A method for producing a shaped article comprising two closely-spaced substantially parallel walls enclosing a volume therebetween which is filled with foam

摘要

Articles are blow moulded from thermoplastic polymeric materials containing high proportions of fillers such as glass fibres. The method comprises extruding the filled polymeric material through a die having a mandrel for constraining the material into a tubular shape; coextruding between the die and the outer surface of the material, a liquid having a freezing temperature lower than that of the material; cooling the liquid and the outer surface of the material during their passage through the die to a temperature below the freezing temperature of the material but above the freezing temperature of the liquid while maintaining the inner surface of the material molten; squeezing the extrudate at suitable intervals to fuse the molten inner surface together and thereby seal discrete lengths; and inflating the sealed lengths to conform to a surrounding mould to produce laminar shapes which are then foam-filled to give stiff panels.