Polycarbonate Glazing - Accelerated Wiper Testing, Surface Characterization and Comparison with On-Road Fleet Data

Exatec® PC glazing technology team, has developed advanced weathering and abrasion resistant coatings technology that can be applied to protect polycarbonate. It is of particular interest to quantify and understand the factors that determine the surface abrasion performance of coated PC in rear window and backlight applications that have a wiper system. In the present study we describe Exatec's lab scale wiper testing equipment and test protocols. We also describe adaptation of optical imaging system to measure contrast and nano-profiling using nano-indenter, as post wiper surface characterization methods. These methods are more sensitive to fine scratches on glazing surface than standard haze measurement and mechanical profilometry. Three coating systems were investigated; Siloxane wetcoat (A), Siloxane wetcoat (B), and Siloxane wetcoat (B) plus plasma coat (Exatec® E900 coating). The performance comparisons were made using all these surface characterization methods. In one study, both wetcoat A and plasma coat show similar wiper abrasion performance with water only and performance is similar to glass after 500K cycle of wiper abrasion testing. Wetcoat systems alone may be enough to withstand environmental conditions where windows do not require a wiper. Exatec® plasma coatings, in another study using a slurry solution instead of water alone, shows superior performance compared to wetcoat and performance is comparable to glass. Hence the Exatec^® E900 plasma coated glazing system can be a more suitable candidate for rear windows with wiper attached to it. Test results obtained with lab scale wiper tester have been correlated with on-road fleet vehicle data to help develop appropriate specifications of accelerated wiper abrasion testing for PC glazing.