毛白杨木粉/聚丙烯复合材料界面相容性的介电弛豫解析
Analysis of dielectric relaxation on interfacial compatibility of poplar wood flour/polypropylene composite

为解析木塑复合材料的界面相容性机制, 通过介电弛豫过程分析研究不同硅烷偶联剂添加量的毛白杨木粉/聚丙烯复合材料的温度谱及频率谱, 并计算介电弛豫过程中的表观活化能和热力学量.结果表明:在添加硅烷偶联剂的毛白杨木粉/聚丙烯复合材料中能观察到基于木材细胞壁无定形区中伯醇羟基的回转取向运动的弛豫过程;弛豫强度随硅烷偶联剂添加量增大先减少而后缓慢增大;随偶联剂添加量的增大, 弛豫时间分布峰呈先变宽、变低, 然后再变尖、变高趋势;表观活化能、活化焓、活化自由能和活化熵随硅烷偶联剂添加量增加先增大后减小.表观活化能在硅烷偶联剂添加量(质量比)为2.0%时达到最大值(28.12 kJ/mol), 与未添加偶联剂的毛白杨木粉/聚丙烯复合材料的(13.86 kJ/mol)相比增加2倍以上, 活化焓在硅烷偶联剂添加量从0%时的12.09 kJ/mol增大到2.0%时的26.35 kJ/mol, 增大了117.9%, 说明弛豫过程中伯醇羟基回转取向运动需要克服的能垒增加, 毛白杨木粉与聚丙烯塑料的相容性更好, 结合更紧密, 界面强度更强, 性能更加稳定. To analyze the interfacial compatibility mechanism in wood flour/polymer composites, the temperature spectra and frequency spectra of polar wood flour/polypropylene composites with different loading levels of silane coupling agent were researched through dielectric relaxation process and then the apparent activation energy and thermodynamic quantity in dielectric relaxation process were calculated. The results show that there is relaxation process in poplar wood flour/polypropylene composites with silane coupling agent which is based on reorientation of the methynol groups in amorphous region of wood cell wall. The dielectric relaxation strength decreases first then slowly increases with silane coupling agent loading. The distribution peaks of relaxation time are high and narrow at the beginning then are broader and lower, finally narrower and higher again with increasing silane coupling agent. The values of apparent activation energy, activation enthalpy, activation free energy and activation entropy tend to increase first and then decrease with increasing silane coupling agent. Apparent activation energy and activation enthalpy of 2.0% silane coupling agent modified composites show the maximal value among all the tested conditions, which is 28.12 kJ/mol and 26.35 kJ/mol,respectively, more than twice and 117.9% as likely to samples without coupling agent. It suggestes that the reorientation of the methylol groups becomes very difficult under the strong hindrance. The compatibility between poplar wood flour and polypropylene plastic is better, and the internal bonding and interface strength is stronger, property is more stable. 国家自然科学基金(30871966)