The interaction of hydrogen sulfide with lead‐ and barium–cadmium–zinc‐stabilized poly(vinyl chloride)

摘要

AbstractPoly(vinyl chloride) polymers stabilized with tribasic lead sulfate discolor upon exposure to hydrogen sulfide gas as a result of lead sulfide formation. The discoloration occurs for samples in both cord and sheet forms and is shown to be a function of total H2S exposure, reaching a limiting value that is determined by the amount of lead stabilizer used in the polymer formulation. The permeation and diffusion constants for H2S through PVC stabilized with tribasic lead sulfate and with a liquid Ba–Cd–Zn formulation are found to bePPb= (6.0 ± 0.2) × 10−9,PBaCdZn= (5.2 ± 0.2) × 10−9(both in cm3gasċcm film/cm2areaċsecċcm Hg),DPb= (1.3 ± 0.2) × 10−7cm2/sec, andDBaCdZn= (6.4 ± 0.6) × 10−8cm2/sec, all measured at 21°C. The stabilizing efficiencies of the formulations were assessed by HCl evolution measurements, which show that exposure to H2S decreases the initial polymer stability for both Pb‐stabilized and Ba–Ca–Zn‐stabilized formulations. Protection of stabilized PVC formulations from diffusing hydrogen sulfide is thus advisable for long‐term stabili