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Both flexible and rigid forms of poly(vinyl chloride) (PVC) were effectively dechlorinated in NaOH/ethylene glycol (EG) solution during ball mill pulverization. The high degree of dechlorination obtained was attributed to the increased surface area of the crushed PVC particles and the resulting enhancement of contact between the PVC and dissolved hydroxide ions. The common additives diisononyl phthalate and CaCO3 were easily separated from the PVC bulk during the dechlorination reaction. The reaction proceeded under chemical control, with degrees of dechlorination for both flexible and rigid PVC increasing with temperature with apparent activation energies of 110 and 80 kJ/mol, respectively. This reaction was accurately represented by a modified shrinking-core model.

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This study examined the chemical modification of polyvinyl chloride (PVC) by substitution with SCN (thiocyanate) as a nucleophile. The effects of temperature, molar SCN/Cl ratio, and solvent on the substitution by SCN and the elimination of HCl were investigated. In SCN/EG (ethylene glycol) solution, the substitution/dechlorination ratio increased with decreasing temperature. The dechlorination yield increased with an increasing molar SCN/Cl ratio, favoring the substitution over the elimination. When N,N‐dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solutions were used as solvents, DMF favored the substitution, whereas DMSO favored the elimination. In the SCN/DMF solution, the substitution yield and the substitution/dechlorination ratio increased with increasing temperature. Higher temperatures favored the substitution over the elimination in SCN/DMF. Furthermore, the reaction of PVC in SCN/tetrahydrofuran (THF)‐DMSO (1:2) proceeded at room temperature, favoring the substitution over elimination. The isomerization of SCN was observed, resulting only in NCS (isothiocyanate) at room temperature and SCN (thiocyanate) at 190°C. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers