Tyre cords coating

In terms of materials, one new tyre cord coating other than brass has been proposed that has actually made it to the tyre testing stage. This cord has shown some unexpected deficiencies, but if they can be overcome, this cord may have a bright future in view of its ease of manufacture and, especially, its much better corrosion resistance and environmental advantages. 

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... 

Coated fabrics, carpet backing Flock and pigment printing, motifs Tyre cord and belt fabric dips... 

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. 

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

Overall this new process is very attractive and has several environmental advantages, if it could replace brass on steel tyre cords. Tests with silane-treated tyre cords are in progress. The authors proposed use of a new tyre cord without brass coating but with a zinc coating instead, as tyre cords without brass coating are difficult to manufacture (the brass lubricates the die in the final wire drawing process). The final zinc-plated cord is then passed through a silane bath and dried. Quite remarkable in this system is that the silane-based film does not impair the adhesion of brass to sulphur-cured compound. If the adhesion of a brass plated cord is mediocre, the silane process actually improves its performance, as shown in Table 6.1 [58]. 

The other major development that needs to be recapped here is that of silane systems for bonding a wide range of metals to a wide range of compound types and formulations. This process may become a panacea for bonding in many industries, but much more work will have to be done before the process can replace the brass-coating process for bonding rubber steel to tyre cords. 

Figure 7.3a Scanning electron micrograph obtained from a brass-coated tyre cord immersed in a squalene mixture without cobalt (magnification x300 left x400 right) Reproduced with permission from G. R. Hamed and R. Paul, Rubber Chemistry and Technology, 1997, 70, 4, 541, Figure 4. 1997, Rubber Division, American...

Figure 7.3b Scanning electron micrograph obtained from a brass-coated tyre cord immersed in a squalene mixture with cobalt naphthenate (magnification x300 left x400 right)...

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... 

Pipes, packaging, radiation shields, linings, coatings, housewares, fibres. Textiles, tyre cords, electrical insulators, magnetic recording, conveyor belts, tapes (films). 

A typical automobile tyre consists of several parts (Fig. 5). The tread and sidewall make up the outside of the tyre. The tread is the portion of the tyre that comes into contact with the road, whereas the sidewall, or wall, is the side of the tyre that connects the tread and the bead. The tread is reinforced from underneath by the belt, which comprises a set of fabrics and/or wires. The plies, found in association with the belt, are layers of rubber-coated cords, which are typically made of fabric, polymer, fibreglass, or steel. The set of belts and plies is often collectively referred to as the cord, or cord body, of the tyre. The cords of the tyre wrap around the bead, the part of the tyre that rests on the tyre rim. The bead consists of both mbber bead filler and a series of steel bead wires. The last major part of the tyre, the innerliner, is a low-permeability... 

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 bond is not unduly sensitive to influences such as humidity, low mix viscosity and low vulcanizing pressures. The main drawbacks are connected with the plating process, which requires considerable investment and expertise. Brass plating has now been largely superseded by the use of proprietaiy bonding agents, except in the tyre industry, where bonding to brass-coated steel cords is still undertaken. ... 

The brass-steel couple is a very unfavourable one from a corrosion standpoint. The presence of the brass coating accelerates steel corrosion when water and salt reach the cords through punctures. However, improved cord constructions and tyre designs have largely eliminated this problem. Water and salt can no longer propagate along the entire circumference of the tyre, as the rubber fills the capillaries of the cords because of the more open cord constructions that have been developed in recent years. 

Steel cord for the Selby belt is purchased from Bekaert (Belgium). As already described, the steel cord used in conveyor belting is derived from that used in tyres. It is purchased from specialist suppliers, such as Bekaert and Steel Cords Ltd. Ordinary suppliers of steel cable for other purposes do not usually supply the rubber industry. There are two reasons for this one is the fluctuation and lack of standardization of demand, and the other is the chemically clean, zinc-coated finish required. 

In a recent publication, the Pirelli group reported that the NiZn top layer had been dropped from the system and a new tyre had successfully been developed with the Znl%Co coating only [63]. By modifying the crystal orientation of the deposit and hy developing an optimised lubricant, a cord could be obtained with equal drawing behaviour. 

Steel cord has been the main reinforcing material for tyres, hoses and conveyor belts for many decades, indeed the first steel reinforced tyres appeared over ninety years ago. However, it was not until the emergence of radial tyres that steel cord became a common form of reinforcement and understandably the adhesion between brass-coated steel cord and rubber compound became a significant factor governing the performance and durability of car and truck tyres. Therefore, it is necessary to achieve a high level of adhesion and sustain this level throughout the service history of the tyre. 

The influence of polymers and additives on the service life of non-tread tyre components is discussed on the basis of results obtained from studies of inner liner, belt and sidewall compounds. The effects of the bromine content of bromobutyl rubbers on the performance of inner hners, and of sulphenamide accelerators on the adhesion of NR belt compounds to brass coated steel cords were investigated. The mechanical properties and ageing and ozone resistance of black sidewall compounds consisting of NR blends with neodymium catalysed polybutadiene protected with different antioxidants and antiozonants were also evaluated. 5 refs. 

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