Effect of weathering variables on the lightness of high-density polyethylene woodflour composites

Abstract

Wood-plastic lumber is promoted as a low-maintenance, high-durability product. After weathering, however, wood-plastic composites (WPCs) often fade. In the first part of this study, 50 percent woodflour-filled high- density polyethylene (HDPE) composite samples were manufactured. Composites were exposed to two accelerated weathering cycles in a xenon- arc type weathering apparatus: either ultraviolet (UV) light only or UV light and water spray. The composites lightened less when they were exposed to only W light compared with exposure to UV light and water spray. In the second part of this study, WPCs with changing wood contents were exposed to UV radiation with water spray. The results were compared with exposure to both a single water soak and a series of cyclical soaking-drying periods. Composites exposed to a single water soak did not lighten, those exposed to cyclical soaking and drying lightened only at high wood contents, and all composites lightened after exposure to UV radiation with water spray. The results of this study demonstrate that exposing WPCs to water spray in combination with UV light is more severe than exposing WPCs to only UV light, or to only water. This is likely a result of water spray washing away the degraded layer and wood extractives during weathering, as well as causing the wood-plastic interface to be compromised through dimensional changes in wood particles.

Citation

Stark, Nicole M. 2005. Effect of weathering variables on the lightness of high-density polyethylene woodflour composites. 8th International Conference on Wood-fiber-Plastic Composites (and other natural fibers) : May 23-25, 2005 ... Madison, Wisconsin, USA. Madison, WI : Forest Products Society: pages 207-212.