THERMAL PROPERTIES OF POLYLACTIDES Effect of molecular mass and nature of lactide isomer
THERMAL PROPERTIES OF POLYLACTIDES Effect of molecular mass and nature of lactide isomer
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DOI：
10.1007/s10973-008-9035-x
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发表时间：
2009-03-01
影响因子：
4.4
通讯作者：
Varshney, S. K.
中科院分区：
文献类型：
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作者：
Ahmed, J.;Zhang, J. -X.;Varshney, S. K.
根据聚乳酸的平均相对分子质量(M-n)数和异构体性质(D、L和DL)，对一系列聚乳酸进行了热分析。结果表明，除多分散指数较高的样品外，不同异构体类型的聚乳酸的玻璃化转变温度(T-g)均随相对分子质量的增加而增加。L同分异构体的熔融温度(T-m)和结晶熔融热(ΔH-f)随M-n从1100增加到27500而增加。结晶度(chi(C)%)随分子质量的增加而增加。但在较低分子质量范围(550-1400)内未检测到结晶峰。降温速率对聚乳酸熔体的非等温结晶行为有显著影响。D和L异构体的热性质差异不大，而相同分子质量的DL丙交酯表现为无定形行为。两种异构体的微观结构变化有显著差异。对这些聚乳酸样品在1200-1230 cm(-1)范围内的FTIR光谱的分析支持了结晶度的DSC观察。
A thermal analysis of a series of polylactides (PLA) was carried out based on the number of average molecular mass (M-n), and the nature of isomer (D, L and DL). It is confirmed that the glass transition temperature (T-g) of PLA increased as a function of molecular mass irrespective of isomer type except sample with a high polydispersity index. The melting temperature (T-m) and enthalpy of crystal fusion (Delta H-f) of L-isomer increased as the M-n was increased from 1100 to 27500. The degree of crystallinity (chi(c)%) increased as a function of molecular mass. However no crystallization peak was detected in the lower molecular mass range (550-1400). The non-isothermal crystallization behavior of the PLA melt was significantly influenced by the cooling rate. Both D and L isomers exhibited insignificant difference in thermal properties and DL lactides exhibited amorphous behavior at identical molecular masses. Change in microstructure showed significant difference between two isomers. Analysis of the FTIR spectra of these PLA samples in the range of 1200-1230 cm(-1) supported DSC observation on crystallinity.