Contaminant Diffusion through a Novel Coextruded Vapor Barrier

Abstract

Organic contaminant diffusion through a novel multilayer coextruded vapor barrier is examined for benzene, toluene, ethylbenzene, xylenes (BTEX), trichloroethylene (TCE), and tetrachloroethylene (PCE). The vapor barrier considered is composed of five materials: linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), ethylene vinyl alcohol (EVOH), a tie layer (TL), and a degradation layer (DL). Parameters for the LLDPE, HDPE, TL, and DL are developed using material-specific diffusion tests. Contaminant-specific permeation coefficients (Pg) for these materials range from 1.4 to 9.2×10−11 m2/s. The diffusion parameters of the EVOH are inferred from testing of a thin (0.0889-mm) coextruded LLDPE/TL/EVOH/TL/EVOH membrane, and the contaminant specific Pg values range from 1.9 to 7.0×10−14 m2/s. These individual layer parameters are used to develop a single set of parameters for each contaminant for the entire vapor barrier, with overall contaminant specific Pg values of 2.7−13.8×10−13 m2/s. The parameters are used to model various vapor intrusion scenarios which show that the multilayer vapor barrier results in significant predicted decreases in airspace concentrations compared to HDPE or no barrier.