CROSS-LINKING OF ISOCYANATE FUNCTIONAL ACRYLIC LATEX WITH TELECHELIC POLYBUTADIENE - I - SYNTHESIS AND CHARACTERIZATION

An ambient curable isocyanate functional acrylic latex was synthesized by incorporating dimethyl meta-isopropenyl benzyl isocyanate (TMI(R)) , an isocyanate monomer, into styrene/n-butyl acrylate copolymer. An a rtificial latex of amino-terminated telechelic polybutadiene was prepa red and blended with the acrylic latex as a curing agent. The isocyana te content in the blended latex was determined by titration and FTIR m easurements. The latex blend properties, in terms of particle size and latex viscosity, and the latex film properties, in terms of stress-st rain behavior and solvent swelling behavior, showed no significant cha nge after 30 days' storage of the latex blend at 50 degrees C. The goo d storage stability was attributed to the stable nature of the latex b lend in which there was little chance for the isocyanate-containing pa rticles to come into contact with the curing agent particles, thus pre venting premature contact of the acrylic chains with the telechelic ch ains. The reactivity of different functional groups in the telechelic polymer was studied; the amino group was found to be the most reactive toward the TMI. In addition, a shorter chain telechelic crosslinker w as found to result in a higher degree of crosslinking, but this was mo re intraparticle than interparticle in nature. (C) 1998 John Wiley & S ons, Inc J Appl Polym Sci 68: 965-975, 1998.