The role of NaOH in the hydrothermal dehydrochlorination of polyvinyl chloride

The role of NaOH in polyvinyl chloride (PVC) dehydrochlorination was studied over a concentration range that yielded the maximum reaction rate. In addition to limiting autocatalysis through HCl scavenging, NaOH also influences the physicochemical evolution of PVC during hydrothermal treatment. In 3 M NaOH, the dechlorination rate peaked because NaOH effectively prevented particle agglomeration and autocatalysis. This is attributed to the action of sodium cations in producing short-range hydration repulsive forces that prevent the adhesion of particles and facilitate significant size reduction. The apparent activation energy was 138 ± 3.0 kJmol−1. In 2 M NaOH, particle agglomeration and pronounced autocatalysis reduced the activation energy to 105 ± 7.2 kJmol−1. Therefore, NaOH influences both the morphological evolution and dechlorination reaction kinetics.