The use of wood-polymer composites (WPC), combination of plastics and lignocellulosic fibers, is developing considerably. However, the effects of weathering, such as color fading and loss in mechanical properties, limit their performance in outdoor applications. WPC produced in Iran and made of high-density polyethylene and sugar cane fibers was studied. The effect of fiber pretreatments (delignification to various levels and, pigmentation) and clear coating on the resistance to weathering and biodegradation, and to their combination, was investigated. Chemical (NIR, ESR and FTIR spectroscopy), physical (color, roughness, wettability), mechanical (vibration, 3 points bending and indentation) and biological (resistance to fungi and termites) observations were made on extruded samples. Delignification generally reduced initial mechanical properties while not preventing degradation and color change due to weathering, except when combined with addition of pigments where the rigidity was stabilized to some extent. Clear coating showed very promising results: it prevented color changes associated to photo and bio-degradations, and reduced the loss of properties due to weathering. Although fungi and termites provoked some surface degradation of weathered samples due to the better accessibility of fibers, the resistance of the products to degradation was good. From the methodological viewpoint, the good correlation between various mechanical parameters suggests the applicability of nondestructive testing methods based on modal analysis or indentation techniques for in-situ characterization of WPC properties or evaluation of the degradation level.
