ELASTOMERIC FILMS FROM STRUCTURED LATEXES

A model structured latex that is capable of forming a self-curable ela stomeric film under mild temperature conditions was developed. In this model latex system, a small amount of dimethyl meta-isopropenyl benzy l isocyanate (TMI(R)) was copolymerized with n-butyl acrylate (BA) ont o poly(butadiene-co-styrene) [(3P(Bd-S)] seed latex particles. In the final stage of the film formation process, the latex particles coalesc e with each other, and interdiffusion of PBA-based polymer chains in t he shell layers of adjacent structured particles occurs. At this stage , the isocyanate groups in the P(BA-TMI) shell layer would begin to cr osslink by either a moisture-cure reaction via trace amounts of water remaining in the latex film or by a post-added crosslinker that contai ns amine groups. Improved elastomeric properties of the latex film are expected from this kind of ''interphase'' crosslinking structure. How ever, latex films prepared from the model P(Bd-S)/P(BA-TMI) core/shell latexes were cracked and brittle, which was explained by the formatio n of a highly crosslinked/grafted core/shell interphase zone. Saturati on of the residual double bonds in the P(Bd-S) seed latex particles by hydrogenation was found to be an effective way to reduce the developm ent of the interphase zone and the degree of crosslinking during the s econd-stage polymerization. An elastomeric film with good mechanical a nd anti-aging properties was formed from this hydrogenated-P(Bd-S)/P(B A-TMI) structured latex. (C) 1997 John Wiley & Sons, Inc.