EVALUATION OF ADHESION STRENGTH AND INTERPHASE INTERACTION IN PLYWOOD STRUCTURE WITH INTERNAL LAYERS OF WOOD-ADHESIVE COMPOSITION

Abstract

Introduction. Involvement in the production of wood composite materials waste of woodwork industries helps to reduce the cost of finished products and their effective utilization. It is advisable to use tarred wood particles of crushed waste concomitant plywood plant for manufacture of the inner layers of plywood. Assessment of adhesive strength and interphase interaction at the borders of phase interface (peeled veneer and wood-adhesive) in plywood structure is of practical interest. The purpose of the work  is to estimate adhesion strength and interphase interaction at the borders of veneer sheets and wood-adhesive composition according to the structure of plywood. Solvable tasks: An estimate of the interphase interaction and adhesion strength of plywood with internal layers of wood adhesive composition depending on the package structure, the recommendation of a rational structure of plywood are the problems under consideration. Methodology. In the absence of a standard methodology for determining the adhesion strength and the value of interphase interaction of plywood with internal layers of wood-adhesive composition is taken as a basis for estimating the adhesion technique tearing strength veneers according to GOST (National standard) 27325 and method of determining the strength of chipping in accordance with GOST (National standard) 9624. Experimental results. Adhesive strength for the main schemes of plywood was determined experimentally be means of uniform avulsion of external and central veneers. The data show that in case of separation of the veneer sheets, cohesive in wood adhesive composition or mixed character of fracture are mainly observed. It indicates high interphase strength of the connection. Character of interphase interaction of  liquid (binder) with the solid body (wood particles and veneer) on the border of their interaction depending on the structure of plywood was determined by cleaving at the contact boundary of the outer sheet veneer and an inner layer of wood-adhesive composition, as well as an inner layer of wood-adhesive composition and the central veneer sheet. Experimental results show that by chipping in adhesive layers, cohesive on wood adhesive composition or a mixed character of fracture, indicating interphase of high strength compound are observed. Interpretation of the experimental results. The maximum limit of tearing strength was observed in the samples of plywood № 2, № 3 with the presence of inner layer of veneer, so it is recommended to use them in critical structures. From the perspective of the technological process organization, simple packet assembly was observed in the schemes № 1 and  № 4. Conclusion. High performance of  adhesive tearing strength of veneer sheets and deep interphase interaction  on  the interface of the layers of veneer  and layers of wood adhesive composition make it possible to make a conclusion about reliability and good bearing capacity of plywood with internal layers of wood-adhesive composition, which can be effectively used as a construction material in various fields.