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Phenol-formaldehyde adhesives are in the wood industry most commonly used for bonding of structural wood composites where high strength and durability of the bond line is desired. Their curing is rather complicated due to the reactions that can occur simultaneously. Based on the acidity or alkalinity of added catalyst during the synthesis, these adhesives are divided into novolak and resol type of resins. In the study, the curing of different commercial resol type phenol-formaldehyde adhesives was analysed with differential scanning calorimetry (DSC). The influence of the addition of basic catalyst on the curing of the selected adhesive was examined, and a simulation of time required for the curing of the adhesive at isothermal conditions was also made. It was found that the curing processes of different adhesives varied. Because the examined phenol-formaldehyde adhesives were already optimised during the process of synthesis by means of optimal catalyst addition, the additional amount of catalyst into selected phenol-formaldehyde adhesive was unnecessary and has a negative impact on its curing.

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.

Due to the increasing global production of wood based panels (particleboards, fiberboards, and plywood) problems with raw material and difficult treatment of recovered wood based panels after life cycle occur. Inorganic pollutants represent the main problem of raw material while treatment of recovered wood-based composites is aggravated due to the presence of synthetic adhesives. Latter and the release of methane during anaerobic decomposition are reasons for using alternative methods instead of sending these composites to landfills. The most promising methods of recovered wood-based panels treatment are: hydrothermal recycling, re-manufacturing of panels, combustion and pyrolysis, composting, re-use and some other less used methods for processing of new recycled products.

Wood liquefaction is the process of wood solvolysis in which basic wood components are degraded to monomers and oligomers in the presence of a suitable solvent and catalyst. These later on react with each other or with the solvent, and insoluble product is produced. The paper describes the mechanisms and kinetics of wood liquefaction and liquefaction of its basic components (cellulose and lignin).

Liquefied wood is a potential alternative to the synthetic adhesives which are used for the bonding of wood. Despite the ability of liquefied wood to self-crosslink, bonds formed during the bonding of wood with liquefied wood do not achieve sufficient shear strength and have poor resistance to water. For this reason the process of the curing of liquefied wood, the influence of various parameters on the shear strength of bonds, and the structure of bonds formed during the bonding were analyzed. It was found that the chemical curing of liquefied wood started after water and solvent had been removed from it. When bonding wood, the curing of liquefied wood takes place faster because, in addition to evaporation, the transition of both vaporous components from the liquefied wood to the lamellas also occurs. During the bonding of 5 mm thick beech lamellas with liquefied wood having a negative pH, at optimal bonding conditions (180 °C, 12 min), a specific type of bond was formed. It consisted of a central part of carbonized wood cells of the bonded lamellas and the cured liquefied wood, and a narrow layer of partly delignified wood cells at the border between the central part and bonded lamella.