Mechanical and thermal properties of graphene nanoplatelets-reinforced recycled polycarbonate composites

Nanocomposites have received significant interest in recent years, as they offer improved properties compared to conventional materials for various applications. Among many available nanofillers, graphene nanoplatelets (GNP) have shown promising results for polymer-based nanocomposite applications. This paper investigates the mechanical and thermal properties of GNP-reinforced virgin and recycled polycarbonate (PC) nanocomposites blended via a twin-screw extruder. Effects of various key processing parameters such as filler concentration, processing speed, barrel/die set temperature, and PC type (virgin and recycled) on the reinforced composites were examined. Mechanical properties were characterised by tensile testing, while thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to characterise the thermal properties. The results show that the processing speed and barrel/die set temperature have a slight influence, while the filler concentration significantly affects the properties of PC/GNPs composites. The Young's modulus and yield strength were enhanced with increasing GNP loading, where the maximum enhancement of Young's modulus was obtained as ∼33% for virgin-PC/GNP and ∼39.5% for recycled-PC/GNP composites at 10 wt.-% GNP loading. However, the failure strain was reduced with the increased GNP loading for both virgin and recycled PC/GNP composites. Embedding GNP into the PC matrix only slightly influenced the thermal stability and glassy transition temperature (Tg). The highest thermal stability for virgin PC/GNP composites was observed with 1 wt.-% (2.74% increase with respect to virgin PC), while for recycled PC/GNP, it was observed with 10 wt.-% (2.42% increase with respect to recycled PC) GNP loading. Under the same GNP loading, recycled PC-based composites showed lower thermal stability than virgin PC-based composites. The Tg evaluated from DSC showed a rise under 1 wt.-% GNP for virgin PC/GNP and decrease afterwards with higher filler loading, while an irregular variation for recycled PC/GNP was observed.