聚丙烯/弹性体复合材料结晶调节机制与性能

Crystallization Adjustment Mechanism and Performance ofPolypropylene/elastomer Composites

高压直流电缆绝缘用聚丙烯虽具有良好的电性能和热稳定性,但是机械强度较差,需要进行改性克服其缺点。该文分析共混改性和热处理两种结晶调节方式。首先,在聚丙烯中共混不同质量分数的弹性体,并对共混物进行热处理,控制非等温结晶过程中冷却速率,得到不同结晶形态的聚丙烯/弹性体共混物。结合物理和电性能测试结果,分析弹性体含量和冷却速率与结晶形态的关系,研究结晶调节对机械性能和直流击穿场强的影响机制与改性效果。实验结果表明,弹性体含量为10%、20%和30%时,受冷却速率影响,结晶时成核方式发生变化,进而影响绝缘性能;弹性体含量为40%时,冷却速率对成核方式的影响减弱,同时,小而密的球晶结构使共混物获得较好机械性能和较高直流击穿场强,在各个冷却速率时击穿场强都能达到160 kV/mm。可知,不同成核方式导致的结晶形态差异是影响聚丙烯/弹性体共混物性能的关键,研究聚丙烯/弹性体共混物的结晶调节机制与性能,对开发用于高压直流电缆绝缘的聚丙烯材料具有重要意义。

Polypropylene for HVDC cable insulation has good electrical properties and thermal stability but has poor mechanical strength and needs to be modified to overcome its shortcomings.In this paper,two types of crystallization modulation by blending modification and heat treatment are investigated.Elastomer with different mass fractions is first blended in polypropylene.On this basis,the blends are heat-treated to control the cooling rate during the non-isothermal crystallization process,and polypropylene/elastomer blends with different crystalline morphologies are obtained.The relationship between the elastomer content,the cooling rate,and the crystalline morphology is analyzed based on the results of physical and electrical property tests.The influence mechanism and modification effect of crystallization adjustment on the mechanical properties and DC breakdown strength are investigated.The experimental results show that at elastomer contents of 10%,20%and 30%,the nucleation mode changes during crystallization as affected by the cooling rate,which in turn affects the insulation properties.When the elastomer content is 40%,the effect of the cooling rate on the nucleation mode is weakened,while the small and dense spherical crystal structure enables the blends to obtain better mechanical properties and higher DC breakdown field strength,which reaches 160 kV/mm at all cooling rates.In summary,difference in crystalline morphology due to different nucleation modes is key to the performance of polypropylene/elastomer blends. The research on crystallization adjustment mechanismand performance of polypropylene/elastomer blends issignificant for the development of polypropylene-basedmaterials for HVDC cable insulation.