Melting behavior of poly(l-lactic acid): X-ray and DSC analyses of the melting process
Melting behavior of poly(l-lactic acid): X-ray and DSC analyses of the melting process
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DOI：
10.1016/j.polymer.2008.02.034
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发表时间：
2008-04
期刊：
影响因子：
4.6
通讯作者：
M. Yasuniwa;Kazunari Sakamo;Y. Ono;Wataru Kawahara
中科院分区：
文献类型：
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作者：
M. Yasuniwa;Kazunari Sakamo;Y. Ono;Wataru Kawahara
为了研究聚L-乳酸（PLLA）的熔融行为，采用广角X射线衍射法对PLLA的等温结晶样品进行了连续的热处理。我们已经提出了PLLA在113°C（=Tb）结晶温度下结晶行为的离散变化以及在Tc≤ T和Tc≥Tb温度范围内获得的ICS的两种晶体变体的形成。X射线衍射图谱的变化表明，在155-165°C（Tc≤Tb）范围内，ICSs发生了从低温晶型（α′-型）到高温晶型（α-型）的相变，而在Tc≥ Tb范围内，ICSs的晶体结构没有发生变化。在加热过程中的再结晶，这是多重熔融行为的起源，被证明是在衍射强度急剧下降之前，由于最终熔融的增加。X射线衍射强度的温度导数曲线与DSC熔融曲线几乎一致。
To clarify the melting behavior of poly(l-lactic acid) (PLLA), the wide-angle X-ray diffraction patterns of the isothermally crystallized PLLA samples (ICSs) were successively obtained during heating. We have already suggested the discrete change in the crystallization behavior of PLLA at a crystallization temperature (Tc) of 113°C (=Tb) and formation of two crystal modifications for the ICSs obtained in the temperature range Tc≤Tband Tc≥Tb. It was elucidated from the change in the X-ray diffraction pattern that the phase transition from the low-temperature crystal modification (α′-form) to the high-temperature one (α-form) occurred in a range 155–165°C for the ICSs(Tc≤Tb), and that the crystal structure for the ICSs(Tc≥Tb) did not change. Recrystallization during heating, which is the origin of the multiple melting behavior, was proved by the increase in the diffraction intensity before steep decrease due to the final melting. A temperature derivative curve of the X-ray diffraction intensity almost coincided with the DSC melting curve.