Impact of crystallinity of poly(lactide) on helium and oxygen barrier properties

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• 作者：Alain Guinault^a ; ^b ; Cyrille Sollogoub^a ; ^b ; Violette Ducruet^c ; Sandra Domenek^d ; ^{sandra.domenek@agroparistech.fr}
• 关键词：Poly(lactide) ; Poly(lactic acid) ; Oxygen permeability ; Gas barrier properties ; Crystallinity ; Rigid amorphous fraction
• 刊名：European Polymer Journal
• 出版年：2012
• 期刊代码：35_00143057
• 类别：ms
• 出版时间：April, 2012
• 卷：48
• 期：4
• 页码：779-788
• 文件大小：1695 K

摘要

The helium and oxygen gas barrier properties of poly(lactide) were investigated as a function of stereochemistry and crystallinity degree. Poly(l-lactide) and poly(d,l-lactide) films were obtained by extrusion and thermally cold crystallized in either 伪鈥? or 伪-crystalline form with increasing crystallinity degree. Annealing of the films at low temperatures yielded to 伪鈥?crystals as well as the creation of a rigid amorphous fraction in the amorphous phase. Unexpectedly, the quantity of the rigid amorphous fraction was highest in poly(l-lactide) crystallized under 伪鈥?form. Unexpectedly, the gas permeability increased with increasing quantity of 伪鈥?crystals in poly(l-lactide) and remained constant with increasing quantity of 伪鈥?crystals in poly(d,l-lactide). A gain in gas barrier properties was obtained upon crystallization at higher temperatures yielding 伪-crystals. The analysis of the oxygen transport parameters, in particular the diffusion and the solubility coefficient showed that the diffusion was accelerated upon crystallization, while the solubility coefficient decreased in an expected manner which led to conclude that it remained constant in the amorphous phase. The acceleration of the diffusion seems to be correlated to the occurrence of the rigid amorphous fraction, which holds larger free volume. To conclude, for optimization of poly(lactide) gas barrier properties by focussing on the decrease of the diffusion coefficient it can be suggested to work with poly(d,l-lactide) and to aim a crystallization in 伪-form avoiding the formation of a rigid amorphous fraction.