Utilizing gamma irradiation-induced oxidation on recycled high-density polyethylene to produce a compatibilizer for fabrication of waste-derived wood-polymer composite

In fabrication of wood polymer composites (WPC), a compatibilizer plays an important role in enhancing interfacial adhesion between polymeric matrix and wood filler. This study investigated the effects of gamma irradiation-induced oxidation on recycled high-density polyethylene (rHDPE) to be used as a compatibilizer for WPC production. FTIR analysis showed that gamma irradiation induces significant functional group modifications, as demonstrated by the rising of carbonyl index as the irradiation doses increase up to 200 kGy. Differential scanning calorimetry analysis reveals that irradiation lowers melting temperature, indicating a chain scission in the rHDPE. Additional assessments of wetting angle, work of adhesion, spreading coefficient, and surface energy confirmed the aforementioned findings. Mechanical testing of the WPC made from rHDPE reinforced with oil palm empty fruit bunch (OPEFB) showed that an optimal formulation of 78 wt% rHDPE, 2 wt% irradiated rHDPE (i-rHDPE) 200 kGy as a compatibilizer, and 20 wt% OPEFB yields the most optimum mechanical strength. This indicates a strong interfacial adhesion between the rHDPE and OPEFB in the presence of i-rHDPE as the compatibilizer. These findings suggest that gamma irradiation has strong potential to induce surface modification through radiation induced-oxidation on the rHDPE and enhance its hydrophilicity properties. Thus, it can be utilized as a compatibilizer for the WPC production.