Environmentally Safe Silane Technology for Adhesion of Rubber to Tire Cord Steel

Current methods of rubber/metal bonding lead to significant environmental concerns. The largest single commercial rubber-bonding application is the bonding of steel tire cords to sulfur-vulcanized natural rubber compounds. The current processes require that cobalt be added to the rubber to provide durable bonds. Cyanide also is used in the brass plating of steel tire cords. Tire separation failures are too frequent, particularly on retread truck tires, causing roadway hazards and visible environmental contamination. In nontire, automotive rubber-bonding applications, a solvent-based adhesive process is used that suffers from environmental shortcomings related to the collection and disposal of solvents. The goal of this Phase II research project is to: (1) develop a system capable of bonding tire cords to rubber for new tires and retreads that does not contain cobalt or require cyanide-based plating, and (2) eliminate solvent pollutants in other rubber-bonding applications. This system also will eliminate volatile organic compounds in other rubber/metal-bonding applications. During Phase I, Aeromet Technologies, Inc., developed excellent silane mixtures and methods, including nanoparticle additions to improve silane coating thickness and interfacial bonding. Hydrolyzed silanes for bonding rubber to metal surfaces have been demonstrated successfully. Characterization techniques have identified the chemical reactions for the mixed silanes, effects of nanoparticles, and the bonding mechanism. A patent has been filed based on the work performed during Phase I. The scope of work for Phase II includes further characterization of the silane mixtures with additives and the study of the actual bonds between the rubber and the metal surfaces using time-of-flight secondary ion mass spectroscopy and fourier transform infrared spectroscopy techniques. The newly identified silane mixtures and application methods from Phase I will be optimized, and production-run tire cords will be tested on prototype and production equipment according to industry-accepted standards. Commercialization studies will include market analysis, potential environmental improvements, and cost-saving opportunities for the tire industry. The tire companies will provide rubber formulations and identify physical tests. A tire cord manufacturer has committed to perform demonstration tests at its facility, and two tire companies have prepared letters of support for Phase II. Based on the success of Phase I, Aeromet Technologies, Inc., has obtained the support of tire cord manufacturers and tire producers. There are excellent opportunities for commercialization in nontire applications and in the tire industry because of reduced environmental impact, lower costs, and additional corrosion benefits over the current methods.