HDPE与PPR全切痕拉伸断裂过程银纹性能测试

摘要

High density polyethylene ( HDPE) and random polypropylene copolymerized ( PPR) were tested by using the circumferentially deep notched tensile (CDNT) specimens with different tensile rates and the properties of tensile fracture of two kinds of materials were analyzed under approximate plane strain condi-tion. Based on the analysis of curves of the stress-extension and the extension-yield stress, the results showed that the yield stress of HDPE and PPR increased with an increase of the tensile rate; at higher tensile rate the tensile fracture of CDNT for HDPE was craze fracture which was controlled by the constant critical extension while these were almost not a constant critical extension for PPR in the CDNT fracture procedure. The micro-photography of fracture surface of HDPE indicated fibril and void were produced at the tensile direction; Cra-zing was easily produced between lamellar crystals in the amorphous region at the CDNT fracture procedure and craze fibrils can be produced at every direction for PPR.%通过对高密度聚乙烯(HDPE)和无规共聚聚丙烯(PPR)进行不同拉伸速率的全切痕拉伸测试,考察了两种材料在近似于平面应变条件的拉伸断裂性能.对其全切痕拉伸过程应力-位移曲线、位移-屈服应力曲线分析:HDPE和PPR的屈服应力均随着拉伸速率的增加而增大；在较高拉伸速率时,HDPE全切痕拉伸断裂可认为是由常临界位移控制的银纹断裂,PPR的全切痕拉伸断裂过程几乎无恒定的常拉伸位移.通过显微镜显示的断裂形貌观察揭示了沿拉伸方向上HDPE有微纤空穴产生；在全切痕拉伸断裂过程中,PPR的银纹化易于发生在非晶区的片晶间,银纹微纤可产生在任意方向上.