The influence of shungite additives in binder on the basis of urea-formaldehyde resin on the properties of particle board

Particle boards are increasingly being used as a structural material. The quality of the wood from which they are manufactured has been steadily declining. This provides the means for tackling possible ways of particle board performance properties preservation and improvement. The methods and results of experimental investigation on the additive influence of shungite powder when mixed in the glue for one-ply particle board are presented in the article. Wooden particles of coniferous and hardwood species as well as glue solution based on carbamide-formaldehyde resin were used for boards manufacturing. The shungite powder containing particles on the average 100 nm by the size and specific surface 120...150 m2/g was used in experiment. The samples were tested to determine their physical-mechanical properties. The addition of fine shungite powder to the glue based on urea-formaldehyde resin allows increasing the strength of one-play particleboard at static bending by 41.0 %, and the tensile strength perpendicular to the board surface - by 104 %. The results of the study also suggest that the greatest value of the tensile strength in both cases is reached when the mass fraction of shungite is in the region of 10 % of the mass of completely dry resin. Also, the results of the study demonstrates that the addition of fine shungite powder into the glue based on urea-formaldehyde resin can reduce water absorption of one-play particleboards by 27 %, and swelling - by 62 %. In this case, the maximum effect was also fixed when the mass fraction of shungite was in the region of 10 % of the mass of completely dry resin. During the study it was found that the introduction of shungite powder in urea-formaldehyde resin entails a significant decrease in the content of free formaldehyde. In particular, at the concentration of shungite 10 % by weight of absolutely dry resin, the emission of free formaldehyde decreased by 17.3 %. As a result of the study it was found that the technological properties of the adhesive composition shungite additive do not worsen. The introduction of 10% shungite by weight of absolutely dry resin into the adhesive composition resulted in the decrease in gelatinization time by 7 %, and viscosity-by 10.5%. The only drawback of the use of shungite additive is the change in the color of the boards. As the proportion of additives increases the board’s color becomes darker.