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

Abstract 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 intended to correlate the loading of GO with the interfacial and thermal-rheological 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 confirmed 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), 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 mJ/m². DSC measurements portrayed partial miscibility and 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. Following further studies that analyse their morphology, mechanical, and thermomechanical properties, the composites could be promising sustainable and environmentally friendly materials for applications like smart packaging, self-sensing and healing, and smart material design.