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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。
The wall slip behavior of two kinds of high density polyethylene (HDPE) melts was investigated with a double capillary flow rheometer and a rotating rheometer. The critical shear stress of wall slip was investigated. The results of shear rate scanning show that both HDPE melts undergo stick-slip transition at higher shear rate. The critical shear stress of stick-slip transition of HDPE in the temperature range of 150 ~ 230 ℃ is 0.20 ~ 0.38 MPa, which is consistent with the reported value in the literature. Moreover, the critical shear stress with stick-slip transition increases linearly with temperature, which is consistent with the unwinding mechanism proposed by Brochard and de Gennes. Wall slip extent was used to characterize the degree of wall slip, and it was found that the wall slip lengths of HDPE melt of both grades were all in the range of 0.05 to 0.09 mm.