Kinetic Analysis of the ⁶⁰Co γ Ray-Initiated Inverse Emulsion Polymerization of Sodium Acrylate Solutions

Abstract

The kinetics of the 60Co γ ray-initiated inverse emulsion polymerization of aqueous sodium acrylate solutions in kerosene with Span 80 as the emulsifier was investigated. The conversion−time curves were analyzed using the equation [εx/(1 − ε) − ln(1 − x)] = B (constant) + [n̄k p/(V p ∞ N A)]t, derived on the basis of a monomer droplet nucleation mechanism. The following expressions were obtained for K = [n̄k p/(V p ∞ N A)] under the experimental conditions investigated: K ∝ [dose rate]0.9[sodium acrylate]0.5 [Span 80]0.4, which was simplified to n̄ ∝ [dose rate]0.9, n̄k p ∝ [sodium acrylate]0.5, and n̄/V p ∞ ∝ [Span 80]0.4. The polymerization rate during the steady state (approximate conversion range 20−80%) could be expressed by R p = KxC 0 ∝ [dose rate]0.9[sodium acrylate]1.5[Span 80]0.4. The kinetic analysis suggests a dose rate independent polymerization process for the system studied such that, at any time, there was only one active passage of radiation through a droplet, viz., all polymer radicals resulting from a radiation passage were terminated before another passage.