聚醋酸乙烯酯熔体的力学谱  

Mechanical Spectroscopy Investigation of Poly(vinyl acetate) Melt

作　　者：吴学邦[1] 朱震刚[1] 周学懋[1] 刘长松[1] 

机构地区：[1]中国科学院固体物理研究所材料物理重点实验室,合肥230031

出　　处：《上海交通大学学报》2010年第5期675-678,共4页Journal of Shanghai Jiaotong University

基　　金：国家自然科学基金资助项目(50803066;10874182;10674135)

摘　　要：利用液态内耗仪研究了聚醋酸乙烯酯(PVAc)在其玻璃化转变温度(Tg)及其以上温度区域的力学弛豫行为.结果表明:PVAc内耗与温度的关系曲线上存在α和α′2个弛豫型内耗峰,α峰与PVAc的玻璃化转变有关,α′峰则对应于一种液/液转变,且两者的弛豫时间均满足Vogel-Fulcher-Tamman关系;在PVAc熔体内耗与频率的关系曲线上,交叉温度TB≈387 K处的α′峰的弛豫时间、弛豫强度和分布参数均出现了一个转折,这是由于降温过程中TB至Tg之间分子耦合作用显著增强的结果.The molecular relaxation dynamics in poly（vinyl acetate）（PVAc） was studied by mechanical spectroscopy above the glass transition temperature（Tg）.The temperature-dependent mechanical spectra reveal the existence of two relaxation modes： α,ascribed to the glass transition,and α′,which might be related to the liquid-liquid transition.The relaxation time follows Vogel-Fulcher-Tamman law for both of the relaxation modes.A detailed analysis of the frequency-domain spectra above T_g shows a dynamic crossover at temperature TB ≈387 K through the temperature dependence of relaxation time,relaxation strength,and shape parameter.According to the phenomenological coupling model,the crossover is suggested to be caused by the strong increase of intermolecular cooperativity below TB with decreasing temperature.

关 键 词：聚合物熔体 弛豫 内耗 

分 类 号：O469[理学—凝聚态物理] O631.2[理学—电子物理学]