Utilisation des lignines industrielles comme renfort dans les composites à base de polyéthylène

Authors: Hu, Lei
Advisor: Rodrigue, DenisStevanovic-Janezic, Tatjana
Abstract: This PhD project was carried out to promote the use of industrial lignins in polyethylene biocomposites production, which contributes to decease the generation of greenhouse gases by replacement of synthetic by renewable source polymers. Several methods were developed to improve the compatibility between industrial lignins and polyethylene. In the first part of this work, a literature review is presented in order to clarify the effect of lignin addition on the mechanical, morphological and thermal properties of thermoplastic materials. The existing methods of enhancing lignin-based composites' compatibility are also summarized. Afterwards, four compatibilization approaches for Kraft lignin-HDPE composites are investigated: partial esterification of lignin, surface esterification of lignin, catalytic grafting of polyethylene onto lignin surface, and adding a modified copolymer based on poly(styrene-ethylene-butylene-styrene) (SEBS). It was found that modified SEBS behaved as compatibilizers for Kraft lignin-HDPE composites, whereas the other three methods failed to increase the mechanical properties of the composites. The second part was devoted to the development of new unreactive compatibilizers based on SEBS for lignin-polyethylene composites. SEBS was subjected to nitration followed by amination in order to obtain functionalized copolymers (SEBS-NO2 and SEBS-NH2). SEBS-NO2 is shown to be less efficient than SEBS-NH2, the latter displaying compatibilizing efficiency comparable to that of a reactive compatibilizer (MAPE). The morphological and mechanical properties of lignin-polyethylene composites are improved by adding SEBS-NH2. Finally, a facile and low-cost method to improve the compatibility of lignin-polyethylene is suggested and investigated, which is radical-mediated melt grafting. It is confirmed that free-radical treatment exerted negative effects on the mechanical properties of neat HDPE. However, melt grafting efficiently improves the compatibility of the composites containing up to 60 wt% of Kraft lignin or esterified lignin. A detailed study of the effect of lignin esterification and adding free-radical generator on the properties of the composites is reported. Keywords: Lignins; polyethylene; composites; compatibilization; greenhouse gases.
Document Type: Thèse de doctorat
Issue Date: 2015
Open Access Date: 20 April 2018
Permalink: http://hdl.handle.net/20.500.11794/25543
Grantor: Université Laval
Collection:Thèses et mémoires

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