Improvement of Plywood Manufacturing Technology Using Slag-Modified Urea–Formaldehyde Resins

The production of wood composite materials and, in particular, plywood is one of the most effective ways to utilize waste in order to increase the recycling of by-products. The purpose of the work was to study the possibility of using steelmaking acidic slag as a modifying additive in urea–formaldehyde resins for plywood production and to determine the effect of steelmaking slag on the strength of plywood adhesive joints. The main sources of slag are the oxidation products of cast iron and scrap impurities (silicon, manganese, phosphorus, chromium, etc.), charge materials (lime, limestone, iron and manganese ore, scale, bauxite, fluorspar, etc.), and products of the destruction of refractory linings. As a result of the study, it has been found that the introduction of lignosulfonates, kaolin, and slags into urea–formaldehyde resin increases the reactivity of the finished glue. The ability of metal oxides in slag to bind hydroxyl groups has been proven; in this regard, when heated during pressing, the polymer does not break down into simple monomers, and the free formaldehyde of the urea–formaldehyde resin enters into a polycondensation reaction and is not evaporated from the glue.