Project: High-frequency impregnation of wood overview

For some European wood species, a sufficient degree of protection by fire retardants or preservatives cannot be reached due to their limited treatability. Wooden products constructed by such wood species often suffer from degradation and a shortened service-life. Hi-FreTech aimed at improving the service-life and the performance of wooden products by developing a new impregnation process that enables a deep and even penetration with protection agents into wood species that are difficult to treat, without causing structural changes to the wood. The main approach was the use of high-frequency (HF) electromagnetic waves during the impregnation process. The HF-treatment did not affect the mechanical properties of the wood, but also showed no direct impact on the treatability of spruce or eucalypt wood at laboratory or pilot-scale. A pre-treatment of eucalypt wood with microwaves in the range between 286 and 429 MJ/m³ did result in an improved solution uptake in a subsequent impregnation process, but was accompanied with a loss in stiffness and bending strength. However, the use of a preheated impregnation solution during a traditional impregnation process increased the solution uptake considerably without decreasing the mechanical properties. Compared to the use at room temperature, pre-heating the impregnation solution to 80 °C approximately doubled the solution uptake of spruce and eucalypt wood. For selective fire retardants and preservatives, no impact of a short- and mid-term (2 hours maximum) heating on their composition and effectiveness was found. Tests on industrial-scale verified the effect of the pre-heating and showed that an energy-effective technique to heat up the impregnation solution can be integrated into existing impregnation plants. Field-tests with prototypes impregnated with preheated impregnation solutions are on-going.

Duration 01/01/2011 - 30/04/2014
Website visit project website
Network WoodWisdom-Net 2
Call Sustainable, competitive processing and end-use concepts for forest-based industries

Project partner

Number Name Role Country
BASF Group Germany
Danish Wood Technology AS Denmark
Forest and Wood Technology Research Centre Spain
Georg-August-University Göttingen Coordinator Germany
National Institute for Agriculture and Food Research and Technology - Forest research centre Spain
Norwegian Institute of Wood Technology Norway
Romerike Trelast AS Norway
Sauerländ Spanplatte GmbH & Co. KG - Spanplattenwerk Gotha Germany
Tinastur S.C.L Spain