Effects of pigments on the UV degradation of wood‐flour/HDPE composites

Abstract

Abstract The effects of different color pigments on the durability of wood‐flour/high‐density polyethylene composites (WF/HDPE) were evaluated by UV‐accelerated weathering tests. WF/HDPE composites were dyed using three different color inorganic pigments, which were added at 2% based on the weight of the composite. Samples were weathered in Q‐panel UV aging equipment for 1500 h. All samples showed significant fading and color changes in exposed areas. Changes in surface chemistry were studied using spectroscopic techniques. X‐ray photoelectron spectroscopy (XPS) was used to verify the occurrence of surface oxidation. Changes in carbonyl groups (CO), PE crystallinity, cellulose CO, and lignin aromatic CC were detected by Fourier transform infrared (FTIR) spectroscopy. The results indicate that surface oxidation occurred immediately within exposure 250 h for all samples; the surface of the control WF/HDPE composites was oxidized to a greater extent than that of the dyed WF/HDPE. This suggests that the addition of pigments to the WF/HDPE composites results in less weather‐related damage. The surface configuration observed by scanning electron microscopy revealed that WF/HDPE composites degraded significantly on accelerated UV aging, with dense cracking apparent on the exposed surface. Carbon black had a more positive effect on color stability than the other pigments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010