Supertough Shape Memory Bionanocomposites of Thermoplastic Vulcanizates Based on PLA- EVA and Cellulose Nanocrystal

Abstract

Polylactic acid (PLA) is the main candidate among the synthetic polymers for food packaging application. However, its poor processing and mechanical performance have limited its practical application. Here, we prepared a supertough thermoplastic vulcanizate (TPV) using PLA and ethylene vinyl acetate (EVA) copolymer with optimized EVA composition. The dynamic curing agent, dicumyl peroxide (DCP), was used as EVA-DCP masterbatch to improve its curing efficiency. Cellulose nanocrystals (CNCs) were further used as the biocompatible and renewable nanofiller, used in the form of PLA-CNC masterbatch, leading to improved mechanical strength and shape memory performance (SMP). Dynamically curing the thermoplastic elastomer (TPE) precursors diminished the temperature-dependency of elastic modulus (\(E^{\prime}\)) prior to PLA’s glass transition. Thus, improving the shape fixity (FR) of the TPVs compared to their TPEs as the TPVs showed \(FR>98\%\) while the TPV60 (60% PLA) showed the highest FR of 100%. The TPVs showed higher recovery ratio (RR) with \(RR>87.25\%\) with the TPV60 containing 1.5% CNC, which showed the highest RR of 94.1%. The mechanical performance analyses showed that the optimized TPV: CNC possesses a supertough nature, achieved by tuning the rheological behavior and morphology of the final TPVs. The results were quite promising for smart food packaging applications.