Effect of glycidyl methacrylate on the physical properties of wood–polymer composites

Chemical modification of pinewood was carried out by impregnating the wood with styrene as the impregnating monomer and in combination with a crosslinking monomer glycidyl methacrylate (GMA). Polymerization was carried out by catalyst heat treatment. Dimensional stability in terms of antiswell efficiency was determined and improved on treatment with polymer. Water uptake percentage was also improved for styrene‐GMA treated wood samples over styrene treated or untreated wood samples. Mechanical properties such as bending strength measured in terms of modulus of elasticity and modulus of rupture of polymer‐treated samples showed an improvement over untreated ones. Treatment also resulted an improvement in compressive strengths. Thermal properties of the wood samples were evaluated by thermogravimetric analyzer and differential scanning calorimeter. Biodegradability of the treated and untreated wood samples was determined and improvement was obtained on treatment. As a whole, styrene‐GMA treated wood samples showed more improvement over untreated or styrene‐treated samples. POLYM. COMPOS., 28:1–5, 2007. © 2007 Society of Plastics Engineers     

Studies on dimensional stability and thermal properties of rubber wood chemically modified with styrene and glycidyl methacrylate

Rubber wood (Hevea brasiliensis) was impregnated with styrene and glycidyl methacrylate (GMA) as the crosslinking monomer. After impregnation, the polymerization was accomplished by catalyst heat treatment. Water uptake (%) and water vapor exclusion (%) of the rubber wood were found to be improved on treatment. Dimensional stability expressed in terms of volumetric swelling in water vapor (90% relative humidity) as well as in liquid water and water repellent effectiveness (WRE) of the treated samples were determined and also found to be improved. The wood–polymer interaction was confirmed by FTIR spectroscopy. Thermal properties of untreated and treated wood samples were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetery (DSC) and an improvement in thermal stability was observed for the wood–polymer composites. The improvement in properties observed as more with styrene–GMA (1:1) combination. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1938–1945, 2004     

FTIR characterization of tropical wood–polymer composites

Wood–polymer composites (WPC) of Geronggang (Cratoxylon arborescens), a light tropical hardwood, impregnated with methyl methacrylate (MMA), methyl methacrylate-co-acrylonitrile (1 : 1; MAN), and styrene-co-acrylonitrile (3 : 2; STAN), were prepared by in situ polymerization using gamma radiation or the catalyst–heat treatment. The FTIR spectra of the three types of WPC, with polymer loadings ranging from 10 to 70%, were compared with that of the wood itself and the respective polymers. Characteristic peaks due to C?O vibration of MMA, C?N stretching of acrylonitrile, and ring stretching and bending of styrene monomers, were prominent in the samples that had higher polymer loadings. For the copolymeric systems, quantitation of the FTIR spectra of these characteristic peaks enabled calculations of incorporated acrylonitrile and styrene monomers in the composites to be made. The FTIR spectra of the residues remaining, after exhaustive extraction to remove homopolymer, showed that graft copolymerization of wood components with acrylonitrile and styrene monomers was possible, but not with MMA. Composites prepared by the two methods, gamma radiation and the catalyst–heat treatment, were shown to be chemically very similar.     

Wood–polymer composites prepared by the in situ polymerization of monomers within wood

Wood–polymer composites (WPCs) were prepared from poplar wood (P. ussuriensis Komarov) in a two‐step procedure. Maleic anhydride (MAN) was first dissolved in acetone and impregnated into wood; this was followed by a heat process; and then, glycidyl methacrylate (GMA) and styrene (St) were further impregnated into the MAN‐treated wood, followed by a second thermal treatment. Finally, the novel WPC was fabricated. The reactions occurring in the WPC, the aggregation of the resulting polymers, and their interaction with the wood substrate were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and dynamic mechanical analysis. The performance of WPC was also evaluated in terms of the mechanical properties and durability, which were then correlated with the structural analysis of the WPC. The test results show that MAN and GMA/St chemically reacted with the wood cell walls in sequence, and the quantity of hydroxyl groups in the wood cell walls was evidently reduced. Meanwhile, St copolymerized with GMA or MAN, and the resulting polymers mainly filled in the wood cell lumen in an amorphous form, tightly contacting the wood cell walls without noticeable gaps. As a result, the mechanical properties, decay resistance, and dimensional stability of the WPC were remarkably improved over those of the untreated wood, and its glass‐transition temperature also increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

木粉疏水改性对HDPE基木塑复合材料性能的影响

采用一种操作简便且易于工业推广的方法对木粉进行疏水改性,具体过程为：将3种可热聚合的单体,即甲基丙烯酸甲酯（MMA）、甲基丙烯酸丁酯（BMA）和苯乙烯（St）均匀喷洒在木粉上,经过预热处理后,与配方中其他组分,如高密度聚乙烯（HDPE）和马来酸酐接枝聚乙烯（MAPE）等通过高速混合机混合均匀,采用双螺杆挤出机造粒后,注射制备木塑复合材料（WPC）样条,测试其力学性能。另外,考察了疏水改性对WPC接触角、维卡软化温度、洛氏硬度、吸水性能、热性能的影响规律。结果表明：疏水改性后WPC的接触角增大,木粉和HDPE的界面相容性改善,力学性能得到明显提高。其中,当MMA、BMA和St的添加量为3%时,WPC的力学性能最好,与疏水改性前相比,弯曲强度分别提高了17.3%、26.3%和27.5%,弯曲模量分别提高了24.4%、24.4%和26.0%,冲击强度分别提高了54.7%、57.7%和60.5%。 此外,疏水改性后WPC的维卡软化温度、洛氏硬度、耐水性和耐热性也得到改善。     

Catalyst–accelerator method for the preparation of wood–polymer composites at ambient temperature

Wood–polymer composites (WPC) are materials which may be prepared by impregnating wood with a variety of monomers which are subsequently polymerized by either gamma irradiation or by conventional radical initiators. The inclusion of the polymer into the wood matrix improves the physical properties of the composite compared to plain wood. The catalyst–accelerator method allows in situ polymerization of vinyl monomers at ambient conditions and thus reduces the loss of the volatile monomer during curing, which is a major disadvantage of the heat–catalyst method. The combination of peroxide initiators with an aromatic amine accelerator was optimized for the methyl methacrylate system. Polymer loadings and mechanical properties of WPC prepared from Pinus radiata using the catalyst–accelerator method were compared with those obtained using the gammaradiation method. © 1995 John Wiley & Sons, Inc.     

Chemical modification of rubber wood with styrene and glycidyl methacrylate

Rubber wood was impregnated with styrene and glycidyl methacrylate (GMA) as the crosslinking monomer. Polymerization was accomplished by catalyst heat treatment. Compressive strength both in parallel and perpendicular to fiber directions was measured and improvement was observed for wood polymer composites. Bending strength in terms of Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) was measured and found improved on treatment over the untreated wood samples. Hardness for treated wood was also improved. Dynamic Mechanical Analysis (DMA) indicated an increase in interaction between wood, styrene, and GMA. Biodegradation of the treated and untreated wood samples was also determined and found to be improved on treatment. Scanning electron microscopy (SEM) study showed the wood polymer interaction. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Compression wood as a source of reinforcing filler for thermoplastic composites

Compression wood (CW) is a reaction wood formed in gymnosperms in response to various growth stresses. Many of the anatomical, chemical, physical, and mechanical properties of CW differ distinctly from those of normal wood. Because of different properties, the CW is much less desirable than normal wood. This study was conducted to investigate the suitability of CW flour obtained from black pine (Pinus nigra Arnold) in the manufacture of wood plastic composite (WPC). Polypropylene (PP) and CW flour were compounded into pellets by twin‐screw extrusion, and the test specimens were prepared by injection molding. WPCs were manufactured using various weight percentages of CW flour/PP and maleic anhydride‐grafted PP (MAPP). Water absorption (WA), modulus of rupture (MOR), and modulus of elasticity (MOE) values were measured. The results showed that increasing of the CW percentage in the WPC increased WA, MOR, and MOE values. Using MAPP in the mixture improved water resistance and flexural properties. CW flour of black pine can be used for the manufacturing of WPC as a reinforcing filler. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of polymer in situ synthesized from methyl methacrylate and styrene on the morphology,thermal behavior,and durability of wood

A novel fast‐growing poplar wood, Populus ussuriensis Kom, was prepared into wood‐polymer composite by the in situ polymerization of methyl methacrylate and styrene through a vacuum/pressure and subsequent catalyst‐thermal process. scanning electron microscopy observation, FTIR, X‐ray diffraction, dynamic mechanical analysis, and thermogravimetric/derivative thermogravimetric analysis indicated that the resulted polymer well filled up wood cell lumen in an amorphous form and reinforced wood matrix, which resulted in the improvement of glass transition temperature, storage modulus, and thermal stability of wood. The decay resistance and dimensional stability of wood were also improved. Such wood‐based composite could be potentially used as reinforced material in construction fields. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Wood–polymer composites made with acrylic monomers,isocyanate, and maleic anhydride

Wood could provide better service in some applications if it were harder and more dimensionally stable. In this study, wood–polymer composites (WPC) made with different chemical combinations were evaluated for dimensional stability, ability to exclude water vapor and liquid water, and hardness. Pine, maple, and oak solid wood were combined with different combinations of hexanediol diacrylate, hydroxyethyl methacrylate, hexamethylene diisocyanate, and maleic anhydride. Treatment slowed the rates of water vapor and liquid water absorption. Although the resultant dimensional stability was not permanent, the rate of swelling of WPC specimens was less than that of unmodified wood specimens. In addition, WPC were harder than unmodified wood. The chemical combination of hexanediol diacrylate, hydroxyethyl methacrylate, and hexamethylene diisocyanate greatly decreased wetting and penetration of water into the wood. This chemical combination also gave the hardest and most dimensionally stable WPC. In general, WPC prepared using hydroxyethyl methacrylate were harder than specimens made without hydroxyethyl methacrylate and excluded water and moisture more effectively. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2493–2505, 1999     

Rubberwood–polymer composites based on diallyl phthalate and methyl methacrylate

Wood–polymer composites (WPC) of rubberwood (Hevea brasiliensis), were prepared by impregnating the wood with methyl methacrylate (MMA), and the combinations of MMA and diallyl phthalate (MMA/DAP). Polymerization was carried out by catalyst heat treatment. Impregnated samples showed significant improvements in compressive and impact strengths, hardness, and dimensional stability (toward water) over that the untreated rubberwood. © 1995 John Wiley & Sons, Inc.     

Fungal degradation of wood‐plastic composites and evaluation using dynamic mechanical analysis

Small samples of two wood–polyethylene (HDPE) composite formulations were incubated with either the white‐rot fungus Trametes versicolor or the brown‐rot fungus Gloeophyllum trabeum for 24 and 77 days in an agar‐block test. Noninoculated, side‐matched controls were employed in the tests to serve as references, and solid wood samples of yellow‐poplar (Liriodendron tulipifera L.) inoculated with T. versicolor were included as positive controls. Potential changes in storage and loss moduli because of fungal colonization and moisture were determined using dynamic mechanical analysis, whereas weight loss and visual observation served as indicators of fungal decay. Severe losses in storage modulus (E′) and loss modulus (E″) following incubation of yellow‐poplar with T. versicolor were observed. However, the E′ of the two wood–plastic composite (WPC) formulations increased after 24 days of incubation with T. versicolor. The same effect was observed for G. trabeum, but only in one formulation. The increase of E′ was attributed to a reinforcing effect of the fungal hyphae present in the interfacial gaps between the wood filler and the polymer matrix. Dynamic temperature scans revealed a peak in E″ between 30°C and 63°C, depending on the frequency and fungal treatment. The peak temperature of E″ represents the α‐transition of HDPE. Increased activation energies were required for the α‐transition in WPC samples incubated with T. versicolor for 77 days as compared to controls. This observation confirmed that incubation of WPC with T. versicolor improved interfacial adhesion and reinforced the composite under the assay conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3138–3146, 2006     

Flexural properties of surface reinforced wood/plastic deck board

Decking and railing is the largest and fastest growing market for wood–plastic composites (WPCs). Despite WPC's advantages in comparison to lumber, its modulus and creep resistance need to be further improved for demanding structural applications. In this study, WPC deck boards were reinforced by the composite sheets made of commingled glass and polypropylene fiber. Various reinforcement arrangements were carried out to identify the optimal one. Scanning electron microscopy revealed good bonding at the reinforcement/WPC interface. All reinforced samples exhibited considerably increased modulus of rupture, modulus of elasticity, and strain at break. The creep resistance of the reinforced WPC boards was also greatly improved. Creep strain was simulated with Findley's model. Master curves of creep compliance were generated by time–temperature–stress superposition principle. The Prony series was found to be the analytical expression of the master curves with acceptable accuracy. With improved mechanical properties, the reinforced WPC board can be used in more demanding applications. POLYM. ENG. SCI., 47:281–288, 2007. © 2007 Society of Plastics Engineers.     

Study on properties of nanocomposites based on HDPE,LDPE, PP,PVC, wood and clay

Wood polymer nanocomposite (WPC) was prepared by solution blending of high density polyethylene, low density polyethylene, polypropylene and polyvinyl chloride (1:1:1:0.5) with wood flour and nanoclay. Xylene and tetrahydrofuran were used as solvent and the ratio was optimized at 70:30. TEM study revealed better dispersion of silicate layers in WPC loaded with 3 wt% of clay. WPC loaded with 3 wt% nanoclay exhibited higher thermal stability compared to WPC loaded with 1 and 5 wt% clay. The storage and loss modulus were found to enhance on incorporation of clay to WPC. The damping peak was found to be lowered by the addition of clay to WPC. Limiting oxygen index value increased due to incorporation of nanoclay. WPCs were subjected to exposure to cellulase producing Bacillus sp. and it showed the growth of bacteria as revealed by SEM study. Mechanical properties of WPC decreased due to degradation by bacteria. Water vapour uptake of WPC decreased due to addition of nanoclay.     

木粉改性处理与木塑复合材料性能研究

通过对木粉进行改性处理,研究了不同改性剂及处理条件对高密度聚乙烯木塑复合材料物理力学性能的影响。结果表明:改性剂使木粉的玻璃化温度降低,纤维素的结晶度提高;随着改性剂用量的增加,木塑复合材料的弯曲强度、拉伸强度、弹性模量都有所提高,吸水率也略有升高;50℃下处理48h的木粉制备的木塑复合材料的物理力学性能较好;改性剂C处理的木塑复合材料综合性能较好。     

基于电子束辅助固化的木塑复合材料的研究

在辐射剂量为56kGy的双面电子束辐照工艺条件下，制备了苯乙烯(St)、苯乙烯与不饱和聚酯树脂(St／UPE)混合物以及苯乙烯与环氧丙烯酸酯树脂(St／EA)混合物浸渍的冬瓜木和松木系列木塑复合材料，研究了木材和浸渍液体种类以及电子束辐射对浸渍液体的聚合和固化程度以及所得木塑复合材料性能的影响。结果表明在电子束辅助固化工艺条件下，浸入木材的St、St/UPE和St／EA的聚合率以及St／UPE和St／EA的固化率均可大于90％。木塑复合材料的硬度和压缩强度较原木材可提高2～6倍，其1昼夜吸水率则从原木材的64．6％和52．8％分别降低到8．9％～12．9％和7．0％～7．9％。     

Dimensional stability of wood–polymer composites

Wood–polymer composites (WPC) were prepared by impregnation of polymeric monomers in wood and in situ polymerization. Three polymeric chemicals were chosen for this study: methyl methacrylate (MMA), hydroxyethylene methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA). The effects of polymeric monomers and their combinations on moisture adsorption (M), anti–moisture adsorption efficiency (AME), liquid water uptake (D), water repellency efficiency (WRE), longitudinal, radial, tangential, and volumetric swelling properties (S) after soaking, and antiswelling efficiency (ASE) were investigated. It was found that M was different for different methacrylate combinations and depended not only on the composition of the impregnants, but also on wood properties. Liquid water uptake was similar regardless of the formulation of the WPC. Wood–polymer composites with high MMA content displayed enhanced dimensional stabilities, but WPCs with high HEMA content did not. Tangential and volumetric ASEs were strongly dependent on the type of treatment. Mold growth tests showed that wood treated with HEMA alone had no surface mold growth, and wood treated with MMA alone also showed less mold growth than did the control samples. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 5085–5094, 2006     

Use of nanoparticles for controlled release of biocides in solid wood

The fungicides tebuconazole and chlorothalonil were successfully incorporated into polymeric nanoparticles with median particle diameters of 100–250 nm. Polyvinylpyridine (PVPy) and polyvinylpyridine‐co‐styrene (10% styrene and 30% styrene) were employed as the polymer matrix. The size of the nanoparticle increased with increased styrene content. The biocide also affected particle size, with chlorothalonil consistently yielding larger nanoparticles than tebuconazole. The release of the biocides from the polymeric nanoparticles was studied by suspending them in water. The release rate of both tebuconazole and chlorothalonil decreased with increased styrene content in the matrix, and chlorothalonil consistently released more slowly from the polymeric nanoparticles than did tebuconazole. It was found that biocides were successfully introduced into solid wood by incorporating them within polymeric nanoparticles, suspending the nanoparticles in water, and using the suspension to treat the wood with conventional pressure treatments. Once in the wood, the polymer matrix serves as a reservoir for the biocide and controls its release rate into the wood. Southern pine sapwood samples were treated with biocide‐containing nanoparticles suspended in water, then exposed to the wood decay fungus Gloeophyllum trabeum using a simple wafer test. Samples exhibited fungal resistance at appropriate levels of biocide incorporation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 458–465, 2001     

The effect of zinc oxide nanoparticles on the weathering performance of wood-plastic composites

In recent years, wood-plastic composites (WPCs) have become among the most popular engineering materials. Most of their usage areas are outdoors, where they encounter various damaging factors. The weathering conditions cause significant deterioration to WPC surfaces, which negatively influences their service life. In this study, zinc oxide nanoparticles at different concentrations (1%, 3%, 5%, 10%) were added to a high-density polyethylene-based WPC matrix. The effect of zinc oxide nanoparticles on the weathering performance of WPC was evaluated after 840 hours of an artificial weathering test. The highest colour changes (∆E*) were monitored with control samples exposed for 840 hours. Adding zinc oxide nanoparticles improved the ultraviolet (UV) resistance and decreased the colour changes. The wood flour content also affected the colour changes on the WPC surface. A combination of 10% zinc oxide nanoparticles and 50% wood flour content provided the lowest colour changes. The barrier effect of nanoparticles protected the WPC surfaces from UV light. Zinc oxide nanoparticles also positively affected the load transfer, which restricted the reduction in mechanical properties after the weathering test. The degradation on the surface of WPCs was also investigated using attenuated total reflectance-Fourier Transform–infrared analysis. The changes in the characteristic bands of polymer and wood indicated that surface degradation was inevitable. Light and scanning electron microscopy images also demonstrated micro-cracks and roughness on the surface of WPCs. It is concluded that UV degradation is unavoidable, but zinc oxide nanoparticles can improve surface resistance against weathering conditions.     

New wood-polymer composites containing ethyl α-hydroxymethyl acrylate polymers

Ethyl α-hydroxymethyl acrylate (EHMA) was synthesized and evaluated as a candidate for wood impregnation and in-situ polymerization. Southern Pine softwood was impregnated under a variety of conditions with EHMA alone and with various comonomers plus free radical initiator. Following thermal polymerization, the wood-polymer composites were tested for increased dimensional stability (water soaking swell resistance) and mechanical properties over untreated wood. The greatest increase in dimensional stability was attained using EHMA alone, while the maximum compression modulus was achieved by impregnating with 1:1 EHMA-styrene and styrene alone. The composites were further characterized by ¹³C CP/MAS solid state NMR and scanning electron microscopy.