基体分子运动对聚偏氟乙烯/碳纤维复合材料的聚合物基正温度系数性能的影响  

Effect of Matrix Molecular Motion Ability on Positive Temperature Coefficient Behaviors of Poly(vinylidene fluoride)/Carbon Fibers Composite

作　　者：刘仁鹏 邹会昭 黄炎昊 刘正英[1] 杨伟[1] 杨鸣波[1] Ren-peng Liu;Hui-zhao Zou;Yan-hao Huang;Zheng-ying Liu;Wei Yang;Ming-bo Yang(College of Polymer Science and Engineering,Sichuan University,Chengdu 610065)

机构地区：[1]四川大学高分子科学与工程学院,成都610065

出　　处：《高分子学报》2021年第3期312-320,共9页Acta Polymerica Sinica

基　　金：国家自然科学基金(基金号21674069,51721091)资助项目.

摘　　要：聚合物基正温度系数(PTC)材料中,基体分子在熔体状态下的运动能力可显著影响填料分布、PTC强度及稳定重复性等,明确其机理有利于高灵敏性且稳定可重复的PTC复合材料的设计与制备.通过探究基体熔体黏度不同的聚偏氟乙烯(PVDF)/碳纤维(CF)的电阻-温度响应行为,可以发现复合材料PTC转变温度区间仅取决于基体化学结构与结晶性,而PTC循环稳定性却受到基体分子运动能力的显著影响.当基体分子运动能力较强时,分子链极易黏附填料在CF表面形成包覆层,导致局部填料间距增大到隧穿距离以上,不利于复合材料导电网络的重建,导致随热循环次数增加,复合材料的室温电阻率有所升高,PTC可重复性略微降低.而对基体分子链缠结明显的PVDF/CF复合材料中,运动能力较弱的分子链不会包覆CF粒子,在多次升温-降温循环后导电通路能恢复到初始状态,复合材料呈现良好的PTC可重复性,将其应用于电路过热保护装置时,复合材料表现出灵敏的温度响应特性及可多次循环的开关特性.Conductive polymer composites with positive temperature coefficient(PTC)effect have been widely utilized in electronic industry due to their low density,excellent processibility and abundant adjustability.At the melting temperature,the phase transition of crystalline region results in volume expansion,which leads to a dramatic increase in volume resistivity of the composite.Therefore,the PTC performances are highly correlated with the melting process and melt properties of polymer matrix,which means the motion ability of molecules chain during matrix melting affects the performances of the composite such as PTC intensity and reproducibility.Making a thorough inquiry of the effects of polymer molecular motility on PTC behavior is helpful for the design and fabrication of polymer based PTC materials with highly sensitive response to temperature and stable reproducibility in heating-cooling cycles.In this study,the resistance-temperature characteristic of carbon fibers(CF)filled poly(vinylidene fluoride)(PVDF)composites with varied melt viscosity of PVDF was investigated.All the samples showed significant PTC effect during heating processes without negative temperature coefficient(NTC)effect even at temperatures much higher than the melting point of polymer matrix.It can be found that the PTC transition temperature range depended only on the chemical structure and crystallinity of PVDF,while the cyclic stability of PTC behavior was significantly affected by the motion ability of the matrix molecules.For the PVDF(710)/CF composite with matrix of stronger molecular motion,during the heating cycles,the molecular chains possibly stuck to the fillers surface to form an insulating layer,which resulted in wider gaps between fillers and thus reduced tunneling current.After cooling,the reconstruction of conductive paths in composites was impeded,resulting in higher resistivity at room temperature,lower PTC intensity and worse reproducibility.On the contrary,in the PVDF(5130)/CF composites with higher matrix viscosity,the mol

关 键 词：聚偏氟乙烯 导电高分子材料 正温度系数 分子链运动能力 

分 类 号：TB332[一般工业技术—材料科学与工程]