Rheology and extrusion foaming of chain‐branched poly(lactic acid)

Polymer Engineering and Science - Tập 50 Số 3 - Trang 629-642 - 2010
Mihaela Mihai1,2, Michel A. Huneault2, Basil D. Favis1
1CREPEC, Chemical Engineering Department, École Polytechnique de Montréal, Montréal, Québec, Canada H3C 3A7
2Industrial Materials Institute, National Research Council of Canada, Boucherville, Québec, Canada J4B 6Y4

Tóm tắt

AbstractIn this study, the effect of macromolecular chain‐branching on poly(lactic acid) (PLA) rheology, crystallization, and extrusion foaming was investigated. Two PLA grades, an amorphous and a semi‐crystalline one, were branched using a multifunctional styrene‐acrylic‐epoxy copolymer. The branching of PLA and its foaming were achieved in one‐step extrusion process. Carbon dioxide (CO2), in concentration up to 9%, was used as expansion agent to obtain foams from the two PLA branched using chain‐extender contents up to 2%. The foams were investigated with respect to their shear and elongational behavior, crystallinity, morphology, and density. The addition of the chain‐extender led to an increase in complex viscosity, elasticity, elongational viscosity, and in the manifestation of the strain‐hardening phenomena. Low‐density foams were obtained at 5–9% CO2for semi‐crystalline PLA and only at 9% CO2in the case of the amorphous PLA. Differences in foaming behavior were attributed to crystallites formation during the foaming process. The rheological and structural changes associated with PLA chain‐extension lowered the achieved crystallinity but slightly improved the foamability at low CO2content. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

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Polymer Engineering and Science

Tập 50 Số 3

629-642

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