The effect of graphene nanoplatelets on dynamic properties, crystallization, and morphology of a biodegradable blend of poly(lactic acid)/thermoplastic starch

Based on the capabilities of nanographenes in improving the properties of polymeric blends, the effects of graphene nanoplatelets on compatibility, morphology, and crystallinity of the biodegradable thermoplastic starch/poly(lactic acid) (TPS/PLA) blends have been investigated. The localization of graphene nanoplatelets has also been predicted by wetting coefficients. TPS was first prepared and added in various concentrations to the PLA melted in an internal mixer instrument. After that, various amounts of graphene nanoplatelets as 0, 1, 2, and 3 wt% were added to the PLA/TPS blends at two different 90/10 and 70/30 weight compositions. The blends were examined by DMTA, SEM, and DSC tests. The wetting coefficient was evaluated by contact angle measurements to predict the dispersion and localization of graphene nanoplatelets, and also to confirm the predicted results with those obtained by other tests. DMTA results demonstrated that the addition of 1wt% graphene nanoplatelets into the PLA/TPS blend has increased the compatibility of the two phases. SEM images revealed the dependence of the TPS-dispersed phase particles on the blend composition and amount of graphene nanoplatelets. DSC thermograms showed a reduction in cold crystallization temperature to zero due to the addition of graphene nanoparticles to PLA/TPS blends. Based on the wetting coefficient values, the localization of graphene nanoplatelets was found to be at the interface of PLA and TPS phases.