mode, concertina mode and mixed mode. In these models, the interaction of the wood sawdust filler on the final mode of collapse of the PVC tubes has been incorporated. The mean crushing load of the PVC tubes collapsing into the mixed mode is considered as the average mean of that of the concertina mode, the multi-lobe mode and that causing crushing of wood sawdust. Compression tests on wood sawdust were used to extract its mechanical properties and the results have been used in the validation of the analytical model. The analytical results obtained for the mean crushing load agree reasonably well with those from experimental observations.

Investigating interphase development in woodpolymer composites by inverse gas chromatography

The influence of secondary interactions on the development of interfacial structure in composites of wood and amorphous thermoplastic polymers is not well understood. This study used inverse gas chromatography to investigate the effect of different polymers on the surface energy of partially or fully coated white pine wood meal. In this way, the development of the interphase was monitored as a function of polymer depth on the wood surface. The polymers were selected to provide a range of functional groups and included polystyrene, poly(methyl methacrylate), poly(vinyl chloride), polymethacrylic acid, and polymethacrylonitrile. The overall variation of the dispersive component of the surface energy and the ratio of acceptor to donor coefficients appeared to group themselves into two categories based upon the polarity of the polymer's functional groups. In addition, the high loadings required for stabilization of the less polar polymers suggested that a relatively large volume of the matrix phase is affected by the wood filler.

Thermoplastics Reinforced with Wood Fillers: A Literature Review

Problems concerning the processing of thermoplastics reinforced with wood fillers are discussed. The high level of moisture absorption by the filler, its poor wettability, as well as the insufficient adhesion between untreated filler and the polymer matrix are reasons for the low tensile strength and high moisture sorption of composites. These shortcomings of composites can be prevented by the modification of the interface. The fiber-matrix compatibility and the composites properties can be improved by using some physical (e.g., steam explosion, corona, cold plasma) and chemical (cross-linking and acetylation of cellulose, grafting, use of coupling agents) methods. Modified wood-polymer interaction mechanisms are complex and specific for each definite system and processing conditions. Cellulose cross-linking and acetylation reduce hygroscopicity and swelling of wood and wood composites. Grafting of styrene to wood is effective for wood-polystyrene systems. The best coupling agent for wood-thermoplastics is polymethylenepolyphenyl isocyanate. Silanes coupling effect can be increased with additives to the polymer matrix. Optimizing of technological parameters of wood-thermoplastics processing is necessary.

The Effect of Lignin and Surface Activation on the Mechanical Properties of Rubberwood-Polypropylene Composites

Lignin was employed in rubberwood-polypropylene (RW-PP) composites to serve as a bridging agent between polar wood filler and non-polar PP. Incorporation of lignin in the composites was able to improve the flexural and tensile properties of the composites. SEM showed evidence of improved adhesion as the result of the addition of lignin. Activation of the wood surface with sodium hydroxide (NaOH) improved the flexural and impact properties of the composites. The tensile modulus was improved, especially at 5% lignin loading. However, no improvement was detected in the tensile strength.

Morphology and Properties of Wood-Fiber Reinforced Blends of Recycled Polystyrene and Polyethylene

Material properties of composites produced from recycled plastics and recycled wood fiber were compared. A blend of high-density polyethylene and polystyrene was used as a simulated mixed plastic. Stiffness was generally improved by the addition of fiber, as expected, but brittleness also increased. Pretreatment of the wood filler with phenol-formaldehyde resins did not significantly affect material properties. Differential scanning calorimetry indicated no interaction between the polyethylene phase and the other phases present in the composite. Glass transition temperatures for the various combinations of components indicated a possible interaction between the polystyrene phase and untreated wood filler. This was supported by scanning electron micrographs, which indicated a less-coalesced morphology for samples filled with treated wood flour compared to those with untreated wood flour.

Physical properties of moldings from liquefied wood resins

AbstractThe liquefied wood resins obtained by liquefying wood in the presence of phenol using phosphoric acid as a catalyst were applied to prepare the moldings by using hexamine as a hardener. The effects of the molding conditions and the moldings' compositions on flexural properties and water‐sorption kinetics of the moldings were investigated. It was found that the liquefied wood resins had satisfactory and almost uniform curing reactivity, although they were composed of different kinds of wood components. The flexural properties of the liquefied wood moldings were enhanced with an increase in the amount of combined phenol within the liquefied wood and became comparable to those of the commercial novolak when the amounts of combined phenol were larger than 75%. Furthermore, it was also found that with an increase in the content of wood fillers the flexural properties of the liquefied wood moldings were enhanced more effectively than were the cases of the commercial novolak moldings, exhibiting that the liquefied wood resins could gain a greater reinforced effect from compounding with the wood fillers than did the commercial novolak resins, and the greater the amount of combined phenol, the higher the reinforcing performance of wood fillers. In addition, water‐sorption measurements and the SEM observations of the moldings indicated that the liquefied wood resins had much greater hydrophilicity than that of the novolak and revealed a greater compatibility with wood fillers. © 1995 John Wiley & Sons, Inc.

Ultraviolet curing acrylated chlorinated low‐molecular‐weight guayule rubber wood filler and finish

AbstractAcrylated chlorinated low‐molecular‐weight guayule rubber (ACLMWGER) has been systhesized and characterized with Fourier Tranform infrared spectroscopy, solid‐state nuclear magnetic responance spectroscopy, and differential scanning calorimetry, We have found that ACLMWGER is useful as a prepolymer in 100% solids ultraviolet (UV) curing wood coatings. The properties of the coatings are equal or superior to coatings prepared from acrylated chlorinted rubber synthesized from commerical masticated natural rubber. However, when low‐molecular‐weight guayule rubber (LMWGR) serves as the feedstock, the cost of producing ACLMMWGR is significantly reduced since no mastication is needed. © 1994 John Wiley & Sons, Inc.

Thermal Degradation of Wood Fillers at the Melt-Processing Temperatures of Wood-Plastic Composites: Effects on Wood Mechanical Properties and Production of Voiatiles

Abstract The objective of this research was to clarify the effect of wood thermolysis during melt processing on the properties of wood-plastic composites. Oven-dried sugar pine wood strips were subjected to thermal degradation in a stirred molten metal bath in the temperature range 220°C to 260°C. Exposure times ranged from 4096 to 4 minutes. The bath and wood strips were kept free of oxygen. Degraded wood specimens and undegraded ones (used as controls) were tested for bending modulus and strength, toughness, and weight loss. Toughness was most affected by the degradative treatment, followed by bending strength and then bending modulus. Apparent Arrhenius parameters for the thermal degradation process were determined from rates of property loss, and times required to produce various relative property losses were calculated. Losses in wood mechanical properties during a single composite extrusion probably would not significantly alter composite properties, but multiple melt processing steps could be delet...

Axial crushing of wood-filled square metal tubes

The behaviour of thin tubes made of sheet metal and not so thin extruded tubes filled with wood and subjected to axial crushing is studied. Experiments show that the mode of elastic buckling is changed by the presence of the wood filler. The plastic crushing of thin tubes resulted in Euler-type buckling, while a considerable enhancement in the load carrying capacity and energy absorption was seen in the case of thicker walled tubes which were examined both under quasi-static and dynamic loading conditions. A new idealized deformation mechanism for the progressive crushing of the wood-filled tube is suggested and analysed. The results obtained for the mean loads agree reasonably with experimental observations. An alternative method employed to predict the mean crushing load of empty tubes and using a thickness that provides an equivalent stiffness to that of a filled tube is also seen to produce reasonable agreement with the experiment.

ルーメン充填における填料粒子の挙動

Filler particles can be loaded into fibre lumen by agitating a suspension of wood pulp and filler for a certain period. A considerable amount of particles remains even after a subsequent washing treatment of the pulp. The behaviours of filler particles such as calcium carbonate, TiO2 and plastic pigment, in lumen-loading were investigated and following results were obtained.(1) The amount of TiO2 filler particles loaded in lumen of softwood bleached sulphate pulp fibres after a washing treatment was higher than that of hardwood pulp. Beating did not affect on the filler content in washed lumen-loaded pulp fibres.(2) For washed lumen-loaded fibres with calcium carbonates of cube-shaped and rod-like forms, of which average diameters were from 0.1 to 0.8 μm, it was observed that the filler content increased with filler amounts added and levelled off at above 200% addition. This was observed at both 0.1 and 0.8 μm.(3) In case of cubical calcium carbonate of various diameters, the smaller the particle size decreased to, the more filler was retained after washing. There was a big difference between behaviours of the particle size of 0.1 and 0.3 μm.(4) Average cross section of cubical calcium carbonate particles captured in lumen of softwood bleached sulphate pulp fibres was 0.24 μm2, compared to 0.52 μm2 of the original.(5) The amount of lumen-loaded prismoidal calcium carbonate was on the similar level to that of cubical carbonate of a diameter equivalent to the length of minor axis of the prismoidal. It was also observed that some prismoidal particles pierced the fibre cell walls.(6) With recycling of wetting, defibration, agitation with newly added TiO2, washing and drying, the TiO2 content increased with the recycling, time. However, when the drying step was not included, increase of the filler content was less. The filler content of the pulp, which was lumenloaded only at the first time and then 5 times recycled without TiO2 addition was found to be as much as 2.4%.

Heat and mass transferring properties of some polymer composite heat-insulating materials

New experimental data on heat and mass transferring properties of the foam plastics PSB, PPU-3N, FRP-1, FPB and FPB containing from 5% to 10% wood filler, used as thermal insulators of fencing structures in building, are given. The heat and temperature conductivity ratios as well as the volumetric calorific capacity dependence of these materials on the temperature (in the range of 253–298 K) and moisture content (from the dry condition up to soakage), are investigated. The sorption isotherms at temperatures of 280, 298 and 313 K are established. The values of average specific isothermic mass capacity of the investigated materials and their thermogradient coefficients are calculated. The analysis of the actual data is carried out. The presented data on heat and mass transfer properties of the investigated materials can be used for calculations of heat and moisture conditions of protection structures according to the climatic singularities of their application.

Modern Developments in Wood-Finishing Materials

Abstract Wood-finishing materials as used today are classified according to composition, color, drying time, use, or other properties. The paper details the development work that has produced the modern finishes, and covers the purpose that they are designed to serve and the materials upon which they are used. The many stains, wood fillers, coaters and sealers, lacquers, and varnishes are described, their constituents are revealed, and their method of application is fully covered.