The tribological behaviour of skin equivalent materials and ex-vivo human skin during sliding contact with artificial turf

Abstract

The use of synthetic materials for outdoor and indoor sport fields has increased over the last decades. Artificial turfs, commonly used on football fields, are basically infilled with recycled crumb rubber derived from old tires, the main of which are NBR (acrylonitrile butadiene rubber) and SBR (styrene-butadiene rubber) with fibers usually made of Polyethylene (PE) or Nylon. The use of these polymers for artificial turf designing purposes has caused controversy to whether their impact in human health, especially in skin abrasions during players sliding on the artificial turf. We have studied the tribological performance of different artificial human skin and real human skin against NBR, PE and Nylon 6.6 at different environmental conditions: normal conditions (25 ˚C and 50% of relative humidity) and high humidity conditions (37 ˚C and 80% of relative humidity) and forces of 2 and 4 N to achieve the association between friction and skin damage. The applied forces correspond to a range of pressures of 121 to 175 kPa and the experiments were conducted at 50 mm/s. The friction coefficient was obtained for different artificial skin samples: Lorica, Silicone L7350, pure PDMS, Cutinova and ESE (an epidermal skin equivalent developed by us), and these results were compared to those obtained from excised human skin samples obtained from healthy people after a surgery carried out at the Radboud Hospital of Nijmegen. Later on the human skin samples were analyzed with confocal microscopy and histological images to study the case of the surface properties of skin and determine any possible damage on the Stratum Corneum related to the tribological tests.