Effect of blend ratio and nanofiller localization on the thermal degradation of graphite nanoplatelets-modified PLA/PCL

A variety of poly(lactic acid) (PLA)-poly(ε-caprolactone) (PCL) samples with different PLA:PCL ratios, containing different contents of graphite nanoplatelets (GrP), were analysed in a thermogravimetric analyser (TG) under, respectively, nitrogen and oxygen atmospheres, and in a differential scanning calorimeter (DSC) in a nitrogen atmosphere. Their respective morphologies were determined through scanning electron microscopy. The TG analyses in nitrogen gave fairly predictable results, but the analyses in oxygen gave complex results that seemed to be dependent on the respective morphologies of the blend samples and on the presence and amount of GrP in the respective samples. It was observed that, depending on the blend or nanocomposite morphologies, the GrP could have played the role of catalysing the degradation process, or inhibiting the onset of degradation by immobilizing the polymer or free radical chains and by delaying the evolution of the degradation products from the respective samples. The DSC results clearly showed the influence of the respective components in the blends and composites on the crystallization behaviour and crystallinities of the two polymers.