Photodegradation and photostabilisation of wood – the state of the art

In this article we try to give an overview of the photodegradation of wood and the different ways available to stabilise this complex substrate. The mechanisms of wood photodegradation have been investigated and it appeared that lignin is the key structure because this component is able to absorb in the UV/visible region due to its chromophoric groups. Thus, some solutions can be offered to protect wood against photodegradation. One of the easiest consists in applying finishes such as paints, coatings, varnishes etc., but it is also possible to modify the substrate chemically (e.g. by acetylation) or to stabilise its colour by thermal and photochemical pre-weathering. The use of UV absorbers, HALS, antioxidants and the recent development of new additives help to prevent the degradation of the coated wood system.