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。     

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。     

炭黑/聚烯烃导电复合材料PTC效应的研究

对炭黑/聚烯烃导电复合材料PTC效应做了较全面的论述,介绍了此类材料的导电机理和一些新的理论观点,总结了影响其PTC效应的主要因素及目前国内外研究这种新型功能材料的典型方法。文中详细讨论了工艺条件、基体与导电填料的性质、频率等方面对材料性能、PTC效应的影响,对研究、开发和应用高性能的PTC复合材料有重要的参考价值。     

炭黑/二氧化硅/环氧树脂基复合材料的PTC效应

在25～200℃范围内,炭黑/二氧化硅/环氧树脂基复合材料的电阻率随温度的升高而增加,表现出正的温度系数效应(PTC).当温度低于800c,低碳含量复合材料(14%和19%,基于聚合物的质量)的温度稳定性较好,这是因为炭黑用量的减少,将有利于环氧树脂与异佛尔酮二异氰酸酯之间亲核加成反应的发生,材料中形成了更多的交联链.在一定程度上限制了聚合物骨架的运动性,降低了其对炭黑形成的导电通路网的破坏作用.当温度高于160℃,高碳含量复合材料(24%和33%,基于聚合物的质量)的温度稳定性好,这是因为高温条件促进了热激发的电子越迁过程,在一定程度上抵消由于组分热膨胀性差异而引起的对导电通路的破坏作用;而热激发的电子越迁过程对炭黑颗粒间距小的高碳复合材料的影响更为显著.扫描电镜、红外光谱和差示扫描热量法分析结果支持上述结论.     

聚乙烯/炭黑导电复合材料PTC特性的研究(Ⅱ)--辐射交联对导电复合材料PTC性能的影响

采用^60Coγ-射线对HDPE／CB导电复合材料进行辐射处理，研究了辐射剂量对于该复合材料室温电导率、PTC性能及稳定性的影响。结果发现，在50-300kGy范围内，随着辐射剂量的增加，复合材料的PTC强度增大，且复合材料的稳定性有所提高，NTC效应有所降低；同时，辐射交联对体系的室温电阻率影响不大。DSC测试表明，当辐射剂量为150kGy时，辐射处理对于HDPE的熔点、结晶度影响不大。     

炭黑／HDPE复合导电材料的PTC／NTC效应

首次引入时温等效原理和松弛理论，在恒温条件下研究了材料电阻率与时间的关系，在此实验结果的基础上，对PTC／NTC的形成过程及机理提出了新的观点，使之更能全面地解释实验中的各种现象。     

PVDF/炭黑导电复合材料的PTC性能研究

研究炭黑种类和用量及ＰＶＤＦ种类对ＰＶＤＦ／炭黑导电复合材料ＰＴＣ特性的影响。结果表明,大粒径、比表面积小的Ｎ７６５炭黑填充导电复合材料的ＰＴＣ性能较好,出现ＰＴＣ现象的炭黑用量范围大;随着ＰＶＤＦ分子量的增大,ＰＶＤＦ／Ｎ７６５炭黑导电复合材料出现最大ＰＴＣ强度的炭黑用量减少,最大ＰＴＣ强度也随之增大。     

共混高聚物－炭黑复合材料的导电特性

本文讨论了共温高聚物－ＣＢ复合材料比之单一高聚物－ＣＢ复合材料的不同的导电特性及其作用机制。     

聚烯烃/炭黑导电复合材料研究

研究了聚烯烃种类、聚烯烃共混物、炭黑种类及用量和加工方法对聚烯烃／炭黑导电复合材料电学和力学性能的影响     

炭黑填充聚合物基PTC材料的研究进展

对炭黑填充聚合物基PTC材料进行了较为全面的论述，介绍了此类材料的导电机理，总结了影响其PTC效应的主要因素，并对该材料的应用和发展方向进行了详细的讨论。     

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     

具有PTC效应的聚合物基复合材料发展概况

本文对具有PTC效应的聚合物基复合材料的导电机理进行概述,并对该类材料的发展概况及研究展望作详细论述。     

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     

Characterization and preparation of new multiwall carbon nanotube/conducting polymer composites by in situ polymerization

Composites based on poly(diphenyl amine) (PDPA) and multiwall carbon nanotubes (MWNTs) were prepared by chemical oxidative polymerization through two different approaches: in situ polymerization and intimate mixing. In in situ polymerization, DPA was polymerized in the presence of dispersed MWNTs in sulfuric acid medium for different molar composition ratios of MWNT and DPA. Intimate mixing of synthesized PDPA with MWNT was also used for the preparation of PDPA/MWNT composites. Transmission electron microscopy revealed that the diameter of the tubular structure for the composite was 10–20 nm higher than the diameter of pure MWNT. Scanning electron microscopy provided evidence for the differences in the morphology between the MWNTs and the composites. Raman and Fourier transform IR (FTIR) spectroscopy, thermogravimetric analysis, X‐ray diffraction, and UV–visible spectroscopy were used to characterize the composites and reveal the differences in the molecular level interactions between the components in the composites. The Raman and FTIR spectral results revealed doping‐type molecular interactions and coordinate covalent‐type interactions between MWNT and PDPA in the composite prepared by in situ polymerization and intimate mixing, respectively. The backbone structure of PDPA in the composite decomposed at a higher temperature (>340°C) than the pristine PDPA (～300°C). This behavior also favored the molecular level interactions between MWNT and PDPA in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3721–3729, 2006     

Ni-C复合镀层在高分子PTC热敏电阻器上的应用

给出了Ni-C复合镀层生产工艺流程及工艺规范。介绍了提高铜箔粗化度及加强碳黑分散的工艺措施。讨论了电流密度、pH、温度及搅拌等操作对镀层及Ni-C共沉积的影响。总结了镀液维护及注意事项。实验结果表明,该Ni—C复合镀层制作的电极片质量全部达到PTC热敏电阻器性能要求。     

炭黑/环氧树脂复合材料的电性能研究进展

介绍了炭黑/环氧树脂(EP)复合材料的制备工艺,讨论了炭黑/EP复合材料导电性能的影响因素,评述了炭黑/EP复合材料电阻正温度系数效应的机理解释和研究进展,展望了这一类材料的研究重点和发展前景。     

Polyurethane/conducting carbon black composites: Structure,electric conductivity,strain recovery behavior,and their relationships

The polyurethane composites with conducting carbon black (CB) were prepared by a solution‐precipitation process, which was followed by melt compression molding. The polyurethane used has good shape memory effect. The morphology of CB fillers in polyurethane matrix and the resulting conductivity of the composites were investigated. It has been found that CB fillers exist in the forms of aggregates. The percolation threshold is achieved at the CB concentration of 20 wt %. The presence of CB fillers decreases the degree of crystallinity of polycaprolactone (PCL) soft segments of the polyurethane. However, the composites still have enough soft‐segment crystals of polyurethane to fulfil the necessary condition for the shape memory properties. Dynamic mechanical data show that CB is an effective filler for the reinforcement of the polyurethane matrix, but does not deteriorate the stable physical cross‐link structure of the polyurethane, which is necessary to store the elastic energy in the service process of the shape memory materials. Addition of CB reinforcement in the polyurethane has influenced the strain recovery properties, especially for those samples with CB concentrations above the percolation threshold. The response temperature of the shape memory effect T_r has not been affected too much. Strain fixation S_f, which expresses the ability of the specimens to fix their strain, has been improved in the presence of the CB fillers. The final recovery rates R_f and strain recovery speeds V_r of the shape memory measurements, however, have decreased evidently. It is expectedly ascribed to the increased bulk viscosity as well as the impeding effect of the inter‐connective structure of CB fillers in the polymer matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 68–77, 2000     

Ionic interactions in polyacrylonitrile/polypyrrole conducting polymer composite

A conducting polymer composite was prepared by the postpolymerization of pyrrole in a polyacrylonitrile (PAN) matrix film. To enhance the electrostatic interaction between the two phases, a small amount of a sulfonate or a carboxylate (COO⁻) group was incorporated into the PAN structure. The presence of electrostatic interaction between the conducting polypyrrole and the anion-containing PAN copolymer was elucidated by examination of the morphology and the electrical properties of the composite. The aromatic sulfonate-containing matrix provided the composite with the best results in the electrical conductivity, the environmental stability of conductivity, and the morphological property. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2641–2648, 1998