Bonding of Rubber

Rubbep-to-Fabric Bonding. Rubber-to-fabric bonding is of considerable commercial significance in the tire industry and industrial rubber goods such as conveyor belts and rubberized ftibrics. In the tire industry, the so-called resorcinol-formaldehyde (RF) latices are still used predominantly for bonding rayon, whereas mainly resorcinol-formaldehyde-vinylpyridine latices are used for bonding nylon and adhesively finished polyester yams, which, unless specially pretreated, adhere very poorly to rubber. 

In industrial rubber goods, which exhibit considerably greater variations in rubber composition, solutions of unvulcanized rubber mixtures are used. They are applied to the fabric as a first coat with the addition of polyisocyanates to improve adhesion. Directly adhering rubber mixtures containing resorcinol-formaldehyde donors and an acidic silica filler are also used for the production of fabric-reinforced rubber materials. 

Rubber-to-Metal Bonding. In the Ebonit or hard rubber process [76], the bonding agent is a reaction product of natural or synthetic rubber with 30-40% sulfur, which is thermoplastic in character, adheres firmly to metal, and provides for good adhesion to soft rubber. This process is still in use today in the lining of vessels and, to a certain extent, in the manufacture of large-diameter rolls. 

The brass process makes use of the fact that electrodeposited brass of certain composition and crystal structure is capable of directly bonding rubber mixtures, providing their composition is compatible with the adhesion process [77]. Whereas today the brass process is of only minor significance for the production of rubber-metal composites, it is widely used in tire manufacture for bonding the bead wires and for bonding the carcass mixture of steel cord. 

Certain polyisocyanate adhesives allow bonding of rubber to metal with far less technical effort than by the brass process. However, polyisocyanates are extremely sensitive to atmospheric moisture and react with compounds containing OH and NH2 groups, such as antiagers. This reaction leads to a weakening of adhesion. 

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Many isocyanates have good adhesive properties and one of them, triphenyl-methane-pp /7"-triyl tri-isocyanate, has been successfully used for bonding of rubber. Isocyanates are, however, rather brittle and somewhat limited in application. Somewhat tougher products are obtained from adhesives involving both polyols and isocyanates, i.e. polyurethane-type materials. The major application of these materials to date is in the boot and shoe industry. 

Degradation of rubbers and resins can also be produced by ozone attack. Ozone directly reacts with, and cleaves, the carbon-carbon double bonds of rubbers and resins. Thus only polymers with backbone unsaturation will be cracked by ozone. Unlike oxidation, ozone attack cannot be accelerated by increasing the... 

Copper-zinc Copper-zinc alloys are deposited for two main purposes (a) as a decorative finish, e.g. on steel and (b) as a means of obtaining an adhesive bond of rubber to other metals. 

As noted in the Chapter 7 Focus On, rubber is a naturally occurring polymer of isoprene, or 2-methyl-l,3-butadiene. The double bonds of rubber have Z stereochemistry, but gutta-percha, the E isomer of rubber, also occurs naturally. Harder and more brittle than rubber, gutta-percha has a variety of minor applications, including occasional use as the covering on golf balls. 

A material used to promote the bonding of rubber to other materials, principally metal and textiles. 

When compared with compression molding, transfer molding provides better product consistency, shorter cycle times, and better bonding of rubber to metal [55]. However, considerable amount of material is lost as scrap in the transfer pad, sprues, and flash. The basic three-plate multiple cavity mold is more complex and expensive than a comparable compression mold but is suited better for intricate parts or securing inserts [56]. 

The effects of carbon blacks on vulcanization kinetics and crosslink yields are not discussed here, as they do not usually involve bonding of rubber to the surface. 

Efforts to bond rubber to metal without the use of metal plating led to what is believed to be the first research efforts in surface preparation prior to adhesive bonding. Strong and durable bonds of rubber to metal were necessary for rubber shock mounts for automobiles in the late 1920s, but they were limited to proprietary formulations used on specific metals. In 1927 solvent-based thermoplastic rubber cements for metal-to-rubber bonding were prepared from rubber cyclized by treatment with sulfuric or other strong acids. With these rubber cements strong bonds could be made to either vulcanized or unvulcanized rubber. 

The fact that rubber cannot be distilled also seems to suggest low-molar-mass cyclic compounds held together by partial valence. It was known that associated substances have a much higher boiling point than nonassociated ones. Pickles/ on the other hand, suggested the even now accepted chain structure for rubber. As proof of constitution he carried out the first relevant polymer modification, namely, the addition of bromine across the double bonds of rubber. Since the bromine addition did not alter the molecular size. Pickles considered natural rubber to be a true molecule. However, his conclusions were not generally accepted. 

In the adhesive mechanism of rubber to metal surface, ZnO plays an important role. In the bonding of rubber to brass, ZnO reacts with copper oxide on the brass surface to form a tightly adhering zinc-copper salt. 

Experiments with steriospecifically labeled [4- H]MVA (Archer and Audley, 1967, 1973) have indicated that the cis double bonds of rubber are... 

Uses preparation of polyurethane resin and Spandex fibers bonding of rubber to rayon diisocyanate in the production of polyurethane lacquers, foam plastics, rubber, and glues A... 

In cases other than the above, plastics pipes should only be bonded with the approval of the pipe manufacturer. Similarly, the bonding of rubber hose requires care and specialised knowledge. 

A peculiar example of spin-labelling is 1,3-dipolar addition of paramagnetic nitrones (XIV) to the double bonds of rubbers [117] ... 

The depth of the bonded seal can be less and the space between the bore and the outside diameter can be changed for ease of fitting. The bonding of rubber to metal is an important... 

Polyisocyanates, particularly triphenylmethane 4,4, 4"-triisocyanate, are used for the bonding of rubber to rubber, metals, glass and synthetic fibres. They may be used in rubber-containing cements or, in the case of triphenylmethane triisocyanate, alone. 

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