Ionic liquid-plasticized hybrids based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with enhanced ductibility and shape memory properties
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biocompatible and biodegradable aliphatic polyester, considered an alternative to substitute synthetic polymers. Brittleness is the main disadvantage of PHBV. Blending, plasticization and the addition of nucleating additives are recommended to improve PHBV mechanical properties. In this work, extruded PHBV and poly(ethylene-co-vinyl acetate) (EVA) neat blends and hybrids were prepared and characterized. To prepare hybrids, an ionic liquid and a reduced graphene oxide-zinc oxide composite (rGO-ZnO) were incorporated as a plasticizer and nucleating agent, respectively. The ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was used at a constant composition. Infrared spectroscopy indicated PHBV and EVA immiscibility. X-ray diffractometry (XRD) showed that rGO-ZnO was well-dispersed within the polymer matrix. XRD and differential scanning calorimetry results indicated that the crystallinity of PHBV was reduced in the hybrids. Tensile tests showed improved mechanical properties for the hybrids in relation to PHBV. For the plasticized hybrids, elongation at break values varied from 307.5% to 822.6%. All materials tested exhibited thermally-induced shape memory effect. Enhanced shape recovery ratios, between 96.3% and 97.2%, were determined for the plasticized hybrids. Blending, plasticization and incorporation of rGO-ZnO sheets may potentially expand PHBV use.
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