Invited feature articleTemperature dependence of wood photodegradation monitored by infrared spectroscopy

- The photodegradation of wood was investigated at 30 °C, 80 °C, 120 °C and 160 °C.
- The combined effect of photodegradation and thermal degradation was studied.
- Chemical changes were detected by IR spectroscopy.
- Softwoods were more sensitive to UV light at the elevated temperatures than hardwoods.

The temperature dependence of the photodegradation of hardwoods (beech, Fagus sylvatica L. and poplar, Populus x euramericana cv. Pannonia) and softwoods (Scots pine, Pinus sylvestris L. and spruce, Picea abies Karst.) was investigated. Samples were irradiated by a strong UV emitter mercury lamp at 30 °C, 80 °C, 120 °C and 160 °C. A series of samples was treated in the same chamber set to 30 °C, 80 °C, 120 °C and 160 °C but without light irradiation (pure thermal treatment). The chemical changes were detected by infrared spectroscopy. The same light irradiation generated much greater absorption change at 160 °C than at 30 °C. The simultaneous thermal and UV treatment generated much greater absorption increase in the whole investigated infrared region than the sum of absorption increases generated by the individual thermal treatment and UV radiation, separately. Softwoods were more sensitive to the light irradiation at elevated temperatures than hardwoods. Results revealed that four bands around 1770, 1750, 1720 and 1690 cm−1 emerged in the unconjugated carbonyl region as a result of the UV irradiation at elevated temperatures. The intensity change of these bands is highly dependent on the wood species. Absorption increase was found at 1066 and 1035 cm−1.

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