EVA对HDPE/EVA/CB导电复合材料性能的影响

分别研究了HDPE/CB、EVA/CB两种复合材料的导电性能,并研究了不同含量EVA对HDPE/EVA/CB复合材料性能的影响,包括体系结晶度的变化和微观形态。根据TEM图片发现,CB在HDPE/EVA/CB复合材料中主要存在于HDPE相中,EVA的加入增加了复合材料的室温电阻率,同时,提高了材料的熔体指数。当EVA含量在37.5%～50.0%之间时,可以得到较理想的加工性与导电性能的平衡点。     

PS-HI／EVA／CB复合材料导电性能的研究及结构分析

采用XRD、DSC、SEM等研究了低熔点、半结晶聚合物EVA对非晶聚合物高抗冲聚苯乙烯／炭黑(PS-HI／ CB)复合材料的结构、导电性和正温度系数(PTC)效应的影响,结果表明,EVA,可提高复合材料的PTC强度,当PS- HI/EVA/CB=70:30:30时复合材料的PTC强度由不加EVA的2．2提高到5．1;复合材料的PTC转变温度与EVA 的熔点接近,因此,通过添加不同熔点的聚合物可实现控制复合材料的PTC转变温度的目的;SEM照片显示,随着 EVA含量的增加,两相结构发生变化,PS-HI由连续相转为椭圆形分散相,EVA由共连续结构转为网络状结构,直至网络状结构消失,而这种两相结构变化与复合材料的电阻率变化一致。     

高分子PTC导电复合材料加工流变行为研究

以高分子PTC（正温度系数）导电材料LLDPE／CB、HDPE／CB、PVDF／CB为研究体系,考察了剪切速率、加工温度对复合材料加工流变行为的影响,并分析了3种体系的粘流活化等流变数据,得到了适于3种材料生产的加工条件。     

正温度系数导电复合物加工流变行为

以高分子PTC（正温度系数）导电材料LLDPE／CB，HDPE／CB，PVDF／CB为研究体系，考察了剪切速率，加工温度对复合材料加工流变行为的影响，并分析了3种体系的粘流活化能等流变数据，得到了适于3种材料生产的加工条件。     

CB／HDPE复合材料导电性能及导电行为研究

通过熔融共混的方法制备了CB／氯化聚乙烯（CPE）／HDPE复合材料和复合热稳定剂（15％抗氧剂1010,35％抗氧剂DLTP,50％硬脂酸钙）／CB／HDPE复合材料。通过导电性能测试研究TCPE和合热稳定剂对复合材料的导电性能和PTC导电行为的影响。DSC测试研究了复合材料热性能及其对复合材料的导电行为的影响。结果表明,随着CPE用量的增加,复合材料的导电性能提高;复合热稳定剂提高了复合材料的热稳定性,提高热老化后复合材料的PTC强度,可达4个数量级。     

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。     

聚偏氟乙烯在智能PTC自控温加热电缆研究中的应用

研究了以聚偏氟乙烯（PVDF）为基体,以油炉法炭黑（炉法CB）为导电载流子制备的PTC（positivetemperaturecoefficient）导电材料的逾渗行为、PTC阻温特性。并讨论了采用PVDF／CB导电复合材料制备的智能PTC自控温加热电缆的电致发热行为、功率行为、伏安情性及通断电稳定性,得到了自控温度130－140℃级防冻保温用新型电加热电缆。     

LLDPE/EVA/CB复合体系的导电和发热性能

对LLDPE/EVA(乙烯醋酸乙烯酯共聚物)/CB(碳黑)三元复合材料的导电性能及发热特性进行了研究。讨论了碳黑种类及含量对复合导电材料性能的影响,探讨了复合材料的伏-安特性、功率-温度特性以及辐照交联工艺对复合材料稳定性的影响。结果表明,添加乙炔碳黑,可使复合材料具有最佳的导电性及PTC(正电阻温度系数)特性,辐照交联使材料具有良好的电阻稳定性,由此制得的电缆经过一年的通电试验,其工作温度稳定在70℃±5℃,具有良好的限温作用。     

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。     

LLDPE／炭黑导电复合材料电阻稳定性研究

提出了一种改善有机PTC（Positive Temperature Coeffcient,即正温度系数）导电材料电性能重复稳定性的新途径，即在发热体材料LLDPE／CB中引入一种与炭黑粒子表面有亲和性的极性接枝物作为第3组份，使其在界面形成一种所谓“束缚组成物”或“相互贯入型树脂组成物”，使炭黑粒子在基体LLDPE中分散稳定，结果表明，该法可以消除NTC效应，提高电阻稳定性及PTC强度，从基体与导电粒子表面相互作用的观点对结果作出解释。     

热处理对PVDF复合体系形态及性能的影响

利用ＤＳＣ、ＷＡＸＤ和ＳＥＭ等测试手段，研究了不同热处理条件下聚偏二氯乙烯合金／炭黑导电复合体系的结晶形态及正温度系数效应特性。结果表明，热处理可以改善基体结晶行为。使结晶度提高，从而使导电复合体系的室温电阻率下降、ＰＴＣ强度提高、ＰＴＣ曲线的重复稳定性变好。     

低熔点有机晶体对HIPS/CB复合材料导电性能的影响及分析

探讨低熔点有机晶体对高抗冲聚苯乙烯（HIPS）／炭黑（CB）复合材料室温电阻率及温度-电阻率曲线的影响，并采用SEM、XRP、DSC等测试手段对含有低熔点有机晶体的HIPS／CB复合材料的结构进行分析。实验结果表明，加入有机晶体后，HIPS／CB复合材料的室温电阻率明显降低，同时随晶体含量的变化呈不同强度的正温度系数PTC（Positive Temperature Coefficient）效应，且强度明显要高于未填充有机晶体的HIPS／CB材料，含有有机晶体的复合材料FFC转变温度在晶体熔点附近，可设想通过添加不同熔点的有机晶体达到控制复合材料FFC转变温度的目的。     

CPE在PE／EVA／CB型PTC材料体系中的作用

本文以聚乙烯／乙烯－醋酸乙烯酯共聚物／炭黑（PE／EVA／CB）体系为研究对象，采用熔融共混挤出成型制样的方法，探讨了氯化聚乙烯（CPE）在体系中的稳定作用，结果表明，在体系中加入CPE可以起到相容剂的作用，能大大改善炭黑在聚合物中的分散，提高材料体系中各相间的结构稳定性，降低材料体系的电阻率，使炭黑和聚合物间的复合更为均一，从而可以在一定程度上提高材料的导电性及稳定性。并在体系中加入2．5％（质量百分比）的CPE时即可收到明显效果。     

Electrical properties and morphology of carbon black‐filled HDPE/EVA composites

The sensitive effect of weight ratio of the high‐density polyethylene (HDPE)/ethylene‐vinylacetate copolymer (EVA) on the electrical properties of HDPE/EVA/carbon black (CB) composites was investigated. With the EVA content increasing from 0 wt % to 100 wt %, an obvious change of positive temperature coefficient (PTC) curve was observed, and a U‐shaped insulator‐conductor‐insulator transition in HDPE/EVA/CB composites with a CB concentration nearby the percolation threshold was found. The selective location of CB particles in HDPE/EVA blend was analyzed by means of theoretical method and scanning electron micrograph (SEM) in order to explain the U‐shaped insulator‐conductor‐insulator transition, a phenomenon different from double percolation in this composite. The first significant change of the resistivity, an insulator‐conductor transition, occurred when the conductive networks diffused into the whole matrix due to the forming of the conductive networks and the continuous EVA phase. The second time significant change of the resistivity, a conductor‐insulator transition, appeared when the amorphous phase is too large for CB particles to form the conductive networks throughout the whole matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Positive temperature coefficient effect and mechanism of compatible LLDPE/HDPE composites doping conductive graphite powders

Linear low density polyethylene (LLDPE)/high density polyethylene (HDPE) blends doped conductive graphite powders were constructed by the traditional melt‐blending method to acquire the conductive compatible polymer composites, and corresponding positive temperature coefficient (PTC) effect of electrical resistivity was investigated. The results indicated that the room‐temperature resistivity gradually decreased and PTC effects were remarkably enhanced by regulating the graphite contents or LLDPE/HDPE ratios. Especially, with increasing graphite contents, the polymer‐fixed composites showed the notable double PTC effects, originating from the volume expansion of the co‐crystallization or their fraction. Whereas, with increasing the LLDPE/HDPE ratio, the PTC effects of the graphite‐fixed composites occurred at the lower temperature, even far below the melting points of the co‐crystallization. Therefore, the regulation of co‐crystallization morphology of compatible polymer matrices was a new idea in the improvement of PTC materials. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46453.     

Nylon 6 induced morphological developments and electrical conductivity improvements of polypropylene/carbon black composites

In this study, a polar conductive filler [carbon black (CB)], a nonpolar polymer [polypropylene (PP)], and a polar polymer [nylon 6 (PA6)] were chosen to fabricate electrically conductive polymer composites by melt blending and compression molding. The morphological developments of these composites were studied. Scanning electron microscopy results showed that in a CB‐filled PP/PA6 (CPA) composite, CB particles were selectively dispersed in PA6 phases and could make the dispersed particles exist as microfiber particles, which could greatly improve the electrical conductivity. The PA6 and CB contents both could affect the morphologies of these composites. The results of electrical resistivity measurements of these composites proved the formation of conductive networks. The resistivity–temperature behaviors of these composites were also studied. For CB‐filled PP (CP) composites, there were apparent positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects and an unrepeatable resistivity–temperature characteristic. However, for CPA composites, there were no PTC or NTC effects from room temperature to 180°C, and the resistivity–temperature behavior showed a repeatable characteristic; this proved that CB particles were selectively dispersed in the PA6 phase from another point of view. All experimental results indicated that the addition of PA6 to a CP composite could lead to an expected morphological structure and improve the electrical conductivity of the CP composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

CTBN对CB/EP基导电复合材料电性能的影响

以低结构CB(炭黑)为导电填料、EP(环氧树脂)为基体、CTBN(端羧基液体丁腈橡胶)为改性剂和2,4-EMI(2-乙基-4-甲基咪唑)为固化剂,采用超声分散法制备CB/EP基导电复合材料.研究结果表明:CB/EP基导电复合材料具有明显的导电渗流行为,其渗流阈值为w(CB)=7.1％;当w(CTBN)=12％时,含CT...     

Morphology,resistivity, and thermal behavior of EVOH/carbon black and EVOH/graphite composites prepared by simple saponification method

Poly(ethylene‐co‐vinyl alcohol) (EVOH)/carbon black (CB) and EVOH/graphite (GP) electro‐conductive composites were prepared by saponification of poly(ethylene‐co‐vinyl acetate) (EVA)/CB and EVA/GP composites in ethanol/KOH solution. The electrical resistivity change and positive temperature coefficient (PTC) behavior of these composites were investigated. The volume resistivity of EVA/CB and EVA/GP composites was decreased with saponification time. It can be observed that EVA/CB10 and EVA/GP05 composites showed a significant reduction in resistivity after saponification for 1 h. With the increase in saponification time, PTC peak temperature of both composites was shifted at a higher temperature. Tensile properties, morphology, and thermal behavior of the prepared composites have been also evaluated using universal test machine, scanning electron microscopy, and differential scanning calorimetry, respectively. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Performance stabilization of conductive polymer composites

Conductive polymer composites used as candidates for positive temperature coefficient (PTC) materials are faced with performance decay characterized by gradually increased room‐temperature resistivity and decreased PTC intensity. Considering that deterioration of the properties is mainly related to the capability of conductive networks established by conductive fillers to recover from the effect of repeated expansion/contraction in a timely manner, the present work introduces chemical bonding into the filler/matrix interphase. The experimental results indicate that in the composites consisting of conductive carbon black (CB), low‐density polyethylene (LDPE), and ethylene–vinyl acetate copolymer, CB particles can be covalently connected with LDPE through melt grafting of acrylic acid. As a result, the composites are provided with reduced room‐temperature resistivity and significantly increased PTC intensity. Compared with the composites filled with untreated CB, the present composites possess reproducible PTC behavior and demonstrate stable electrothermal output in association with negligible contact resistance at the composites/metallic electrodes contacts. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2438–2445, 2003