Thermal behavior of PLA plasticized by commercial and cardanol-derived plasticizers and the effect on the mechanical properties

This paper is aimed at studying the thermal properties of poly(lactic acid), PLA with different plasticizers. Plasticized PLA was obtained by mixing and extruding PLA with 20 mass% of neat cardanol, epoxidized cardanol acetate (ECA) and poly(ethylene glycol) (PEG) 400. The glass transition of completely amorphous samples, melting and crystallization behavior of plasticized PLA were analyzed by differential scanning calorimetry. Results obtained show that, below T-g, a higher enthalpy relaxation occurs for PLA plasticized by cardanol derivatives. This is indicative of a faster mobility of PLA chains below T-g, when cardanol derivatives are used as plasticizers. On the other hand, an opposite behavior was observed for the crystallization studies. In facts, a much faster crystallization was found for PLA plasticized by PEG, which in turn indicates a much higher mobility of PLA chains above T-g compared to PLA plasticized by cardanol derivatives. Mechanical properties obtained on completely amorphous samples show that PLA plasticized by ECA is characterized by lower modulus, which is indicative of a more efficient plasticization. On the other hand, the thicker crystals formed during crystallization of PLA plasticized by ECA involve a more relevant increase in the modulus in semicrystalline samples.

Automated summary

This study investigates the thermal properties of poly(lactic acid) with different plasticizers, revealing that PLA plasticized with cardanol derivatives shows higher enthalpy relaxation below T-g, while PLA plasticized with PEG exhibits higher mobility above T-g. In terms of mechanical properties, PLA plasticized with ECA has a lower modulus but forms thicker crystals during crystallization, leading to a more significant increase in modulus in semicrystalline samples.