Photochlorination of Poly(vinyl Chloride). I. Kinetics and Quantum Yield

Casted PVC films have been chlorinated by UV irradiation in the presence of chlorine gas at room temperature. For each chlorine atom fixed to the polymer chain, one molecule of hydrogen chloride was found to be evolved. The observed slowing down of the chlorination rate was attributed to the decrease of the number of methylene groups available as chlorination proceeds. Calculated values of the chlorination quantum yield (φCl) are in the range 0.6 to 2 and remain constant for conversion degrees up to 40%. The observed influence of the light intensity on the quantum efficiency, φCl ≃ I−0.5, confirms that chlorination of PVC proceeds by a chain reaction mechanism. The photochlorination process was shown to develop as far as 30 μm deep into a PVC film plasticized with 4% of casting solvent.