Improvement of Homogeneity of SBR/CR Rubber Blends with SBR-g-AA Grafted Rubber.

The graft copolymerization of acrylic acid (AA) onto styrene butadiene rubber (SBR) was carried out in toluene at 80°C using benzoyl peroxide (BPO) as initiator. The synthesized styrene butadiene rubber-g-acrylic acid (SBR-g-AA) was characterized with Raman IR spectroscopy. A study was conducted on the use of SBR-g-AA for improving the homogeneity of styrene butadiene rubber/chloroprene rubber (SBR/CR) blend. The SBR-g-AA was incorporated into SBR/CR blend with different blend ratios. The homogeneity of such blends was examined with scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and determination of the dielectric properties. The scanning electron micrographs illustrate improvement of the morphology of SBR/CR rubber blend as a result of the incorporation of SBR-g-AA onto that blend. Also, the dielectric constant (permittivity) and the dielectric loss plots versus the SBR/CR blend ratio show straight lines upon incorporation SBR-g-AA, indicating and confirming the homogeneity of that blend. Physico-mechanical properties of the blend vulcanizates, in presence and absence of SBR-g-AA, were determined, and their thermal stability was evaluated after accelerated thermal aging. The results reveal that SBR/CR (25/75) blend possesses the best thermal stability. Swelling behavior in toluene, in motor oil, and in brake fluid of the blend vulcanizates was also assessed. [ABSTRACT FROM AUTHOR]