极低密度聚乙烯与其它聚乙烯的共混

BLENDS OF VERYLOW DENSITY POLYETHYLENE WITH OTHER POLYETHLYENES

从结构角度，用ＤＳＣ，ＷＡＸＤ，ＳＡＸＳ研究了聚乙烯（ＰＥ）家族中极低密度聚乙烯（ＶＬＤＰＥ）与其它ＰＥ的互容性．ＨＤＰＥ／ＶＬＤＰＥ是共晶互容的，以其大量无规部分“溶解”了ＨＤＰＥ的结晶缺陷部分，提高了ＨＤＰＥ的Ｔｃ，Ｔｍ，Ｘｃ，结晶峰半高宽变窄，晶胞参数随组成而有最低值．ＶＬＤＰＥ与ＬＬＤＰＥ结构极为相似，ＤＳＣ及ＷＡＸＤ证明其共混物是共晶相容体系．ＬＤＰＥ／ＶＬＤＰＥ的结晶度符合按组成的计算值，但晶胞参数ａ，ｂ以及晶粒尺寸增大，ＤＳＣ上有分别相应于两组份的两个Ｔｍ；ＶＬＤＰＥ的Ｔｃ，Ｔｍ峰高之和高于按组份的计算值，ＬＤＰＥ的Ｔｍ，Ｔｃ则低于计算值．认为是正如ＬＬＤＰＥ／ＬＤＰＥ，ＬＤＰＥ向充满整个体积的ＶＬＤＰＥ中不断填入，以ＶＬＤＰＥ为晶核而结晶，形成相分离的不相容体系．

Compatibility of very low density polyethylene (VLDPE) with other commercial polyethylenes is studied by DSC, WAXD and SAXS. HDPE/VLDPE blends are compatible through cocrystallization. Copious amorphous part in VLDPE `dissolves' the crystallite defects of HDPE, improving the latter's Tc, Tm and Xc. Half width of HDPE's WAXD crystallite peaks becomes narrower, and unitcell parameters show minimum values with composition. VLDPE and LLDPE are similar in structure, and they are cocrystalline compatible. Mutual interaction between LDPE/VLDPE is evidenced by the increase in unitcell parameters and crystallite dimension, the appearance of two individual Tm's, and the constantly higher Tc, Tm values of VLDPE and lower Tc, Tm of LDPE than expected of their composition. This is due to the continuous filling of LDPE into VLDPE occupying the space, forming separate incompatible system.