Room temperature initiated and self-heating polymerization via concentrated emulsions: Application to acrylonitrile based polymers

A novel concentrated emulsion polymerization procedure, in which the polymerization is initiated at room temperature and the heat generated by the reaction accelerates the process, is proposed. The polymerization of acrylonitrile (AN) and its copolymerization with vinylidene chloride (VDC) are used as examples. AN (alone or with a comonomer) containing an oxidant was first dispersed in water to generate a concentrated emulsion. The polymerization of the monomers was initiated at room temperature by introducing an aqueous solution containing a mixture of reductants (ferrous sulfate and sodium metabisulfite) into the concentrated emulsion. The heat generated in the system increased its temperature and accelerated the polymerization. The polymerization was completed in one hour with conversions higher than 90%. The small volume of the continuous phase in a concentrated emulsion constitutes an advantage of the procedure, since only a small amount of the produced heat is used for its heating. In addition, because the reductant, which is present in the water phase, together with the oxidant, which is present in the oil phase, constitute the initiator, the large oil-water interfacial area of the concentrated emulsion constitutes an additional advantage.