An approach for compatibilization of the starch with poly(lactic acid) and ethylene-vinyl acetate-glycidyl-methacrylate

Abstract

In this study, we evaluated the possibility of dimethyldidodecylammonium bromide (DDAB)-modified graphene oxide quantum dots (DDAB-GOQDs) as a new compatibilizer to improve the compatibility of hydrophilic starch with hydrophobic polylactic acid (PLA) and ethylene-vinyl acetate-glycidylmethacrylate (EVA-GMA). The successful synthesis of DDAB-GOQDs was verified by Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and Zeta-Plus assay. The differential scanning calorimetry (DSC), polarized light optical microscopy (POM) and iso-thermal crystallization kinetics analysis showed that 0.25% DDAB-GOQDs could significantly increase the crystallization rate and nucleation density as well as reduce the spherulites size of the nanocomposites. Compared to pure composites, the nanocomposites containing 0.25% DDAB-GOQDs showed obvious enhancement in thermal stability and surface hydrophobicity, with an increase of ~22 °C and ~24.1° in the maximum decomposition temperature and contact angle, coupled with similar improvement in the storage modulus and UV-shielding capacity. Morphological analysis, FTIR and creep behavior experiments revealed that adding 0.25% DDAB-GOQDs enhanced the interface compatibility of the nanocomposites by promoting the formation of the interpenetrated network through strong polar hydrogen bond or electrostatic force within the polymeric components. Overall, (0.25%) DDAB-GOQDs can serve as an effective compatibilizer for the PLA/starch/EVA-GMA system due to improved crystallization, thermal stability, barrier properties and creep-resistance.