Residual monomer in acrylic polymers

Three proprietary dental resins were found to include acrylates (as distinct from methacrylates). As acrylates are well known to have adverse skin reactions, the nature and content of the acrylates were obtained. One resin contained methyl acrylate, and the other two ethyl acrylate. Also, the extractable free monomer from one proprietary and one experimental bone cement was determined as a function of time. This was carried out: (a) on unpolymerized material as soon as it formed a coherent dough; and (b) on already polymerized material. The extraction of n-butyl methacrylate from the experimental bone cement was very much less than that of methyl methacrylate from the proprietary bone cement. In both cases, whilst the kinetics of loss for short times appeared to conform to diffusion theory, subsequent loss did not; this was attributable to both continued polymerization of the monomer and to the concentration dependence of the diffusion coefficient.