【作者】 徐信武；

【导师】 周定国； 吴清林；

【作者基本信息】 南京林业大学 ， 木材科学与技术， 2003， 博士

【摘要】 该研究探讨了热处理前后稻草的力学、化学、热反应及机械加工性能;采用异氰酸酯和乳化石蜡为胶粘剂和防水剂试制稻草刨花板,探讨其力学性能及吸湿特征。全论文分“研究背景与研究内容”、“稻草的综合性能及热处理的影响”、“稻草刨花板制造工艺和综合性能”,以及“总结论”等四大部分。结果表明: 稻草具有相当强的纵向抗拉能力,热处理会略微降低稻草的抗拉强度;稻草表面聚积着大量的SiO₂和脂肪类物质,采用热水处理的方法,能够溶解部分脂肪类物质,使内层的羟基部分露出;稻草各层的热反应性能不同,热处理改善了稻草与合成树脂之间的热反应性能;热处理极大地提高了稻草的机械加工性能,刨花形态得到优化。 采用异氰酸酯试制的稻草刨花板,当密度超过0.75/cm³,施胶量为3～5%时,抗弯性能达到美国ANSIA208.1标准中M3级木质刨花板的要求;密度达到0.90g/cm³,施胶量达到5%时,板子内结合强度达标;板子的表面抗拉性能与木质中密度刨花板相当。 稻草刨花板在湿润环境中发生明显的面内变形和厚度膨胀。密度、施胶量和石蜡施加量与板子的形状和尺寸稳定具有密切的关系。稻草刨花板的吸湿变形以吸着饱和点（SSP）为临界含水率。在SSP以下,稻草刨花板具有与木材或木质复合材料等纤维组织类似的吸着等温线,吸着滞后比接近1.0。采用Nelson模型能较好地描述稻草刨花板的吸着等温线。更多还原

【Abstract】 Rice straw as a newly-evaluated raw material for manufacturing composites was investigated in mechanical, chemical, thermal, and machining properties in this dissertation. With modified polymeric methylene diphenyl diisocyanate (MMDI) and wax emulsion as the binder and dimensional stabilizer, respectively, rice straw-based particleboards (RSPB) were experimentally fabricated. Mechanical properties, i.e., bending modulus (MOE) and strength (MOR), internal bond (IB) strength, and in-plane tensile modulus (ITM) and strength (ITS), as well as hygroscopic performances, i.e., water absorption (WA), linear expansion (LE), and thickness swelling (TS) of RSPB were tested according to ASTM D 1037. The tested results were assessed with ANSI A 208.1 for M3 wood-based particleboard. The influences of density, resin level, and wax content on above properties of RSPB were specifically discussed. Simultaneously, parallel wood- and agro-based particleboards were manufactured to clarify the advantageous and disadvantageous aspects of RSPB in mechanic-hygroscopic properties.This dissertation was composed of five sections as: 1) General Introduction; 2) The Influences of Heating on the Properties of Rice Straw; 3) Manufacture and Physic-mechanic-hygroscopic Properties of RSPB; and 4) Conclusions. Through above investigations, it was shown that:Rice straw had high tensile strength in fiber direction, which decreased slightly with heating. The abundant mineral and waxy substances in the surface layers of rice straw, namely silicon dioxide and long-chain hydrocarbons, prevented from effective bonding between synthetic resins and rice straw. By heating, the hydrocarbons were partially dissolved and hydroxyls inside were let out for resins to set up bonds. This was further proved by DSC tests in detecting the thermal reactivity of straw with MDI and UF resins. Simultaneously, particle geometry was optimized through heating.RSPB showed comparative mechanical properties as expected. Density and resin level were demonstrated to be the two most influential factors deciding the mechanical properties of RSPB. With 3 to 5% MDI, RSPB denser than 0.75g/cm~3 had MOEs and MORs higher than the ANSI-specified minimum values. And with 5%MDI, the 0.90g/cm~3 RSPB achieved IB specification in ANSI A 208.1. RSPB showed comparable tensile performances with medium-density wood-based particleboard. Wax-sizing showed no significant impacts on the mechanical properties of RSPB.Under moist conditions, RSPB showed evident dimensional instability. The three factors, i.e.,density, resin level, and wax content, exerted evident influences on LE and TS of RSPB. Sorption saturation point (SSP) was defined as the critical moisture content (MC) for RSPB to deform with moisture adsorption or desorption. The correlation between equilibrium moisture conten; (EMC) of RSPB and environmental relative humidity (RH) followed the sigmoid sorption isotherm found for wood and wood-based composites, which could be well modeled by Nelson’s mathematical equation. Comparably, RSPB had evidently larger hysteresis ratios close to 1.0.(43 Figures; 18 Tables )更多还原