复合应力场双向自增强聚乙烯管材的性能与形态结构

Properties and Morphology of Biaxial Self-Reinforced HDPE Pipes Under Complex Stress Field

采用自制的剪切拉伸双向复合应力场挤管装置,在常规工艺条件下生产了3种双向自增强的高密度聚乙烯(HDPE)管材。当剪切套转速控制为20 r/min时,牌号为2480、HD4801EX和5421B的HDPE挤出的管材周向拉伸强度与常规挤出管材相比,依次增加24.8%、41.7%和21.5%,而轴向拉伸强度的增加幅度依次为12.7%、16.8%和10.4%。通过SEM、WAXD和DSC测试手段对HDPE(2480)试样进行微观结构分析,发现其经过复合应力场后管材内部的微观结构仍是球晶,但晶体尺寸有所减小,熔融峰升高,结晶度增大。同时,管材周、轴两向的衍射强度都增强,分子链取向有所增强。

Using self-made shearing-drawing biaxial complex stress field die, three types of biaxially self-reinforced high density polyethylene（HDPE） pipe were extruded under traditional process conditions. Compared to regularly extruded pipes, the circumferential tensile strength of three types of HDPE （2480, HD4801 EX and 5421 B） was increased by 24. 8 % ,41.7 % and 21.5 % ,respectively when the rotational speed of shear casing was 20 r/min,while the axial tensile strength increased by 12. 7 % , 16.8 % and 10.4 % respectively. The samples of HDPE （2480） were characterized by SEM, WAXD and DSC. It was found that the microstructure of self-reinforced pipes was still spherocrystal, but crystallite sizes decreased, melting points drifted to high temperature and the degree of erystallinity increased under complex stress field. Meanwhile, the diffraction intensity of biaxial self-reinforced pipe increased and the molecular chain orientation increased too.