Investigation of the effect of graphene oxide loading on the morphology and thermal properties of poly(lactic acid)/ethylene vinyl acetate blends

Poly(lactic acid) (PLA)/Ethylene vinyl acetate (EVA) blends are environmentally friendly and biocompatible materials whose usage aligns with numerous United Nations sustainability goals. However, immiscibility of the polymer interphases limits the applicability of the blends, necessitating reinforcements using suitable materials like graphene oxide (GO). This study investigated the effect of graphene oxide loading on the interfacial, morphological, and thermal properties of PLA/EVA blends, in contribution to the understanding of structure – property relationships of the blends. GO was synthesized via modified Hummer’s method and analysed using Fourier-transform infrared spectroscopy (FTIR). 70/30, 50/50, and 30/70 w/w PLA/EVA blends and their composites with 1, 3, and 5 wt% GO contents were prepared via melt mixing, and characterised through Melt Flow index (MFI), Surface energy evaluation system (SEES), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), and Thermogravimetric (TGA). PLA and EVA had MFI values of 2.64 and 0.500 g/10 min, indicating complementary viscosities. SEES results suggested the possibility of GO settling on the interface of the two polymers, with a wetting coefficient of 0.523. SEM results illustrated the compatibility and phase homogenizing effect of GO on the PLA/EVA blends. DSC measurements portrayed partial miscibility and possible plasticisation effects of GO on the polymers. TGA analyses proved GO instrumental in improving the thermal stability of the polymers at higher temperatures. The 50/50 w/w PLA/EVA composition (blend and composites) was deemed ideal and superior in the analysed properties, compared to other compositions. Future work will focus on conducting mechanical and thermomechanical studies to develop an overall idea of the composites’ usability in applications like smart packaging, self-sensing and healing, and smart material design.