DRYING BEHAVIOR OF ACRYLIC LATEXES

The drying behavior of a series of monodisperse acrylate-based emulsio n polymers was studied with respect to two existing drying models. The latexes were all film forming poly(methyl methacrylate-co-butyl acryl ate)-based materials, having different polymer morphologies. Crosslink s were introduced via the addition of ethylene glycol dimethacrylate c omonomer to the emulsion synthesis, while the molecular weight was red uced by addition of CBr4 chain transfer agent. Weight loss experiments showed no discernible differences in the drying behavior of the vario us latexes, but environmental scanning electron microscopy (ESEM) indi cated marked differences. It was found that a percolation model develo ped by Croll describes the drying process well. However, certain exper imental observations were not consistent with theory. ESEM revealed th at the most 'fusible' of the latexes formed a skin during drying, prio r to the complete evaporation of the water. It was postulated that the skin remained sufficiently porous to allow unhindered water flux.