Sulfonated Kraft lignin addition in urea–formaldehyde resin

Urea–formaldehyde (UF) resins are widely used over the world as an adhesive, principally in the civil construction, but its use leads to formaldehyde emissions when exposed to higher temperatures. In this way, the aim of this study was to evaluate the partial replacement of adhesives made of UF resin by sulfonated Kraft lignin, up to 30 mass%, and study its effects on the mechanism and on the kinetic/thermodynamic parameters of the thermal degradation, as well as on the thermal stability of the UF resin through thermogravimetric analysis and using isoconversional methods. The results showed that the lignin addition to the UF resin was beneficial, as there was synergy between the materials and verification of enhancement of thermal stability. Aside from the changes in the thermal behavior, the probable reduction of the emission of formaldehyde in the second step of degradation of the UF resin was also observed. These results indicate that the lignin can be used as a potential material to partially replace the UF resin.