Abstract: Polyvinylidene fluoride compositions have their flexibility improved by incorporation therewith of a minor proportion of one or more esters formed between at least one aliphatic diol such as 2,2-dimethyl 1,3-propanediol, a polyethylene glycol, propylene glycol, a polypropylene glycol, tetramethyleneglycol, a polytetramethyleneglycol or an aliphatic triol such as glycerol, and a monocarboxylic acid of aliphatic chain containing 2 to 10 carbon atoms or a monocarboxylic acid of aromatic radical such as benzoic acid. Polyvinylidene fluorides of improved flexibility are particularly useful for manufacturing flexible tubes for conveying various fluids such as, for example, hot water, chemical products, hydrocarbons.

Abstract: High- and medium density polyethylene compositions become extrudable and cross-linkable during the extrusion step by incorporating therein a free radical generator and an additive for plasticizing the polyethylene composition, at a relatively low extrusion temperature insufficient to decompose the free radicals generator, consisting of a C.sub.14 to C.sub.24 n-alkyl acrylate polymer having an average molecular weight by number of from 500 to 50,000, used in a proportion from 0.5 to 10% by weight.