Probing the postgelation reactions of epoxidized natural rubber cross-linked with dodecyl succinic anhydride

Pregelled mixes of an epoxidized natural rubber, known as ENR50, containing dodecenyl succinic anhydride (DDSA) as cross-linking agent and dimethyl benzyl amine (DMBA)as catalyst, were cured isothermally at 160 8C, and the progress of the reactions was followed by both thermal analysis (differential scanning calorimetry and thermogravimetric analysis [TGA]) and infrared spectroscopy (Fourier transformnear-infrared and attenuated total reflection).The curing reactions were found to be approximately first order for both heat of reaction associated with cross-linking and the disappearance of the epoxy groups, even though the reduction of epoxy group concentration was found to be substantially greater than the amount expected from reactions with the anhydride, because of the formation of large quantities of vicinal OH groups. The TGA data have indicated that the pregelled mixes undergo anaerobic degradation at higher temperatures than the un-cross-linked elastomer, which is accelerated by the presence of the DMBA catalyst.