热历史对LLDPE／EVA／CB导电材料PTC性能的影响

研究了淬火（液氮冷却），空气自然冷却，空冷后退火，水冷，缓慢冷却等不同热历史条件下LLDPE／EVA／CB导电复合材料的PTC（正温度系数）特性，并借助DMA，DSC，SEM，TEM等手段揭示了LLDPE／EVA／CB导电复合材料PT特性与结晶形态等结构间的关系。结果表明，LLDPE／EVA／CB导电复合材料的PTC行为受结晶度和结晶形态影响很大，结晶度愈高，室温电阻愈小，PTC强度愈高；结晶形态愈复杂，从室温至PTC转变温度的低温PTC效应愈强，熔体缓慢冷却及退火工艺，可提高复合物结晶度，降低取向作用，使电阻率下降。

INFLUENCE OF THERMAL HISTORY ON PTC PERFORMANCE OF LLDPE/EVA/CB CONDUCTIVE COMPOSITES

The PTC (positive temperature coefficient ) characteristics of LLDPE/EVA/CB conductive composite with various thermal history , such as quenched , cooled in air , cooled by water , gradually cooled and annealed were investigated , and the relations between PTC effect and crystalline structure of LLDPE/EVA/CB composite were revealed by DMA , DSC , SEM and TEM . The results showed that the PTC behavior of LLDPE/EVA/ CB conductive composite depends on its crystallinity and crystalline structure on great extent . The larger the crystallinity is, the smaller the resistivity is at room temperature , and the higher the PTC intensity is; the more complex the crystalline structure is, the more intensive the PTC effect at lower temperature from room temperature to PTC switching temperature is. The crystallinity of the composite could be increased and its orientation and electrical resistivity could be deduced by gradually cooling and annealing of the specimen .