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Dimensional stabilization of wood with dimethylol compounds
1987 - IRG/WP 3412
This study showed that a substantial degree of dimensional stability can be imparted to wood by crosslinking with low concentrations of dimethyloldihydroxyethyleneurea. It was demonstrated that by selecting the right catalyst system the cure temperature can be reduced to the point that strength loss of the treated wood is minimized.
D D Nicholas, A D Williams

Influence of concentration, catalyst, and temperature on dimensional stability of DMDHEU modified scots pine
1998 - IRG/WP 98-40119
Dimethyloldihydroxyethyleneurea (DMDHEU) is being used in textile industry to improve wrinkle recovery. Trials on solid wood have been performed to minimise swelling of the wood. This paper focuses on the effect of various types and concentrations of catalyst and reaction temperature on the dimensional stability of Scots pine. Three different catalysts, NKS (based on magnesium chloride), 3282 (based on aluminium chloride) and citric acid have been tried separately or in combination with tartaric acid. Reaction temperatures between 100° and 125°C have been investigated. The results showed that an anti shrink efficiency of up to 50% can be obtained.
M Van der Zee, E P J Beckers, H Militz

A new process for in situ polymerization of vinyl monomers in wood to delay boron leaching
1998 - IRG/WP 98-40110
Efforts were accelerated on effective use of boron compounds in wood preservation owing to their environmentally safe characteristics and relatively low costs in addition to their well-known high bioactivity and fire resistant properties. Although having these unique favorable properties, they are readily leachable from treated wood at humid conditions. Therefore, they had limited market for exterior applications. A supplementary combination treatment with vinyl monomers; styrene (ST) and methylmetacrylate (MMA) was studied in order to extend the service life of boron treated wood. Sapwood specimens of Japanese cedar (Cryptomeria japonica D. Don) first treated with boric acid (BA) at 1.00% aqueous solution concentration. Vinyl monomers were impregnated after air-drying of BA-treated wood at ambient temperatures. Polymerization was performed during compression of monomer impregnated wood to a 50 to 70% dry set of radial dimension under a hot-press heated to the polymerization temperatures of 60 and 90°C required by the selected catalysts VAZO (a, a' - Azobis-isobutyronitrile) and benzoyl peroxide, respectively. Wood acquired a perfect dimensional stability and remarkably high moisture exclusion efficiency with the minimum water holding capacity with the compressed-wood polymer composite (CWPC) process that was approved by submerging of the test specimens in tap water, boiling water exposure to a 10 cycles accelerated severe weathering. As a result, boron leaching rate from CWPC pretreated with BA was considerably slower than that from ordinary WPC. Scanning electron microscope (SEM) observations were found explanatory for controlled-but-continuous boron leaching determined analytically. An effective bulking was found necessary to accompany to polymerization in cell wall with an even distribution of monomer in wood. Grafting to cell wall components can be tried further to achieve an envelop polymerization of boron deposited sites in WPC for better boron immobility.
M K Yalinkilic, W Dwianto, Y Imamura, M Takahashi

Reactivity of alkoxysilanes with cellulose and lignin in presence of catalysts
2018 - IRG/WP 18-40831
The origin of research was another step in development of a new conservation method for wood cultural heritage. Wood silanisation seemed to be an alternative method to waterlogged wood PEG treatment. The superior aim from the practical point of view was to increase dimensional stability and reduce the hygroscopicity of archaeological wood. The aim of the study was to identify interactions between wood main components and selected alkoxysilanes. Celullose and lignin were modified with alkoxysilanes in presence of catalysts. The scope included methyltrimethoxysilane (MTMOS) and methyltriethoxysilane (TEMS) as modifying agents. Aluminium acetylacetonate (Al(acac)3) and acetic acid (AcOH) were used as catalysts. Samples were measured by using FT-IR. It turned out that cellulose was not so readily reactive to alkoxysilanes as lignin. However, cellulose can react with silanols, which are the product of hydrolysis of alkoxysilanes. For this purpose, catalysts were used to enhance the durability of the interactions between alkoxysilanes and wood main components. In case of lignin, no catalyst addition was needed. In case of cellulose, results clearly showed better reactivity of alkoxysialnes in the presence of catalysts. These results are confirmed by peaks on spectra appeared at e.g. 1270 cm-1 and 777 cm-1. Depending on the formulations the intensity of peaks were different between each other. They corresponded to the Si-CH3 groups. In the case of lignin, peak at 920 cm-1 corresponded to Si-OH bonds which proved that hydrolysis was occurred.
J Siuda, W Perdoch, B Mazela, M Zborowska