| Abstract: | Different emulsion polymerization processes allowed variation in the microstructure of composite natural rubber (NR)-based latex particles. A prevulcanized and a not-crosslinked natural rubber latex were coated with a shell of crosslinked poly(methyl methacrylate) (PMMA) or polystyrene (PS). The bipolar redox initiating system tert-butyl hydroperoxide/tetraethylene pentamine promoted a core–shell arrangement. Furthermore, PS subinclusions were introduced into the NR core. The initiators used for the subinclusion synthesis were azobisisobutyronitrile at high temperature and a redox initiation system consisting of tert-butyl hydroperoxide/dimethylaniline at low temperature. The morphology of the resulting latex interpenetrating networks (IPN) was characterized by transmission electron micros-copy (TEM) and scanning electron microscopy (SEM). Different staining methods allowed us to increase the contrast between the NR phase and the secondary polymers in the composite latex particles. A semicontinuous feeding process decreased the PS subinclusions size by a factor of 6 in comparison with a batch reaction. Depending on the NR/styrene swelling ratio, the crosslinking degree, and the polymerization temperature used, distinct differences of the phase arrangement of polymers in the latex particles were revealed. © 1996 John Wiley & Sons, Inc. |
