【摘要】 研究了线性分子链结构的无规共聚聚丙烯(PPR)和通过化学接枝改性获得少量长支链结构的高熔体强度聚丙烯(HMSPP)的流动不稳定性以及剪切、拉伸流动性能。结果表明:PPR挤出物出现螺纹状畸变,在高剪切速率下发生熔体破裂与入口区压力不稳定性有关;HMSPP入口压力降在测试范围内没有出现明显的压力波动,挤出物仅表现出螺纹畸变;PPR的剪切黏度随毛细管长径比的增大而增大,毛细管长径比对HMSPP的剪切黏度影响较小;PPR和HMSPP的黏流活化能表现出切应力敏感性;PPR的拉伸黏度表现出拉伸软化行为,HMSPP因其特殊的长支链结构表现出不同程度的拉伸硬化行为。HMSPP的支化结构对拉伸硬化有明显的影响。更多还原

【Abstract】 The flow instability, shear and tensile properties of random copolymer polypropylene(PPR) with linear molecular chain structure and HMSPP with high melt strength obtained by chemical graft modification were studied. It was demonstrated that the spiral distortion of PPR extruder and the melt cracking at high shear rate were related to the pressure instability in the entrance zone. The entrance pressure drop of HMSPP did not show obvious pressure fluctuation within the test range, the extrudate only showed screw thread distortion. The shear viscosity of PPR increased with the increase of capillary length-diameter ratio, while the capillary length-diameter ratio had weak effect on the shear viscosity of HMSPP. The activation energies of PPR and HMSPP showed shear stress sensitivity. The elongation viscosity of PPR exhibited elongation softening behavior, well HMSPP exhibited different degrees of elongation hardening behavior due to its special long branched chain structure. The branched structure of HMSPP had obvious effect on elongation hardening.更多还原