木质剩余物轨枕复合材料老化因子及方法的探讨

木质剩余物轨枕复合材料是一种新型环保轨枕材料,木质剩余物轨枕复合材料老化因子及方法的探讨对该材料制备具有重要意义。根据木质剩余物轨枕复合材料的组分和制备工艺流程,结合光照、温度、湿度和氧化等诸多老化因子对材料老化的影响进行分析,并对比常用的老化试验方法,寻求具有针对性的木质剩余物轨枕复合材料老化的研究方法。     

竹木复合层合板老化性能试验

运用ASTM D1037人工加速老化试验方法对一种公交车底板上的竹木复合材料新产品进行6个周期循环老化研究.分析了板材的耐水性、尺寸稳定性、各项力学性能值在加速老化过程中的变化情况,并对老化后该种竹木复合材料的抗弯强度和弹性模量进行回归分析,拟合出一般的力学性能和老化周期的函数方程.研究表明:老化过程中板材的抗弯强度和弹性模量的都呈现下降趋势,但老化过程对纵向抗弯强度的影响程度要小于对纵向弹性模量的影响.     

木质剩余物制备模塑包装材料研究进展

以木质剩余物为主要原料研制模塑包装材料,既能使我国林区剩余物得到有效利用,促进经济发展,又能满足包装市场对绿色包装材料的需求.分析我国木质剩余物的广阔利用空间和植物纤维模塑包装材料的研究价值,论述国内外有关植物纤维制备包装材料的研究现状,阐述利用木质剩余物制备模塑包装材料的制备工艺,对剩余物植物纤维模塑包装材料的发展趋势进行展望.     

利用木质剩余物制备糠醛丙酮树脂的研究

利用木质剩余物提取糠醛制备糠醛丙酮低聚物树脂属剩余物的精深利用。分析木质剩余物的利用现状、合成树脂的需求情况，论述以森林采伐与木材加工剩余物为原料，制备糠醛丙酮低聚物树脂技术的意义及糠醛丙酮低聚物树脂的特性和应用，提出糠醛丙酮低聚物树脂制备的技术路线。     

室外用木质人造板室内加速老化法研究进展

介绍了气候老化因素对室外用木质人造板老化性的影响机理, 以及各种室内加速老化法在国内外的研究应用现状; 针对现行室内加速老化方法中存在的问题, 提出改进方法, 并对系统性加速老化方法的应用前景进行探讨。     

固体火箭发动机粘接界面湿热老化实验

对固体火箭发动机粘接界面试验件进行了不同湿热条件下的加速老化试验,并测量了不同老化时间粘接界面的扯离强度,描述了湿热老化试验和性能测试中的试验现象,结合复合材料微粘接结构吸湿规律对试验现象和撤离强度随老化时间变化曲线进行了分析。研究结果表明:衬层-推进剂粘接界面是固体火箭发动机粘接结构中最薄弱环节,应予以重点考虑;湿热老化促进了环境水分从衬层–推进剂界面向推进剂内部的扩散和渗透,致使弱边界层向推进剂内部扩展,导致了衬层-推进剂界面粘接强度的降低。试验件平均扯离强度随老化时间呈下降趋势,中间有一个强度趋于稳定的平台期。      

铁路轨枕复合材料组分特性及对整体性能影响的分析

分析主要增强材料木质剩余物、辅助增强材料玻璃纤维、基体材料酚醛树脂及填充材料工业灰渣等单独组分的特性及对轨枕复合材料整体特性的影响。结果表明,作为铁路轨枕复合材料的4种主要组分,各自优点突出,特性相互适应,将对复合材料整体产生积极、良好的复合效果。     

刨花板耐老化性能的研究

本文研究加速老化试验对脲醛胶刨花板和酚醛胶定向刨花板物理机械性能的影响。结果表明,脲醛胶刨花板经加速老化处理后机械强度降低,吸水厚度膨胀率明显增大,在选用的5个老化试验中,对刨花扳性质影响最大的是APA D—5老化试验;对脲醛胶刨花板进行浸泡、干燥处理,比单一的进行浸泡处理对平面抗拉强度的影响要大得多;加速老化对刨花板MOE的影响比对MOR的大。     

酚醛刨花板加速老化试验的研究

刨花板的耐老化性质是它作为建筑用材的一项重要指标。本试验采用人工老化方法，讨论加速老化因素对马尾松酚醛刨花板耐老化能力的影响，并对几种加速老化方法进行分析比较。结果表明：循环数、冷冻、喷蒸、干燥等因素对老化结果有不同程度的影响；不同的加速老化试验方法对刨花板ＭＯＲ、ＩＢ和ＴＳ的影响程度也不相同；可采用热水浸泡－干燥循环法代替ＡＳＴＭＤ１０３７的６循环加速老化试验；可把沸水煮１小时方法作为工厂对产品的耐侯性质量控制法。     

浅析木材加工剩余物的利用途径

木材是天然可再生资源,并且在社会中得到了广泛的应用。我国是木质材料生产、加工和消费大国,供需矛盾突出。笔者概述了木材加工剩余物利用的必要性,并简述了木材加工剩余物在生物质燃料、林产工业,以及新型复合材料等方面的应用,为企业充分利用木材加工剩余物开发新的加工途径,提高木材利用率,缓解木材的使用压力提供启示。     

Aging law of spruce wood

Abstract

Accelerated aging of spruce wood samples have been carried out by thermo-hydro (TH) treatments. These treatments were applied to accelerate the chemical reactions that take place during the natural aging of wood. In order to avoid dissimilar chemical reactions between the TH treatments and the natural aging, mild temperatures (between 100 and 150°C) have been selected at low relative humidity (RH). The mechanical properties of non-aged, natural aged and accelerated aged spruce wood have been compared. It is apparent that longitudinal Young's modulus of accelerated aged wood increase slightly at the beginning of the treatment and is followed by a reduction. Along the radial direction, Young's modulus remains almost unchanged. On the other hand the radial strength is severely reduced. From these results, the relative radial strength has been fitted on the chemical kinetic law. The rate constant of this law has been calculated and the treatment temperature and wood moisture content have been integrated. Finally this law has been extrapolated to standard climatic conditions in order to predict the loss of strength of old wood by knowing its age and its mean climate history of temperature and RH (ambiance condition).     

Effect of accelerated aging on some physical and mechanical properties of bamboo

The objective of this study was to investigate the effect of accelerated aging on compression strength, modulus of rupture, modulus of elasticity, color change, volumetric swelling, and volumetric shrinkage of bamboo specimens with and without node sections. In the study, these properties were compared with those of Scots pine and beech wood specimens. Depending on bamboo sections, the aging procedure reduced modulus of rupture, modulus of elasticity, and compression strength. Bamboo specimens showed relatively high strength properties compared to wood specimens due to having high density. Strength properties increased from bottom to top of bamboo culms. The presence of nodes in the specimens reduced compression strength and modulus of rupture but affected modulus of elasticity slightly. Remarkable color changes in specimens were observed after aging. Volumetric swelling and shrinkage of bamboo specimens exposed to aging decreased probably due to heat effect of aging procedure.     

Micromorphology,moisture sorption and mechanical properties of a biocomposite based on acetylated wood particles and cellulose ester

Abstract

One of the major issues in a long-term perspective for the use of wood–plastic composites (WPCs) in outdoor applications is the moisture sensitivity of the wood component and the consequent dimensional instability and susceptibility to biological degradation of the composite. In this work, the effects of using an acetylated wood component and a cellulose ester as matrix on the micromorphology, mechanical performance and moisture uptake of injection-moulded WPCs have been studied. Composites based on unmodified and acetylated wood particles, specially designed with a length-to-width ratio of about 5–7, combined with both cellulose acetate propionate (CAP) and polypropylene (PP) matrices were studied. The size and shape of the wood particles were studied before and after the processing using light microscopy, and the micromorphology of the composites was studied using a newly developed surface preparation technique based on ultraviolet laser irradiation combined with low-vacuum scanning electron microscopy (LV-SEM). The water vapour sorption in the composites and the effect of accelerated weathering were measured using thin samples which were allowed to reach equilibrium moisture content (EMC). The length-to-diameter ratio was only slightly decreased for the acetylated particles after compounding and injection moulding, although both the unmodified and the acetylated particles were smaller in size after the processing steps. The tensile strength was about 40% higher for the composite based on acetylated wood than for the composite with unmodified wood using either CAP or PP as matrix, whereas the notched impact strength of the composite based on acetylated wood was about 20% lower than those of the corresponding unmodified composites. The sorption experiments showed that the EMC was 50% lower in the composites with an acetylated wood component than in the composites with an unmodified wood component. The choice of matrix material strongly affected the moisture absorptivity of the WPC. The composites with CAP as matrix gained moisture more rapidly than the composites with PP as matrix. It was also found that accelerated ageing in a Weather-Ometer® significantly increased the moisture sensitivity of the PP-based composites.     

可降解木塑复合缓冲包装衬垫材料的研究综述

可降解木塑复合发泡材料的研究可提高木质剩余物的利用率,缓解资源短缺的压力,同时可以减少通用塑料发泡缓冲材料对环境的污染,具有重要的社会意义和经济效益.从天然纤维及其性质、增韧改性、界面相容性等方面对国内外可降解木塑复合发泡材料的研究现状进行分析,指出木塑复合发泡缓冲材料存在的问题,并对可降解木塑复合缓冲材料的发展趋势作出展望.     

Structural mechanics of wood composite materials I: Ultrasonic evaluation of internal bond strength during an accelerated aging test

This research attempts to observe indirectly the variation of internal bond characteristics for wood composite materials during accelerated aging test treatment using ultrasonic pulse-transmission techniques. Particleboard (PB) and oriented strandboard (OSB) were the representative specimens. The transit time of the ultrasonic wave propagating through the samples along the nominal length and thickness directions was recorded using an apparatus called PUNDIT (C.N.S. Electronic, London). The transit times were measured in the samples under an oven-dried condition after treating them with boiling water at different treating time stages, and the velocity was then calculated based on the transit time. Examination of the internal bond strength conducted on the same samples was done according to JIS A 5908. A study of the relations among springback, internal bond strength, and velocity indicated that a high correlation existed between ultrasonic velocity measured in the length or thickness direction and the internal bond strength for the PB specimen, but no significant correlation was observed between the velocity measured in the length direction and the internal bond strength for the OSB specimen. The results of this research suggested that ultrasound techniques can be applied to predict or evaluate the internal bond state of some wood-composite materials made of relatively small particles, such as PB especially, during accelerated aging test treatment processes.Part of this paper was presented at the 47th annual meeting of the Japan Wood Research Society, Kochi, April 1997     

Effects of Natural Weathering on A Wood Fiber/HDPE Composite and Application of Additives

In this study,the durability of rubber wood(Hevea brasiliensis) which was thermally treated at 170,185,200,and 215℃for 3 h respectively was investigated.The results showed that the durability of heat-treated rubber wood was improved,and the improvement became more obvious with the increase of the treating temperature. When treated at 185℃or lower temperature,the decay resistance of treated wood had no significant improvement.The lowest weight losses were 21.6%and 6.8%after attack by brown rot fungi(Gloeophyllum trabeum) and white rot fungi (Coriolus versicolor) respectively,which were reached by the specimens treated at 215℃.Their resistance to mold fungi was not improved,but the heat-treated wood performed better than untreated wood when both were painted.In field test,the heat-treated specimens exhibited no advantage in termite resistance compared to untreated.     

Analysis of Markov model on predicting wood composite weathering

Summary This paper evaluated the wood composite weathering over time step by Markov theory. By the null hypothesis (H₀), the panel weathering under the long-term outdoor exposure was determined to be a Markov process. The transition matrix which derived from the practical data can be calculated by program Markov and thus the future outcome of wood composite weathering can be forecasted. Also, the utility of the Markov model was successfully testified from the example of 3-year natural aging waferboard in Ottawa, Saskatoon, Fredericton areas.     

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.     

木片热磨机械浆增强尼龙复合材料

本文研究了木片热磨机械浆 (TMP)增强尼龙复合材料的力学性能、热学性能、加工性能。用多元统计分析中的主成分分析法优化设计木片热磨机械浆增强尼龙复合材料 ,合理地确定多项性能兼优的最佳纤维含量。分析了复合材料的界面改性及其微观结构。在木片热磨机械浆与尼龙复合材料复合时加入具有线型结构的羧化聚合物偶联剂 ,会形成氢键结合 ,可提高木片热磨机械浆与尼龙之间的相容性 ,产生良好的界面粘合作用。