文献类型：期刊文献

英文题名：Research on a strengthening method and mechanism of expanding polypropylene pipe

作者：Ji, Huajian[1];Wang, Yu[1];Zhu, Huihao[1];Ni, Hui[1];Ma, Yulu[1];Xie, Linsheng[1]

机构：[1]East China Univ Sci & Technol, Sch Mech & Power Engn, Shanghai, Peoples R China

年份：2021

卷号：61

期号：9

起止页码：2233

外文期刊名：POLYMER ENGINEERING AND SCIENCE

收录：;EI(收录号：20213110704678);WOS:【SCI-EXPANDED(收录号:WOS:000678871000001)】；

基金：National Natural Science Foundation of China

语种：英文

外文关键词：expanding; phase transformation; PP pipe; beta crystals

摘要：The expansion of deformation-induced crystallization of polypropylene (PP) pipes was studied. The crystal structure and melting characteristics of the samples after expanding at different expansion strains and expansion temperatures were analyzed. The results showed that the crystallinity was improved when the PP pipes were expanded, and the expansion effect made the crystal structure more perfect while the expanding temperature did not exceed the crystallization temperature. However, once expanding temperature exceeded crystallization temperature, some beta lamellae crystal were stretched and transformed into alpha crystals structure. It showed that the expansion effect could cause the crystal phase transformation of the sample. In addition, when the expanding strain was less than 15%, the beta crystal diffraction peak intensity of the sample decreased, but the alpha crystal diffraction peak intensity increased, and the original sparse distribution lamellae structure gradually became compact. With the expanding strain continued to increase, the oriented molecular chains underwent stress relaxation, which hindered the conversion of beta crystals to alpha crystals. The oriented crystal structure formed by the crystal phase transformation made the PP pipe have excellent tensile and impact strength. As a result, the hoop tensile strength is increased by 13%, and the impact strengths are increased by 36%.