Preparation and characterization of low expansion transparent copolyimide films
ZHANG Ming-yan1,2, GAO Sheng1, WU Zi-jian1,2, CUI Hong-yu1, GAO Yan1
1. School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040, China;
2. Engineering Dielectrics and Its Application Key Laboratory(Ministry of Education), Harbin University of Science and Technology, Harbin 150080, China
Abstract：Five transparent polyimide thin films with different proportions of 1,2,4,5-,pyromellitic dianhydride (PMDA) were made by copolymerization of 4,4'-(six fluoro isopropenyl) two phthalic anhydride (6FDA), 4,4'-two amino -2,2'-double three trifluoromethyl biphenyl (TFMB) and PMDA, and their properties were characterized. The results show that thermal stability and heat resistance are increased after the introduction of rigid monomers; the dielectric constant of the films is increased with the increase of PMDA content; homopolymer film has higher light transmission rate than copolymer films in visible light; tensile test shows that adding a small amount of PMDA, the tensile strength and elastic modulus of the film are increased, but when the content of PMDA is higher than 40%, the mechanical properties are decreased; the coefficient of thermal expansion of the films are decreased obviously while PMDA content is increased.
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