Surface modification of waste tire dust under pre-irradiation emulsion grafting technique

In recent years, the rate of waste tire disposal has increased dramatically, jeopardizing world ecological equilibrium. The utilization of this waste in polymer composite as a sustainable and low-cost filler is one of the possible solutions. However, the compatibility of waste tire dust (WTD) with most matrices is limited which results in the degradation of the composite's mechanical properties. The goal of this study was to enhance the interfacial bonding at the rubber-matrix interface. This was done by utilizing the carbonyl group of tripropylene glycol diacrylate (TPGDA) using pre-irradiation emulsion grafting techniques to develop grafted WTD (G-WTD) which can generate a strong chemical bond between the rubber and the polymer matrix. The WTD was initially modified via radiation-induced grafting (RIG) techniques with a TPGDA emulsion. The effect of grafting parameters on the grafting yield (GY) was calculated and grafted WTD's physicochemical properties were confirmed. Finally, the compatibility of irradiated ethylene vinyl acetate (EVA) with the integration of un-grafted WTD and grafted WTD were determined and compared. Electron beam (EB) irradiation dose at 100 kGy and lower is preferred in this study for WTD, as it has minimal effect on the WTD and maintains the WTD stability upon irradiation. In addition, the 0.4 wt% of Tween 20 (Tw-20) surfactant was chosen as the optimal amount needed as the amount is sufficient to maintain the stability of the TPGDA emulsion during the grafting process for 24 hours. The RIG technique was successful in this experiment, with a maximum GY of 930 % obtained at an ideal grafting parameter of 5 w/v % monomer concentration, 60 kGy absorbed radiation dosage, 3 h reaction time, and 60 ºC reaction temperature. According to the chemical identification and wettability analysis, the RIG method successfully introduced a large number of carbonyl groups into the WTD surface, as demonstrated by the creation of a new peak at 1720 cm-1 and a reduction in the angle of contact between the rubber surface and the water. The grafted WTD surface morphology has thickened, swelled, and coated in comparison to WTD. Additionally, it can be shown that by integrating the TPGDA monomer into the backbone of the WTD, the grafted WTD's average diameter was expanded by approximately 111.5 %. The incorporation of non-grafted WTD in the EVA blend decreased the tensile strength and hardness of the blend. However, the EVA blend containing grafted WTD has higher tensile strength and hardness compared to EVA blend with non-grafted WTD. An irradiated blend containing grafted WTD has shown an increase in tensile strength as well as hardness. The increment is due to the radiation-induced crosslinking process and improved compatibility between the grafted WTD and EVA matrix in the blend. It can also be seen that the gel content increase as the irradiation dose increases which further prove the increase in crosslinking density in the blend. The findings indicate that surface modification of WTD using the RIG technique is successful, resulting in an improvement in mechanical properties as a result of better interfacial bonding between the grafted WTD and the EVA blend.