Effects of coupling agents on structure and properties of polyimide/Al ₂O₃ nanocomposite films

Purpose - The purpose of this paper is to investigate the effects of coupling agents on the structure and properties of the nanocomposite films and clarify their mechanism. Polyimide (PI)/Al₂O₃ nanocomposite films were prepared using different coupling agents. Design/methodology/approach - Poly(amic acid) (PAA) was firstly synthesised from appropriate pyromellitic diannanocomposite and oxydianiline in N-dimethylacetamide. Calculated amount of nano-Al₂O₃ particles modified by different coupling agents (KH550, KH560, KH570 and AE3012) were added to PAA solution by an ultrasonic-mechanical method and PI/nano-Al₂O₃ film was fabricated by heat curing. The microstructure, thermal stability, mechanical properties and electric breakdown strength of the films were characterised. Findings - The addition of coupling agents could greatly improve the dispersion homogeneity of Al₂O ₃ nano-particles in PI matrix. Results of corresponding characterisations indicated that both the thermal stability and mechanical properties of PI/Al₂O₃ nanocomposite film with KH550 were greater/better than others, while AE3012 could improve the electric breakdown strength. Research limitations/implications - In the present discussion, the effects of different coupling agents, KH550, KH560, KH570 and AE3012, were investigated. Results of this research work would be beneficial to an in-depth understanding on the relationship between microstructure and properties of PI composites, and further promote the development of the high-performance PI insulating materials. Originality/value - The four coupling agents, KH550, KH560, KH570 and AE3012, were firstly used to disperse the nano-Al ₂O₃ particles in PI matrix. The effects of coupling agents on microstructure and properties of composites were discussed by the authors in detail.