Weathering characteristics of modified rubberwood (Hevea brasiliensis)

Abstract

AbstractSurfaces of rubberwood treated with dilute aqueous solutions of chromium trioxide, chromic nitrate, ferric chloride, and ferric nitrate and modified with acetic anhydride were weathered outdoors for periods from 1 day to 1 year. Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, light microscopy (LM), and scanning electron microscopy (SEM) were used to analyze chemical and microscopic changes in treated and untreated weathered wood surfaces. Severe delignification and hemicellulose degradation occurred in untreated samples, evident from rapid decreases in IR band intensities at 1505 and 1740 cm−1, respectively. Surface delignification occurred after 1 day's exposure, with severe lignin loss within 2–3 days and almost complete surface delignification after 1 week of exposure. Fluorescence spectra of weathered wood surfaces showed a rapid decrease in intensity and a large red shift in emission maxima. Scanning electron microscopy of untreated wood surfaces exposed for 125 and 360 days showed them to have ridges in the S3 cell‐wall layer adjacent to the lumen, together with wall checking and pit degradation. Fungal spores and hyphae were observed in wood cell lumens. Pretreatment of wood surfaces with chromium trioxide (chromium VI compound) significantly restricted weathering deterioration and microbial colonization, whereas ferric chloride was most effective in preventing microbial colonization. Acetylation also partially prevented delignification and fungal staining. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 622–631, 2002