毛细管动态挤出下聚合物熔体非线性流变行为的研究

采用毛细管动态流变仪,选用PELD、PP、PS和PA等典型物料,研究了毛细管动态挤出下各聚合物熔体的非线性流变行为。结果表明,不同物料的流变行为对振动力场的响应特性有较大差异,只有在一定的振幅和频率下振动力场才能有效降低熔体的黏度。实验首次发现,PP、PS和PA存在窄的振动参数区域,在此区域内,熔体的动态表观黏度值大于相应的稳态值,出现“加振变黏”现象。这一新的发现表明,并非“只要引入振动就一定有利于聚合物材料的成型加工”,必须考虑不同分子结构的聚合物材料对振动的不同响应规律。

Research on Nonlinear Rheological Behavior of Polymer Melts During Dynamic Extrusion by a Capillary Rheometer

The dynamic rheological behavior of melts of PE-LD,PP,PS and PA was studied with a dynamic capillary rheometer. It showed that the response of the rheological behavior to the applied vibration varied not only with the chemistry nature of the polymer, but also with the amplitude and frequency. Only in limited ranges of amplitude and frequency could the melt viscosity be decreased by vibration. For PP,PS and PA, there existed a small range of vibration of small amplitude and frequency where the dynamic apparent viscosity of polymer melt was increased, i.e., "vibration-thickening". This showed that the introduction of vibration do not always cause the "thinning" and for this reason, vibration does not always promote the melt processing.