聚合物基正温度系数材料的研究进展

从材料设计的角度系统总结了聚合物基正温度系数(PTC)材料的理论研究成果,分别介绍了基体材料、导电填料、填料的分散形态对PTC特性的影响和PTC材料性能稳定化的方法,并对PTC材料未来的发展趋势进行了展望。     

聚合物PTC材料的老化失效规律研究

聚合物PTC材料在很多领域都有广泛应用，但材料稳定性一直制约着各种产品的进一步发展，以聚乙烯－醋酸乙烯酯共聚物／炭墨体系为研究对象，采用熔融共混挤出成型的方法进行制样，研究了聚合物PTC材料老化失效规律及老化失效过程预测，提出了相应的经验公式。     

尼龙12/炭黑高转变温度PTC材料的研究

研究了以尼龙12(PA12)为基体树脂,炭黑(CB)为导电填料的高转变温度正温度系数(PTC)材料.采用熔融共混方法制备了尼龙12/炭黑聚合物PTC复合材料,考查了炭黑含量,热循环等因素对材料PTC性能的影响.并采用示差扫描量热分析(DSC)、热机械曲线分析(TMA)研究了材料PTC效应与材料结构的关系.实验结果表明尼龙12/炭黑复合材料具有高转变温度的PTC特性,将复合材料进行多次热循环实验,此复合材料仍具有较强的PTC效应.     

金属Ni/石墨/BaTiO3基复合PTC材料的研究

探讨了降低BaTiO3基的PTC陶瓷室温电阻率的新途径，即在BaTiO3基的VIE陶瓷配方中加入石墨或金属Ni。目的是将石墨或金属Ni优良的导电性和BaTiO3陶瓷的PTC效应相结合，制备出具有较低室温电阻率又有较好PTC效应的复合材料。通过对大量实验和数据分析。优化了实验配方和工艺条件．获得了性能良好的复合PTC材料。     

添加物、烧成温度对PTC特性的影响

讨论了加入Mn、CaTi03对PTC材料的常温电阻、α系数、耐电压、晶粒尺寸等的影响，得出了AST的引入可降低材料电阻率的结论。同时分析了烧成温度、升温速度、降温速度对PTC材料性能的影响。     

PTC BaTiO3陶瓷薄膜的制备工艺

本文重点研究了PTC BaTiO_3陶瓷薄膜的制备工艺过程,讨论了PTC薄膜材料的优越性,并对其发展远景进行了概述.     

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％。     

环氧树脂基导电复合材料的PTC特性研究进展

介绍了聚合物基正温度系数（PTC）材料的导电机理;综述了国内外对环氧树脂基PTC复合材料的研究现状;分析了影响环氧树脂基导电复合材料PTC特性的因素,包括导电填料、环氧基体、第三基体组分、固化剂和固化温度、加工工艺等;并对该材料的应用和发展方向进行了讨论。     

PTC热敏电阻的开发应用现状

介绍了正温度系数(PTC)效应,PTC材料的分类、发展历史及现状,分析其电阻温度、电压电流和电流时间三大特性,通过对PTC材料三大特性的研究概述了陶瓷基PTC热敏电阻作为恒温加热元件和自动开关元件,高分子基PTC热敏电阻作为自控温加热元件和过电流保护元件等领域的应用状况及产业化发展情况,展望了今后PTC材料及生产工艺的技术发展动向。     

加工工艺对高分子基PTC自限温电热丝性能的影响

研究了乙炔炭黑填充LDPE智能型电热丝的挤出加工工艺参数，及热处理与辐照交联等后加工手段对高分子基PTC自限温电热丝导电性能的影响。结果发现，电热丝挤出口模温度、螺杆转速(或牵引速度)、护套挤出方式及护套厚度、护套材料性能对PTC自限温电热丝性能有很大影响；热处理、辐照工艺与通电时间次序对智能PTC导电材料的电阻率亦有影响。     

Designs of conductive polymer composites with exceptional reproducibility of positive temperature coefficient effect: A review

Conductive polymer composites with positive temperature coefficient (PTC) effect have gained intensive attention for the potential application in the smart heating field. The PTC reproducibility is significantly essential to guarantee the security and utility of PTC composites. Regrettably, during the repeated temperature cycles, the irreversible self-aggregation of conductive filler and the random reconstruction of conductive network lead to unsatisfactory performance of PTC reproducibility. Extensive efforts have been conducted to address this issue by strategies, including modification of fillers, cross-linking of a polymer matrix, hybrids of fillers, and application of binary polymer matrix. Nevertheless, there are very limited reviews about this issue. In this review, the recent advances in fabricating PTC composites with the enhanced PTC reproducibility have been systematically summarized. Meanwhile, the current challenges and future prospects of PTC composite are also presented. We hope that this review will provide some inspirations for designing PTC materials of long-term performance for commercial applications.     

高抗冲聚苯乙烯/炭黑导电复合材料 PTC效应的研究

采用SEM、XRP、DSC和体积膨胀等手段对非结晶形HIPS／CB（聚苯乙烯／炭黑）导电复合材料的导电行为进行分析。实验结果表明，HIPS／CB导电复合材料的渗流区域较窄，炭黑含量为30～40g时，电阻发生急剧降低，在渗流阀值附近导电复合材料的电阻率变化最大，跃迁强度为2.2个数量级；HIPS／CB导电复合材料的PTC起始转变温度在85℃左右，与HIPS的玻璃化转变温度接近，HIPS作为非晶材料其体积膨胀较弱，并不足以单独解释PTC效益。     

PTC型炭黑/高聚物导电复合材料的研究

正温系数导电高分子材料在工业中得到了广泛的应用。本文综述了炭黑／高聚物导电复合材料ＰＴＣ效应的影响因素,探讨了ＰＴＣ效应稳定化的途径。     

Glass transition temperature as a guide to selection of polymers suitable for PTC materials

It has been shown that the only way to predict the size of the PTC effect displayed by a crystalline polymer when filled with conductive particles is through the knowledge of the glass transition point of the polymer. The size of the PTC anomaly is found to decrease sharply with rise in glass transition temperature and for a polymer to be a useful PTC material its glass transition must be below 0°C. It has not been possible to explain this relationship by any of the current theories of the PTC mechanism in filled polymers.     

Chemical modification of poly(2,6-dimethyl-1,4-phenylene oxide) via phase transfer catalysis

The chemical modification of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) has been performed under phase transfer catalyzed (PTC) conditions. Four types of reactions: Williamson etherification, cyanide displacement, esterification, and heterocyclic group transfer have been identified as positive reactions involving the nucleophilic displacement on PPO. In reaction with alcohols, under PTC conditions, functional yields as high as 100% were obtained while for the esterification reaction functional yields of 92% were reached. Low conversions were found in reactions with cyanides and heterocylic compounds. Possible interactions of the reactive sites leading to additional crosslinking are being suggested. Minor changes in thermal stability of substituted PPO compared with the parent polymer were recorded. The modification of their permeation properties to gases was attributed to changes in polymer chain mobility and packing as well as to changes in polymer side chain polarity.     

Electrical behavior of carbon black-filled polymer composites: Effect of interaction between filler and matrix

The effect of interaction between carbon black and polymer on electrical behavior was studied using the ESR method. The polymer matrices used were HDPE, LDPE, and ethylene/vinyl acetate (EVA). Two kinds of carbon blacks (CB), high structure CSF-III and low structure FEF, were used as a conductive filler. Compared to that of the HDPE/FEF compound, the positive temperature coefficient (PTC) intensity is lower and electrical reproducibility is worse for the HDPE/CSF-III compound; however, it can be improved significantly by radiation cross-linking. On the other hand, the cross-linking has no practical effect on the PTC intensity of the LDPE/CSF-III compound while it can be achieved by mixing the compound for a longer time. The great PTC intensity was obtained in the HDPE/EVA/CSF-III compound, and it is greater than that of HDPE/CSF-III or EVA/CSF-III. We explain these results using the concept of interaction between the filler and matrix. The absorption of the polymer on the carbon black surface may be physical or chemical; the latter is caused by the free-radical reaction between the polymer and carbon black, and it can occur during the radiation or preparation process of the compound. These “bound polymers” are essentially important for materials to have a great PTC intensity and good reproducibility. © 1994 John Wiley & Sons, Inc.     

Electrical properties of polymer composites prepared by sintering a mixture of carbon black and ultra-high molecular weight polyethylene powder

Conductive polymer composites were prepared by sintering a mixture of ultrahigh molecular weight polyethylene (UHMWPE) powder and carbon black. Two processing parameters—time and temperature—were shown to have a notable effect on the resistivity of the composites. The relationships between the processing parameters and morphology were studied using optical microscopy and transmission electron microscopy (TEM). The results of the optical microscopy studies indicate that the carbon black is distributed in the interfacial regions between the UHMWPE particles. The dimension of the carbon black channels increases with the carbon black concentration. TEM micrographs show that a high degree of intermixing between the carbon black and the polymer occurs at higher temperatures and longer processing times, resulting in higher resistivities. A positive temperature coefficient (PTC) effect was observed for these materials. A mechanism for the PTC effect in this system is proposed. The magnitude of the PTC effect is found to be inversely proportional to the dimension of the carbon black channels in the composites. The dimension is directly related to the carbon black concentration. The PTC effect is a result of the polymer volume expansion caused by melting of the crystallites. A large PTC effect is observed for the composites with a low carbon black concentration and vice versa. No negative temperature effect (NTC) is observed at temperatures substantially above the melting point of the polymer.     

接枝聚忆烯改性高分子复合PTC材料性能的研究

利用化学接枝法地线性低密度聚乙烯（LLDPE）进行接枝改性,研究发现适量接枝物的加入,明显改善了材料的PTC性能,使PTC强度提高了一个数量级,而TC性能基本不变,通过对比研究发现乙烯－醋酸乙烯酯共聚物（EVA）对高分子LLDPE－CB体系的PTC强度也有一定的改善作用,但不如接枝物。极性化学接枝物更有利于炭黑在LLDPE中均匀分散,使高分子复合PTC材料具有更好的稳定性。     

可控自发热高分子材料的研究进展

可控自发热高分子材料是利用炭黑填充结晶高分子材料的PTC特性,制成的具有自动控温性能的功能高分子材料。本文综述了该领域国内外研究状况和发展趋势,认为我国应加强此类功能化高分子材料的研究和开发。