Effects of virgin Ethylene–Propylene–Diene–Monomer and its preheating time on the properties of natural rubber/recycled Ethylene–Propylene–Diene–Monomer blends

• Reactive processing method is applied to improve the properties of NR/R-EPDM blends.
• Mechanical properties are obviously improved by applying reactive processing method.
• The enhancement in tensile strength is in good agreement with result observed in SEM.
• Applying reactive processing method is clearly successful to NR/R-EPDM blends.

Blending of natural rubber/recycled Ethylene–Propylene–Diene–Monomer (NR/R-EPDM) blends was carried out. A fixed amount of carbon black and virgin Ethylene–Propylene–Diene–Monomer (EPDM) were also introduced into the blends. Applications of two different processing methods were carried out to improve the cure compatibility, crosslink distribution, and hence mechanical properties of the blends. Simple processing method was done by mixing the entire additives and rubbers on a laboratory-sized two-roll-mill at ambient temperature. Whereas, reactive processing method was conducted by mixing virgin EPDM, recycled EPDM and other compounding ingredients using an internal mixer, the compound was later preheated according to designated time before blending with natural rubber and carbon black. Results revealed that the enhancement of the physical and mechanical properties was significantly achieved towards preheating time of EPDM/R-EPDM blends. The improved properties in the blends suggested that the reactive processing method had led to more homogeneous blends due to a better crosslink distribution and more homogeneous carbon black distribution.

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