TECHNOLOGY FOCUS - POLYMERS - Preferred Materials: The optional alpha -olefin comonomer in (A) is propylene, 1-butene, 1-hexene, 1-octene or 1-decene. The reactive function X in (B) is carboxylic anhydride, preferably in the form of maleic anhydride units; or epoxide, preferably in the form of glycidyl methacrylate units. The polyethylene (A) has an ethylene unit content of at least 90% and a density of more than 0.92 (preferably more than 0.93). The polyolefin (B) contains ethylene units, and is especially an ethylene-alkyl (meth)acrylate-maleic anhydride copolymer. (I) optionally contains one or more additives selected from coupling agents, crosslinking agents, UV absorbers, dyes, optical brighteners and fire retardants. EXAMPLE - A film (Ia) of thickness ca. 0.5 mm was produced from a blend (50:50 by weight) of 1020 FN 24 (RTM: medium density polyethylene of density 0.922 g/cm3, melt index 2.1 g/10 minutes and m.pt. 109 degrees C) (A1) and Lotader 6200 (RTM: ethylene-ethyl acrylate-maleic anhydride copolymer (90.7:6.5:2.8 by weight) of melt index 40 g/10 minutes and m.pt. 102 degrees C) (B1), by extrusion using a screw rotating at 85 rpm, successive heated zones at 125 degrees C, 125 degrees C, 125 degrees C and 133 degrees C and a die plate at 125 degrees C. (Ia) had a moisture transmission rate (DIN 53122, method E, at 23 degrees C and 85% relative humidity) of 9 g/25 mu m/m2.24 h; and a peeling force, in delamination tests on a glass plate-(Ia)-backsheet assembly (the backsheet being of polyvinylidene fluoride (PVF)-polyethylene terephthalate-PVF laminate), of 29.5 N/15 mm (breakage occurring by delamination of the backsheet). The corresponding data for an ethylene-vinyl acetate (EVA) copolymer control film (II) were moisture transmission rate 400 g/25 mu m/m2.24 h and peeling force 2 N/15 mm (adhesive breakdown taking place). (Ia) thus showed greatly superior water vapor permeability and peeling resistance to (II); and when used as encapsulant instead of (II) in a photovoltaic module provided superior anti-moisture protection of the photovoltaic panel, eliminated delamination of the different layers and increased the operating life of the module.