USAGE OF BI- AND POLYFUNCTIONAL COMPOUNDS AS AN ALTERNATIVE OF SYNTHETIC RESINS IN FI-BERBOARD TECHNOLOGY

Abstract

Due to the high chemical activity of its filler, fiberboard is a unique material, it's formation can be ensured by chemical reactions of wood components. However, under hot pressing modes, typical for dry-process boards, chemical reactions do not have time to go through to the required extent, which requires the use of special modifiers that enhance the activity of the wood fiber. Bi- and polyfunctional compounds - sucrose, carbamide, and citric acid - were investigated as modifiers. The lowest efficiency was shown by sucrose, which is not able to ensure the compliance of the physical and mechanical parameters of the fiberboards with the requirements of standards; The use of urea and citric acid makes it possible to produce fiberboards that are not inferior in their properties to materials from urea-formaldehyde resin. Using the methods of chemical and instrumental analysis (IR spectroscopy, solid-state 13C NMR spectroscopy), it was found that during hot pressing, urea and citric acid react with components of the wood cell wall. Urea decomposes during pressing with the formation of ammonia and isocyanic acid, which, in turn, provides interfiber interaction. During hot pressing, citric acid reacts with hydroxyl groups of cell wall components by the esterification mechanism. Using the example of citric acid, it was found that plates that meet the requirements of the TSN-30 standart can be made only with a pressing time of 0.4 min / mm of the fiberboard thickness, which exceeds the technology requirements by more than two times. To ensure the competitiveness of the selected modifiers with respect to existing synthetic resins, it is necessary to find ways to reduce the pressing time.