Evaluation of shape memory effect in PLA/copolymers blends

In this work, polylactic acid (PLA)/copolymer blends were prepared by melt blending. Ethylene-glycidyl methacrylate (E-GMA) and ethylene-butyl acrylate-maleic anhydride (EBA-MAH) functional block copolymers were used. A ternary blend of PLA/E-GMA/EBA-MAH was also studied. FTIR analyses evidenced the occurrence of reactive compatibilization of E-GMA and EBA-MAH with PLA in the binary blends due to the reactivity of the GMA and MAH functional groups with the terminal hydroxyl and carboxyl groups of PLA. Rheological measurements evidenced the occurrence of cross-link reactions between E-GMA and EBA-MAH copolymers in the ternary blend. Three distinct morphologies were observed in the blends: PLA/E-GMA exhibited a sea-island structure, PLA/EBA-MAH exhibited a co-continuous structure, and PLA/E-GMA/EBA-MAH exhibited a semi-interpenetrating polymer network (SIPN) structure. The shape memory effect (SME) of PLA and PLA/copolymers blends was evaluated by three different methods: fold-deploy, tension, and torsion. Fold-deploy tests were conducted in a water bath, whereas the tension and torsion tests were conducted using a rheometer. All methods proved to be effective; however, some precautions must be taken to choose the most suitable test for a given purpose, which is thoroughly discussed in this work. The SME of PLA was enhanced through the incorporation of the copolymers. Blending PLA with E-GMA, EBA-MAH, and E-GMA/EBA-MAH copolymers increased its shape recovery from 32% to 84%, 79.2%, and 80%, respectively, while its shape fixity remained around 100%.

Automated summary

In this study, polylactic acid (PLA) copolymer blends were prepared by melt blending using ethylene-glycidyl methacrylate (E-GMA) and ethylene-butyl acrylate-maleic anhydride (EBA-MAH) functional block copolymers. Reactive compatibilization between E-GMA/EBA-MAH and PLA was confirmed through FTIR analyses. Rheological measurements indicated cross-link reactions in the ternary blend. Three different morphologies were observed in the blends: PLA/E-GMA exhibited a sea-island structure, PLA/EBA-MAH exhibited a co-continuous structure, and PLA/E-GMA/EBA-MAH exhibited a semi-interpenetrating polymer network (SIPN) structure. The shape memory effect (SME) of PLA and its blends was evaluated using three methods, and the incorporation of copolymers enhanced the SME of PLA.