Low atmospheric temperature dependence on photodegradation of wood

This paper deals with the photodegradation of wood in low atmospheric temperature region (−40 to 50 °C), and discusses the changes in color and IR spectra. The color and IR spectra of wood hardly changed with photo-irradiation at −40 °C but did at −20 °C. Therefore, it is thought that the photo-energy causes the scission of chemical bonds or the production of radicals; however, heat energy is needed to yellow of wood (i.e., to produce quinone). In case of softwoods, the absorption of the carbonyl band consisted of two sub-bands, and the carbonyl band at around 1710 cm−1 increased at lower temperature than that at around 1760 cm−1 by light-irradiation. Such IR measurement due to lignin degradation means that the photodegradation of softwoods is faster than that of hardwoods. The color change by exposure to light in the low temperature was also caused by the degradation of lignin.