Revitalizing Used Automotive Rubber: Silicone Rubber Composites

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Scientists increasingly have an obligation to develop sustainable processes. After only a few years use, otherwise high value, resilient automotive tire rubber is typically burned, pyrolyzed to low value products, partly devulcanized, or converted to crumb; the process of taking non-renewable petroleum and using it once, or a second time in low value products, is not sustainable. Silicone polymers are sought after in many markets because of their attractive properties, including adhesion to glass, and metal surfaces, flexibility/stability to temperature fluctuations, and degradability in the environment; these are not met by organic alternatives. We have discovered a route to activate the surface of rubber crumb recovered from automobile tires to permit it to be incorporated in silicone elastomers to make high value composites. The cost of the composite is much lower than normal silicones, the elastomers exhibit enhanced reinforcement and, at end of life, the composite is readily recycled to silicones and recovered crumb that can be incorporated in new composites.This grant will determine the type and quantity of inexpensive rubber crumb that can be used to reinforce silicone elastomers to enable the development of large scale production that can be targeted to appropriate markets. Formulation objectives include: 1) control of the crumb surface, with different silicone precursors provided by our supporting organization Siltech, 2) selection of appropriate silicone cure technologies giving elastomers that can be utilized, for example, in products like mountain bike parts and commercial sealants (e.g., construction glazing), and 3) quantification of the process variables for composite creation, and correlating formulation to resulting physical properties.In these applications the low cost and high performance of silicone composites that contain the rubber crumb enables facile entry into existing markets. The complete recyclability of the composites will be demonstrated to permit a high sustainability score for the product. The rubber-in-silicone composite, based on Canadian IP, will allow Canadian companies (silicone/tire recycling) to enter new markets.