Semi-interpenetrating Networks in Blends of Epoxidized Natural Rubbers

Blends of immiscible ENRs are crosslinked by dicarboxylic acids at 180 degrees C in the presence of 1,2-dimethylimidazole. Due to the different epoxidation levels, the cure of ENR50 is complete well before that of ENR10. Depending on the ratio ENR10/ENR50, the blend morphology of the resulting materials, switches from diacid-enriched nodules of ENR50 dispersed in a soft matrix of ENR10 to a continuous texture, giving rise to elastomeric properties. Even in minority, ENR50 is able to create a network by semi-interpenetrating the non-crosslinked ENR10. This behavior is associated with the migration of the dicarboxylic acid into the more reactive ENR50. Since ENR10 remains still available for further crosslinking, the system opens the door to elastomeric materials based on interpenetrated networks.