聚丙烯拉伸断裂过程中的银纹性能研究

在18℃和26℃两种测试温度下,分别以0.1、0.5、1、5、20和50 mm/min的拉伸速率对无规共聚聚丙烯(PP-R)全切痕拉伸样条进行拉伸测试,以观察PP-R的银纹性能,并对PP-R全切痕拉伸过程中应力-位移曲线、位移-屈服应力曲线和拉伸断面进行了分析。结果表明:PP-R的屈服应力随着拉伸速率的增加而增大,并且随温度的上升而减小;在较低温度和较高拉伸速率时,PP-R的全切痕拉伸断裂可能是由常临界位移控制的银纹断裂;而在较高温时,PP-R的全切痕拉伸断裂过程几乎无常临界应力和常临界位移存在,说明PP-R拉伸断裂前几乎无沿拉伸方向的银纹微纤产生。

Study on Craze Behavior of Polypropylene during Tensile Fracture

In order to observe and analyze the properties of craze zone of random copolymerized polypropylene(PP-R),the circumferentially deep notched tensile(CDNT) specimens of PP-R were tested with the tensile rate of 0.1,0.5,1,5,20 and 50 mm/min respectively at the temperature of 18℃ and 26℃.The stress-extension curves,extension-yield stress curves and the tensile fracture surfaces of the specimens were analyzed.The results show that the yield stress of PP-R increases with the increase of tensile rate and decreases with the increase of temperature;at lower temperature and higher tensile rate,the CDNT specimens may be craze fracture which is controlled by the constant critical extension,while at higher temperature there are barely constant critical stress and constant critical extension,which infers that craze fibril is not generated at the tensile direction before fracture of PP-R.