A series of poly(amic acid)s(PAAs) was prepared by reacting 4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride)(BPADA) as the anhydride monomer and 2,2′-bis(trifluoromethyl) benzidine (TFB), bis(3-aminophenyl)sulfone (APS), 4,4′-methylenebis-(2-methylcyclohexylamine) (MMCA), or bis[4-(3-aminophenoxy) phenyl] sulfone (BAPS) as the amine monomer with 5 mol% melamine in N,N-dimethylacetamide (DMAc). Colorless and transparent polyimide (PI) films were obtained by casting the PAAs at various heat treatment temperatures. The thermo-mechanical properties and optical transparency of the PI films were investigated. The thermal properties of the PI films were examined using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermomechanical analysis (TMA), and their optical transparency were measured by spectrophotometry. The coefficient of thermal expansion (CTE) and yellow index (YI) values of all samples were in the range of 46.89-64.24 ppm/℃ and < 3.0, respectively.

무수산인 4,4′-(4,4′-isopropylidene-diphenoxy)bis(phthalic anhydride)(BPADA)와 아민계인 2,2'- bis(trifluoromethyl)benzidine(TFB), bis(3-aminophenyl)sulfone(APS), 4,4′-methylene-bis-(2-methylcyclohexylamine)(MMCA), bis[4-(3-aminophenoxy)phenyl]sulfone(BAPS)에 melamine을 각각 5 몰%로 반응시켜 N,N′-dimethylacetamide(DMAc) 용매 속에서 폴리아믹산(poly(amic acid), PAA)들을 얻었다. 용액 상태의 PAA를 캐스팅하여 각각 다른 반응 온도에서 열처리를 통해 무색 투명한 폴리이미드(PI) 필름을 얻었다. PI의 열적 성질, 광학적 특성을 다양한 아민 구조의 변화에 따라 조사하였으며, 열적 성질은 differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), thermomechanical analysis(TMA)를 이용해 측정하였고, 광학적 투명도는 색차계 (spectrophotometry)를 이용하였다. 제조된 모든 필름의 열 팽창계수는 48.53－64.24 ppm/℃ 사이의 값을 얻었으며, 모든 필름 시료의 노란색 지수(yellow index, YI)는 3 이하를 나타내었다.

Keywords: colorless PI; melamine; films; thermal property; optical transparency