Coupling between Crystal Melting and Rigid Amorphous Fraction Mobilization in Poly(ethylene terephthalate)
Coupling between Crystal Melting and Rigid Amorphous Fraction Mobilization in Poly(ethylene terephthalate)
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DOI：
10.1021/ma101035h
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发表时间：
2010-09-28
期刊：
影响因子：
5.5
通讯作者：
Wunderlich, Bernhard
中科院分区：
文献类型：
--
作者：
Di Lorenzo, Maria Laura;Righetti, Maria Cristina;Wunderlich, Bernhard
详细分析了聚对苯二甲酸乙二酯（PET）的熔融行为。在190 ℃下等温结晶，然后冷却至室温，提供了由移动的非晶部分、结晶部分和刚性非晶部分组成的三相结构。PET中刚性无定形部分的多重熔融和失透之间的密切联系是通过常规和温度调制量热法揭示的。PET晶体在高温下的重排涉及部分熔融后的再结晶/退火/晶体完整性，这仅在与晶体/熔体相边界偶联的无定形链部分具有足够的迁移率时才可能发生。这种流动性可以实现以上的玻璃化转变的无定形链段与刚刚熔化的晶体耦合。在准等温调制过程中监测的反向热容与所得结构的热性能的组合分析表明，在低于210摄氏度的温度下退火不会导致相当大的重组和完善的晶相。210摄氏度的温度似乎是与晶相结合的刚性非晶部分获得足够的移动性以允许具有增加的完美性和因此更高的热稳定性的晶体的发展的点。
A thorough analysis of the melting behavior of poly(ethylene terephthalate) (PET) is detailed in this contribution. Isothermal crystallization at 190 degrees C followed by cooling to room temperature provides a three-phase structure composed of a mobile amorphous, a crystalline, and a rigid amorphous fraction. A close connection between multiple melting and devitrification of the rigid amorphous fraction in PET is revealed by conventional and temperature-modulated calorimetry. Rearrangements of PET crystals at high temperatures involve recrystallization/annealing/crystal perfection following partial melting, which can occur only if the amorphous chain portions coupled to the crystal/melt phase boundary have sufficient mobility. Such mobility can be achieved above the glass transition of the amorphous chain segments coupled with the just-melted crystals. Combined analysis of the reversing heat capacity monitored during quasi-isothermal modulation with the thermal properties of the resulting structure suggests that annealing at temperatures below 210 degrees C does not result in considerable reorganization and perfection of the crystal phase. The temperature of 210 degrees C seems to be the point at which the rigid amorphous fraction coupled with the crystal phase attains sufficient mobility to allow development of crystals with increased perfection and thus higher thermal stability.