THERMOMECHANICAL DEVULCANIZED EPDM AS A FUNCTIONAL ADDITIVE FOR PVC COMPOSITES: EFFECTS ON MECHANICAL PROPERTIES AND PHASE COMPATIBILITY

We evaluated the performance of thermomechanical devulcanized ethylene-propylene-diene terpolymer rubber (dEPDM), obtained from postconsumer automotive weather seal rubber, as a functional additive in plasticized poly(vinyl chloride) (PVC) formulations. The formulations contained 0–40 phr dEPDM by varying the dEPDM-to-plasticizer ratio. The effect of poly(ethylene-co-propylene-co-5-ethylidene-2-norbornene) grafted with maleic anhydride (EPDM-g-MAH) on compatibility was evaluated at concentrations of 1.5, 3, and 6 phr. The results indicated that the inclusion of dEPDM led to a reduction in elongation at break while simultaneously enhancing mechanical properties, such as hardness, tensile strength, Young’s modulus, and wear resistance. Differential scanning calorimetry (DSC) confirmed an increase in glass transition temperature (T_g). Scanning electron microscopy (SEM) demonstrated significantly improved interfacial adhesion between PVC and dEPDM in the PVC containing 20 phr of dEPDM after modification with 1.5 phr of EPDM-g-MAH. These findings were further substantiated by dynamic mechanical analysis (DMA), which revealed an increase in T_g and a decrease in tan δ peak height. Overall, dEPDM was shown to be an effective functional additive for improving strength and wear resistance in PVC, but its content should not exceed 20 phr to maintain flexibility and achieve a balanced performance suitable for shoe sole applications.