Chemical foaming extrusion of poly(lactic acid) with chain-extenders: Physical and morphological characterizations

• The effect of chain-extender addition on chemical foaming of PLA was quantified.
• Chain-extenders induce a decrease in cell size and open cell content.
• Chain-extenders induce an increase in tensile properties, especially the yield stress.
• Chain-extenders can be useful to better control the cell morphology.

The effects of an epoxide-based chain-extender (CE) on the properties of poly(lactic acid) (PLA) foams obtained by chemical foaming extrusion using 4 wt.% of chemical foaming agent (CFA) were studied. PLA/CE blends with different weight ratios of CE were initially processed using a co-rotating twin-screw extruder. PLA/CE foams were then produced using a single-screw extruder. Various PLA/CE foams characterizations, including solution viscosity, thermal properties (DSC, TGA), cellular structure (void fraction, cell size, open cell content), mechanical and dynamic rheological behaviors, were investigated. Results show that the addition of CE enhances the viscosimetric average molecular weight and rheological properties (viscosity and storage modulus) of PLA, but it has no significant effects on the thermal properties of PLA, except the occurring of a cold crystallization. The CE incorporation also led to a decrease in the void fraction of cellular PLA, in the cell size and in the open cell content and to an increase in the cell density. Furthermore, the tensile mechanical properties such as yield stress and elongation at break of cellular materials increased with the addition of CE.

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