聚乙烯醇/聚乙烯基吡咯烷酮共混体系的结晶行为

用DSC、WAXD和SAXS研究了聚乙烯醇(PVAl)/聚乙烯基吡咯烷酮(PVP)共混体系的结晶行为.PVAl的结晶度随PVP含量增加而减少,并存在结晶度为零的组成(PVAl)的重量分数约为50％.与纯PVAl相比,共混物的温度区间T_m-T_g减小,表明PVP对PVAl的结晶起抑制作用.共混物中PVAl的结晶速度下降,具体表现为PVAl过冷区随PVP含量增加而扩大,动力学速度常数减小,球晶增长速度下降.纯PVAl和共混体系的等温结晶速率均遵循Avrami方程.退火样品的长周期、片晶厚度和过渡层厚度大于相同组成未退火样品.两者长周期随PVP含量增长加显著增大,片晶厚度增长次之,过渡层厚度变化不大.

CRYSTALLIZATION BEHAVIOUR OF POLY (VINYL ALCOHOL)/POLY (VINYL PYRROLIDONE) BLENDS

The crystallization behaviour of poly (vinyl alcohol) (PfAl)/poly (vinyl pyrrolidone) (PVP) blends was investigated by using DSC, WAXD and SAXS. The crystallinity of PVA1 was decreased with increasing of the content of PVP and there was no any crystallinity when the content of PVA1 was less then 50 wt.%. Comparing with plain PVA1 the difference between Tm, and Tg of blends was low which emerged that PVP could prohibit the crystallization of PVA1 in blends. The kinetic crystallization behaviour could be described by Avrami equation. The rate of crystallization of PVA1 in blends was slower than plain PVA1 which could be verified by the facts that the supercooling of blends was increased and the growing rate of spherulites and the kinetic constant were decreased. Long spacings, the thicknesses of lamellae and transition layers of annealing samples were higher than unannealing one. The composition had a dramatic influence on long spacings, some extent of influence on the thickness of lamellae and little on the thicknesr of transition layers.