The photodegradation of wood during solar irradiation

Coating Acetylated Wood

“…It is generally accepted that the degradation process is influenced by UV and visible light up to 500 nm [8,9]. The main degrading reaction is the photochemical degradation of lignin leading demethylation and the formation of quinones that cause a darkening of the wood.…”

Microtensile Testing of Wood – Overview of Practical Aspects of Methodology

“…the influence of water on the inter-fibre bonding and on the microfibrilar bonding. Derbyshire and Miller (1981) and Evans and Banks (1990) came to the same conclusions that the chemical and ultrastructural changes accord with the losses in tensile strength of thin strips and that the failure mode can reveal the nature of chemical decomposition of wood constituents. Evans et al (1992aEvans et al ( , 1992b showed that finite span testing reveals delignification more rapidly than zero span testing.…”

“…Raczkowski (1980) assessed the surface "corrosion" based on the long range tensile testing of 100 μm thick spruce (Picea abies, L.) strips to evaluate the combined effects of sunlight and atmospheric pollutants. Derbyshire and Miller (1981) additionally observed fungal colonization, which was negligible in dry and sunny periods, but very intensive in late autumn and winter. They also tested the influence of different spectral regions of solar radiation on the photodegradation rates.…”

“…It is of interest, therefore, to distinguish between the microfibril strength, or essential fibre strength, and the overall strength, where the inter-fibre bonding, especially in the CML region, plays a significant role. Attempts were made to separate the tensile properties of the cellulosic material from the intercellular material by determining wet strength values of the thin strips so that the CML would be excessively plasticised by water (Derbyshire and Miller, 1981;Evans et al, 1992b). Nevertheless, it proved necessary to carry out the investigations by means of tests in which the initial separation of the jaws could be set to a span less than the average length of cellulose microfibrils.…”

“…Microtomed wood sections can also be applied in monitoring photodegradation (Kalnins, 1966; Raczkowski, 1980; Derbyshire and Miller, 1981). Most recent comprehensive work in that area may be found in the thesis of Živković (2011).…”