联苯型聚酰亚胺复合管膜的制备及其电性能研究

Preparation and Electrical Properties Investigation of Biphenyl-PI Composite Tubular Film

通过原位缩聚,采用3,3′,4,4′-联苯四羧酸二酐(BPDA)和4,4′-二氨基二苯醚(ODA)为主要原料制备了聚酰亚胺(PI)复合管膜。首先合成聚酰胺酸(PAA),并旋涂制备了聚酰胺酸管膜,然后将溶有碳粉的氟树脂与纯聚酰胺酸管膜复合并热亚胺化,最后再涂覆保护层,制得PI复合管膜。采用傅里叶红外光谱仪(FT-IR)、差式扫描量热法(DSC)、热重分析(TGA)、精密阻抗分析仪和高阻计分别对聚酰亚胺复合管膜的结构、玻璃化转变温度(Tg)、分解温度(Td)、介电性和电阻率进行了表征。研究结果表明,聚酰亚胺管膜的Tg为312.5℃,失重5%的分解温度为560℃。PI复合管膜的介电常数较纯PI管膜稍有增加,碳粉层的加入有效改善了纯PI管膜的介电常数随频率的突变行为,而介质损耗方面,PI复合管膜比纯PI管膜稍有降低。PI复合管膜的表面电阻率比纯PI管膜降低了92.85%,体积电阻率比纯PI管膜降低了77.30%。

A kind of biphenyl polyimide composite tubular film was prepared. First, polyamic acid （PAA） was synthesized by in-situ polycondensation using 3, 3′, 4,4′-biphenyltetracarboxylic dianhydride acid（BPDA） and 4, 4＇-oxydianiline（ODA） as main materials, and composite PAA tubular film was prepared by spin coating, and then fluroresin with carbon powder was overlaid on PAA film and imidized. Lastly, fluroresin was coated as a surface layer. The chemical structure, glass transition temperature（Tg）, decomposition temperature（Td）, dielectric performance and electrical resistivity of the obtained film were characterized by Fourier transform infrared spectroscopy （FT-IR）, differential scanning calorimetry（DSC）, thermogravimetric analysis（TGA）, precision impedance analyzer and megohmmeter, respectively. The results show that the Tg of PI tubular film is 312.5℃, the Td with 5% loss is 560℃. With adding of carbon powder, dielectric constant of PI composite film is reduced, the wave of dielectric constant versus frequency is effectively improved, while the dielectric loss reduced, surface resistivity decreased by 92.85% and volume resistivity 77.30%.