基于片晶滑移的水树结晶破坏机理

Crystalline Destruction Mechanism Caused by Water Tree Based on Lamella Slip

该文研究水树对低密度聚乙烯(LDPE)结晶结构的破坏,并提出基于片晶滑移模型的结晶破坏机理。采用水针法对LDPE样品进行加速水树老化500h后,使用扫描电镜(SEM)观测到水树缺陷中的微通道呈现平行排布的形态,这种形态与机械应力导致聚乙烯片晶滑移破坏形成的缺陷结构相似。通过分析和计算,水树微通道前端的电-机械应力大于聚乙烯片晶滑移所需的临界应力,足以在水树生长过程中引发片晶滑移。片晶滑移导致微通道的形成,同时导致部分片晶的破坏从而形成更多的晶相界面,进而导致聚乙烯结晶度下降而中间相含量提高。使用拉曼光谱(RS)和差示热扫描(DSC)法对比分析有/无水树样品的结晶参数,结果表明,水树的生成导致LDPE的结晶度下降,无定形相的含量不变,而中间相含量明显提高。因此,该文认为电-机械应力导致的片晶滑移是水树对聚乙烯结晶相破坏的主要作用机制。

In this paper,the crystalline destruction of low density polyethylene(LDPE)caused by water tree was discussed,and a destruction mechanism based on lamella slips was proposed.After 500 hours of accelerated water tree aging on LDPE samples by the water-needle method,the cultivated water trees were observed by scanning electron microscope(SEM).The captured parallel distributed micro-channels are similar to the defects formed by mechanical-stress-caused lamella slip during tensile deformation.Through theoretical analysis,the electro-mechanical stress at the tips of the water tree micro-channels is able to cause the lamella slip.The crystalline parameters of the samples with/without water tree were analyzed by Raman spectroscopy(RS)and differential scanning calorimetry(DSC).The results reveal that the growth of water trees leads to the decrease of crystallinity and the increase of interfacial content,and the amorphous content remains unchanged.Therefore,this paper believes that the crystalline destruction mechanism was proposed based on the lamella slip caused by electro-mechanical stress is the main mechanism of the crystalline destruction.