The relationships between rheological curves and extrudate distortions of polymer melts were discussed by a capillary rheometer.The results show that for some melts with linear chains,the adsorption between melts and wall is strong,a flow stress concentration occurres at boundary by high speed extrusion,it leads to melts desorption from wall,the stress-shear rate curves break,and accordingly some regular distortions at surface of extrudate.For some melts with long branched chains,the melts elasticity is strong,then a strong flow stress concentration occurres at die inlet by high speed extrusion,it leads to the inlet drawing flow unstability,and accordingly an integral irregular distortion or melts fracture.%采用恒速型双筒毛细管流变仪研究熔体流变曲线与挤出畸变的关系.结果表明:有些线形链聚合物,熔体/管壁边界黏附力强,高速挤出时边界应力集中,导致剪应力曲线断裂,相应地挤出物发生表面畸变.有些长链支化聚合物,熔体弹性高,入口区应力集中,高速挤出时入口强拉伸流导致流场失稳,相应地挤出物发生整体扭曲或熔体破裂.
展开▼
