Preparation and characterization of inherently heat-sealable polyimides with high glass transition temperatures.

A series of inherently heat-sealable copolyimides (CPIs) with high glass transition temperatures were synthesized from 2,3,3',4'-oxydiphthalic anhydride (aODPA) and bicomponent diamines, 4,4'-oxydianiline (ODA) and para-phenylenediamine (PDA). The PI chain rigidity was manipulated by the regulation of the diamine ratio, and its effects on the heat sealability and thermal resistance of the derived CPI films were investigated in detail. The results show that these films are in possession of both good heat sealability and thermal resistance due to the synergetic effect of the asymmetry of aODPA and the rigidity of PDA. It is also found that there exists one critical PDA content that distinguishes the heat-sealing behaviors of the CPI films, and the relevant mechanism was established. Especially for CPI-5, the heat-sealing strength is up to 350 N m^–1 simultaneously with a relatively high T_g of 310°C. [ABSTRACT FROM AUTHOR]