Influence of hygro-thermal treatment temperature and duration on dimensional stabilisation of wood modified with poly(butylene succinate)

IRG/WP 17-40813

C Grosse, M Noël, L Rautkari, P Gérardin

To improve wood properties, especially dimensional stability, a treatment based on poly(butylene succinate) oligomers (OBS) was experimented. After impregnation in wood, a further hygro-thermal treatment (HTT) was carried out in a pressurized reactor at 100% relative humidity (RH) at differing temperatures for differing durations. The aim of HTT is to induce partial swelling of wood cell walls so that the OBS can diffuse into the structure. A final thermal post-treatment (PT) was carried out to dry the treated samples and attempt the oligomers fixation in wood. Due to OBS sensitivity to water, especially at high temperatures, the oligomers hydrolysis in the process is possible. This article relates the products flow in wood structure under varying HTT conditions, as well as the influence of OBS diffusion in wood on the treatment anti-swelling efficiency (ASE*). After HTT, there is an effective diffusion of the oligomers into wood cell walls. This was evidenced by the residual wood swelling after complete treatment (HTT and PT). Wood dimensional stabilisation correlates with the amount of OBS into the wood cell walls. Dimensional stability was improved by all treatments, but seemed to reach a maximum value of ca. 50%. HTT temperature played an essential role into treatment efficiency. Temperature as high as 130°C led to the highest ASE* obtained in this experiment set, not improved by longer HTT. However, longer HTT allowed to reach the same efficiency at 100°C. For higher temperature, the leaching rate increases significantly, up to 20%.

Keywords: wood, chemical modification, PBS, hygro-thermal treatment, swelling

Conference: 17-06-04/08 Ghent, Belgium

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