Effect Of Polyols On The Properties Of Cross-linking Modified Wood

Cross-linking modification is an essential approach to improve the dimensional stability and durability of wood and has huge market potential. However, traditional crosslinking-modified wood becomes brittle and degraded by acid catalyst. Many attempts have been made by combining crosslinking modification with other methods in order to further improve the properties of treated wood. But till now, there’s no systematic research on this topic and some findings of the previous investigations are inconsistent.In the present work, glutaraldehyde was chosen as the basic crosslinker and has been combined with different polyols, in order to investigate the effect of two main combined systems (cell-wall modified and lumen modified). Southern pine(Pinus sylvestris) was treated by different combined systems of glutaraldehyde (GA), polyols (glycol (EG), polyethelene glycol (PEG), poly (vinyl alcohol) (PVA)) and silicon-containing compounds. Afterward, physical and mechanical properties of the control and treated samples were determined. Fourier transform infrared spectroscopy and scanning selectron microscope were used to investigate the modification mechanism. The main results of this study are summarized as below.(1) Certain amount of EG and PEG can penetrate into wood cell wall with GA and form stable crosslinkage, less or more may bring negative effect. The bulking efficiency of PEG (M,,= 600) is higher than EG in combination treatments. But EG-GA combination treated wood showed better mechanical properties than PEG-GA combination treated ones. In general, wood treated with 5% concentration of both EG and PEG in combination with 10% GA showed best comprehensive performance.(2) The combination of different concentrations (5%,10%,15%,20%) of PVA (polymerization = 300) and 10% GA are able to provide stable crosslinking systems with wood cell wall. This formation enables high swelling efficiency and mechanical strength compared with untreated group.(3) Higher concentration of PVA brings in lower degree of cell wall crosslinking and denser combined crosslinkage layer across cell wall, thus causes less improved dimensional stability and better mechanical properties.(4) Nano-SiO2 has little influence on the physical properties of GA treated wood. However, it can significantly improve the mechanical properties of treated wood through enhancing PVA film.(5) OTS and TOS can further decrease the water adsorption and hygroscopity of treated wood, but the leaching resistance is low.