利用超临界二氧化碳制备低介电常数聚酰亚胺微孔薄膜

Preparation of Cellular Polyimide Film with Low Dielectric Constant Using Supercritical Carbon Dioxide

利用超临界CO2发泡技术,制备了一种低介电常数的聚酰亚胺微孔薄膜。扫描电子显微镜观察表明,微孔薄膜具有实心表层及中心微孔层结构,中心微孔层内泡孔孔径约2μm,泡孔分布均匀。在相同的发泡温度下,发泡时间在10 s内,随着发泡时间增长,孔径较小(<1μm)的泡孔数目明显减小,泡孔尺寸增大。发泡约10 s后,泡孔尺寸变化略微增加。在230℃~270℃范围内,发泡温度越高,微孔薄膜中心微孔层内的泡孔孔径越小,孔径分布越均匀,泡孔密度越大,薄膜密度也越小。拉伸性能测试表明,随着密度减小,聚酰亚胺微孔薄膜的拉伸强度和拉伸模量下降。介电性能分析表明,聚酰亚胺微孔薄膜的介电常数明显下降,当密度为0.75 g/cm3时,聚酰亚胺微孔薄膜的介电常数降至2.21;在102Hz^107Hz频率范围内,微孔薄膜的介电常数具有较高的频率稳定性。

Cellular polyimide( PI) films with low dielectric constant were prepared by foaming with supercritical carbon dioxide( CO2). SEM image shows that the cellular polyimide films have solid outer layers and cellular core layer which contains plenty of homogeneously dispersing cells of about 2 μm. As the foaming temperature increasing in 230 ℃~ 270 ℃,the average size of the cells in core layer decreases,the size distribution becomes homogeneous,the cell density increases,and the density of the films decreases accordingly. The tensile tests show that the tensile strength and modulus of the cellular PI films decrease with their density decreasing. Dielectric property analysis shows that the dielectric constant of the cellular PI films decreases obviously. The dielectric constant of the film with density of 0. 75 g /cm3drops down to 2. 21. In the frequency range of 102Hz ~ 107Hz,the dielectric constant of cellular PI films has good frequency stability.