Effects of Epoxidized Natural Rubber (ENR-50) and Processing Parameters on the Properties of NR/EPDM Blends Using Response Surface Methodology

The effects of epoxidized natural rubber (ENR-50) and processing parameters on the properties of natural rubber/ethylene-propylene-diene rubber (NR/EPDM; 70 : 30 phr) blends were studied. The compounds were prepared by melt compounding method. Using response surface methodology of two-level full factorial, the effects of ENR-50 contents (-1 : 5 phr; +1 : 10 phr), mixing temperature (-1 : 50 degrees C; +1 : 110 degrees C), rotor speed (-1 : 40 rpm; +1 : 80 rpm), and mixing time (-1 : 5 min; +1 : 9 min) in NR/EPDM blends were evaluated. Cure characteristics and tensile properties were selected as the responses. The significance of factors and its interaction was analyzed using ANOVA and the model's ability to represent the system was confirmed using the constant of determination, R-2 with values above 0.90. It was found that the presence of ENR-50 has the predominant role on the properties of NR/EPDM blends. The addition of ENR-50 significantly improved cure characteristics and tensile strength up to 5.12% and 6.48% compared to neat NR/EPDM blends, respectively. These findings were further supported by swell measurement, differential scanning calorimetry, and scanning electron microscopy. (C) 2014 Wiley Periodicals, Inc.