Optimization of mechanical and dynamic-mechanical properties of electron beam irradiation of reclaimed tire rubber/poly (ethylene-co-vinyl acetate) nanocomposite by design of experiment

Considering the high volume of tire consumption in the world, reuse of tire in the rubber industry is important from an economical and environmental point of view. For this purpose, nanocomposites were prepared successfully through the melt-mixing process based on thermoplastic polyethylene-co-vinyl acetate (EVA) and reclaimed tire rubber (RTR). The samples with different weight ratios of EVA and PTR (30/70, 40/60, and 50/50) and including Cloisite 30B organoclay (2, 4, and 6 phr) were cured through electron beam (EB) irradiation with doses of 100, 150, and 200 kGy. Two types of compatibilizers such as epoxidized natural rubber (ENR 50) and maleic anhydride-grafted ethylene vinyl acetate copolymer (EVA-g-MA) were employed to enhance the dispersion of nanoclay and its interaction with the polymer phases. To study the simultaneous effect of all parameters, their interactions and to reduce the number of samples, two-level partial factorial method with central points and ANOVA was used in Minitab software. The extent of nanolayer intercalation was evaluated using an X-ray diffractometer (XRD). The results indicated the formation of intercalation structure of clay nanoplatelets. Energy-dispersive X-ray (EDX) analysis was studied to analyze the elemental composition of the rubber-clay samples. The EDX maps confirmed the good distribution of nanoclay platelets. Furthermore, tensile test and dynamic mechanical analysis (DMA) were performed. The results of software-aided optimization showed that the highest mechanical properties and the lowest loss factor (Tan delta)(max), at its maximum of two phases of the blends were obtained for a sample compatibilized with EVA-g-MA and including 50/50 EVA/RTR and 6 phr nanoclay cured under 200 kGy irradiation dose. The sample compatibilized with ENR50 under similar conditions was ranked next.