Abstract
Uron resin, a kind of urea-formaldehyde (UF) resin containing much more uron structure, were prepared. Several modied UF resins were obtained from mixing uron resins with normal UF resins as well as synthesizing UF resin with uron resin as raw material. � is work demonstrated that the introducing of the uron structure reduced free formaldehyde content of UF resin and formaldehyde emission levels in bonded plywood panels signicantly, the former were reduced by 76% and 84% in the latter. � e synthesis time of uron resin can be shortened to 8 hours. � e test result of free formaldehyde content, formaldehyde emission levels and bond strength indicated that specimen of 20 parts uron resin synthesized in 8 hours mixed with 100 parts UF resins (F/U molar ratio of 1.3) had a potential advantage to industrial application. � e benecial eect of uron resin on the performance of UF resin can be attributed to the opening of uron cycle structure and the following reaction with free formaldehyde and its oligomeric glycol forms.
Highlights
Uron resin, a kind of urea-formaldehyde (UF) resin containing much more uron structure, were prepared
Uron initially aroused interest due to its lower formaldehyde emission e ect on UF resin which was synthesized at very acid pH (Gu et al 1995). e following research con rmed that the introduction at lower reaction temperatures of the additional strongly acid condensation step was the formation of sometime considerable quantities of Uron (Gu et al 1995). us, the critical parameters for maximizing the portion of Uron present at the end of the UF resin synthesis was proposed, and the particle board bonded with uron-rich resins showed the considerable bond strength (Soulard et al 1999)
Mixing uron resins with UF resins under the conditions in table 1 made the viscosity of mixed UF resins decreased rapidly. e probable reason for this is that the uron cyclic structures are series of relatively independent ingredients in the mixed UF resin
Summary
A kind of urea-formaldehyde (UF) resin containing much more uron structure, were prepared. E formaldehyde emission levels of plywood made with UF-U which were synthesized by urea, formaldehyde and Uron-C as its raw material are relatively high, these values reduced as the amount of uron resin addition increased.
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