热历史对β-PP结晶和熔融行为的影响

摘要

The commercialβ–PP materials are obtained by addingβnucleating agents into PP. Theβcrystal content of final products is significantly influenced by heat history during processing procedure. In order to study the factors affect the formation ofβcrystal,the influence of thermal history on crystallization and melting behaviors ofβ–PP was systematically investigated by using a commercially availableβ–PP through differential scanning calorimetric (DSC) method. The study results show that:β–α phase transition inβ–PP matrix can happen during heating process,which results in a decreasedβcrystal relative content and an increasedαcrystal relative content. In addition,the slower heating rate will introduce more obviousβ–αphase transition,while faster heating rate is less inclined to cause this phenomenon. Recrystallization forα crystal which resulted by incompletely meltαcrystal inherently existed in the matrix together with newly formedα crystal due toβ–αphase transition upon heating will happen during cooling process. The eventually-formedα crystals possess more perfect crystalline structures and higher melting points.%商业化的β晶聚丙烯(PP)(β–PP)原料是通过在PP中添加β成核剂改性而得，其最终制品中的β晶含量受加工过程中热历史的显著影响。为了研究影响β晶形成的因素，选用一种市售β–PP，通过差示扫描量热(DSC)法系统研究了热历史对其结晶和熔融行为的影响。研究结果显示，β–PP在加热过程中会发生β–α相转变，导致β晶相对含量减少、α晶相对含量增加；较慢的升温速率将导致显著的β–α相转变，而较快的升温速率可在一定程度上减小产生该现象的趋势；熔体中含有的未完全熔融的α晶以及在加热过程中因β–α相转变新形成的α晶在冷却过程中会发生重结晶，形成结构更完善、熔点更高的α晶。