The aim of this study was to increase the durability of adhesive bonds containing liquefied wood (LW). LW was obtained with liquefaction of black poplar wood in ethylene glycol (EG) as the solvent and sulphuric acid (SA) as the catalyst. An optimal time of 120 minutes and a wood:EG mass ratio of 1:3 was defined for liquefaction at 180 °C. After liquefaction, the EG was evaporated in order to achieve a low solvent content LW with a final mass ratio of 1:1. Four different adhesive mixtures were prepared: LW with a mass ratio of 1:1 (LW1:1), LW with a mass ratio of 1:3 (LW1:3), LW with a mass ratio of 1:1 and added condensed tannin (CT) (LW1:1/CT), and LW with a mass ratio of 1:3 and added CT (LW1:3/CT). The solid beech wood lamellas which were bonded with these adhesive mixtures were tested directly after bonding, and later on, after 7, 30 and 50 days. The test results indicated greater bonding shear strength in the case of LW1:1 compared to LW1:3. The addition of CT did not contribute to essentially higher shear strength values.
COBISS.SI-ID: 1935753
Chemical composition of spruce and pine has been investigated by X-ray Photoelectron Spectroscopy (XPS). Chemical compositions calculated from XPS data differ from those obtained from microanalyses. XPS analysis indicated high carbon contents explained by migration of lipophilic extractives. These results evidenced that extractives are able to migrate from the bulk of the sample to the surface when put into ultra high vacuum necessary for XPS. XPS presents, therefore, some limits in the case of the analysis of softwoods containing extractives able to migrate to the surface during analysis.
COBISS.SI-ID: 1808265
Liquefied wood is a product of wood solvolysis and can be used as a material for bonding of wood elements. The main problems of bond lines, prepared with liquefied wood, are their low shear strength and durability. This can be the consequence of low reactivity of liquefied wood or pH value, respectively. Curing of liquefied wood was elucidated using rheological measurements. Influence of different pH values of liquefied wood on shear strength value of bond lines and their durability was investigated in this work, as well.
COBISS.SI-ID: 1930121