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.     

PE-UHMW/GNPs导电复合材料的制备和表征

采用超声溶液分散法制备出超高分子量聚乙烯/石墨烯(PE-UHMW/GNPs)导电复合材料,研究了该材料的导电渗流行为和阻-温特性。研究发现,PE-UHMW/GNPs导电复合材料的导电渗流阈值为3.8%,即当导电填料在体系中的质量分数达到3.8%时,材料内部逐渐形成较为完善的导电网络,从而实现其导电特性。研究和探讨了PE-UHMW/GNPs导电复合材料的正温度系数(PTC)效应和负温度系数(NTC)效应。研究发现,PE-UHMW/GNPs导电复合材料的PTC效应会随着GNPs含量的增加逐渐增强,当导电填料GNPs的添加量达到3.8%时,通过阻-温曲线可以观察到,PE-UHMW/GNPs导电复合材料具有最大的PTC强度和相对较低的室温体积电阻率。场发射扫描电子显微镜分析结果表明,GNPs和PE-UHMW之间的相互作用会随着热循环次数的不同而发生变化,最终会影响到材料的PTC效应。     

复合填料/PP复合材料正负温度系数效应的研究

采用熔融共混方法首先得到交联型炭黑／PE导电材料，将其碾磨粉碎和过筛得到新型的复合导电填料，再和PP经过熔融共混得到一种新的导电复合材料。由于HDPE和PP结晶相在各自的熔点的熔融行为，使复合材料发生热体积膨胀，从而使材料产生了双正温度系数(PTC)效应。同时，负温度系数效应(NTC)基本消除。复合导电材料扫描电镜(SEM)的形态结构进一步证实了这种结论。     

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.     

OMMT对PE–HD/CB导电复合材料电性能的影响

以炭黑(CB)为导电填料,高密度聚乙烯(PE–HD)为基体,有机蒙脱土(OMMT)为有机粒子,通过熔融共混法分别制备了PE–HD/CB与PE–HD/CB/OMMT导电复合材料,并研究了OMMT的加入对导电复合材料中CB分布的均一性及材料电性能的影响。研究发现,适当OMMT的加入可以改善CB在导电复合材料中的分布状态,在保持电性能的基础上降低导电复合材料的渗流阈值;当OMMT质量分数为3%时,PE–HD/CB/OMMT导电复合材料的渗流阈值为3.7%,与未添加OMMT的PE–HD/CB导电复合材料渗流阈值4.0%相比有所降低。在此基础上,选取PE–HD/CB导电复合材料(CB质量分数为5%)并测定其PTC强度为0.26;后加入质量分数为3%的OMMT,测得PE–HD/CB/OMMT导电复合材料(CB质量分数为5%)的PTC强度为0.79,后者有所提高。     

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。     

EP/GNSs复合材料的电性能研究

以KNG–180石墨烯微片(GNSs)为导电填料,双酚A型环氧树脂(EP)E–54为基体,并分别用2-乙基-4-甲基咪唑(2,4-EMI)和甲基四氢邻苯二甲酸酐(Me THPA)为固化剂,采用超声分散法制备了EP/GNSs导电复合材料。研究了不同固化剂及GNSs含量对EP/GNSs复合材料电性能的影响。结果表明,两种固化剂固化的复合材料均具有明显的导电逾渗行为和正温度系数(PTC)效应;2,4-EMI固化的复合材料的逾渗阈值为5.1%,Me THPA固化的为4.5%;Me THPA固化的复合材料具有更强的PTC效应和更低的室温电阻率,但大量实验发现Me THPA固化的复合材料电性能实验结果重复性相对较差,且易存在负温度系数效应,故仍采用2,4-EMI作为EP/GNSs导电复合材料的固化剂。随GNSs含量增加,2,4–EMI固化的复合材料室温电阻率逐渐降低,PTC强度先升高后降低,当GNSs质量分数达到8%时,复合材料的PTC强度最高,达到2.3,且经过3次热循环之后,其阻–温曲线的热循环稳定性变好。     

石墨/聚乙烯导电复合材料PTC效应稳定性的研究

研究了制备方法、硅烷交联、热处理对石墨/聚乙烯复合材料的热循环稳定性的影响,讨论了改善正温度系数(PTC)导电高分子材料稳定性的原因.研究发现,用溶液混合法制备的复合材料具有良好的热循环稳定性;用硅烷偶联剂交联得到的复合材料,负温度系数(NTC)效应得到了有效抑制;热处理也可以有效改善材料的PTC效应的稳定性,经过热处理,材料的室温电阻率、PTC强度变化比较小.     

石墨烯改性PVDF复合材料的结构和性能

为了实现PVDF力学性能、导电性、热稳定性的综合改性,以氧化石墨烯(GO)为填料,通过超声分散和原位还原法制备了不同配比的GNS(石墨烯)/PVDF复合材料。分别采用扫描电镜(SEM)、导电性能测试、拉伸性能测试、差示扫描量热分析(DSC)、热失重分析(TGA)等方法系统研究了GNS含量对GNS/PVDF的导电性能、力学性能和热稳定性能的影响。结果表明,GNS的质量含量为1%时,还原后的石墨烯单片层均匀分散于PVDF中。导电性能测试表明,随着GNS填料的加入,复合材料中逐步形成局部导电网络,当GNS的含量为2%时,导电率达到8.2×10~(-5)S·m~(-1),与纯PVDF相比,大约提高了13个数量级。但当GNS含量过高时易在基体中发生团聚,不利于导电网络的形成。GNS的加入,使得复合材料界面结合力增强,提升了力学强度。当GNS的质量分数为2%时,复合材料的拉伸强度可达38.23MPa,较纯PVDF提高了23%。DSC测试显示,PVDF/GN2的T_m为172.6℃,比纯PVDF升高了5.2℃,说明GNS可以促使PVDF结晶。TGA测试则表明,GNS会改善PVDF的热稳定性,且随着GNS含量的增加逐渐提高。     

炭黑/环氧树脂复合材料阻温特性研究

分别以低结构炭黑(F101)和高结构导电炭黑(XE2)作为导电填料,不同牌号(E-54,E-51和E-44)的环氧树脂(EP)作为基体树脂,采用超声分散溶液混合法制备了炭黑/环氧树脂(CB/EP)复合材料.研究了CB结构、CB含量和EP基体等对复合材料正温度因数(PTC)效应的影响.结果表明:F101/EP复合材料具有...     

Temperature‐conductivity characteristics of the composites consisting of fractionated poly(3‐hexylthiophene) and conducting particles

Poly (3‐hexylthiophene) (P3HT) synthesized by oxidative polymerization was fractionated by molecular weight by using organic solvents. The fraction of higher average molecular weight gave higher regioregularity and conductivity. Composites of the P3HT fraction having the highest molecular weight were prepared by use of the following conducting particles as fillers: titanium carbide (TiC), indium tin oxide (ITO), and carbon black (CB). Temperature‐conductivity profiles of the composites showed that the resistance change with PTC (positive temperature coefficient) effect was strongly influenced by the content and size of conducting particles and the molecular weight of P3HT. Although no significant PTC effect for P3HT‐CB composite and little effect for P3HT‐ITO composite system were observed, the P3HT‐TiC composite containing TiC of 70–80 wt % showed an obvious PTC effect that brought the conductivity change by about four orders of magnitude near the glass transition temperature of P3HT. However, such a remarkable PTC effect was not observed for the P3HT‐TiC composite prepared with the P3HT fraction of low‐molecular weight. It was shown that a good PTC effect could be achieved by the composite consisting of the P3HT of high‐molecular weight and the conducting particles of relatively large size. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3069–3076, 2000     

All polymer PTC devices: Temperature‐conductivity characteristics of polyisothianaphthene and poly(3‐hexylthiophene) blends

The present article is concerned with the temperature‐conductivity characteristics of blends consisting of polyisothianaphthene (PITN) particles and a soluble poly(3‐hexylthiophene) (P3HT). PITN was synthesized by direct conversion of 1,3‐dihydroisothianaphthene (DHITN) monomer using N‐chlorosuccinimide (NCS) as an oxidation/dehydrogenation reagent. The high conductivity and thermal stability of the doped and dedoped PITN were confirmed. Microscopic investigation by scanning electron microscopy (SEM) showed that the as‐prepared PITN exhibited diversified shapes and sizes, with large rectangular particles having an average size of 2 ～ 5μm and fine round particles ranging from 0.1 to 0.3 μm. The PITN particles were blended with the chemically synthesized P3HT as a high conductivity component to improve the conductivity and simultaneously maintain the positive temperature coefficient (PTC) effect of the original P3HT near its melting point. The temperature‐conductivity characteristics for PITN‐P3HT blends with various PITN contents showed that a blend having both a high conductivity (nearly 3 ～ 4 orders higher than that of the original P3HT) and a good PTC intensity could be obtained with a PITN content of 20 ～ 25%. The different temperature‐conductivity behavior of P3HT blends filled with PITN as compared to other conducting particles, for example, carbon black, was explained by its unique dispersion structure due to a relatively higher adhesive interaction of PITN particles with the P3HT matrix during the precipitation process. The results from heating recycles revealed that the PTC effect of PITN‐P3HT blends was not just related to the conductivity decrease of the P3HT matrix, arising from the conformational change of the conjugated backbone during the melting, but also to the dilution effect of the conducting percolation network due to the mobility of PITN particles induced by the viscosity decrease of the P3HT matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1848–1854, 2005     

金属－PTC陶瓷复合材料研究

研究低Ｔ＿ｃＰＴＣＲ复合材料的制备工艺，测试所制成样品的阻温特性。通过样品Ｘ射线定性相分析，探讨该复合材料所表现的ＮＴＣ阻温特性机理。     

华光导电炭黑填充胶料的负温度系数（NTC）效应

研究以华光导电炭黑填充天然橡胶和氯丁橡胶胶料的电阻率随温度变化的规律,试验结果表明：两种炭黑填充的胶料均具有ＮＴＣ效应;以华光ＨＧ－Ⅱ导电炭黑最为明显,且当用量小于２０Ｐｈｒ时,胶料的电阻率对温度较敏感。     

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％。     

多施主掺杂PTC陶瓷材料的研究

本文在双施主掺杂高ＴｃＢａＴｉＯ_３基ＰＴＣ陶瓷材料的基础上,对ＢａＴｉＯ_３的Ａ、Ｂ、Ｏ位同时进行离子置换以实现多施主掺杂,同时还研究了烧结温度对阻温特性的影响。研究结果表明,多施主掺杂试样的烧成温度对ｐ－Ｔ性能影响很大,在一定配方及工艺条件下,获得的ＰＴＣ陶瓷材料的室温电阻率变化不大,升阻比明显提高。     

Pyroresistivity in conductive polymer composites: a perspective on recent advances and new applications

Conductive polymer composites (CPCs) with pyroresistive behaviour are of interest for a wide variety of applications such as safe batteries, resettable fuses, temperature sensors and self‐regulating heating devices. Due to their ease of processing, low density, tunable electrical properties, good oxidation resistance, and good flexibility and toughness, CPCs have become the preferred choice of pyroresistive materials in a number of applications. The pyroresistive behaviour of CPCs can be tuned to satisfy the specific requirements of different applications. In this perspective paper, recent progress in the use of pyroresistive CPCs is reviewed. In particular, various factors influencing their performance are discussed and compared, in connection with the associated application, with a special focus on reproducibility and positive temperature coefficient intensity levels. Some of the remaining challenges are identified, together with future prospects in this evolving field. © 2018 Society of Chemical Industry     

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。     

Preparation of positive‐temperature coefficient heaters using platinum‐catalyzed silicone rubber

Various output heaters were extruded with acetylene black–filled platinum‐catalyzed silicone rubber. The resistivity–temperature behavior of extruded heaters exhibited a positive‐temperature coefficient (PTC) effect without any negative‐temperature coefficient (NTC) effect. Resistivity and thermal reproducibility of the extruded heaters were investigated during heating and cooling cycles at an applied voltage of 220 V. These heaters initially showed poor reproducibility of resistivity during the repeated cycles and this effect increased significantly as the acetylene black content decreased. PTC effect and electrical reproducibility were improved significantly during the thermal ageing process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1611–1617, 2004