Abstract:
The aim of this research was to investigate the behaviors of epoxy resin blended with epoxidized natural rubbers (ENR). ENRs were prepared from HA concentrated natural rubber latex via 'in situ' epoxidation method with various amount of hydrogen peroxide, formic acid and surfactant at 50°C for 4, 6, 8, 10, 14 and 16 h. FT-IR spectra showed that the obtained ENRs contained epoxide groups 25, 40, 50, 60, 70 and 80 mole percent and were nominated ENR 25, ENR 40, ENR 50, ENR 60, ENR 70 and ENR 80 respectively. The amounts of ENRs in the blends were 2, 5, 7 and 10 parts per hundred of epoxy resin. After curing, mechanical properties, thermal behaviors and morphology of polymer blends were examined. From the results, it was found that epoxy resin blended with ENR 40 at the amount of 2 phr showed highest impact strength. However, a high amount of epoxide group in the blends seemed to decrease the impact strength of the specimens due to the stiffness of the epoxide group. Tensile strength and Youngs modulus were found to decreased with an increasing epoxide group in ENR and also with an increasing amount of ENR in the blends. Meanwhile, percent elongation at break slightly increased when ENR content was not over 5 phr. In addition, flexural strength and flexural modulus of the blends were mostly lower than the epoxy resin. Fracture surface of all specimens was examined by SEM. The results suggested that the toughening of epoxy resin was induced by the presence of ENR globular nodules attached to the epoxy matrix. Finally, TGA and DSC were employed to investigate thermal behaviors of polymer blends. They revealed that thermal decomposition temperature and glass transition temperature of the samples showed slightly different and were in the range of 351-364℃ and 51-63℃ respectively.