| Abstract: | Three acrylate monomer systems were deposited by redox emulsion polymerization at room temperature into the fibrous matrix of 2-mm-thick chrome-tanned cattlehide over a wide range of composition. Polymer not bound to the matrix was separated by hot benzene extractions. Monomers used were methyl methacrylate, a mixture of n-butyl acrylate and methyl methacrylate and n-butyl acrylate, each selected to produce composites having wide variation in glass-transition temperature. The same three systems were introduced into the free space of leather by bulk and solution polymerization. All conversions were close to 100%. When the emulsion technique was used, with feed composition variable, overall deposition efficiency depended on the characteristic rate of deposition for the individual acrylate monomers. Observed orders in deposition rate and overall efficiency were: methyl methacrylate > comonomer > n-butyl acrylate. However, specific deposition efficiencies declined roughly monotonically with feed or time increase, but maintained the same order. Microscopic examination of thin sections revealed polymer only in the outer region of the leather cross section. Information on polymer location and its influence on specimen thickness for composites prepared by both emulsion and solution methods of deposition were obtained by correlating experimental densities with theoretical density–composition curves for various assumed models. The foregoing, together with observations of greatly reduced grafting frequency, in view of the maximum theoretically attainable, made a dominant grafting mechanism unattractive. A mechanism involving diffusion controlled monomer transport to occluded radicals in localized polymer deposits was suggested as an alternative. |
