Preliminary study of viscoelastic properties of MAPP-modified wood flour/polypropylene composites

Viscoelastic properties of maleated polypropylene (MAPP)-modified wood flour/polypropylene composites (WPC) were investigated by both a compression stress relaxation method and dynamic mechanical analyses (DMA). Three wood to polymer ratios (40:60, 60:40, and 80:20) and five MAPP loading levels (0, 1, 2, 4 and 8%) were used to study their effects on the viscoelastic properties of MAPP-WPC. The results show that: 1) higher wood to polymer ratio corresponds to higher stress relaxation levels for unmodified WPC. The modification with MAPP has an obvious effect on the stress relaxation of MAPP-WPC at higher wood to polymer ratios (60:40 and 80:20), but almost no effect at the 40:60 wood to polymer ratio. The optimal MAPP loading level for the wood to polymer ratio of 60:40 appears at 1%; 2) the storage modulus reaches its maximum at a MAPP loading level of 1% for wood to polymer ratios of 40:60 and 60:40, while for the 80:20 wood to polymer ratio, a higher storage modulus is observed at higher MAPP loading levels, which is quite consistent with the stress relaxation results. The results suggested that a suitable loading level of MAPP has a positive effect on the viscoelastic properties of WPC at higher wood to polymer ratios. Excessive MAPP loading would have resulted in adverse effects.     

Cellulose esters as compatibilizers in wood/poly(lactic acid) composite

One of the important issues relevant to wood/plastic composite molding is the compatibility between hydrophilic wood and hydrophobic plastic. Polyolefins modified with maleic anhydride, which have been frequently used for wood and polyolefin composites, are not effective for poly(lactic acid) composites. Because compounds with both hydrophilic and hydrophobic groups are potential compatibilizers, cellulose esters of several carboxylic acids, RCOO-cellulose (R = CH₃, C₂H₅, C₃H₇, C₄H₉, C₅H₁₁, C₁₁H₂₃), were synthesized and their effects as compatibilizers of wood/poly(lactic acid) composites (WPLC) were examined in this study. The mechanical properties of WPLC were improved with a small amount of added cellulose esters, especially cellulose butyrate or cellulose valerate. The relevant effect of added cellulose esters on the thermal properties of wood/PLA composite was analyzed by measuring dynamic viscoelasticity. Part of this report was presented at the 56th Annual Meeting of Japan Wood Research Society, Akita, August 2006 and the 9th International Conference on Frontiers of Polymers and Advanced Materials, Cracow, Poland, July, 2007     

Dielectric properties of Simon poplar wood flour/polypropylene composite at oven-dry state

Interfacial compatibility is a crucial factor to the performance of wood-plastic composites （WPCs）. Yet, so far, the coupling mechanisms of WPC have not been completely understood. In order to further clarify the interfacial coupling mechanism, the dielectric constant and dielectric loss factor of Simon poplar wood flour/polypropylene composites without additives at different wood contents were measured at oven-dry state, and parameters and thermodynamic quantities of the relaxation process were also analyzed and calculated. Consequently, an obvious relaxation process based on the reorientation of methanol groups in amorphous region of wood cell wall was observed exactly that its dielectric loss factor peak decreased with the decreasing wood content within the measured range of 50%-100%. With the trend of dielectric relaxation strength, the two changing trends both revealed that the existence of polypropylene could hinder reorientation of methanol groups. Following the decreasing wood contents, the effect of the hindrance on the dielectric properties turned obvious gradually. It elucidated that introduction of polypropylene caused the quantities of hydrogen bonds formed between each methanol group and the groups around it change. The same conclusion could be drawn from the analysis of thermodynamic quantities during the dielectric relaxation progress.     

Dynamic-mechanical analysis and SEM morphology of wood flour/polypropylene composites

Introduction It is well known that over the past few decades, polymers have replaced many conventional materials, such as metal and wood in many applications. This is due to the advantages of polymers over conventional materials (Maurizio et al. 1998; Adr…     

Properties of PEG/thermally modified wood flour/polypropylene (PP) composites

In order to improve the dimensional stability of wood-polymer composites, wood flour pre-treated by polyethylene glyco1 (PEG) at two different concentrations and then thermally treated at 140°C, was used as raw material to produce wood flour/polypropylene (PP) composites at a wood content of 40%. The structure of modified wood flour was analyzed with a scanning electron microscope (SEM) and its effect on the physical and mechanical properties of wood flour/PP composites was evaluated. The SEM results indicated the "bulking" effect of PEG on wood flour, which resulted in reduced water uptake. The combination of PEG and heat treatment further improved the moisture resistance of the composites. However, PEG modification had a negative effect on the flexural modulus of rupture (MOR) and the modulus of elasticity (MOE); whereas heat treatment partly compensated for this reduction. For dynamic mechanical properties, PEG treatment decreased the storage modulus (E′). However, the heat treatment resulted in an increase of E′ of the wood flour/PP composites, with the temperature of loss factor peaks shifting to a higher temperature.     

木／塑纤维复合材料力学性能平衡性初探

用于轿车内衬件的木／塑纤维复合材料,既要求有一定的力学强度又要求有一定的弹性和韧性,本文就木／塑纤维复合材料力学性能的平衡性（主要指静曲强度与弹性模量的平衡）进行了研究。试验表明：不同的胶粘剂对木／塑纤维复合材料的力学性能的平衡性具有很显著的影响。     

偶联剂对木塑复合材料性能的影响

研究了两种偶联剂——马来酸酐(偶联剂1)和异氰酸酯(偶联剂2)对木塑复合材料性能的影响。确定木材纤维与热塑性聚合物的比例7:3、复合材料的设计密度为0．7g／cm3,在热压温度175℃、热压时间8min、偶联剂1或偶联剂2 加入比例均为2％的试验条件下,对比分析偶联剂产生的作用。结果表明:偶联剂2对复合材料的力学性能影响显著;对于同一种偶联剂,所用的热塑性聚合物材料不同,对复合材料性能的影响也存在较大的差异。     

西南桤木木塑复合材料处理工艺的研究

以西南桤木作为试材,注入不饱和烯烃类单体。通过正交试验,分析了真空度、真空时间、浸注压力和加压时间4个因素对木材单体留存率的影响。并用光学显微镜和扫描电镜检测浸渍处理后高聚物在木材细胞壁内的分布情况。提出了较为理想的西南桤木木塑复合材处理工艺参数,能初步实现西南桤木木塑复合材的有效制备。     

碳纤维增强聚合物 重组竹复合材的弯曲力学性能

重组竹已广泛应用于室内高档装饰、园林景观、室外防腐地板等领域,但重组竹的弹性模量比较小,为钢材的1/7~1/5,应用于建筑领域时难以充分发挥其自身高强度的特性。针对重组竹刚度较小的问题,提出一种重组竹板和碳纤维增强聚合物(CFRP)厚板嵌合粘接的新型重组竹复合材料,采用三点弯曲试验和有限元仿真方法,对CFRP 重组竹复合试件的失效模式、荷载 位移关系、应变曲线、胶层界面剥离影响等进行了研究。结果表明:重组竹试件失效模式是跨中位置处拉伸区域竹纤维断裂,且出现若干水平分层破坏,CFRP 重组竹复合试件的失效模式是CFRP与重组竹层间胶层出现大面积剥离;CFRP 重组竹复合试件的变形过程分为线弹性阶段和界面破坏阶段;CFRP可以明显提高重组竹梁的弹性模量和静曲强度,复合试件弹性模量是重组竹试件的2.33~2.94倍,静曲强度是重组竹试件的1.49~1.58倍;胶层界面剥离是CFRP 重组竹复合试件失效的重要因素,胶层界面剥离对复合试件的应变分布和挠度都有较大影响,完全剥离后试件的挠度是未剥离时的3.09倍。     

三种塑料与木纤维复合性能的研究

选用线性低密度聚乙烯(LLDPE)、聚丙烯(PP)、聚苯乙烯(PS)为原料,以2种比率与木纤维复合,用热压法制备了3种木塑复合材料,分析了塑料种类对复合材料的物理力学性能的影响.结果表明,LLDPE与木纤维的复合性能最好,其复合材料的抗冲击性好,但弯曲强度和弹性模量最低;PS与木纤维的复合性最差,其复合材料抗冲击性很差,但弯曲强度和弯曲弹性模量高;木纤维与PP复合材料的综合性能最佳.由此提出用LLDPE与PS共混改性制造木/塑复合材料的设想.     

Utilization of pine (Pinus pinea L.) cone in manufacture of wood based composite

Physical and mechanical properties of medium density fiberboards (MDF) made from various mixtures of wood fibers and stone pine (Pinus pinea L.) cones were evaluated using European standards. MDF panels were manufactured using standardized procedures that simulated industrial production at the laboratory. Six panel types were made from mixtures of wood fiber/cone flour, 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 percents, respectively. Addition of the cone flour into the MDF significantly reduced formaldehyde emission from the panel. In addition, the addition of 10% cone flour also improved water resistance of the MDF panels made using urea–formaldehyde (UF) resin. However, further addition of the cone flour into the panel negatively influenced their water resistance. Flexural properties and internal bond strength decreased with the increase of cone flour content in the panel. The UF resin is the main source of formaldehyde emission from the UF-bonded wood-based panels. Depending on addition of the cone flour in the panels, the formaldehyde emission values ranged from 2.6% to 55.3% lower than the panels made from 100% wood fiber. Based on the findings obtained from this study, pine cone can be used as a renewable biological formaldehyde catcher as an alternative to the traditional formaldehyde catchers for E1 Class MDF manufacture.     

SEBS-g-MAH和原位接枝MAH对木粉/废旧塑料混合物复合材料力学性能的影响研究

由聚丙烯（PP）、高密度聚乙烯（HDPE）和聚苯乙烯（PS）组成的混合废旧塑料与木粉经高速混合机混合后,采用双螺杆/单螺杆串联挤出机组制备了木粉/混合废旧塑料复合材料。探讨了马来酸酐接枝苯乙烯-乙烯/丁烯-苯乙烯嵌段共聚物（SEBS-g-MAH）和原位接枝马来酸酐（MAH）对木粉/混合废旧塑料复合材料力学性能的影响。结果表明,与使用MAH和DCP的原位反应共混相比,SEBS-g-MAH显著提高了复合材料的抗冲击性能,但对拉伸和弯曲性能的改善不如原位反应共混显著。总的来说,混合废旧塑料制备的复合材料的力学性能要低于纯塑料混合物制备的复合材料,尤其是拉伸断裂伸长率。微观形态研究表明,添加SEBS-g-MAH和原位接枝MAH均可提高木粉与塑料混合物之间的界面相容性,但与添加SEBS-g-MAH相比,原位接枝MAH能更好的改善PP、HDPE、PS与木粉之间的界面结合。原位接枝MAH可被看作是一种改善木粉与塑料混合物间界面相容性的有效途径。此外,采用动态力学分析（DMA）进一步表征了复合材料的储能模量和阻尼因子。     

汽车用木粉/聚丙烯复合板的研制

通过气味检测、红外光谱和热失重法,分析出木粉/聚丙烯复合材料产生刺激性气味的原因在于材料的热稳定性较差;应用碱处理、预涂偶联剂、掺入吸附剂和增容剂等方法对木粉进行预处理,测试结果表明,采用碱处理木粉压制的WPC,其气味等级可达到上海某汽车制造企业PV 3900标准3.0级要求.     

苯乙烯(St)/甲基丙烯酸甲酯(MMA)/丙烯腈(AN)三元接枝共聚塑合木研制

本文报道了采用苯乙烯／甲基丙烯酸甲酯／丙烯腈（ＳＭＡ）三元共聚单体浸入木材细胞壁与激活的纤维素进行接枝聚合反应,构成新型的高分子复合材料（ＳＭＡ－ＷＰＣ）,经物理机械性能、吸水性、耐酸性检测,该材料硬度比素木提高了２０％～３５％,抗压强度提高了３５％～４５％,经９８％浓硫酸３天浸泡,重量损失率下降２２％,而在水介质８天浸渍,吸水率下降５０％,并通过扫描电镜观察了塑化前后的微观结构。     

西南桤木木塑复合材料的研究

采用乙烯基类系列单体——丙烯腈(AN)、甲基丙烯酸甲酯(MMA)、丙烯酸(AA)三元共聚单体注入西南桤木木材中，制成新型的高分子复合材料(AMA—WPC)。单体的注入用满细胞法，聚合用热引发法，并采用添加氯化锌对木材细胞壁进行活化等工艺对木塑复合材进行了研究和分析。实验样品按照国标GBl927—1943有关规定进行测试，并结合傅立叶红外光谱和扫描电镜探讨了各因素对AMA—WPC材料接枝率及性能的影响。结果表明：改性后西南桤木木塑复合材料具有优异的物理、力学性能。与素材相比较，AMA—WPC的密度提高了59．8％，顺纹抗压强度提高了76．7％，抗弯强度提高了90．4％，抗弯弹性模量提高22．2％，端面硬度提高102．3％，径面硬度提高153．6％，弦面硬度提高152．2％，吸水率降低56．7％，湿膨胀率降低19．0％。     

聚合物基/稻壳粉复合材料的表面改性研究

使用JC2000A型接触角测量仪测试并研究了蒸馏水和甘油两种液体在稻壳粉填充聚乙烯(PE)、聚丙烯(PP)、聚氯乙烯(PVC)复合材料表面的接触角.研究表明:通过酸碱处理可明显改变接触角及其随时间变化的规律;其中效果最好的是以水作为探测液时,经酸处理后的PE/稻壳粉复合材料.通过方差分析得知表面改性处理方式对接触角有相当显著的影响.     

混炼工艺参数对木/塑复合材料性能的影响

通过混炼工艺进行复合材料配方试验，研究木／塑混和比、偶联剂种类和加入比例以及混炼时间等工艺参数对复合材料性能的影响。结果表明；加入偶联剂可使材料的主要强度指标增加；混炼时间对材料性能影响不显著。     

Moisture and decay resistance and reaction to fire properties of self-binding fibreboard made from steam-exploded grey alder wood

A study of self-binding fibreboards pressed without synthetic adhesives is reported. The board samples of steam-exploded grey alder (Alnus incana L. Moench) particles hot-pressed under a variety of conditions including moisture content of the mat (8% and 12%), temperature (150°C, 160°C, 170°C and 180°C) and pressure (0.2–8 MPa) are tested for moisture resistance (standard EN 1087-1), decay resistance (standard ENV 12038) and reaction to fire performance (ISO 5660-1). The moisture resistance of the board samples is found to satisfy the standard EN 622-5 for load-bearing medium-density fibreboard for use in humid conditions (MDF.HLS). The tested board samples are not fully resistant to the Trametes versicolor fungus, the mass loss of specimens exceeding 3%. Reaction to fire performance of the self-binding board evaluated by the average rate of heat emission being by about 25% higher is worse compared with MDF.HLS.     

废弃纺织物/木刨花复合板制备工艺

采用常规热压法对废弃纺织物和木刨花制备复合人造板相关工艺进行了试验,并讨论了各因素对板性能的影响。结果表明:利用废弃纺织物和木刨花制备人造板在工艺上是可行的。制造复合板的较优参数:纺织纤维形态为碎布条或絮状纤维、刨花/碎布条配比为7∶3、施胶量为12%、密度0.7 g/cm3,最优配比制备的板材其物理力学性能都已达到GB/T4897.2-2003要求。     

Effect of maleic anhydride grafted styrene-ethylene-butylene-styrene （MA-SEBS） on impact fracture behavior of polypropylene / wood fiber composites

MA-SEBS as compatibilizer and impact modifier was incorporated into Polypropylene/Wood Fiber （PP/WF） to enhance interface adhesion and impact strength of the composite. The effect of MA-SEBS content on the impact fracture behavior of PP/WF composites was studied. The impact properties of composites with 8% MA-SEBS reached the maximum value. And further increasing of MA-SEBS content to 10% did not improve the fracture toughness, but improved the stiffness of composites by DMA analysis. This was attributed to the improved PP/WF adhesion. As the MA-SEBS content is more than 8%, the molecule interaction of PP and WF was expected to much stronger than lower MA-SEBS. Scanning electron microscopy （SEM） was performed to analyze the impact fracture surface and showed a stronger affinity for the wood surfaces.