Cross‐Linking efficiency of styrene‐butadiene rubber with dicumyl peroxide and evaluation of interaction parameter

The cross‐linking efficiency of dicumyl peroxide with styrene‐butadiene rubber (SBR‐1507) has been measured by the swelling method. The values are found to be 2.5 and 5.0 for unpurified and purified SBR, respectively. The lower value in the former case has been ascribed to the destruction of peroxy radicals by the antioxidants present in the rubber. The physical cross‐links due to chain entanglement for purified SBR are found to be 0.14 . 10−4 mole/g of rubber (0–07.10−4 cross‐links due to chain entanglement/g of rubber). The solubility parameter for purified SBR as determined from both swelling and viscosity measurements is found to be 8.45 (kcal/ml)1/2 or cohesive energy density as 71.403 kcal/ml. Using this value of the solubility parameter, the solvent‐polymer interaction parameter is calculated and is further verified by HUMMEL'S method. The average value is found to be 0.37.