Accelerated UV Aging of a Wax-Based Binder Used in Synthetic Granular Composite Equine Sports Surfaces

A series of controlled ultraviolet (UV) exposure tests were conducted on a virgin high-oil content, paraffin-based wax binder used in an operational US Thoroughbred horse racetrack to simulate multiyear outside exposure. This type of hydrocarbon binder is commonly used in synthetic granular composite surfaces used in North American Thoroughbred horse racetracks and other equine sports surfaces. The binder coats the sand, fiber, and rubber particulate that make up the surface. Previous research on this binder, extracted yearly from the same racetrack over a six-year period, showed that environmental oxidation increased steadily (no material was added to the surface during this period). Chemical and compositional changes to the binder have been shown to affect the mechanical performance of the overall surface, which may impact the safety of both horse and jockey/rider. The results of this study demonstrate that two days of accelerated aging in the laboratory using a UV-modified convective furnace generates binder oxidation consistent with six years of natural environmental exposure. The increase in oxidation over time, determined using the 1,700 cm−1 carbonyl absorption peak in the infrared absorption spectrum, was found to be linear in nature, thus giving a practical method to correlate aging over time with other synthetic racetrack surfaces and associated wax-based binders. Results were substantiated by Fourier transform infrared spectroscopy, with supporting data from differential scanning calorimetry, and gas chromatography–flame ionization detection.