聚乙烯及其共聚物熔体有规挤出畸变的定量描述

采用双毛细管流变仪详细研究了聚乙烯及其共聚物的挤出畸变、管壁滑移及挤出压力振荡现象。理论推导得到恒速型流变仪中熔体发生壁滑的滑移速度和临界外推滑移长度的计算公式。计算结果与实验现象相符。实验发现 ,线型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。而有较大侧基或分子量分布宽的材料 ,挤出畸变现象较轻 ,实验未观察到压力振荡现象。挤出速率越大 ,压力振荡频率变大 ,周期变小 ,振幅变化不大。挤出温度升高 ,压力振荡频率减小 ,周期变大 ,外推滑移长度有变小趋势

Quantitative Description of the Regular Extrution Distortion of PE and Its Copolymer Melts

The melt fracture behaviors of HDPE, EPDM, POE etc were studied by double capillary rheometers of constant speed type. A method to analyse and calculate the melt slide speed at wall v s and the critical slide length b c in the measurement was obtained. It is indicated, that the melt slide at wall and the extrusion pressure vibration were easily occurred for linear macromolecule melts but not for polymer melts with bigger side-group or broader molecule weight distribution. The higher the extrusion speed, the higher the frequency of extrusion pressure vibration and the shorter the vibration period. The vibration amplitude was not affected by extrusion speed. When the extrusion temperature was increased, the pressure vibration frequency and critical slid length decreased, while the vibration period increased.