Rubber bonding mechanism

Detonation and Mechanical Properties of Rubber Bonded Sheet Explosives are discussed by W. Kegler R. Schall in the 4thONRSympDeton (1965), pp 496-501... 

The ozone sensitivity of natural rubber under mechanical stresses double bonds are broken an example is found in, e.g. laboratories where glass tubes are connected with rubber hoses at the connection where the rubber is subjected to stresses, in the long run little tears are formed. 

For the ensuing discussion of mechanical reinforcement effects it will for the most part be sufficient to regard the carbon black-rubber bond as predominantly physical, with a relatively minor, but significant portion of the surface involved in the formation of chemisorptive attachments or polymer grafts. 

Straining the macromolecules result in generation of stresses that may activate some bonds. Mechanically induced chain scission has been explored for grafting polymers and rubbers. 

The reclaiming oils and chemicals are complex wood and petroleum derivatives that swell the rubber and provide access for breaking the rubber bonds with heat, pressure, chemicals, and mechanical shearing. Approximately 2—4 parts of oil are used per 100 parts of scrap rubber. Some examples of reclaiming oils include monocyclic and mixed terpenes, i.e., pine-tar products, saturated polymerized petroleum hydrocarbons, aryl disulfides in petroleum oil, cycloparafinic hydrocarbons, and alkyl aryl polyether alcohols. 

Aerobic adhesives were developed as an advance over anaerobic and cyanoacrylate adhesives. Anaerobic (threadblocking) adhesives are used to augment mechanical fasteners such as screws, bolts, or press-fits. Cyanoacrylates tend to be used for nondurable bonding on rigid surfaces and for durable rubber bonding. 

The thin coating of brass on the steel cord is the primary adhesive used in steel-to-rubber bonding. The quality of this bonding system built up during vulcanization of, for example, a radial tire will influence the performance of the steel ply or steel belt in the tire and, ultimately, the durability of the product. Though the mechanism of bond formation in rubber-steel cord adhesion is very complex, a brief review of the current understanding of wire to rubber adhesion is presented. 

The physical bonding mechanism relies on van der Waals and London Dispersion forces. This omnipresent mechanism is favoured by the low surface energy and high degree of mobility of the polymeric chains. It is the basis of the Release property of silicone rubbers and coatings. 

The increased use of rubber in automotive, aerospace, and industrial applications has driven the requirement for strong and robust bonds between rubber and metal. Much literature has been published on the history and technology of bonding rubber to metal [1,2,3,4,5,6,7, 8]. The earliest historical methods of attaching rubber to metal involved attaching the rubber by mechanical means or by the use of ebonite. Mechanical... 

The rubber to metal bonding mechanism is very complex as there are several reactions occurring simultaneously. All these reactions must take place in a very short period of time (i.e., during the press cure time of the rubber) in order for a strong bond to form. The different reactions taking place are shown in Figure 2.3. 

The Handbook of Rubber Bonding 3.2.1 Mechanical Treatment of Metals Solvent degreasing... 

This chapter will discuss the state-of-the-art of bonding rubber compounds to brass, a technology primarily used on steel tyre cords. The literature is reviewed since 1991 when the previous review was published [1]. An updated mechanism for the rubber adhesion mechanism of brass is presented. Some new developments, such as proposed alternatives to brass, are also discussed. 

The diurethane vulcanization chemistry is even more interesting in the context of bonding mechanisms since certain of its rubber formulations exhibit self-adhering properties. For this reason, it would be instructive to review the diurethane chemistry briefly. 

Results obtained by Van Ooij in his ESCA studies on the composition of interfaces between rubber and brass" confirm that cobalt salts and HRH form essentially the same inter-facial products with a standard brass surface. Therefore, the mechanism of brass-rubber bonding must be the same for both bonding systems and differences in adhesion values must be explained by a modification of rubber properties (crosslink density, cure rate, modulus, etc.) or the rate of brass attack. Clearly, adhesion of brass to HRH-NR compounds cannot be explained on the basis of hydrogen bonds with the substrate, as in rubber-to-textile bonding. 

The use of additives to make the surface of precipitated silica less hydrophilic and more rubberphilic facilitates incorporation, dispersion, and more intimate filler-elastomer contact during compoimding. This provides an improvement in rubber physical properties, as would be expected from a high surface area, high oil absorption filler. However, reinforcement comparable to that obtained with carbon black requires a polymer-filler bonding mechanism comparable to that provided at the carbon... 

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