Journal of Applied Polymer Science, Vol.57, No.10, 1155-1171, 1995
Mechanism of Radiation Vulcanization of Natural-Rubber Latex Sensitized by Monoacrylates
The mechanism of radiation vulcanization of natural rubber with 2-ethyl hexyl acrylate (2EHA) monomer was investigated using electron spin resonance spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The primary radicals formed in the acrylate molecule were found to abstract the allylic hydrogens of the polyisoprene. Crosslinking may occur through the allylic radicals and/or main chain radicals formed on the polyacrylate. Acrylate was found to concentrate in the rigid regions of the crosslinked rubber indicating heterogeneity and a nonuniform distribution of the acrylate in the latex particles. The addition of the acrylate and the irradiation seems to effect the Brownian motion of the latex particles. Both the viscosity and the NMR peak widths are effected by the irradiation. Addition of 5% 2EHA increases the crosslinking by a factor of 3.6. The thermal stability of the rubber first increases with the dose in the presence of acrylate, but drops at higher doses due to peroxide formation.
Keywords:POLYFUNCTIONAL MONOMERS;RADICALS