Polymer Engineering and Science, Vol.39, No.9, 1597-1603, 1999
Performance of polyethylene/ethylene-vinyl alcohol copolymer/polyethylene multilayer films using maleated polyethylene blends
Blends of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted with maleic anhydride (LLDPE-gMA) were used to promote adhesion between LLDPE and ethylene-vinyl alcohol copolymer (EVOH) in a coextruded three layer flat film, trying to avoid the use of a tie layer. These particular films could be an option when the equipment for a five layer system is not available. The effect of the modified polymer on the surface of cast films was characterized through contact angle measurements. T-peel strength, and oxygen and water Vapor transmission rate of the multilayer films were measured as a function of LLDPE-gMA content. Compressed films with 0%, 0.03%, and 0.08% of maleic anhydride (MA) were also analyzed by infrared spectroscopy (FTIR). The increased T-peel strength observed when using MA contents higher than 0.08% suggests a good interfacial adhesion between layers. This increase could be associated with specific interactions between the LLDPE-gMA and the EVOH, as the development of covalent bonds through the reaction of the anhydride with the EVOH hydroxyl groups across the interface. This was proved by the FTIR analysis that showed an increase in the ester band absorbance with an increase on the maleated polymer content and bonding time indicating that a chemical reaction occurred, at the interface. The observed changes on the oxygen and water vapor barrier properties of the films were not significant.