Formaldehyde emission and high-temperature stability of cured urea-formaldehyde resins |
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| Authors: | Shin -ichiro Tohmura Chung -Yun Hse Mitsuo Higuchi |
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| Institution: | (1) Forestry and Forest Products Research Institute, Tsukuba Norin Kenkyu Danchi, PO Box 16, 305-8687 Ibaraki, Japan;(2) Southern Research Station, USDA, Forest Service, 71360 Pineville, Louisiana, USA;(3) Faculty of Agriculture, Kyushu University, 812-8581 Fukuoka, Japan |
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| Abstract: | A test method for measuring formaldehyde from urea-formaldehyde (UF) resins at high temperature was developed and used to assess the influence of the reaction pH on the formaldehyde emission and heat stability of the cured resins. Additionally, solid-state13C CP/MAS nuclear magnetic resonance (NMR) techniques were used to investigate the structure of cured UF resins before and after high temperature heating. Formaldehyde emissions during the cure were related to the UF resins' methylol group content. The heat stability of cured UF resins synthesized under strongly acidic conditions was much higher than that of the other resins, which were prepared in weakly acidic and alkaline media. Solid-state13C CP/MAS NMR spectra showed that formaldehyde emission from cured UF resins after heating is mainly ascribable to decreased methylol groups and dimethylene ether linkages. Significantly, it was revealed that uron structures characteristically found in the cured UF resin synthesized under strongly acidic medium indicated high heat stability.Parts of this paper were presented at the 44th annual meeting of the Japan Wood Research Society, Nara, April 1994; and at the 52nd annual meeting of the Forest Products Society, Merida, Mexico, June 1998 |
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