Development of the adhesive composition for joining solid wood in the conditions of Siberia
Increasing popularity of wooden housing construction is due primarily to the use of wood - an environmentally friendly material with a pleasant to the touch surface, creating a favorable atmosphere inside the room. Wooden housing construction in Siberia means the use of glued massive wood: CLT-panels, BSP, X-lam, glued wall beam. Glued wooden structures must comply with the requirements of GOST 20850-2014 " Wooden glued bearing structures ", based on the standard EN 14080: 2005. Sufficient heat and frost resistance of the glued panels is provided by glues of polycondensation and polymerization types: C3, D3, C4, D4 to EN 204. According to GOST 20850-2014 and EN 14080: 2005, a polymer-isocyanate (EPI) emulsion, resorcinol-formaldehyde adhesives (RF ), melamine-urea-formaldehyde adhesives (MUF, MF), polyurethane adhesives (PUR) are allowed in construction. In Russia, polyurethane PUR-adhesives can’t be used in the production of glued wooden structures, even in low-rise housing construction, and in Europe EPI emulsion is not allowed for production. Resorcinol-formaldehyde glutinous systems are used today in very rare cases, since they form a glue line of black color, resistant to chemical aggressive compounds. Thus, to provide a colorless glue seam, it is possible to use PUR-adhesives, MUF, MF-adhesives, but they are quite expensive. Polyvinyl acetates (PVA), like urea-formaldehyde glues (UF), are relatively inexpensive public adhesives, but due to the need to provide a certain class of structural responsibility, they can’t be used in glued wooden construction products. The prohibition is explained by the nature of the chemical compound created by them and their inability to carry a prolonged static load. Therefore, it is timely to search for modifiers for inexpensive adhesive compositions that will be able to provide the necessary indices of strength properties of glue joints and, most importantly, heat, water and frost resistance.