Adhesives for rubber

Chemlok . [Lrad] Bonding agent, adhesive for rubber, urethanes, polyolefins, thermoplastic elastomers. 

There is little practical value in complete hydrogenation since the end-product, at least in the case of the polybutadienes, can be prepared by the direct polymerization of ethylene. Partially hydrogenated materials, still capable of cross-linking by residual unsaturation, are of interest for a variety of possible applications including adhesives for rubber-to-metal bonding. 

Today, multipurpose adhesives based on polychloroprene rubber generally are used as adhesives for rubber articles. 

The adhesive properties of nitrile rubber can be further improved by chemical modification. Nitrile rubber treated with isocyanate was mixed with a polyisocyanate and found to be an excellent adhesive for rubber to sailcoth laminates. In other work, methyl methacrylate was grafted onto nitrile rubber to give a material with good adhesive strength. 

Cross-linkable rubbery polyesters have been produced but are now no longer produced. Rubbery polyester-amides were introduced by ICI under the trade name Vulcaprene as a leathercloth material but later were used primarily as leather adhesives and as flexible coatings for rubber goods. A typical polymer may be made by condensing ethylene glycol, adipic acid and ethanolamine to a wax with a molecular weight of about 5000. 

Casein is used for a number of miscellaneous purposes in which foimolisation is not required. These include adhesives, stabilisers for rubber latex, paper finishing agents and miscellaneous uses in the textile industry. Mention may also be made of casein fibres, available in Italy between the two world wars under the name of Lanital. 

Butyl phenolic resin is a typical tackifier for solvent-borne polychloroprene adhesives. For these adhesives, rosin esters and coumarone-indene resins can also be used. For nitrile rubber adhesives, hydrogenated rosins and coumarone-indene resins can be used. For particular applications of both polychloroprene and nitrile rubber adhesives, chlorinated rubber can be added. Styrene-butadiene rubber adhesives use rosins, coumarone-indene, pinene-based resins and other aromatic resins. 

Pigments and fillers are added to rubber base adhesives for various purposes ... 

The solvent plays an important role in the performance of rubber base adhesives. The solvent is the carrier for all components of the adhesive. Furthermore, the solvent controls the viscosity, open time, tack and adhesion of rubber base adhesives. 

The homopolymers, which are formed from alkyl cyanoacrylate monomers, are inherently brittle. For applications which require a toughened adhesive, rubbers or elastomers can be added to improve toughness, without a substantial loss of adhesion. The rubbers and elastomers which have been used for toughening, include ethylene/acrylate copolymers, acrylonitrile/butadiene/styrene (ABS) copolymers, and methacrylate/butadiene/styrene (MBS) copolymers. In general, the toughening agents are incorporated into the adhesive at 5-20 wt.% of the monomer. 

Where resorcinol adhesives are not suitable, resins can be prepared from modified resorcinol [128], Characteristic of these types of resins arc those used for tyre cord adhesives, in which a pure resorcinol-formaldehyde resin is used, or alternatively, alkyl resorcinol or oil-soluble resins suitable for rubber compounding are obtained by prereaction of resorcinol with fatty acids in the presence of sulfuric acid at high temperature followed by reaction with formaldehyde. Worldwide more than 90% of resorcinol adhesives are used as cold-setting wood adhesives. The other most notable application is as tyre cord adhesives, which constitutes less than 5% of the total use. 

Higher values of A indicate better adhesion for a particular composite, because they imply small differences in the values of rs and rf. For hard-core materials, where Ef Em, the radius q must be always larger than rf, and Ef > Em, therefore the logarithm of the ratio r /rf is a positive number and since log (Ef/Em) > 0 the values of A are always positive. This means that for a hard-core composite it is always valid that q, >q2. On the contrary, for rubber-core composites log(Ef/Em) is also negative and therefore it is valid that Pj < q2. 

Author thanks M.D. Romero-Smchez and C.M. Cepeda-Jimenez for obtaining most of the experimental results included in this chapter. Author also thanks the Spanish Research Agency (MICYT, Ministerio de Educacion y Ciencia) and the Valencian Community Research Agency (Conselleria de Educacion y Ciencia, Generalitad Valenciana) for granting different projects in the improvement of adhesion of rubber. 

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