纳米胶体二氧化硅改性聚酰亚胺薄膜的制备及性能研究

Preparation and Properties of Polyimide Films Modified with Colloidal Silica Fillers

首先,通过缩聚法制备了基于均苯四甲酸二酐(PMDA)与4,4′-二氨基二苯醚(ODA)单体的聚酰胺酸(PAA),在聚合过程中加入不同质量分数的胶体SiO_(2)/N,N-二甲基乙酰胺(DMAc),制得PAA/SiO_(2)杂化胶液。然后将杂化胶液在洁净干燥箱中于室温~350℃进行亚胺化,制得了PI/SiO_(2)复合薄膜。对PI/SiO_(2)复合薄膜进行衰减全反射傅里叶红外光谱(ATR-FTIR)、扫描电子显微镜(SEM)、热重分析(TGA)、动态机械分析(DMA)和热机械分析(TMA)测试,并采用阻抗分析法测试SiO_(2)的引入对复合薄膜介电性能的影响。结果表明:成功制得了预期结构的复合薄膜,SiO_(2)在PI基体中分布较为均匀。SiO_(2)的引入提高了复合薄膜的耐热性和热尺寸稳定性,SiO_(2)含量为25%的PI-25薄膜5%失重温度(T5%)和750℃时的残余质量分数分别为611℃与73%,分别较PI-0薄膜(未添加SiO_(2))提高了14.7℃和9.2%。在103~106 Hz频率范围内,复合薄膜表现出较为稳定的介电常数(D_(k))与介质损耗因数(D_(f))。纳米SiO_(2)的引入略微提高了复合薄膜的D_(k)值,PI-25薄膜在1 MHz时的D_(k)值为3.58,较PI-0薄膜略有上升(D_(k)为3.20)。

At First,a poly(amic acid)(PAA)based on pyromellitic dianhydride(PMDA)and 4,4′-oxydianiline(ODA)was prepared by polycondensation procedure,and the PAA/SiO_(2) composite solutions were obtained by adding different mass fraction of colloidal SiO_(2)/N,N-dimethylacetamide(DMAc)during the polymerization.Then a series of PI/SiO_(2) composite films were prepared by thermal imidization of the PAA/SiO_(2) composite solutions in a clean oven from room temperature to 350℃in nitrogen.The PI composite films were characterized by the attenuated total reflectance Fourier transform infrared(ATR-FTIR),scanning electron microscopy(SEM),thermal gravimetric analysis(TGA),dynamic mechanical analysis(DMA),and thermo-mechanical analysis(TMA),and the effect of SiO_(2) on the dielectric properties of composite film was tested by the impedance analysis measurement.The results show that the composite films with expected structure are prepared,and the SiO_(2) disperses in PI matrix uniformly.The incorporation of SiO_(2) improves the heat resistance and dimensional stability at high temperature of the PI composite films.The 5%weight loss temperature(T_(5%))and 750℃residual weight ratio(R_(w750))of the PI-25 film with 25%of SiO_(2) are 611.3℃and 73.1%,respectively,which are 14.7℃and 9.2%higher than those of the PI 0 film(without silica).The PI composite films exhibit stable dielectric constant(D_(k))and dielectric loss factor(D_(f))in the frequency range of 10^(3)−10^(6) Hz.The incorporation of nano-silica slightly increases the D_(k) of composite films,and the D_(k) of the PI-25 film at 1 MHz is 3.58,which is a bit higher than that of the PI-0 film(D_(k) is 3.20).