高密度聚乙烯的壁面滑移行为

A Rheological Study on Wall Slip Behavior of HDPE

用双筒毛细管流变仪和旋转流变仪研究了两种牌号的高密度聚乙烯(HDPE)熔体的壁滑行为,考察了发生壁滑的临界剪切应力。通过剪切速率扫描的方法发现两种牌号的HDPE熔体在较高的剪切速率下均发生粘滑转变,在150～230℃温度范围内,HDPE发生粘滑转变的临界剪切应力位于0.20～0.38 MPa范围内,与文献报道值一致;而且发生粘滑转变的临界剪切应力随温度线性增加,这与B rochard和de Gennes提出壁滑的解缠机理一致。用壁滑外推长度表征壁滑程度,发现两种牌号的HDPE熔体的壁滑外推长度均处于0.05～0.09 mm范围内。

Wall slip behavior of two high-density polyethylene （HDPE） melts were studied experimentally by using a capillary rheometer with twin bores at different temperatures and a rotational rhemeter,the critical shear stress for the onset of wall slip was investigated. It was found that a stick-slip transition was observed for the two HDPE melts as the shear rate sweep was done in an increased order. The critical shear stress for the onset of stick-slip transition was in the range of 0. 20 0. 38 MPa,which agreed with the reported value in literature, and it increased linearly with temperature, which accorded with the disentanglement mechanism proposed by Brochard and de Gennes. While the extrapolation length used to quantify the magnitude of the transition remains about 0. 05 - 0. 09 mm for the two HDPE melts.