聚丙烯催化合金结构表征

用IR、DSC、NMR分析了聚丙烯催化合金中乙丙共聚物的微结构 ,发现在一定条件下合成的乙丙共聚物主要由两部分组成 :无规乙丙共聚物和各种不同序列长度的乙丙嵌段物组成 .加上丙烯均聚物 ,聚丙烯催化合金是一种具有多分散性结构的混合物 .这种特殊的结构是聚丙烯催化合金具有高抗冲性的主要原因

MICROSTRUCTURE ANALYSIS OF POLYPROPYLENE REACTOR ALLOY

The PP alloy was synthesized directly in the reactor with a 4 th generation Ziegler|Natta catalyst.It is very different from mechanically blended PP alloys,its properties,especially its impact strength,are superior to those of the latter.However,so far the studies on the stucture of this kind of PP alloys have not been reported.The microstructure of a PP alloy was characterized by IR,DSC,and 13 C|NMR.The sample was first fractionated and 8 fractions were obtained.The IR analysis showed that the ethylene content of each fraction is different.Except for the first fraction,which is an elastomer,the others are all hard powders at room temperature.Therefore,the fractions above 50℃ perhaps are all composed of ethylene|propylene block copolymers.DSC analysis showed that the melting curve of the PP alloy became broadened compared with that of i |PP,and a small peak appeared at 120℃.The extracts of PP alloy in boiling heptane and every fractions of PP alloy all exhibited many small peaks.These peaks demonstrated that the macromolecular chains in PP alloy are composed of ethylene|propylene blocks,whose sequence length are very different.The 13 C NMR spectrum of fraction at 90℃, similar to other fractions at 50～100℃,also indicated that there are long ethylene sequences in macromolecualr chains of PP alloy.According to the above analysis,a conclusion was reached that the E|P copolymer in PP alloy is composed of EPR and E|P blocks,with different ethylene sequence length.This polydispersity structure in PP alloy made it possess very high impact property.