Thermal transitions in high oil content petroleum-based wax blends used in granular sport surfaces

Five waxes were extracted from five different synthetic horse race tracks in the United States. These tracks included two cool weather tracks (Kentucky and Northern California) and three warm weather tracks (Southern California). All of these tracks operate over a significant range of temperatures and some even have large temperature swings within a single day of operation. Waxes used in these surfaces are generally a blend of normal paraffins, hydrocarbon oil, and microcrystalline wax that most likely originated from a de-oiling process where the lower carbon distributions had been removed. In this work, a solvent separation was used to remove the wax from samples of material obtained from each of these five tracks after they had been used for at least 3 months. The drop melt temperatures of the wax separated from the five tracks ranged from 67 to over 84 °C. Gas chromatography (GC) tests showed n-paraffin mass percentages ranging from 31.4% to 37.9% with the more complex oil and microcrystalline isomers making up the remainder. The drop melt temperatures increased as the ratio of weight average molecular weights for normals and isomers for each wax approached one. GC carbon distributions spanned from approximately C22 to C67. Curves for waxes obtained using differential scanning calorimetry (DSC) for each wax also showed distinct thermal behavior. All of the waxes show indications of two thermal peaks; however, in several cases the peaks showed significant overlap. Two wax samples also had small tertiary peaks. One wax contains two well-defined GC distributions of n-paraffins (low and high number carbon) and isomers and is believed to be a blend of two different waxes. The first peak corresponds to paraffin wax melting temperature ranges while the secondary and tertiary peaks correspond to melting of high carbon number microcrystalline wax and other complex isomers containing high melting temperatures. The DSC melting transition temperatures for all the waxes studied were found to occur within expected operational temperature ranges for racing surfaces. The temperature range was obtained from a representative track over a 4-day period of operation. Given the observed changes in the properties of the waxes it is possible that the mechanical properties of the tracks will also change with temperature. The results from this analysis suggest important temperatures to consider for further analysis of the materials containing these high oil content waxes.