自然老化对木粉/HDPE复合材性能的影响及添加剂的应用

研究木粉/高密度聚乙烯(WF/HDPE)复合材在不同朝向的自然老化条件下使用时颜色与表面化学成分的变化,并分析采用光稳定剂、抗氧剂和颜料作为防老化剂的效果.户外使用的木粉/HDPE复合材在夏天暴晒1个月颜色就会发生明显变化,南面和东面更加显著,红外分析表明:复合材料表面C=O增加、木材指数下降,有氧化现象发生.人工加速稳定老化检测结果表明:与抗氧剂和光稳定剂相比,颜料的使用对减小变色有明显作用,但颜料、抗氧剂和光老化剂3种助剂对延缓WF/HDPE复合材的抗弯性能下降没有起到明显作用.     

竹纤维/聚丙烯复合材料的耐老化性能

采用挤出成型制备了竹粉增强聚丙烯复合材料,研究竹粉/聚丙烯复合材料在紫外加速老化与湿热老化后的力学性能变化与尺寸稳定性.结果表明:在紫外线加速老化200 h后,复合材料的弯曲强度与弯曲模量无显著变化,试件宽度与厚度在紫外加速老化前后也无显著改变;但湿热老化对复合材料的弯曲强度与弯曲模量有显著影响,在沸水中浸泡2h后,复...     

Analysis and characterization of microstructures of a TiO2/bamboo charcoal composite and modified poplar veneer

A type of TiO 2 /bamboo charcoal composite made by a dip-dry method was loaded onto wood veneer with a vacuumpressure method in order to prepare modified poplar veneer.The pore structure parameters and surface morphology of the TiO 2 /bamboo charcoal composite were determined and analyzed by means of a porosimetry analyzer and SEM.The results show that the surface morphology of the composite does not change after being loaded with nano TiO 2.However,its specific surface area (359.814 m 2 ·g-1),pore volume (0.317 cm 3 ·g-1) and average pore diameter (3.526 nm) increased;particularly the cumulative volume of pores was increased by 65.83%.In addition,the distribution range of the pores was wider than that of the bamboo charcoal.Combining the SEM of unmodified and modified poplar veneer,the results of X-ray photoelectron spectroscopy revealed that actually some TiO 2 compounds,i.e.,4.08%,are imbedded in the modified poplar veneer.     

稻秸/淀粉胶复合材料性能研究

为充分利用农作物废弃物,研究环境友好材料,通过热压成型方法制备稻秸/淀粉胶全降解复合材料。研究了预处理、胶黏剂、增塑剂和阻湿剂含量对复合材料内结合强度(IB)、弯曲强度(FS)、弯曲弹性模量(MOE)、冲击韧性(IR)、拉伸强度(TS)、拉伸模量(MOR)、含水率及2h吸水厚度膨胀率的影响,并观察了复合材料细观表面。结果表明:水热处理复合材料力学性能除IB外均较高;含胶量为10%时力学性能除MOR外均较高;1%增塑剂提高了IB、FS及TS,2%增塑剂提高了IS,增塑剂对MOE和MOR有负面影响;阻湿剂降低了复合材料力学性能。增塑剂、阻湿剂均能不同程度的增大复合材料MC。复合材料2h吸水厚度膨胀率大,防水性能差。复合材料基体和增强体两相界面结合存在明显缝隙、空洞及分层现象。     

林木根系与黄土复合体的三轴试验

以林木根系为研究对象,将根系与土壤视为一个整体,用三轴压缩试验方法研究根土复合体的应力-应变及强度特性,探讨不同根系直径、根系分布方式、复合体含水量和围压下的极限主应力差和加根效果,得出根土复合体的强度指标.结果表明:根土复合体在含水量相同的情况下,随根径增大,复合体的强度提高率增大.水平根的根土复合体随含水量增加,复合体的强度提高率减小;垂直根和复合根的复合体随含水量增加,复合体的强度提高率增大.垂直根和复合根的根土复合体能明显提高土体的强度,水平根的根土复合体对于提高土体强度效果不是很明显.     

Effects of high drying temperatures and restraint on twist of larch (Larix)

During drying, timber changes its shape, mainly as a result of specific properties such as shrinkage anisotropy, radial differences in longitudinal shrinkage and spiral grain. The distortion, causing severe downgrading, can be reduced by restraining the timber and by using special drying schemes. The research described here is related to a project on the improvement of shape stability of Norway spruce. In the present part, different larch species from three stands were dried at high temperatures (80, 120 and 170°C). The effects of restraint during presteaming, drying and steaming on short-term twist reduction were investigated. The permanency of drying distortions was investigated in subsequent moisture cycling. Results showed a clear dependency of twist on the distance to pith. Restrained specimens sawn close to pith experienced reduced twist. This twist reduction was permanent during subsequent moisture variations. Drying temperature did not significantly influence twist and twist amplitude in moisture cycling.     

Fundamental studies on wood/cellulose-plastic composites: effects of composition and cellulose dimension on the properties of cellulose/PP composite

Although wood/cellulose-plastic composites (WPC) of low wood/cellulose content have been more accepted worldwide and are promoted as low-maintenance, high-durability building products, composites containing high wood/cellulose content are not yet developed on an industrial scale. In this study, flow properties, mechanical properties, and water absorption properties of the compounds of cellulose microfiber/polypropylene (PP) and maleic anhydride-grafted polypropylene (MAPP) were investigated to understand effects of the high cellulose content and the dimensions of the cellulose microfiber. The molding processes studied included compression, injection, and extrusion. It was found that fluidity is not only dependent on resin content but also on the dimension of the filler; fluidity of the compound declined with increased fiber length with the same resin content. Dispersion of the composite was monitored by charge-coupled device (CCD) microscope. Increasing the plastic content in the cellulose-plastic formulation improved the strength of mold in addition to the bond development between resin and filler, and the tangle of fibers. The processing mode affected the physicomechanical properties of the cellulosic plastic. Compression-molded samples exhibited the lowest modulus of rupture (MOR) and modulus of elasticity (MOE) and the highest water absorption, while samples that were injection-molded exhibited the highest MOR (70 MPa) and MOE (7 GPa) and low water absorption (2%).     

Sorption of Cr(VI) on the wood of Japanese larch treated with concentrated sulfuric acid

A carbonaceous sorbent was prepared from the wood of Japanese larch (Larix leptolepis) by dehydration with concentrated sulfuric acid in a 69% yield. The abilities of the sorbent to remove Cr(VI) from aqueous solutions were investigated. Research parameters included the initial solution pH, temperature, and initial concentration of Cr(VI) in solution. The removal of Cr(VI) was highly solution pH dependent and was mainly governed by physicochemical sorption under weak acidic conditions. The equilibrium data fit well in the Langmuir isotherm model. The Langmuir constants were calculated at different temperatures, and the sorption capacity increased with rising temperature, indicating the endothermic nature of the Cr(VI) sorption onto the sorbent. The desorption experiments suggest that the Cr(VI) sorption is generally irreversible, owing to strong interaction of HCrO ₄ ⁻ with the active sites of the sorbent.     

Chemical characterization of smoke from the production process of wood-plastic composites

The chemical composition of unpleasant smell, emitted from the production process of wood-plastic composites using Manchurian ash sawdust (Fraxinus mandschurica Rupr.) and polypropylene powder as the raw material, was investigated. Wood sawdust and polypropylene powder were subjected to heat treatment to 290°C during 8 min (the conditions were similar to those employed on an industrial scale). The emitted compounds were collected and analyzed by gas chromatography-mass spectrometry (GC-MS). The analytical r...     

Current Research and Development on Deformation and Fixation of Bended Wood and Wood-based Composites

There are many advantages of bended wood,such as good-looking shape,simple process and low cost.The product,however,is easy to get recovery,which is urgent to be dealt with.This paper concludes the features of deformation and recovery of bended wood and wood-based composites and summarizes four treating methods to keep dimensional stability.Compared to bended solid wood,some elementary perspectives on the research of bended wood-based composites are presented.The purpose of this paper is to suggest:1)to investigate the optimum heating time and temperature that bended wood and wood-based composites need from the formation of deformation to the recovery and to the permanent fixation,according to its changes of dimensional stability such as curvature radius;2)to measure the composites comprised of wood and adhesives on the changes of stress relaxation,dynamic viscoelasticity and crystal1ization field;3)to quantitatively analyze changes of the major components in wood cell wall polymers as well as the composites under heat/steam treatment and untreated conditions.It will be helpful for subsequent research to clarify on the mechanisms of permanent fixation of bended wood and also contribute to that of wood-based composites.