The role of graphene on thermally induced shape memory properties of poly(lactic acid) extruded composites

Abstract

In this work, the effect of reduced graphene oxide (rGO) on the thermally induced shape memory properties of poly(lactic acid) (PLA) was studied. rGO was incorporated within PLA at various contents (0.1–1.0 mass%) by melt-extrusion. X-ray diffraction showed that PLA/rGO nanocomposites presented decreased crystallinity compared to PLA alone. Differential scanning calorimetry revealed that rGO particles favored the formation of more imperfect PLA crystals. Results from thermogravimetric analyses showed that the PLA/rGO composites presented slightly improved thermal stability. Time-domain nuclear magnetic resonance indicated increased molecular mobility for PLA/rGO nanocomposites in relation to PLA. Dynamic mechanical analysis results showed that Tg = 62.9 °C for PLA and that this value was reduced for the composites, reaching 54.2 °C when the rGO content was 1.0 mass%. The storage moduli (E′) were reduced with the increase in rGO content, with a 44% decrease for the composition with 1.0 mass% of rGO. However, above 65 °C the E′ values increased substantially, which suggested the role of graphene to fix the heat-relaxed molecules of PLA. For the composites, the thermally induced shape memory data revealed an increase in the maximum strain ( $$\varepsilon_{\text{m}}$$ ), reaching 39% and 51% for the composites with the incorporation of rGO at 0.5 and 1.0 mass% content, respectively. The effect of rGO particles on enhancing the shape memory properties of PLA was confirmed by the increases in the recovery rates (Rr) observed for the composites.