Preparation and characterization of low expansion transparent copolyimide films
Ming-yan ZHANG1,2, Sheng GAO1, Zi-jian WU1,2,*(), Hong-yu CUI1, Yan GAO1
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
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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