Elastomeric films from structured latexes

✍ Scribed by Y. He; E. S. Daniels; A. Klein; M. S. El-Aasser

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 183 KB
• Volume: 64
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19970509)64:6<1143::aid-app14>3.0.co;2-x

✦ Synopsis

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.