Curing Characteristics of low Molar Ratio Urea-formaldehyde Resins

摘要

Five low molar ratio Urea-formaldehyde (LUF) resins were prepared as the object resin in this paper. The effects of molar ratio, free formaldehyde content and catalysts on the curing beharior of LUF resins were characlerized by free formaldehyde content, pH value change after catalysts added, curing rate, pot life, its cured appearance, and thermal behavior. The results indicate that: 1) The LUF resin with less molar ratio than 1. 0 can still cure; 2) Free formaldehyde content is not the main factor in affecting curing rate of LUF resin; 3) Compared with ammonium chloride as a traditional catalyst, persulfate salts markedly accelerate the curing rate of LUF resin, and result in the different appearance; 4) the addition of sodium chloride to catalysts can accelerate the curing rate of LUF resin, but the effect is inconspicuous.