STUDY ON PHASE TRANSITION AND CRITICAL PHENOMENA IN POLYMER CRYSTALS BASED ON LIGHT-HEATING MODULATED DTA AND HIGH PRESSURE MEASUREMENT

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There had been no reports in the world, which strictly proved appearance of second-order phase transition in polymer crystals. We recently discovered the second-order phase transition in polyamide crystals on the basis of X-ray structure analysis under high-pressure. Through such studies, we noticed that the quantitative analysis had not been performed for specific-heat measurement under high-pressure in the world, which must give us one of the most important information to discuss the phase-transitional phenomena in material. It is the reason why we started this project.The first step of this project is to construct the high-pressure system of light-heating modulated temperature DTA(HP-LMTDTA) to perform the dynamical thermal measurement of polymers. After construction, we examined performance of the system by using the phase-transitional phenomena of 1,4-trans-polybutadiene crystal to prove it possible to measure the thermal property for the dynamical process during the phase transit … More ion under high-pressure up to 300 Mpa.Through this project, we mainly analyzed the phase-transitional phenomena in nylon and fluoro-copolymer crystals to show that the first- and/or second-order phase transition occurs only in nylon 6Y (Y : even number ≦8) crystals even under normal and high pressure. It was also found that structural changes in vinylidene fluoride(VDF)-trifluoroethylene(TrFE) copolymer crystals are transformed from continuous (cooled phase(CP) to high-temperature phase(HP)) to discontinuous one (low-temperature phase(LP) to HP) with increasing VDF molar content or external pressure for VDF 65 % sample, where the transition from CP to LP occurs prior to the first-order phase transition from LP to HP. The sample with 65 % of VDF is composed of only CP, and LP suddenly appears in VDF 68 % sample and another LP is suggested to exist in VDF 71 and 77 % samples. Percolation theory may be applicable to explain such structural transformation very sensitive with VDF content.Such results indicate that this system can be applied for various studies under high pressure on polymers at molecular level such as crystal growth and melting, formation process of spherulite, electrical properties etc. Less