1977 Volume 34 Issue 11 Pages 785-791
Permeability coefficient of oxygen has been examined for ethylene-inyl alcohol copolymer (EVA) films with different ethylene contents and its relation to the physical properties was discussed. The EVA films used in this study were obtained by melt-extrusion without any further heat-treatment or drawing. The logarithm of the permeability coefficients for EVA which contain ethylene over 30 mol% increased linearly with increasing ethylene content under a humidity below about 30%, although those of EVA with lower ethylene contents than 30 mol% deviated from this linearity by showing higher permeability coefficient than expected. These may be attributed to an accelerated molecular motion in the non-crystalline region of EVA caused by an adsorption of water between the molecular chains. Provided that the rate-determining process of the diffusion and permeation of oxygen would depend to a large extent on the formation of ‘hole’ the size of which is comparable to that of oxygen, the permeability coefficient for a randam copolymer was found to be expressed by the following equation:
ln P=V1ln P1+V2ln P2
where P and V are the permeability coefficient and volume fraction, respectively. Suffixes 1 and 2denote the components of random copolymer.
