Service properties of pine after combining an impregnation treatment with a thermo-hydro modification process

The aim of the present research was to obtain a wood material with improved service properties, by combining two industrially used processes - namely a thermo-hydro treatment (THT) and an impregnation (Imp) with a commercial biocide - through the application of both a lower preservative retention and lower modification temperature, respectively. In the study, specimens from Scots pine (Pinus sylvestris L.) sapwood were used. The properties of the wood obtained with the sequence Imp-THT were extensively studied. Impregnation was performed in a pilot scale autoclave by a vacuum-pressure-vacuum process using a copper-azole type wood preservative, whilst THT was carried out in a WTT laboratory pilot device in a water vapour medium under elevated pressure. To improve physical properties while maintaining strength properties, the THT regime 160 degrees C/1 h was used. The properties (strength, swelling, water uptake, colour, biocide (Cu) fixation properties as well as bioresistance to rot fungus) of combined treated pine wood were compared with those of the wood obtained in the respective separate processes.