In-Depth Analysis of the Complex Interactions Induced by Nanolayered Additives in PHBV Nanocomposites

Abstract

New nanocomposites based on biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) are processed via extrusion, using low content of calcined hydrotalcite (CHT) and cloisite 20A (C20A) as additives (3 wt%). The aim of this work is to characterize the thermal and viscoelastic response of the structures induced by the presence of the additives. Field-emission scanning electron microscopy and laser profilometry are utilized to analyze the effect of the additives on the surface finish of extrusion filaments, detecting a smoother surface induced by additives. A lower degradation temperature is observed via thermogravimetry for composite containing CHT (PHBV+3%CHT), while such a phenomenon is not present in composite with C20A (PHBV+3%C20A). An increase in crystallinity due to the nucleating effect of additives is measured via differential scanning calorimetry. The intercalation of the biopolymer in the layered structure of the additives is observed via X-ray diffraction, reflecting the effective interaction in the composite matrix. The viscoelastic behavior of the samples is evaluated by means of rheology and dynamic-mechanical analysis, showing a non-Newtonian behavior and an enhancement of the vitreous state response. All results converge to the conclusion that the incorporation of the additives induces the formation of long-term structures that present variable sensitivity to temperature and frequency.