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4739748 
Journal Article 
Barrier permeation properties of EVOH thin-film membranes under aqueous and non-aqueous conditions 
Mcwatters, RS; Rowe, RK 
2018 
Yes 
Geotextiles and Geomembranes
ISSN: 0266-1144 
Elsevier Ltd 
46 
4 
529-541 
English 
WOS:000434004800015 
Ethylene vinyl alcohol (EVOH) copolymers can provide a superior barrier to hydrocarbons and are increasingly being used in co-extruded geomembranes for geoenvironmental applications. These thin-films behave differently under different humidity conditions. This study investigated the permeation properties of toluene through two EVOH thin-films (32 mol% ethylene and 44 mol% ethylene) for both non-aqueous and aqueous solutions. The results of this study are used to gain a better understanding of the behaviour of the EVOH layer used in co-extruded geomembranes. The thin-film results are compared with published values for co-extruded linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) geomembranes with an EVOH core. Permeation coefficients are presented over a range of contaminant concentrations from 25 ppm to 99% toluene based on almost five years of continuous testing and the effect of moisture is discussed. A number of EVOH thin-films were affected by humidity (i.e., where moisture diffused into the film) prior to diffusion testing under nonaqueous conditions. This observation led to an investigation of the effect of moisture uptake on the permeation of toluene under non-aqueous testing. In these cases, the 44 mol% thin-film had lower toluene permeation coefficient values than the 32 mol% thin-film. These values were similar to toluene permeation coefficient values from tests with aqueous solutions. When relative humidity was less than 60%, the 32 mol% had slightly lower permeability values than 44 mol% thin-film. However, even when affected by humidity, the permeability of both thin-films were considerably (two to three orders of magnitude) lower than previously observed in a water-saturated solution. Permeation of toluene from a 1/1 toluene/hexane solution was also examined for the 32 mol % EVOH thin-film at temperatures of 23-50 degrees C and results fit well with a conventional Arrhenius relationship of increasing P g values with increasing temperature. 
Ethylene vinyl alcohol; Geomembranes; Vapour barriers; Diffusion; Relative humidity; Organic contaminants; Temperature