Branched Chain Natural Rubber Derivatives Obtained by Reaction with Azodicarboxylates

Abstract

Abstract 1. Ethyl azodicarboxylate (EAD) and ethylene dis-ethyl azodicarboxylate (DEAD) react quantitatively with natural rubber to form branched and cross-linked derivatives, respectively. 2. The mechanical properties of vulcanizates from natural rubber containing side branches (obtained with the aid of EAD) differ greatly from the properties of unbranched vulcanizates. 3. Analysis of the load-extension diagrams shows that the introduction of EAD side chains into natural rubber results in the formation of vulcanizates with high extensions at low loads. Vulcanizates without EAD have steeper load-extension diagrams and lower extensions at break. 4. As the temperature rises from 20 to 100°, the elastic modulus and mechanical losses (or the logarithmic damping decrement) of vulcanizates cross-linked with DEAD decreases greatly (about 4–7 times). Addition of 10 per cent (g-equiv.) of EAD side chains approximately doubles the mechanical losses in comparison with vulcanizates without EAD.