RADIATION CROSS-LINKING OF ETHYLENE-VINYL ALCOHOL COPOLYMER FUNCTIONALIZED WITH M-ISOPROPENYL-ALPHA,ALPHA-DIMETHYL BENZYL ISOCYANATE

An ethylene vinyl alcohol copolymer was functionalized with m-isoprope nyl-alpha,alpha-dimethyl benzyl isocyanate using reactive processing i n a mixer. The functionalization introduces pendant unsaturation to th e polymer, which allows radiation cross-linking to gel contents > 70% at radiation doses below 100 kGy. Unfunctionalized ethylene vinyl alco hol copolymer, on the other hand, forms no gel upon irradiation. The f unctionalization was completed within a few minutes of reactive mixing , which was confirmed with both FTIR and C-13-NMR measurements. The ox ygen permeability of ethylene vinyl alcohol copolymer increased with i ncreasing degree of functionalization, and irradiation of the samples formed trapped radicals, which act as oxygen scavengers. Consequently no oxygen permeability was detected. However, radical activity was inh ibited by annealing the samples at 110-degrees-C resulting in a 24% hi gher oxygen permeability value for the irradiated unfunctionalized cop olymer. The oxygen permeability values of the irradiated functionalize d samples were approximately 13% lower. Laminates of m-isopropenyl-alp ha,alpha-dimethyl benzyl isocyanate functionalized ethylene vinyl alco hol copolymer and m-isopropenyl-alpha,alpha-dimethyl benzyl isocyanate functionalized ethylene hydroxyethyl methacrylate copolymer acquired improved adhesive strength both at dry and wet conditions as well as a t elevated temperatures upon exposure to radiation. (C) 1993 John Wile y & Sons, Inc.