Natural UV protection of wood surfaces through cellulose fibres 

Wood surfaces often become coarse and discoloured when exposed to sunlight and rain. This project focuses on ways to prevent damage to wood through weathering and thus make wood more competitive in relation to other materials for external use.

Background
Wood used in the exteriors of buildings generally suffers most on the surface. Depending on the type and intensity of the factors affecting it, the result may be degradation of the wood substance or significant aesthetic alterations. Central to this process is the photochemical transformation of lignin and similar wood components through sunlight. In this reaction, the chromophore groups that give the wood its natural colour are transformed into substances that are soluble in water and subsequently washed out with the moisture, be it rain or snow. The wood surfaces become coarse and strongly discoloured and the material is degraded.

Aim
The aim of the project is to develop and stabilise a natural protection against the harmful effects of ultraviolet radiation (UV protection) on the surface of wood. Such protection can primarily be achieved through layers and wads of cellulose fibres. In an initial phase, the researchers analyse different possibilities of delignification. In particular, they assess the deep effects of lignin degradation and the mechanical and optical changes to the surface. In a second phase, they study to what extent the delignified surface can be mechanically stabilised and made water-repellant. For this purpose, they test the suitability of functionalised reagents, on the one hand, and polymeric substances, on the other.

Significance
Should the researchers succeed in developing a method to delignify wood surfaces and at the same time to permanently stabilise them, such surfaces would be better protected in the exteriors of buildings. This could increase the competitiveness of wood in relation to other building materials and lead to a wider use of wood in the exteriors of buildings.

Original title: Development of a natural UV protection of wood surfaces by cellulose-rich layers

Grant: CHF 273,928
Duration: 36 months

Project leaders
- Dr Thomas Volkmer, Architecture, Wood and Civil Engineering, Bern University of Applied Sciences, Bienne
- Martin Arnold, Laboratory of Applied Wood Materials, Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf
- Prof. Francis W. M. R. Schwarze, Laboratory of Applied Wood Materials, Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf

Contact

Dr Thomas Volkmer
Architecture, Wood and Civil Engineering
Bern University of Applied Sciences
Solothurnstrasse 102
CH–2504 Bienne
Phone: +41 32 344 03 46
E-mail: thomas.volkmer@bfh.ch
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