A method for producing an extruded polystyrene foam in which when a foamable melted product, obtained by heat-melting a styrene resin composition and adding a foaming agent thereto in an extruder provided with a die slit section having an opening a (mm) in the thickness direction, is extrusion-foamed through the die slit section into a low pressure zone to form a plate-shaped foam, thereby obtaining an extruded polystyrene foam having a density of 20 kg/m.sup.3 or more and 45 kg/m.sup.3 or less, a closed cell ratio of 90% or more, and a thickness A (mm) of 10 mm or more and 150 mm or less, a foaming agent containing hydrofluoroolefin and other organic foaming agent is used, a thickness extension ratio A/a of an opening a in the thickness direction of the die slit section and a thickness A of the extruded polystyrene foam is adjusted to 18 or less, and a foamable melted product, just before the extrusion from the die slit section, is pressurized to 4.5 MPa or more and 10.0 MPa or less.

Poly(ethylene tetrafluoroethylene) (ETFE) polymers having an average molecular weight of at least 300,000 g/mol and a melt enthalpy of at least 57 J/g are provided. The ETFE polymer may include at least one additional comonomer. The ETFE polymer is used to form a porous tape or membrane that has a node and fibril structure. A porous ETFE tape may be formed by lubricating the ETFE polymer and subjecting the lubricated polymer to pressure at a temperature below the melting point of the ETFE polymer. Optionally, the ETFE tape may be expanded at a temperature below the melting temperature of the ETFE polymer to form an expanded ETFE membrane. Alternatively, the ETFE polymer may subjected to heat and pressure without the addition of a lubricant to form a dense preform. The dense preform may be subsequently slit in a length direction and stretched to form a dense ETFE fiber.

A multilayer film includes an inner layer system having a first surface and a second surface; a first layer bound to the inner layer system at the first surface of the inner layer system; and a second layer comprising a first surface and a second surface, wherein the second layer is with its first surface bound to the inner layer system at the second surface of the inner layer system; a coating layer bound to the second layer at the second surface of the second layer; wherein the inner layer system consists of a polymer formulation (A) comprising: 10.0 and 90.0 wt % of a first ethylene-based polymer being LLDPE-A; and 10.0 and 90.0 wt % of HDPE having a density of 940 and 970 kg/m.sup.3; the first layer contains a polymer formulation (B) including LLDPE-A, the second layer contains a polymer formulation (C) including a modified polyethylene; and the coating layer includes a polyurethane; wherein the multilayer film is a bi-directionally oriented film, and the orientation in both directions is introduced in the solid state. Such multilayer film exhibits reduced oxygen transmission rates and/or water vapour transmission rates.