PREPARATION AND MORPHOLOGICAL CHARACTERIZATION OF 2-COMPONENT AND 3-COMPONENT NATURAL RUBBER-BASED LATEX-PARTICLES

Different emulsion polymerization processes allowed variation in the m icrostructure 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 polys tyrene (PS). The bipolar redox initiating system tert-butyl hydroperox ide/tetraethylene pentamine promoted a core-shell arrangement. Further more, PS subinclusions were introduced into the NR core. The initiator s used for the subinclusion synthesis were azobisisobutyronitrile at h igh temperature and a redox initiation system consisting of tert-butyl hydroperoxide/dimethylaniline at low temperature. The morphology of t he resulting latex interpenetrating networks (IPN) was characterized b y transmission electron microscopy (TEM) and scanning electron microsc opy (SEM). Different staining methods allowed us to increase the contr ast between the NR phase and the secondary polymers in the composite l atex particles. A semicontinuous feeding process decreased the PS subi nclusions size by a factor of 6 in comparison with a batch reaction. D epending on the NR/styrene swelling ratio, the crosslinking degree, an d the polymerization temperature used, distinct differences of the pha se arrangement of polymers in the latex particles were revealed. (C) 1 996 John Wiley & Sons, Inc.