Monitoring hardeners of low toxic urea-formaldehyde resins

Abstract

According to European standards, the most stringent standards for the content of formaldehyde belong to the emission class E 0.5. The hardening of resins with different formaldehyde content is different and it has not yet been sufficiently studied. The production of the woodworking industry face difficulty in the use of low toxic urea-formaldehyde resins. On the one hand, life and standards require environmentally friendly products, on the other hand, the use of low-toxic resins leads to a large percentage of defects in the production process, reduced productivity and deterioration of the strength properties of the finished product. The polycondensation reaction of low-toxic resins using a classical hardener-ammonium chloride is slower in comparison with resins with a high content of formaldehyde, that is, performance is reduced. The paper examines the influence of various hardeners on the physical and chemical properties of the glue (gelatinization time, viability, pH of liquid and cured adhesives). All the studied preparations can be used as a hardener of low-toxic urea-formaldehyde resin, but its content should be adjusted taking into account the physical and chemical parameters of the initial state of the resins and production conditions.