The hydrolytic stability and structure of the cured melamine-urea-formaldehyde resin

The hydrolysis of cured melamine-urea-formaldehyde (MUF) resin leads to the increment of formaldehyde emission of the MUF resin-bond wood boards. To learn the influencing factors on the hydrolytic stability of cure MUF resin, a variety of amino resins (UF resin, MF resin, MUF resin) were synthesized in the laboratory. The amount of formaldehyde liberated and mass loss of cured amino resins were attained after acidic hydrolysis. The branched structure of cured MUF resins with different melamine levels added at different addition stages was characterized by the XRD technology. The relationship between the hydrolytic stability and branched structure of cured MUF resin was disclosed. The TG and DSC curves of MUF and UF resins were obtained by the differential scanning calorimetry (DSC) at the normal pressure. Their DTG curves were obtained by taking the first derivative of TG curves. The DTG curve shows the variation of the mass-loss rate of UF resin and MUF resin with temperature. The results indicate that the hydrolytic stability of cured MUF resin is lower than that of cured UF resin. The melamine decreases the hydrolytic stability of cured MUF resin by increasing the branched degree of cured MUF resin. The melamine added at different stages affects the branching structure of cured MUF resins in different ways.