聚乙烯熔体的挤出畸变与非线性粘弹性的关系

采用毛细管流变仪等仪器研究了一类聚乙烯熔体的挤出畸变与熔体非线性粘弹性的关系。实验发现线形大分子或带小侧基的大分子熔体，容易发生壁滑和挤出压力振荡；而有较大侧基、或相对分子质量分布宽、或带大量短支链的熔体，挤出畸变现象较轻。挤出畸变与熔体的弹性及熔体一壁面吸附状态紧密相关：容易发生壁滑和挤出压力振荡的熔体，弹性较大(人口压力降大)；在壁面的吸附作用强(壁面临界剪切应力大).稳态剪切粘度大小与挤出畸变和压力振荡的关系不大；而拉伸应力和拉伸粘度大的熔体较易发生壁滑和挤出压力振荡。

The Relationships of Melt Fracture Behaviors and the Non-linear Viscoelasticity of PE and Its Copolymer Melts

The relationship between the melt fracture and the non-linear viscoelasticity for PE-HD, POE, and PE-LLD was studied using a capillary rheometer. It was indicated that the melt slide at wall and the extrusion pressure vibration were easier to occur for melt of linear chains, but more difficult to occur for melt of branched chains or broad molecule weight distribution. The higher the melts elasticity, the greater the shear stress between melts and the stronger the wall slide and the pressure vibration. The melts fracture was seriously affected by extensional viscosity, but less by the steady shear viscosity of melts.