高密度聚乙烯的拉伸塑性形变与空洞化行为

Plastic-deformation and cavitation in uniaxial stretching process of high-density polyethylene

通过改变高密度聚乙烯(HDPE)试样的结晶条件得到3种不同片晶厚度的HDPE试样。采用同步辐射小角X射线散射技术在线观察HDPE试样在单轴拉伸过程中的微观结构演变。实验结果表明,薄片晶试样(片晶厚度为13.8 nm)在拉伸过程中发生塑性形变,试样经历了应力诱导的晶块破碎和重结晶过程;厚片晶试样(片晶厚度分别为21.3 nm和28.1 nm)在拉伸初期出现空洞化现象,在线实验证明了空穴的发生及转向;具有相似结晶度但不同片晶厚度的体系,产生的空穴形状也不同,片晶越厚,塑性形变的能力越差。

The deformation mechanism of high-density polyethylene,which crystallized under different conditions,in uniaxial stretching process was studied by means of synchrotron small angle X-ray scattering（SAXS）. The results showed that there were the plastic deformation and cavitation in the stretching process. The sample quenched in ice water showed the plastic deformation of stressinduced fragmentation and recrystallization. The sample crystallized at high temperature showed the cavitation behavior in the initial stage of the stretching process. In addition,the SAXS data demonstrated that the samples with similar crystallinity but different crystal lamellar thickness showed different plastic deformation behavior and the cavities with different shape formed in the stretching process.