Investigations into the photodegradation of wood using microtensile testing

This paper describes an investigation into the influence of temperature on photodegradation rates in wood. Ten different softwood species were subjected to artificial weathering in the Xenotest 1200 at temperatures of 25, 35, 45 and 55 C for periods of up to 400 hours. The rates of photodegradation were determined for each species at the different temperatures by monitoring the loss in microtensile strength. Photodegradation rates for the different species were shown to be temperature dependent and to increase with rising temperature. The tests appeared capable of discriminating between the photoresistance of the various species. Arrhenius plots for the species were linear with activation energies in the range 5, 9-24, 8 kj/mol. It is concluded that the test methodology has the potential to differentiate the susceptibility of different wood species to photodegradation.