Synthesis and Characterization of Polyimide/Silica Nanocomposites with Coupling Agent
In this study, silica particles were introduced into a polyimide (PI) matrix to enhance its thermal and mechanical properties. Monomers of 3,3’,4,4'-biphenyl tetracarboxylic dianhydride (BPDA) and p-phenylenediamine (p-PDA) were employed to synthesize the poly(amic acid) (PAA). Polyimide/SiO2 composites were obtained through a sol-gel process using tetraethoxysilane and multi-step thermal curing processes. The properties of the PI/SiO2 composites with various kinds of coupling agents to enhance the bonding between them were also studied. TGA results indicated that silica particles were dispersed uniformly in the PI matrix at the nano-scale level, as observed in SEM images. The coefficient of thermal expansion was decreased by an increase of the silica content.