Volumes of plywood production with increased water resistance for indoor and outdoor use (FSF brand) are increasing in Russia. The demand for it in the country and in the world continues to grow. The phenol-formaldehyde oligomer during the curing process passes through the stages of resol, resitol and resite. Ensuring long-term water resistance of plywood is possible only if the resite stage is reached and the solidified phenol-formaldehyde resin (FFR) reaches non-melting and insoluble state. The problem is that the industrial process of FSF plywood pressing is carried out in the rezitol temperature range. In literature, there are conflicting data on the temperature ranges of the stages of the FSF polycondensation process. The authors have proposed to operate with scientific data on the temperature ranges of FFR curing, confirmed by the results of spectroscopic studies. It is necessary to develop phenol-formaldehyde binder compositions capable of curing to the resite stage at lower pressing temperatures than unmodified FSF to ensure the necessary operational characteristics of FSF plywood. In this study, a number of modifiers have been proposed that potentially reduce the time it takes to press plywood at low temperatures. The gelatinization time of the phenol-formaldehyde binder based on the SFZh-3014 resin (according to 20907-2016 State Standard) and modifying additives (hydrogen peroxide, eight-water zinc sulfate, ammonium alum, anhydrous magnesium chloride, six-water iron chloride, six-water aluminum chloride, aluminum dimethyl sulfate, dimethyl glyoximate, and sulfate, sulfosalicylic two-water acid) have been determined. A study of the gelatinization process in the presence of a large number of modifying additives (more than 1.5%) revealed a significant deterioration in the spreadability of the binder. Therefore, it is recommended to use FFR curing accelerators in the amount not exceeding 1-1.5%.

The problem of stabilizing the properties of the urea-formaldehyde binder during storage is relevant for both glued products and resins. Changing the performance of the resin during storage makes it difficult to apply a binder and leads to a deterioration in the physical and mechanical properties of plywood. The effect of glycerol, mono- and triethanolamine, as well as a mixture of glycerol and monoethanolamine on the nominal viscosity of the resin after 56 days of storage, has been studied. The use of glycerol and monoethanolamine (including in the complex) reduces the nominal viscosity of the resin by 13.5-24.8%. The use of triethanolamine as a stabilizer makes it possible to reduce the nominal viscosity by 35% in comparison with the index of an unstabilized oligomer. Mechanical properties of FC plywood based on the stabilized and unstabilized binder has been studied. It was found that glycerol additive (or glycerol in combination with monoethanolamine) significantly reduces strength characteristics of plywood, which makes it irrational to use these stabilizers. The addition of 0.2% triethanolamine to CFS allows a 35% reduction in the nominal viscosity of the resin, while the cohesive strength of the binder decreases by 1.5%. The result is within the framework of the dispersion of the indicator, i.e. strength reduction is negligible. The static bending strength of plywood with a stabilized triethanolamine binder is more important than that of control specimens without the addition of stabilizers. The results of the study enable to recommend the addition of triethanolamine in an amount of 0.2% by weight of urea-formaldehyde resin as a rational stabilizer

Improving the production process of FSF waterproof plywood has been relevant since the beginning of its pro-duction. Only the criteria for improving the quality of plywood products are changing. At the present stage, the costs of improving the quality of plywood cannot be compensated by an increase in prices. Reduction in production costs is required. A rational way to improve operational properties is to reduce pressing temperature and introduce modifying additives that increase adhesive and cohesive strength of phenol-formaldehyde binder. The problem is that when press-ing temperature is reduced to 150 °C or lower, phenol-formaldehyde binder does not reach the resite stage. It negatively affects the strength and water resistance of FSF plywood. It was decided to use modifying additives in the adhesive composition to bind free methylol groups of the oligomer and increase the number of active sites in the curable phenolic binder network. The strength properties of FSF plywood with the use of nine modifying additives have been investigated. The consumption of modifiers varied in the range of 0.25-1.5% in increments of 0.25%. Pressing was carried out at a temperature of 120 °С. An improvement in the tensile strength of plywood when shearing on the adhesive layer was found to be 5-15% (in comparison with control samples without the addition of a modifier) when aqueous solutions of hexavalent aluminum chloride, anhydrous magnesium chloride, eight-zinc zinc sulfate, sulfosalicylic acid, dimethylglyoxime with a different proportion of additives were used as modifying additives to phenol-formaldehyde binder. Tensile strength under static bending of plywood is also increased when using modifiers with different proportion of additives

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Soft wood waste is mainly used for fuel purposes. Non-returnable vegetable spinning waste is currently not used in the production of products, disposed of by incineration or disposal to landfill. Emissions of carbon-containing gases are the dominant source of anthropogenic emissions into the atmosphere, which leads to disruption of the natural carbon cycle. The aim of the study is to develop a method for recycling waste spinning flax and cotton fibers and soft wood waste by producing composite thermal insulation material. Physical and mechanical parameters and thermal conductivity coefficient of composites are determined.