MODIFICATION OF NATURAL-RUBBER LATEX .3. NATURAL-RUBBER POLYSTYRENE COMPOSITE LATEXES SYNTHESIZED USING AZOBISISOBUTYRONITRILE AS INITIATOR

Materials which may be classified as interpenetrating polymer networks have been prepared by the in situ polymerization of styrene in natural rubber latex using azobisisobutyronitrile (AIBN) as the initiator. The resulting materials have been characterized by electron microscopy, Soxhlet extraction coupled with proton nuclear magnetic resonance spectroscopy, dynamic mechanical analysis, and stress-strain analysis. The styrene polymerizes within the natural rubber latex particles to give a relatively fine phase-separated morphology with some evidence for a limited degree of segmental mixing. Moreover, it is clear that AIBN, despite what is stated in the literature, does lead to some grafting of polystyrene, and, in addition, causes significant degradation of the natural rubber molecules when the styrene content is low.