Novel wood modification processes for window and cladding products
A Krause, C Hof, H Militz
Because of the low natural durability and low dimensional stability of European wood species, the usage of wood for window frames has decreased dramatically during the last decade. In a joint project of several German research institutes and the window industry, following wood modification systems were compared.
heat treatment (3 different materials from 2 companies)
acetylation (pine sapwood and beech wood acetylated with acetic anhydride)
polymerisation (melamine resin treated pine sapwood, Interlace treatment, furfurylation)
wax treatment (pine sapwood, which was impregnated with natural resin and waxes)
Investigated was the moisture content, dimensional stability, capillary water uptake and the durability.
The dimensional stability show a high increase for following materials: heat treated wood, acetylated pine, interlace treated wood and furfurylated wood. The melamine resin treated wood and the wax treated wood show no significant increase in the dimensional stability.
The biological durability against different basidiomycetes was tested according to the EN 113. As test fungi, Coniophora puteana, Poria placenta and Coriolus versicolor were used. The results show a very high increase in the durability for most of the treated wood. The wax treated wood shows no significant increase in durability.
A novel window frame consists of several functional layers. Different wood properties are demanded for the single layers to achieve optimal window properties. Every modified wood shows a special potential for the use in a functional layer.