Wire adhesion, brass

The brass coated steelcord used in adhesion tests was of a 3+9x 0.22-hI construction with a Cu content of 63%. The rabber to metal adhesion characteristics were determined according to ASTM 2229-85. The wire adhesion data quoted are averages of 10 individual tests. Wire adhesion samples were aged under the following conditions ... 

Tire Cord. Melamine resins are also used to improve the adhesion of mbber to reinforcing cord in tires. Textile cord is normally coated with a latex dip solution composed of a vinylpyridine—styrene—butadiene latex mbber containing resorcinol—formaldehyde resin.. The dip coat is cured prior to use. The dip coat improves the adhesion of the textile cord to mbber. Further improvement in adhesion is provided by adding resorcinol and hexa(methoxymethyl) melamine [3089-11 -0] (HMMM) to the mbber compound which is in contact with the textile cord. The HMMM resin and resorcinol cross-link during mbber vulcanization and cure to form an interpenetrating polymer within the mbber matrix which strengthens or reinforces the mbber and increases adhesion to the textile cord. Brass-coated steel cord is also widely used in tires for reinforcement. Steel belts and bead wire are common apphcations. Again, HMMM resins and resorcinol [108-46-3] are used in the mbber compound which is in contact with the steel cord to reinforce the mbber and increase the adhesion of the mbber to the steel cord. This use of melamine resins is described in the patent Hterature (49). 

Insoluble Sulfur. In natural mbber compounds, insoluble sulfur is used for adhesion to brass-coated wire, a necessary component in steel-belted radial tires. The adhesion of mbber to the brass-plated steel cord during vulcanization improves with high sulfur levels ( 3.5%). Ordinary rhombic sulfur blooms at this dose level. Crystals of sulfur on the surface to be bonded destroy building tack and lead to premature failure of the tire. Rubber mixtures containing insoluble sulfur must be kept cool (<100°C) or the amorphous polymeric form converts to rhombic crystals. 

The patented wire is again cleaned with acid, rinsed, and brass plated just before the second drawing. The brass acts as a drawing lubricant and as well as an adhesive to mbber. The brass composition is typically 60—70% copper with 2inc as the remainder. The patented, brass-plated wire is drawn into filaments of 0.15—0.38 mm diameter. 

Changes observed in the composition of the rubber/brass interphase correlated well with results of adhesion tests carried out on brass-plated steel wires embedded in blocks of rubber [46]. The force required to pull the wires out of the blocks decreased steadily as vulcanization temperature increased. This effect was especially pronounced when the specimens were aged at elevated temperature and humidity for several days before the wires were pulled out of the rubber blocks. 

Geon and Seo [47] also determined the effect of vulcanization time on the adhesion of natural rubber to brass-plated steel. For relatively short times, there was a peak at the end of the copper profile that corresponded well with a peak in the sulfur profile. Similarly, peaks in the zinc and oxygen profiles corresponded well. These results showed that copper sulfide and zinc oxide mostly formed at short times but some evidence for formation of zinc sulfide was also obtained. For long times, the peak in the sulfur profile no longer corresponded with that in the copper profile. Instead, the peak in the sulfur profile corresponded to the peak in the zinc profile. It was concluded that the formation of zinc sulfide increased substantially at long times. An increase in vulcanization time correlated well with a decrease in the force required to pull brass-plated steel wires out of rubber blocks. 

The manufacture of a sandwich fusehead proceeds in the following manner. Brass or other metal foils are fixed on each side of a sheet of pressboard with a suitable adhesive. The pressboard is then stamped into combs of the shape shown in Fig. 10.3 and steps are cut in the tips of the heads. Fine resistance wire is stretched across the heads and soldered to the foil on each side of the pressboard. These operations were originally all carried out by hand now many are carried out mechanically. 

Braiding hoses with wires to resist high burst pressures or for external protection is common, using a braiding machine. The wires used, usually of steel, will be either zinc- or brass-coated to achieve adhesion during vulcanisation. The gauge of the wire and its tensile properties will be matched to the expected service demands for the hose. 

Wire coats good adhesion to brass coated steel wire and to adjoining rubber compounds, tear, fatigue, and age resistance... 

Adhesion Tests. The wire used for testing was National Standard single strand, brass-plated wire (diameter, 0.16"). Two polyester cord materials were used, DuPont T-68-1300/3 and Fiber Industries T-785-1000/3. 

Table VII. Static Adhesion Data for DHA-4VP Copolymers on Brass-Plated Steel Wire ...

The bead is constructed from a number of turns or coils of high tensile steel wire coated with copper and brass to ensure good adhesion of the rubber coating applied on it. The beads function as rigid, practically inextensible units that retain the inflated tire on the RIM. 

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. 

Wire and fiberglass, being high-modulus inorganic belt cords, are not processed like textile cords. Steel cord is brass plated at the foundry and, thus, can be used directly at the calendars. Glass yarn is treated with adhesive dip and then used directly in the weaving operation. 

The adhesive layer between the rubber and cord is generally considered to be formed by the interaction between the copper and the vulcanization system. As a result of this, optimization of the vulcanization system with respect to adhesion is critical. Also, a change in the composition of the brass coating on the steel wires, or a change in the thickness, can require a change in the vulcanization system in order to maintain the optimum level of adhesion. 

Silicas, which are in competition with carbon blacks as functional fillers for plastics and rubbers, have one significant advantage their white color [62]. The most important role of silicas is as elastomer reinforcements, inducing an increase in the mechanical properties. Other functions, in addition to their use as antiblocks for PE, PP, and other films, are (a) to promote adhesion of rubber to brass-coated wires and textiles, (b) to enhance the thermal and electrical properties of plastics, (c) in accumulator separators, and (d) as rubber chemical carriers. 

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 role of silica-only systems on adhesion has been studied using model compounds with squalene [59]. It was shown that the mechanism for increased adhesion to brass-coated wire-to-rubber was not just a simple improvement of the physical properties of the rubber, but that silica moderated the thickness and composition of the interfacial layer by a chemical interaction. SEM-EDX (scanning electron microscopy with energy dispersive analysis of X-rays), XPS, AES and PIXE (proton induced X-ray emission spectroscopy) revealed that silica affected the relative concentrations of compounds present in the interfacial layer, promoting zinc oxide formation in particular. 

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