二硼化钛导电型PTC复合功能材料的制备及性能研究

发布时间：2018-06-24 17:29

  本文选题：TiB_2 + 成分设计　； 参考：《合肥工业大学》2015年硕士论文

【摘要】：聚合物基PTC复合材料是当今国内外研究最为热门的功能高分子材料之一,目前已广泛应用于自控温加热系统、过流保护元件等领域。对于该类PTC材料的广泛应用,除了应具有优异的PTC特性外,还需解决PTC特性的不稳定和高温NTC效应等缺陷。本文采用熔融共混法制备具有明显PTC效应的PE/TiB2-CB复合材料。对复合体系进行SEM形貌观察、升温电阻特性测试、多次热循环电学稳定性测试、热分析等,研究组织成分、制备工艺等对复合材料PTC特性的影响,并对其PTC机理进行初步探索。实验结果表明：TiB2颗粒与聚乙烯基体之间无化学键连接,所以两者之间有明显的界面层存在。选择以7：3的HDPE、LDPE配比作为基体,加入24%TiB2和6%CB作为导电填料,且在其混合过程中经多次搅拌、研磨和干燥处理。在压力6MPa,温度为160℃下压制后于空气中冷却制得的复合材料结晶度为48.4%,室温电阻率为0.65Ω·m, PTC强度高达5.1；影响试样PTC特性的各因素的主次关系是：热压成型后冷却方式热压温度热压压力。随着热压压力和温度的升高,复合材料PTC特性呈现先上升再下将趋势；合适的热压温度和成型后冷却方式可以提升复合材料的结晶度,且结晶度越高,PTC效应越明显；120℃退火处理后复合材料峰值电阻率和PTC转变温度(Ts)都有所提高,lo σ-T曲线也变得更为陡峭,红外光谱分析显示体系结晶结构也没有被破坏；与未交联试样较差阻-温稳定性相比,交联试样多次热循环的稳定性较好,且高温时NTC效应不明显。复合材料的熔融温度范围和熔融峰温度仅仅依赖于HDPE、LDPE基体的特性。导电填料在聚乙烯基体中是主要分布在基体结晶区与无定形区的界面处以及无定形区中,只有少量填料因热工艺等因素而滞留在基体结晶区。复合材料的PTC效应的产生主要是由聚合物结晶区受热膨胀、熔融破坏导电网络所致,且基体结晶区熔融对复合材料PTC特性的贡献要高于结晶区热膨胀。
[Abstract]:Polymer-based PTC composite is one of the most popular functional polymer materials at home and abroad, and has been widely used in the field of self-controlled heating system, over-current protection elements and so on. For the wide application of this kind of PTC materials, it is necessary to solve the instability of PTC properties and the high temperature NTC effect in addition to the excellent PTC properties. In this paper, PE- / TiB2-CB composites with obvious PTC effect were prepared by melt blending method. The effects of microstructure and preparation technology on the PTC properties of composites were studied by SEM observation, temperature resistance test, multiple thermal cycle electrical stability test, thermal analysis and so on, and the PTC mechanism of the composites was preliminarily explored. The experimental results show that there is no chemical bond connection between TIB _ 2 particles and PE matrix, so there is an obvious interfacial layer between them. In this paper, 7:3 HDPE LDPE was used as matrix, and 24TiB2 and 6 were added as conductive fillers. During the mixing process, they were stirred, ground and dried many times. The crystallinity of the composite is 48.4%, the resistivity is 0.65 惟 m at room temperature, and the PTC strength is as high as 5.1, at 6MPa pressure, 160 鈩，

本文编号：2062378