摘要
选取低密度聚乙烯(LDPE)在80℃下进行了64d的人工加速热氧老化实验。利用热重(TGA)和差示扫描量热(DSC)两种热分析方法对LDPE的热分解过程及老化机理进行了分析,研究了不同老化时间的LDPE热解特性及动力学参数,通过连续自成核退火热分级(SSA)技术揭示了LDPE老化过程中分子链的变化趋势。结果表明,由于断链与支化作用,LDPE热稳定性和熔融特性降低,经SSA后发现,低温熔融峰的特征温度降低,断链作用占主导,短链分子逐渐增多;LDPE活化能呈现先增大后减小的趋势,结晶度同样先增大后减小,老化降解是首先发生在无定形区,然后过渡到结晶区的过程。
Artificial accelerated aging test on low density polyethylene（LDPE） was conducted in 80 ℃thermal- oxidative environment for different time periods up to 64 days. The thermogravimetry（TG） and differential scanning calorimeter（DSC） analyses were applied to study the thermo-decomposing processes and mechanisms of LDPE. The thermal degradation characteristics and kinetics parameters of LDPE for different aging time were studied. The cha- nging trend of molecular during aging process was monitored by successive self-nucleation and annealing（SSA）. The results showed that thermal stability and melting characteristic decreased due to chain scission and branching. The characteristics value of low temperature melting peak decreased and chain scission was predominant when the shorter chain increased gradually after SSA technology. The activation energy of LDPE increased at first and then declined. The aging was a process of transition from amorphous region to crystalline region.
基金
国家科技支撑计划(2012BAF06B04)
重庆市研究生科研创新项目(CYS16239)
