Abstract: Biodegradable polymeric multi-layer substrates in which the tie layer or layers comprise a mixture of at least the polymers forming the substrates on either side of the tie layer wherein the grades of said polymers are selected such that their melt flow indices and their melt viscosities are similar requiring the grade of at least one polymer within the tie layer to be different from the grade of the same polymer(s) comprising one or other substrate adjacent the tie layer. The inclusion of higher melting point polymers in one outer substrate allows the multi-layer substrate to be subsequently peeled from the article to which it has been sealed.