Sunlight Degradation of Polymeric Detectable Warning Surface Products

Abstract

Detectable warning surface (DWS) is a panel product installed at the edge of curb ramps to warn visually impaired pedestrians about the proximity of the roadway. Most DWS products are made of polymers and are subjected to outdoor weathering. Therefore, sunlight degradation is an important factor that affects their service life. In this study, the effects of sunlight on material degradation in four DWS products made from polyester, neopentylglycol (NPG), polyurethane, and polyolefin were evaluated by exposing DWS test coupons in a xenon weatherometer. The exposure conditions were largely based on ASTM D 2565 for a duration of 3,000 h. Color change induced by radiation was measured using a spectro-colorimeter. The fastest discoloration was measured in DWS made from polyurethane. The largest color change occurred between 500 and 1,000 h for polyurethane and between 1,000 and 3,000 h for other polymers. The changes of surface appearance observed under a digital microscope were consistent with the discoloration. The reinforcing fibers in DWS products made from polyester and polyurethane were revealed after 3,000 h exposure. Decrease in surface wear resistance was obtained in tested coupons that were exposed to the highest irradiance level. The product made from NPG exhibited the greatest decrease in wear resistance, while that made from polyolefin showed the least change.