. . . "The temperature at which cross-linking is effected may vary between and 160 C. This method of cross-linking is advantageous by comparison with the cross-linking of graft copolymers containing non-saponified ethylenevinyl ester copolymer by means of radical forming compounds, such as peroxides, in that when cross-linking with the aforementioned crosslinking components (for example diisocyanates), i" .