Elastomeric films from structured latexes

A model structured latex that is capable of forming a self‐curable elastomeric film under mild temperature conditions was developed. In this model latex system, a small amount of dimethyl meta‐isopropenyl benzyl isocyanate (TMI®) was copolymerized with n‐butyl acrylate (BA) onto poly(butadiene‐co‐styrene) [(P(Bd‐S)] seed latex particles. In the final stage of the film formation process, the latex particles coalesce with each other, and interdiffusion of PBA‐based polymer chains in the shell layers of adjacent structured particles occurs. At this stage, the isocyanate groups in the P(BA‐TMI) shell layer would begin to crosslink by either a moisture‐cure reaction via trace amounts of water remaining in the latex film or by a post‐added crosslinker that contains amine groups. Improved elastomeric properties of the latex film are expected from this kind of “interphase” crosslinking structure. However, latex films prepared from the model P(Bd‐S)/P(BA‐TMI) core/shell latexes were cracked and brittle, which was explained by the formation of a highly crosslinked/grafted core/shell interphase zone. Saturation 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 development of the interphase zone and the degree of crosslinking during the second‐stage polymerization. An elastomeric film with good mechanical and anti‐aging properties was formed from this hydrogenated‐P(Bd‐S)/P(BA‐TMI) structured latex. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1143–1152, 1997