Mechanical, thermal, flame behavior and weathering performance of graphene nanoplatelet–reinforced wood–plastic composites

Outdoor conditions negatively affect wood plastic composites (WPCs). In this study, WPCs were reinforced with graphene nanoplatelets (GNPs) to enhance their mechanical, thermal, fire and outdoor performance. The modulus of rupture (MOR) of WPCs was increased by nearly 20% at 1% GNPs loading due to the high surface area of GNPs. Meanwhile, the loss of mechanical strength was limited after the weathering test by the GNPs’ barrier properties. The ultraviolet absorption capability of GNPs significantly inhibited surface color change, as confirmed by ATR-FTIR analysis showing stable polymer characteristic intensity peaks at 2916 and 2846 cm −1 despite intensive UV exposure. Microscopic analysis revealed that some surface color change was inevitable; however, GNPs loading reduced color fading and crack formation by absorbing ultraviolet energy. On the other hand, the scanning electron microscope (SEM) combined with EDS carbon mapping revealed that the tendency towards agglomeration increased as the GNPs were loaded, especially at 3% GNP loading. GNPs improved the thermal and fire performance of WPCs. TGA and DSC analysis showed that restricted molecular mobility raised the degradation and crystallization temperature (Tc) due to the nucleating effect of GNPs. They also enhanced char formation, reduced thermal conductivity, and limited gas permeability, increasing LOI values by up to 20% at the highest loading. Moreover, the UL-94 test also indicated that GNPs improved the fire resistance. The inherent properties of GNPs improved the outdoor performance of WPCs, which is important for long service life.