An attempt was made to manipulate the course of the polymerization of VCM by changing the composition of the polymer-rich phase. The addition of n-octane, which is a nonsolvent for PVC, will induce the polymer-rich phase to become denser due to the decreasing solvent quality of the VCM / n-octane mixture.
By increasing the amount of n-octane present in the polymerization mixture the appearance of the hot spot diminishes and finally disappears completely when more than 15 wt % of n-octane is added to the reaction mixture. This disappearance is due to a decreasing polymerization rate as the monomer concentration in the polymer-rich phase decreases with an increasing amount of noctane.
During the overall polymerization process, the pressure inside the reactor decreases continuously with increasing monomer conversion due to a continuous increase of the concentration of noctane in VCM, which causes a lowering of the vapor pressure of the latter. The morphology of the PVC grains changes in case of the presence of n-octane during polymerization, which results in a higher porosity and smaller average pore diameters. Thermal stability of PVC seems to decrease when large amounts of n-octane are added to the polymerization system, as the rate of dehydrochlorination increases significantly. However, besides an obvious increase in the number of chloromethyl branches no significant difference in the number of other defect structures was found