Prediction of vinyl chloride monomer migration from rigid PVC pipe

Abstract

Data on the solubility and diffusion of vinyl chloride monomer (VCM) in PVC resin powders have been combined with published solutions of Fick's diffusion equation to yield predictions of the amount and rate of loss of residual VCM (RVCM) from rigid PVC pipe under storage and service conditions. The principal factors controlling VCM migration are the initial VCM content, thickness of the PVC section, temperature, and the age of the PVC product. Analytic solutions are presented for RVCM loss from freshly extruded pipe (uniform VCM concentration) into either the storage environment or the pipe contents. From these solutions, estimates are made for the real-world situation of closed-system service following variable storage periods. The validity of this approach for rigid PVC pipe in water-service is supported by reasonable agreement between its predictions and experimental laboratory data on the VCM content of water stored in PVC pipes. Both the predictive model and experimental data indicate that PVC pipe containing 5 1 mgikg (1 part per million) residual VCM will result in VCM concentrations in water of less than 0.002 mgikg under any expected service conditions.

Effect of variable storage times on the calculation of diffusion coefficients characterizing small molecule migration in polymers

“…As an example, if one assumes a film thickness of 40 mils (0.1016 cm) and a diffusion coefficient of 2.0 X 10~12 cm2 [a typical value for migration of small molecules in glassy polymers (Berens and Daniels, 1976)], the plots in Figure 1 which describe the apparent fractional loss (M//MJ) as a function of the square root of apparent time (t 0 for given storage times can be calculated using eq 8 in conjunction with eq 3 or eq 4. A similar plot of apparent fractional loss as a function of dimensionless apparent time, ' b Dt'/t2, for given dimensionless storage times, 8 = Dta/£2, is presented in Figure 2.…”

Effects of kinetic and transport parameters on accelerated migration of reactive additive from plastic sheet

“…Figure 12 compares the effect of Biot number Bi and + on fractional migration for a partially reactive Fg. 8…”

“…reactive migrants (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(19)(20)(21)(22). on the environment type (18,24,27).…”

The diffusion of chloroform and carbon tetrachloride from rigid PVC pipe and rigid CPVC pipe into water

“…xtensive studies have been carried out on the diffusion of heavy metals, vinyl chloride, and other organic chemicals from PVC pipe ( 1 4 ) . A. R. Berens and C. A. Daniels (5) studied the diffusion of residual vinyl chloride monomer (RVCM) from PVC pipe, calculated the diffusion constants, and correctly predicted that low RVCM pipe, 1 mg/kg (ppm), will not give detectable vinyl chloride monomer in water under any expected service conditions. Their study also showed that six-month-old pipe containing 22 mg/kg of RVCM in the pipe would yield less than 5pg/kg (ppb) vinyl chloride monomer in a water extract.…”