Strong and durable bonds between rubber and metals are important in many industries. The largest single commercial application is bonding of steel tire cords to sulfur-vulcanized natural rubber (NR) compounds. The current process for bonding steel tire cords to NR compounds requires the plating of brass on the individual filaments. This brass alloy is applied on the running wire as it is being drawn by electrodeposition from a cyanide plating bath. Alternatively, thin films of copper and zinc are plated sequentially, and the wire is heated so as to diffuse the copper and zinc layers. The use of the brass plating bath, especially when cyanide baths are used, causes serious environmental and waste disposal problems. However, no rubber-steel bonding process that provides the same performance as the brass coating process in terms of aged adhesion and dynamic adhesion has ever been put forward. In nontire automotive rubber-bonding applications, the brass plating process is not used, but is replaced with a two-step solvent-based adhesive process. These adhesives contain low molecular weight rubbers, silanes, fillers, crosslinkers, antioxidants, thickeners, and other components. The two steps comprise a primer coat and a topcoat, and contain relatively large amounts of flammable organic solvents such as toluene, xylene, and others. Water-based adhesives have been proposed but are not yet widely used because their performance lags behind as compared with the solvent-based materials. Although they demonstrate excellent performance for bonding different types of rubber to various metals, the solvent-based adhesives suffer from serious environmental shortcomings because they require the collection and disposal of solvents. In this project, Aeromet Technologies, Inc. (Aeromet) will develop and study a robust process for bonding tire cord to NR compounds. Aeromet will use a system for priming the metal based on the use of two different organofunctional silanes that, in prior research, have been found to be very effective. Additional chemicals will, optionally, be added to the silanes. Thus, this process will have the potential to replace current cyanide processes and eliminate solvent pollutants in other rubber bonding applications. The chances of success for this project are very high because Aeromet has, in preliminary research, already identified several unique silanes that have a high potential for success. Further, Dr. van Ooij of the University of Cincinnati will assure excellent insight into tire cord requirements and the collaboration of companies involved in various stages of tire production in Phase II and beyond. Supplemental
Keywords: small business, SBIR, natural rubber compounds, plating, cyanide, silane, rubber, tire cords
