Innovative methods for researching adhesive joints

To analyze surface phenomena during the formation of adhesive joints, the mutual arrangement of pores on the wood substrate and the depth of penetration of liquid glue into wood, electron microscopy methods, atomic force and scanning tunneling microscopy are used, which make it possible to assess the influence of factors characterizing the interaction between liquid glue molecules and a porous surface. wood. An effective way to improve the quality of plywood that meets the requirements of the consumer is to modify its binder, i.e. purposeful change in physicochemical properties, technological and operational indicators, and often giving special specific properties to synthetic resins. The use of electron microscopic methods, atomic force and scanning tunneling microscopy will allow a comprehensive approach to the study of adhesive joints in general, and in particular to the description of the processes that occur at the stage of formation and destruction of an adhesive joint. The nature of the SEM images indicates the interaction of liquid adhesives modified with cellulose production wastes with wood, the penetration depth of the adhesive is 20–30 μm, which is consistent with the general concepts of the molecular adsorption theory of liquid polymers in interaction with wood. Due to the effect of consolidation, the practical application of the theory of fractals in the production of glued materials, in particular plywood, can be as follows: an increase in the strength characteristics of plywood based on modified urea- and phenol-formaldehyde adhesives is explained. The adsorption capacity of porous bodies (in particular wood) with respect to molecules of different sizes (free formaldehyde, water) will be determined by the fractal dimension of the pores, due to the molecular sieve effect, shungites, as a representative of a wide group of zeolites, absorb free formaldehyde of the urea-formaldehyde oligomer, thereby reducing its content in the finished product. Considering the macrostructure of the adhesive joint, it can be imagined that in the frozen state, the adhesive layer formed without heating is subject only to additional compressive stresses from cell cavities filled with water, while in adhesive joints formed during heating, the adhesive-wood zone, which includes themselves as well as cell cavities, weakened by the additional pressure created in them.

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