摘要
软木是从栓皮树上采剥的树皮,是一种天然可再生的生物质材料。通过对软木的动态黏弹性进行研究,可以揭示许多关于软木材料结构和分子运动的相关信息。本试验主要运用动态力学分析技术研究了栓皮栎软木的动态黏弹性,并和国外栓皮槠软木进行了对比。结果表明:在不同测试频率条件下,再生栓皮栎软木的储能模量(E′)均随温度升高而呈现降低趋势,损耗因子(tanδ)曲线主要出现了3个明显的损耗峰,对应的3个损耗过程分别由软木脂无定形区发生玻璃化转变、软木中有关成分发生熔融和吸着水的损失、纤维素和半纤维素发生热软化或降解所引起。再生栓皮栎软木分别沿轴向、径向和弦向进行拉伸测试时,E′、损耗模量(E″)和tanδ曲线的变化趋势基本一致,但在相同测试温度下,E′和E″在3个方向存在明显差异。在本试验条件下,栓皮栎和栓皮槠软木存在不同温度的损耗峰,主要表现为初生和再生栓皮栎软木的tanδ曲线分别在-10和-19℃出现一个损耗峰,而再生栓皮槠软木对应的损耗峰出现在14℃。
Cork is the bark mainly from Quercus variabilis in China and Quercus surber in Europe and Africa.It is also a natural renewable biomass material with many appreciated properties,such as light weight,low permeability,low thermal conductivity,sound absorption,heat insulation,wear-resistance and chemical stability.The main component of cork is suber,lignin,polysaccharides and extractables.Cork is widely used in many fields,such as cork sealing material,heat insulation layer,building and decoration materials.Cork would be affected by the changing magnitude and direction of force in the practical application,showing two different mechanisms of deformation,namely,elasticity and viscosity,which belongs to the viscoelasticity of cork.Under the action of the cyclic alternating stress(strain),there are strain(stress)hysteresis and mechanical loss,which is the dynamic viscoelasticity of cork.By studying the dynamic viscoelasticity of cork,the change rules of the storage modulus,loss modulus and loss factor with temperature were established.These rules can reveal the relevant information of the cork material structure and molecular movement.The research results were of great significance to determine the processing and use conditions of cork materials,being used to evaluate the impact resistance,sound absorption and damping characteristics of the cork.The dynamic viscoelasticity of the cork from Q.variabilis was mainly investigated by the dynamic mechanical analysis and compared with that of the cork from Q.surber.The results showed that the storage modulus of the reproduction cork from Q.variabilis decreased with the increase of temperature under different test frequencies,and there were three obvious peaks in loss factor curves.The three loss processes were caused by the glass transition in the amorphous zone of suberin,melting of related components in the cork and loss of adsorbed water,and thermal softening or degradation of cellulose and hemicellulose,respectively.When the reproduction cork from Q.variabilis was tested along the axial,radial and tangential directions,respectively,the change trends of storage modulus,loss modulus and loss factor curves were basically the same.While at the same test temperature,the storage modulus and loss modulus were obviously different in three directions.The cork from Q.variabilis and Q.surber had loss peaks at different temperatures under the experimental conditions of this research.The loss peaks of the virgin cork and reproduction cork from Q.variabilis appeared at-10 and-19℃,respectively,and the corresponding loss peaks of the reproduction cork from Q.surber appeared at 14℃.
作者
毕俊杰
王庆国
吴世谦
宋孝周
BI Junjie;WANG Qingguo;WU Shiqian;SONG Xiaozhou(College of Forestry,Northwest A&F University,Yangling 712100,Shaanxi,China)
出处
《林业工程学报》
CSCD
北大核心
2020年第3期59-65,共7页
Journal of Forestry Engineering
基金
国家自然科学基金(31470583)。
关键词
栓皮栎软木
动态黏弹性
储能模量
损耗模量
损耗因子
cork from Quercus variabilis
dynamic viscoelasticity
storage modulus
loss modulus
loss factor
