Comparative studies of thermal and mechanical properties of macrocyclic versus linear polylactide
Résumé
This paper reports the study of the influence of the macrocyclic or linear topology of polylactide (PLA) on its resulting thermal and mechanical properties, when displaying identical molar masses. Even if both macrocyclic and linear PLAs crystallize in the same α phase, the results of the calorimetric study and of the tensile tests show some differences which are directly related to the topology of the polymer. The glass transition temperature of macrocyclic PLA was found to be slightly higher than that of the linear one (56 vs 53 °C) while its melting temperature is lower (165 vs 171 °C). Moreover, the crystallization rate of the macrocyclic PLA is slower than that of the linear PLA. Regarding the tensile tests, it has been observed that the macrocyclic PLA displays an earlier strain-hardening than the linear one when stretched in the rubbery state. These differences were attributed to the fact that the macrocyclic topology involves a more constrained entangled network than its linear analogous and/or that the disentanglement kinetics is faster in linear PLA than in macrocylic PLA.
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