Light-Stabilized Coatings for Preservation of Wood-Plastic Composite Decking

By Robert Waldron, Brett Moyer

Four light stabilizer (LS) options (including a no light stabilizer case and three different combinations of UV absorber and hindered amine free radi­cal scavenger) were tested in each of three waterborne acrylic topcoats on each of two wood-plastic composite (WPC) substrates ( one made with poly­ethylene and a second made with polypropylene).

Corresponding samples, as well as samples of each substrate without any topcoat, were prepared for both accelerated weathering in a xenon arc weatherometer (1000 hr, CAM 7) and for exterior exposure on a test rack.

The unprotected WPC samples exposed to accelerated weathering light­ened significantly. The corresponding CIELAB  values were in the range of 13 to 14. The samples protected with topcoats that lacked light-stabilizer additives fared better, The samples protected with light-stabilized topcoats showed the best color stability, The values corresponding to the best­ performing topcoat resin/light stabilizer combination were in the range of 4 to 6.