缠结对超高分子量聚丙烯腈特性粘度测定的影响

在以粘度法测定超高分子量聚丙烯腈(Ultra-High Molecular WeightPOlyacrylonitrile,以下简称UHMWPAN)分子量时发现,在溶解完全的用于测定特性粘度的UHMWPAN二甲基甲酰胺(DMF)稀溶液中,大分子链间保留着未被溶剂舒解的“天生缠结”(Inborn Entanglement),使所测特性粘度和表观分子量偏大.天生缠结是高聚物在聚合过程产生,它在稀溶液中保留的数量受到溶解和溶液处理条件等因素影响,通过机械剪切,可在无机械降解状态下完全解除大分子链间的天生缠结,得到没有缠结影响的正确特性粘度和分子量,由此确立UHMWPAN特性粘度测定方法.

EFFECT OF ENTANGLEMENT ON THE MEASURING OF INTRINSIC VISCOSITY OF ULTRA-HIGH MOLECULAR WEIGHT POLYACRYLONITRILE

When measuring the molecular weight of Ultra-High Molecular Weight Polyacrylonitrile UHMWPAN by the method of viscosity, it is found that there exists unsolved Inborn Entanglements between macromolecular chains in the dilute solution of UHMWPAN in dimcthylformamide (DMF) being well-prepared for measuring intrinsic viscosity, which makes the results of measured intrinsic viscosity and molecular weight larger than the actual. Inborn entanglements of polymers are formed during the process of polymerization, whose quantity in dilute solution is affected by conditions of dissolving and solution treating, etc. By mechanical shearing, inborn entanglements between macromlecular chains can be removed completely without mechanical degradation of polymers. Hitherto, the correct results of intrinsic viscosity and molecular weight are obtained and the method of measuring intrinsic viscosity of UHMWPAN is established.