The use of natural rubber-based material for the preparation of radiation-curable resin. I. The reaction of epoxidised natural rubbers of low molecular weight with acrylic acid

A synthesis method for the preparation of a new radiation-curable resin based on natural rubber has been established. The method was based on the reaction between epoxidised natural rubbers (ENR) of low molecular weight, i.e. Mn 0f 5,800 to 82,000, with acrylic acid in the presence of a catalyst and an inhibitor. Two grades of ENR namely ENR-25 and ENR-50 corresponding to 25 and 50 mole % epoxidation levels, respectively were used. The acrylation was carried out at temperatures between 95-105 degree C and was monitored by the measurements of the acid value of the reaction mixture as the reaction proceeded. It was confirmed by IR spectroscopic technique that the reaction occurred through the ring opening of the epoxide group of ENR. As a result, the new resin contains radiation-curable acrylate groups as well as hydroxyl groups on its main chain. When formulated with benzophenone, it solidified upon with UV light