Studies on blends of cycloaliphatic epoxy resin with varying concentrations of carboxyl terminated butadiene acrylonitrile copolymer I: Thermal and morphological properties

Differential scanning calorimetric (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) of the blends of cycloaliphatic epoxy (CAE) resin toughened with liquid elastomer such as carboxyl terminated butadiene acrylonitrile copolymer (CTBN) have been carried out. Exothermal heat of reaction due to cross linking of the resin in the presence of diamino diphenyl sulphone (DDS, an amine hardener) showed a decreasing trend with increasing rubber concentration. Enhancement of thermal stability as well as lower mass loss of the epoxy-rubber blends with increasing rubber concentration have been observed in thermogravimetric analysis (TGA). Dynamic mechanical properties reflected a monotonic decrease in the storage modulus (E′) with increasing rubber concentration. The loss modulus (E″) and the loss tangent (tan δ) values, however, showed an increasing trend with rise of temperature up to a maximum (peak) followed by a gradual fall in both cases.