Rubber: tyre cord adhesion

Rubber tyre cord adhesion W J VAN OOlJ Adhesion to brass-coated steel Rubber-based adhesives J M MARTfN MARTInEZ General introduction Rubber-based adhesives compounding J M MARTIN MARTfNEZ Formulations, etc. 

Rubber tyre cord adhesion W J VAN OOIJ Adhesion to brass-coated steel... 

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. 

A static test for determining the adhesion of tyre cord in rubber. The test piece is in the form of a loop shaped like the letter U. 

Applied to a tyre-cord fabric without any weft or cross-threads. The individual cords are spaced out by a reed, passed into an adhesive such as LRF, dried and coated with rubber compound by... 

BS 903 Part A4858 is identical to ISO 4647 and Part A 5659 identical to ISO 5603. It is significant that the equivalent ASTM standards are not produced under the auspices of the committee for rubber but in a subcommittee of the textiles committee specifically covering tyre cord and fabrics. The H-test is in D477660 and the method for steel cord in D222961. There is also a method for strap peel adhesion test of reinforcing cords or fabric in D439362. 

Only types (l)-(4) fall within the scope of this chapter. No further reference will be made to emulsion-polymerized prolybutadiene rubbers, because they are now of little industrial significance relative to the styrene-butadiene rubbers. Poly(vinyl chloride) is discussed elsewhere in this book. Brief reference will also be made in this chapter (Section 15.5) to the production and properties of carboxylated variants of styrene-butadiene rubber latexes. It may also be noted that latexes of rubbery terpolymers of styrene, vinyl pyridine and butadiene, produced by emulsion polymerization, have long been of considerable industrial importance for the specialized application of treating textile fibres (e.g., tyre cords) in order to improve adhesion between the fibres and a matrix of vulcanized rubber in which they are subsequently to be embedded. 

Adhesives are widely used in the textile industry as shown in Table 1. If sizes and tyre cord dips are excluded, approximately 65% are used in carpet backing (mostly styrene-butadiene rubbers). Other major uses of adhesives are in non-wovens as binders (15%), in fabric backing (8%), in flocking and laminating (8%) and in fusible interlinings (2%). 

Similar high-quality rubber-to-textile adhesion can be obtained with glass and polyester woven fabrics. Also corded fabric (e.g. tyre cord) reacts in a similar manner to give bond strength breaks within rubber (R-R) when diisocyanates, such as MDI, are used as adhesive treatments. 

Other types of coupling agents include 1,2-diketones for steel [17], nitrogen heterocyclic compounds for copper [18], and some cobalt compounds for the adhesion of brass-plated steel tyre cords to rubber [19]. 

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. 

Despite this success of silanes, which are easy to use and apply, their use as metal pre-treatments for bonding metals to rubber has been lacking. The only rubber-related use is as a treatment of rubber-grade silica [32, 33]. This process improves the adhesion of the silica to the rubber and therefore the mechanical rubber properties. There is only one patent that describes the use of a silane to bond bare steel cord (in other words not plated with brass) to sulphur-vulcanised tyre cord skim stocks, published by Sharma in 1982 [54]. Good adhesion was reported but only if the compound contained a certain resin. Apparently, the silane reacted more with the resin than with the rubber compound. 

One of the most recent innovations for bonding tyre cord to rubber has been the nse of silanes to promote adhesion and to protect the interface [60, 61]. Other non-metallic systems, such as tetrachlorobenzoquinone [62] and chloropyrimidines and chlorotriazines [63] have also been studied. Regarding copper free coating of steel, alloy systems containing Zn/Ni/Co [64], Zn/Co [65,66] and other zinc alloys [67] have been proposed. 

As with most rubber composites the adhesion system used in power transmission belts is based on an resorcinol/formaldehyde/latex (RFL) type system. General overviews of RFL adhesion systems from a tyre cord perspective have been previously published by Takeyama and Matsui [31], and more recently by Solomon [32]. Bonding with RFL systems is achieved through applying an RFL coating to the fibre structure prior to the... 

Since this time, latices of vinylpyridine-styrene-butadiene terpolymers have found limited use in the treatment of textile fibres (such as tyre cords) to give improved adhesion to rubber. In this application, various vinylpyridines have been utilized but 2-vinylpyridine is the most commonly used. The vinyl-pyridine-styrene-butadiene weight ratio is typically 15 15 70. 

Rubber is frequently used as a composite with other solids, for example in tyres, belting and coated fabrics, or may be in contact with other solids during use. The testing of composite materials or products containing rubber is, in general, outside the scope of this book but certain tests which are usually considered to be rubber tests are included here. These are adhesion to metals, adhesion to fabrics, adhesion to cord, corrosion of metals and paint staining. 

The adhesion of cord, textile or metal, to rubber is a specialised measurement in that virtually all interest centres on tyres and to some extent belting. Most static tests consist essentially of measuring the force to pull a cord out of a block of rubber into which it has been vulcanised and it is apparent that the result is critically dependent on the efficiency with which the test piece was moulded. The measured force is also dependent on the amount that the rubber deforms during the test. 

Tyres are very definitely fatigued during use and, as mentioned for fabric/rubber adhesion above, it is very important to carry out dynamic tests to assess bond efficiency. Methods have not apparently been standardised but a variety of procedures have been reported71 79 Some workers have used the same or a similar test piece as in static tests and applied a cyclic tensile stress or strain, whilst others have used some form of fatigue tester operating in compression/shear to repeatedly stress or strain cord/rubber composite, or even to flex samples in the form of a belt. Khromov and Lazareva80 describe a method using test pieces cut from tyres. 

The introduction of steel cord into the manufacture of automobile tyres led to the need to find additives which would promote the adhesion of steel to rubber. A cobalt complex known commercially as Manobond C-16 has been used for this purpose.70,71 Manobond C-16 is a borate complex with the composition (RC02CoO)3B. The R groups are described as having an average of 21 carbon atoms, five of which are methyl groups. 2 No further structural details seem to be available. 

The classical work of Borroff and Wake in 1949 on the adhesion between the textile cords and the rubber casing in automobile tyres demonstrated that the only significant factor was the penetration of the fibre ends into the rubber. These fibre ends originated from the natural textile fibre (usually cotton), and it was their absence in synthetic fibres (e.g. nylon monofilament) that caused the difficulty in using these for this product. Any specific interaction between the rubber and the fibre was insignificant and only affected... 

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