SBIR Phase I: Surface Modified Ground Tire Rubber for Additives of Asphalt Based Shingles

This Small Business Innovation Research Phase I project relates to the application of a surface modification to ground tire rubber (GTR) particles, enabling use of GTR as an additive to asphalt for roofing shingles, and improving its use in paving. This additive replaces the costly all-polymer additives currently used, while making use of an otherwise waste commodity. Existing processes degrade the GTR, consume excessive energy, are high-cost, and decrease the elasticity of the GTR if devulcanization occurs. Altogether, this makes the final product unsuitable for use in roofing shingles, and reduces its performance in paving asphalt. The objective of this research is to develop alternative approaches to the current technology. The intellectual merit of this proposal arises from the research related to polymer surface modification of GTR particles via a combination click chemistry and atom transfer radical polymerization (ATRP), with a polymer having considerable temperature resistance. The anticipated results and advantages include: simplification of the surface coating process, reduced degradation of the GTR particles in an asphalt compound, optimization of the viscoelastic properties of the rubber-asphalt mixture, shortening of the mixing period, reduction of the cost and energy, and improved dispersion and compatibility of rubber particles within the asphalt. The broader impact/commercial potential of this project will stem from the successful development of a low cost, high quality, thermally stable asphalt additive with high dispersibility. It will be based on surface modified Ground Tire Rubber (GTR), enabling the development of flexible, durable, high-quality roofing materials, and enhanced paving asphalt. The polymer coated GTR particles provide the advantages of a polymer additive, but using far less polymer. Commercial polymers alone have been incorporated into mixtures of asphalt for roofing and pavement, but at high cost, with current market prices of $1.50 to $1.80 per pound. In contrast, the addition of GTR particles would cost only $0.25 per pound. The initial estimated cost to surface modify the GTR particles with a polymer coating has been calculated to be ~30% above material cost. The incorporation of surface-coated GTR particles into the roofing mixture reduces the production cost up to ~20% by reducing and/or substituting the amount of expensive polymer additives currently used. The precursor materials are commercially available at low cost. Aside from enhanced performance, and low cost, using GTR particles will provide an environmental benefit, allowing reuse of tire rubber waste typically disposed in landfills, and substantially reduces use of a nonrenewable resource.