复合型导电高分子材料温敏行为研究进展

复合型导电高分子材料(CPCs)的温敏响应行为主要包括正温度系数效应(PTC)和负温度系数效应(NTC)等。本文综述了PTC型CPCs的研究进展,包括PTC行为的发生机理,PTC强度及PTC行为可重复性的调控方法;概括了PTC后NTC行为的消除方法。分析了NTC型CPCs的工作机制,并对CPCs温敏行为的研究热点和难点进行了展望。     

炭黑粒子偶联处理的HDPE复合材料PTC性能研究

研究了以HDPE为基体,工业炭黑（CB）为导电粒子的高分子复合材料的PTC（正温度系数）导电行为。考察了炭黑及偶联剂种类、用量对高分子PTC导电材料性能的影响,并探讨了偶联接枝机理,从理论上对改性效果进行了分析。结果表明,对炭黑,尤其是槽法炭黑 表面处理可显著提高复合材料的电导率及减小NTC（负温度系数）效应;钛酸酯偶联剂具有最佳改性效果,可明显改善炭黑粒子分散状态,增强材料的PTC效应,其最佳用量为1％质量份。     

线性低密度聚乙烯—炭黑复合物的正温度效应

本文研究了炭黑填充线性低密度聚乙烯复合物的导电性与炭黑含量的关系，PTC强度与CB含量的关系，探讨了未交联与交联复合的PTC效应的热重复性和NTC效应。     

PA1010／CB、CE／CB体系的PTC效应研究

研究了炭黑（CB）含量对LDPE、HDPE、PA1010电阻率的影响,以及LDPE／CB、HDPE／CB、PA1010／CB复合体系的电阻－温度特性,发现PA1010／CB体系的正温度系数（PTC）转变温度较高,但与HDPE／CB体系相比,其PTC强度却很低,不适于制备PTC材料。HDPE／CB体系在160℃附近具有较高的PTC效应,且辐射交联可消除其负温度系数（NTC）效应,容易加工成型,是制备低温区PTC材料的较好体系。     

高密度聚乙烯/多壁碳纳米管和高密度聚乙烯/炭黑导电复合材料阻温特性的研究

采用溶液法制备了高密度聚乙烯/多壁碳纳米管（PE-HD/MWCNTs）和PE-HD/炭黑(CB)导电复合材料,并研究了该复合材料的阻温特性。结果表明,与PE-HD/CB复合材料相比,PE-HD/MWCNTs复合材料的室温电阻率更低,并且可以具有较高的正温度系数（PTC）强度和较小的负温度系数（NTC）效应,因而具有更加广泛的应用前景。同时通过对PE-HD/MWCNTs复合材料阻温全过程进行分析,发现PTC效应由碳纳米管向晶区扩散及基体体积膨胀效应共同导致,而NTC效应则是由于碳纳米管的热运动形成的相互接触所致,而并非粒子附聚。     

GF/PVDF导电复合材料的PTC行为

以石墨纤维(GF)、乙炔炭黑(CB)为导电填料,聚偏氟乙烯(PVDF)为基体,通过熔融共混方法分别制备GF/PVDF、CB/PVDF导电复合材料。讨论了导电填料形状、含量对复合材料正温度系数效应(PTC)的影响。并通过实验现象分析认为具有长径比结构的GF是导电复合材料负温度系数效应(NTC)减弱的原因,结合差示扫描量热分析(DSC)证明PTC效应与聚合物结晶熔融有直接关系。     

PA1 01 O/CB、PE/CB体系的PTC效应研究

研究了炭黑(CB)含量对LDPE、HDPE、PA1010电阻率的影响,以及LDPE/CB、HDPE/CB、PA101/CB复合体系的电阻-温度特性,发现PA101/CB体系的正温度系数(PTC)转变温度较高,但与HDP/CB体系相比,其PTC强度却很低,不适于制备PTC材料.HDPE/CB体系在160℃附近具有较高的PTC效应,且辐射交联可消除其负温度系数(NTC)效应,容易加工成型,是制备低温区PTC材料的较好体系.     

炭黑/高聚物导电复合材料PTC效应的研究

正温系数 (Positive Temperature Coefficient)导电高分子材料 (PTC材料 )在工业中得到了广泛的应用。本文探讨了炭黑 高聚物导电复合材料 PTC效应产生与衰退的机理 ,综述了其 PTC效应的影响因素。     

不同炭黑填充的PVC/EPDM复合NTC材料电性能的研究

首先研究了特导炭黑(HG-1P)和乙炔炭黑(ACET)填充聚氯乙烯(PVC)单组分复合材料的逾渗行为和阻温特性:特导炭黑导电性较好,较少的填充量就能达到较低的室温电阻率,在升温过程中表现出稳定的NTC效应;乙炔炭黑导电性能偏差,达到相同的导电性需要更多填充量,在升温过程中先是出现弱的PTC效应,继而出现NTC效应。然后,引入三元乙丙橡胶(EPDM)、乙丙橡胶(EPR)作为第二组分,EVA作为第三组分,发现多组分复合材料电阻降低,阻温曲线表现出一些新的特征。     

二氧化硅对EP/CB复合材料电性能的影响

以二氧化硅( SiO2)为添加剂,低结构炭黑(CB)为导电填料,环氧树脂(EP)为基体树脂,甲基四氢邻苯二甲酸酐( MeTHPA)为固化剂,采用超声分散溶液混合法制备EP/CB/SiO2复合材料.通过电阻-温度特性测试和扫描电镜等分别对其电性能和微观形貌进行了表征与分析.结果表明,随SiO2含量增加,复合材料的室温体积电阻率先下降后上升,当SiO2质量分数为0.5％时,电阻率达到最小值;含SiO2的EP/CB/SiO2导电复合材料仍具有正温度系数( PTC)和负温度系数(NTC)效应,但其PTC强度小于EP/CB复合材料,NTC效应也弱于EP/CB体系.     

PTC effect in carbon black‐filled ethylene–propylene–diene terpolymer systems

The positive temperature coefficient (PTC) effects of carbon black (CB)‐filled semicrystalline and amorphous ethylene–propylene–diene terpolymer (EPDM) composites were studied. The semicrystalline EPDM/CB composite exhibited a low PTC effect followed by a pronounced negative temperature coefficient (NTC) effect, while the amorphous EPDM/CB composite exhibited only an NTC effect. By the effect of γ‐ray irradiation, not only was the NTC effect of the composites eliminated, but also a high PTC effect appeared. The PTC intensity reached as high as six orders of magnitude even for an amorphous EPDM/CB composite and the PTC transition temperature decreased with the irradiation dose. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1571–1574, 2001     

Carbon black–filled immiscible blends of poly(vinylidene fluoride) and high density polyethylene: The relationship between morphology and positive and negative temperature coefficient effects

Conductive polymer composites were prepared by melt-mixing of an immiscible blend of poly(vinylidene fluoride) (PVDF), high density polyethylene (HDPE), and carbon black (CB). Three major factors—the carbon black content, the carbon black type, and the composite morphology—were shown to have remarkable effects on the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effect of the composites. The relationship between the morphology and the PTC and NTC effects of the composites was investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The OM micrographs indicated that CB was selectively located in the HDPE phase and the SEM micrographs showed that there were some gaps between the two phases. The PTC effect of the composites is caused by the thermal expansion as a result of the melting of the HDPE crystallites. The morphology of the composites greatly affects the PTC and NTC behaviors of the composites. When the CB-filled HDPE formed a continuous phase and the PVDF formed a dispersed phase, the PTC and NTC behaviors of the composites were similar to those of CB-filled neat HDPE composite without crosslinking. When the composite exhibited an interlocking structure, a normal PTC effect could also be observed, but the NTC effect was delayed to higher temperatures. A mechanism was proposed to explain this new physical phenomenon, and the mechanism was verified by another CB-filled polymer blend comprising an alternating copolymer of tetrafluoroethylene-ethylene and HDPE.     

BaTiO3系PTCR材料电学性能的复阻抗解析

采用复阻抗解析法研究了ＢａＴｉＯ３系ＰＴＣＲ材料晶粒、晶界的电学性能。结果表明：使用欧姆接触电极的ＰＴＣＲ材料等效电路的复阻抗为：晶粒电阻呈ＮＴＣ特性，而晶界电阻天Ｔ〈Ｔｃ时呈ＮＴＣ特性，Ｔ〉Ｔｃ时呈明显的ＰＴＣ特性；ＰＴＣ效应是一种晶界效应。     

偶联处理对HDPE/炭黑复合材料PTC性能的影响

以HDPE／工业炭黑(CB)复合材料为研究对象，考察了炭黑及偶联剂种类、用量对高分子PTC(正温度系数)导电材料性能的影响，并探讨了偶联接技机理，从理论上对改性效果进行了分析。结果表明，对炭黑(尤其是槽法炭黑)进行表面处理可显著提高复合材料的电导率，减小NTC(负温度系数)效应；钛酸配偶联剂具有最佳改性效果，可明显改善炭黑粒子分散状态，增强材料的PTC效应，其最佳用量为1％。     

LDPE/carbon black conductive composites: Influence of radiation crosslinking on PTC and NTC properties

The electrical resistivity of low‐density polyethylene/carbon black composites irradiated by ⁶⁰Co γ‐rays was investigated as a function of temperature. The experimental results obtained by scanning electron microscopy, solvent extraction techniques, and pressure‐specific volume‐temperature analysis techniques showed that the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects of the composites were influenced by the irradiation dose, network forming (gel), and soluble fractions (sol). The NTC effect was effectively eliminated when the radiation dose reached 400 kGy. The results showed that the elimination of the NTC effect was related to the difference in the thermal expansion of the gel and sol regions. The thermal expansion of the sol played an important role in both increasing the PTC intensity and decreasing the NTC intensity at 400 kGy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2742–2749, 2002     

Positive temperature coefficient behavior of polymer composites having a high melting temperature

The positive temperature coefficient (PTC) behavior of polymers having a high melting temperature, such as nylon, polyvinylidene fluoride, polyester, and polyacetal, was investigated. Carbon black and nickel powder were used to investigate the influence of their conductive fillers on PTC intensity. The polymer/filler composite was irradiated with gamma rays at dosages of 50, 100, and 150 kGy for the purpose of reducing the negative temperature coefficient (NTC) of a conductive composite. It was found that the PTC temperature depended on the melting point of the polymer matrix. The crosslinking structure enhanced the electrical stability and decreased the NTC effect of the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 394–401, 2004     

V型特性PTC材料的复阻抗解析

采用复阻抗解析法研究了Ｖ型特性ＰＴＣ材料（Ｓｒ０．４５Ｐｂ０．５５）ＴｉＯ３的晶粒和晶界的电学性能。结果表明,Ｖ型ＰＴＣ效应来源于材料的晶界,Ｖ型ＰＴＣ效应是一种晶界效应。     

Temperature and time dependence of electrical resistivity in an anisotropically conductive polymer composite with in situ conductive microfibrils

An anisotropically conductive polymer composite (ACPC) based on conductive carbon black (CB) and binary polymer blend of polyethylene (PE) and polyethylene terephthalate (PET) was successfully fabricated under shear and elongational flow fields. The PET phase formed in situ the aligned conductive microfibrils whose surfaces were coated by CB particles. This ACPC material exhibited a strong electrical anisotropy within a broad temperature range. When the ACPC samples were subjected to isothermal treatment (IT), they showed anomalous variations of the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects. The PTC intensity was attenuated gradually with the increase of the IT time, and the NTC intensity was nearly eliminated after IT of 8 or 16 h. Beyond 16 h, the resistivity in the NTC region rose anomalously with the temperature after the elimination of NTC effect, which was the result of much transformation from the potential pathways to the intrinsic pathways due to the disordering of oriented conductive microfibrils. When the amount of potential pathways was very small, the effect of the intrinsic pathway separation surmounts that of the potential pathways, leading to the anomalous resistivity increase in the NTC region. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012