Layers in the form of sheets, strips or tubing comprise the plastic material described in the parent Specification viz. that produced by reacting an alkaline polysulphide with a compound, other than a halogenated ether, halogenated alcohol, ester of a polyhydric alcohol and a halogenated fatty acid or p-xylylene dichloride, of the general formula X--(CH2)m-R--(CH2)n-X<1>, where X and X<1> are monovalent negative elements or groups, R is a divalent element or group and m and n are integers. Examples of the latter are thioethers, e.g. sym. dibromdiethyl sulphide and p-xylylene dihalides. The plastic material which is cured or stabilized by heating, may be mixed with carbon black, zinc oxide, litharge, iron oxide, magnesium carbonate, barium sulphate, lithopone; with natural or artificial rubber or chloroprene, or with natural or artificial resins, and with softeners such as diphenyl guanidine and tetra-methyl-thiurampolysulphide. Conductors may be covered as by extrusion or by applying as a strip. As the material is particularly oil-resistant, oil or other liquid insulating material may be interposed between the conductor and the covering of plastic material. When rubber is incorporated it is preferable to have little or no paraffin or stearic acid or like compounding oils or softeners in the mixture. The plastic material can be applied to porous or fibrous materials to form a compound fabric or applied as a latex to impregnate fabric and like porous material. It may be used in the manufacture of printers' blankets, rolls, balloon fabrics, meter diaphragms, hose and tubing, washers, gaskets, &c. It may also be applied to woven metal cloth or screens or to wood or artificial boards. The plastic material, particularly when in the form of latex, may be mixed with such fillers as textile or asbestos fibres, leather particles, wood flour, cork &c., coagulated, dried and pressed into various shapes such as rings, gaskets, valve discs, packing sheets or shaped articles or containers. Seals along the edges of floating roofs in crude oil storage tanks may be made of fabric impregnated or coated with the plastic materials. Road markers may be formed of the material compounded with coloured pigments.ALSO:Layers in the form of sheets, strips or tubing comprise the plastic material described in the parent Specification, viz. that produced by reacting an alkaline polysulphide with a compound, other than a halogenated ether or an ester of a polyhydric alcohol and a halogenated fatty acid or p-xylylene dichloride or halogenated alcohol, of the general formula X-(CH2)m-R-(CH2)n-X1, where X and X1 are monovalent negative elements or groups, R is a divalent element or group and m and n are integers. Examples of the latter are thioethers, e.g. sym. dibromdiethyl sulphide and p-xylylene dihalides. The plastic material which is cured or stabilized by heating, may be mixed with carbon black, zinc oxide, litharge, iron oxide, magnesium carbonate, barium sulphate, lithopone; with natural or artificial rubber or chloroprene, or with natural or artificial resins, and with softeners such as diphenyl guanidine and tetra-methyl-thiuram-polysulphide. Conductors may be covered as by extrusion or by applying as a strip. As the material is particularly oil-resistant, oil or other liquid insulating material may be interposed between the conductor and the covering of plastic material. When rubber is incorporated it is preferable to have little or no paraffin or stearic acid or like compounding oils or softeners in the mixture. The plastic material can be applied to porous or fibrous materials to form a compound fabric or applied as a latex to impregnate fabric and like porous material. It may be used in the manufacture of printers' blankets, rolls, balloon fabrics, meter diaphragms, hose and tubing, washers, gaskets, &c. It may also be applied to woven metal cloth or screens or to wood or artificial boards. The plastic material, particularly when in the form of latex, may be mixed with such fillers as textile or asbestos fibres, leather particles, wood flour, cork, &c., coagulated, dried and pressed into various shapes such as rings, gaskets, valve discs, packing sheets or shaped articles or containers. Seals along the edges of floating roofs in crude oil storage tanks may be made of fabric impregnated or coated with the plastic materials. Road markers may be formed of the material compounded with coloured pigments.