Abstract: A method for producing intaglio designs in cast acrylic material, wherein a moulding tool hotter than 600.degree. C. is applied to a surface contact area of an acrylic surface in which the intaglio copy of the moulding tool is to be formed, and the moulding tool is withdrawn from the surface contact area before the temperature of the tool or the acrylic material of said area falls below that at which methyl methacrylate vapor ceases to be produced by the depolymerization of the acrylic material. The preferred withdrawal temperature is above 250.degree. C.

Abstract: A substantially planar reticulated material is formed by the conjunction of a plurality of strips of non-planar material so that the strips lie substantially perpendicular to the plane of the reticulated material with their edges lying coplanar with the reticulated material and forming opposite surfaces thereof. Each strip of nonplanar sheet material is formed on each opposite surface with a pattern of crests and valleys of repetitive wavelength such that each pattern repeat contains at least two crests and at least two valleys; in each pattern repeat the height of at least one crest or valley on at least one surface of the strip is different from that of at least one of the other respective crests and valleys on said surface; the recurring height difference produces a corrugation along the strip having a wavelength greater than the wavelength of the crests and valleys; and adjacent strips are abutted with the corrugation opposed to interfit at least one crest in a valley of each opposed corrugation.

Abstract: Apparatus for stretch-forming a heat softened sheet of thermoplastics material. The apparatus includes a stretching tool and means to move the stretching tool relative to means holding the sheet so as to stretch the sheet in a preselected direction with the tool. The stretching tool includes a plurality of blades having edges for pressing against the sheet to stretch the sheet and a cam to move the blades transversely away from each other to stretch the sheet transversely of the preselected direction as the tool is moved to stretch the sheet in the preselected directions.

Abstract: Method and apparatus for stretch-forming a hollow article from a sheet of thermoplastic material at a temperature higher than 25.degree. C. below the melting point wherein a stretching tool having at least one tip at a temperature lower than 50.degree. C. below the melting point is pressed against the sheet, and the initially stretched sheet is then further stretched and simultaneously dilated. One form of tool comprises a number of blades arranged around a plunger which are moved forward and outwardly after initially stretching the sheet forwardly. The articles so produced can be further formed by blow moulding.

Abstract: A slurry explosive composition which contains fibrous material as a rheology modifying agent.