Better Color and Thermal Stability of Suspension PVC Produced on an Industrial Scale by the Continuous Initiator Dosing Technology

Polyvinyl chloride (PVC) resins obtained by the continuous initiator dosing (CiD) technology and produced on an industrial scale show improved color and thermal stability, as compared with conventional PVC. The thermal stability of the PVC resins was characterized by the dehydrochlorination test, static thermal aging test, and thermogravimetry, while the color was evaluated by spectrophotometric measurements. It could be assumed that the better properties of the CiD PVC resin are ascribed to a slightly lower level of polymer chain defects, but our NMR results are not conclusive in this respect. Hydrogen bond strengths of the radicals generated by the organic peroxide initiators used in CiD and conventional PVC polymerizations were compared with the hydrogen bond dissociation energy of the PVC chain. The lower residual amount of initiator in the CiD PVC resin and practically the energetic inability of its radicals to abstract hydrogen from the PVC chain were considered to be the cause of the better color and thermal stability of the resin.