Abstract: A maintenance-free, non-pneumatic rubber tire for wheels of slow-moving vehicles such as wheelchairs, push-chairs and carts has a base (14) a rim (15), side walls (13) and a tread (11) of generally constant thickness along the width of the tire. The central region of the tire has one or two continuously annular empty space(s) (16) dimensioned to control the spring constant of the tire to a desired value. The tire also contains reinforcement e.g. in the form of a layer of cord (17) or spiral wire.

Abstract: The elastoplastic composition comprises a blend of a thermoplastic polyolefin resin, such as polypropylene, and vulcanized epoxidized natural rubber and has good oil resistance without the use of nitrile rubber and has good mechanical properties without the need for compatibilizing agents. The elastoplastic composition may be prepared by a method which comprises mixing the thermoplastic polyolefin resin and epoxidized natural rubber at a temperature sufficient to soften or melt the resin to give an intimate blend, then while continuing mixing, adding curative for the rubber and vulcanizing the epoxidized natural rubber at a vulcanization temperature.

Abstract: A hydroxyl-functional polymer is reacted with a compound ZCO.N(H).sub.x.N(H).sub.x.CO.OR, where Z is halogen or aryloxy, x is 0 or 1 and R is hydrocarbon, and the reaction product is if necessary oxidized to give an azodicarboxylate functional polymer having the formula QOCO.N:N.CO.OR where Q is an inert polymer group. This polymer is used to react with ethylenically unsaturated natural or synthetic rubber so as to graft groups derived from the polymer on the rubber backbone.

Abstract: Graft copolymers having thermoplastic elastomeric properties are formed by intimately blending together at elevated temperature in the solid state in e.g. an internal mixer (a) an ethylenically unsaturated natural or synthetic rubber and (b) a pre-polymer of a vinyl aromatic monomer having an azodicarboxylate end group reactive towards unsaturated groups of the rubber.

Abstract: An apparatus for extruding latex in tubular form comprises a head block carrying two plugs which respectively have secured in them the upper ends of two tubes disposed coaxially one within the other. The inner surface of the outer tube and the outer surface of the inner tube are accurately formed with respect to the common axis, and an annular chamber opens to an annular space formed between the tubes in the head block. An inlet passage for latex opens to the chamber and is inclined to the radial direction so as to induce a circumferential flow of the latex into the chamber. A valve device may be provided to enable different latices to be fed selectively into the inlet passage, and a stirrer is disposed in the inlet passage where the latices enter for blending the latices on changeover from one to another during uninterrupted extrusion.

Abstract: The invention relates to the production of silica reinforced rubber incorporating a novel azo-silane coupling agent which does not depend on the vulcanization reaction to effect coupling to the rubber. The novel coupling agents are of the general formula:Y -- X -- CO -- N .dbd. N -- CO -- X.sup.1 -- Zwhere X and X.sup.1 are the same or different and each is an imino group, an oxygen atom, or a substituted or unsubstituted methylene group; Y is a substituted or unsubstituted alkyl, aryl or aralkyl group or is the same as Z; and Z as an alkyl, aryl or aralkyl group which has an substituent at least one silane group of the formula: --Si(OR).sub.3 or --OSi(OR).sub.3 in which R is a straight or branched chain alkyl group. The azo-silane is typically used in amounts of from .1 to 10 pphr. Silica reinforced rubber vulcanizates produced using the azo-silane can have improved properties e.g. abrasion resistance, scorch resistance and resilience as compared with vulcanizates made using conventional coupling agents.

Abstract: A method of surface treating elastomer surfaces comprises applying thereto a 4-substituted-1,2,4-triazoline-3,5-dione preferably in solution. The treatment improves adhesion using normal elastomer adhesives, improves resistance to peeling with flexible paints and reduces the surface tack of the elastomer. The method is advantageous over prior art chlorination and halogen donor techniques particularly in that the triazoline diones are relatively non-corrosive and non-toxic.

Abstract: Self-setting products, having utility in sealing pipe-joints, are made by mixing a latex of natural or synthetic rubber and a sensitising agent therefor with a copolymerizable unsaturated organic monomer, and initiating polymerisation of the monomer for example by means of a redox catalyst syatem so as to gel the latex and cause the product to set.