| Résumé | This work investigates the effect of macromolecular chain-branching on polylactide (PLA) rheology, crystallization, and foamability. An amorphous and a semicrystalline PLA 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, with 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 foamed materials 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 starting from 5% CO2 for semicrystalline PLA and only at 9% CO2 in the case of the amorphous PLA. The differences observed between the foaming behaviours and foam microstructures of the two PLA grades were due to their different crystallization behaviours. |
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