PREPARATION AND PROPERTIES OF EPOXIDIZED NATURAL-RUBBER NETWORK CROSS-LINKED BY RING-OPENING REACTION

A rubber network is prepared by reacting epoxidized natural rubber (ENR) with p-phenylenediamine. The ring opening crosslinking reaction was found to have an apparent activation energy of 67.5 kJ/mole. Bisphenol A, a catalyst for the reaction, seems to reinforce the stress-strain properties of the network via hydrogen bonding interaction. Dynamic mechanical analysis and stress-strain measurement indicate that, in comparison to a typical ENR-sulfur network, the ENR-amine structure is more rigid and less stretchable at room temperature as demonstrated by its relatively high glass transition temperature and low rupture point. The ENR-amine network also demonstrates significantly lower tensile strength than the ENR-sulfur one although their crosslink densities are not significantly different. This behavior could be attributed to the former's lack of strain-induced crystallization which is a pronounced feature of the latter.