Correlation between the structure and physical state of polyvinyl chloridein solution and its thermal stability

The effect of structure and physical state of polyvinyl chloride in solutio n arl its thermal stability are analyzed. It is shown that, whatever:the pr ocedure used to change the structure of PVC in solution, either by increasi ng its concentration or by adding poly-cr-olefins as a second inert polymer which is thermodynamically incompatible with PVC, variation of the physica l and structural state of the polymer significantly changes the rate of its decomposition. The change in the rate of thermal PVC dehydrochlorination i n solution depends on the solvent basicity, namely, in solvents with a high basicity factor B the PVC decomposition rate reduces, and in solutions wit h low B values, on the contrary, it increases. Polyvinyl (PVC) of trade mar k S-5870 with M-eta = 157 . 10(3), poly-alpha-olefins: low-density polyethy lene (PE) with Al, 400 . 10(3), polypropylene(PP) with M-w = 500 . 10(3), a nd polyisobutylene (PIB) with M-w = 150 . 10(3) were used in experiments. T he polymer mixture samples were prepared by mixing solutions of individual polymers taken in equal concentrations. Thermal dehydrochlorination of PVC and PVC mixed with other polymers was performed at 423 K in a bubbler-type reactor equipped with a reflux condenser. The evolved HCl was removed from the reaction zone by a nitrogen now. Traps with distilled water in which a certain amount of titrated potassium hydroxide solution and several drops o f alcohol indicator were added to absorb HCl. Time lapsed from the beginnin g of HCl absorption to a change in the indicator color is proportional to c hanges in the PVC dehydrochlorination rate. Solution viscosity was measured following the conventional technique with the aid of an Ubbelohde viscosim eter.