Synthesis Eo Grade Modified UF Resin By Strong Acid Process And Its Application

urea-formaldehyde (UF) resins are widely used as a wood adhesive, because of low prices good adhesive ability and fast curing ability.But the free formaldehyde and unstable structural after UF resin cured, cause the formaldehyde emission.Serious deterioration in the living environment of people.In order to improve the water resistance and reduce the formaldehyde emission of urea-formaldehyde resin, a strong acid process was used to synthesize a low formaldehyde emission and high water resistance UF resin in this paper.PVA, melamine and curing agent were studied, a strong acid process were found to synthesis UF resins for EO grade plywood e.the result show the five layers plywood formaldehyde emission was0.33mg/L and the bonding strength was1.5MPa after immersed in63℃water for3hours, which used4%melamine modified UF resin after hot pressing under115℃with2%curing agent of ammonium sulfate,the formaldehyde emission reached the standard of EO and the bonding strength reached the standard of Class Ⅱ plywood which described in GB/T17657-1999.Also a low-cost urea-formaldehyde resin for EO class substrate was found, which used10%melamine modified UF resin, the nine layers plywood bonding strength could reach2.5MPa after immersed in73℃water for3hours and the specimen did not crack after immersion in boiling water for4hours while formaldehyde emission was only0.4mg/L.Has reached E0grade wood flooring substrates which was described in LY/T1328-2008.Advanced analytical methods (13C-NMR、FUR、SEM、Tg、XRD) also were used to discuss and analyze the theory of UF resins under different strong acid reaction temperature.The results showed that the higher the reaction temperature of acid stage, the lower the formaldehyde emission of UF resin,the More Uron ring structures were form,but methylol decreased.And the C-N became less,the crystallinity reduced after curing.The SEM is displayed that the UF resin with the strong acid stage reaction temperature at70℃is difficult to curing.the TG analysis showed the UF resin with the strong acid stage reaction temperature at70℃More unstable.All study provide a theoretical basis for further optimization of the strong acid process.