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Journal of Wood Science

, Volume 47, Issue 6, pp 451–457 | Cite as

Influence of the melamine content in melamine-urea-formaldehyde resins on formaldehyde emission and cured resin structure

  • Shin-ichiro TohmuraEmail author
  • Akio Inoue
  • Siti Hanim Sahari
Original Article

Abstract

The effect of melamine content in melamine-urea-formaldehyde (MUF) resins on the formaldehyde emission and resin structure was investigated using six MUF resins synthesized with different F/(M + U) and M/U molar ratios. The formaldehyde emission from the plywood decreased as the F/(M + U) molar ratio decreased and the M/ U molar ratio increased. In addition, the bond performance was enhanced as the M/U molar ratio increased in the MUF resins with a fixed F/(M + U) molar ratio. Quantitative solution13C-NMR spectra of MUF resins revealed that the MUF resins with a high melamine content consisted of more highly branched crosslinkage structure and free melamine compared to the resins with low melamine contents. Furthermore, solid-state13C CP-MAS NMR spectra of cured MUF resins proved that more methylol groups, dimethylene ether, and branched methylene structures were present in the MUF resins with a higher F/(M + U) molar ratio, leading to increased bond strength and formaldehyde emission. There is no significant difference in the linkage structure of the cured resins with the same F/(M + U) and different M/U molar ratios except the ratios of carbonyl carbon of urea and triazine carbon of melamine. Therefore, the lower formaldehyde emission from cured MUF resins with a higher M/U molar ratio might be ascribed to the stronger linkages between triazine carbons of melamine than those of urea carbons. Consequently, the melamine contributed to strong crosslinking linkages in the cured resin structures, leading to lower formaldehyde emission and better bond performance.

Key words

Formaldehyde emission Melamine-urea-formaldehyde resin Cured resin structure Solid state13C-NMR analysis 

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Copyright information

© The Japan Wood Research Society 2001

Authors and Affiliations

  • Shin-ichiro Tohmura
    • 1
    Email author
  • Akio Inoue
    • 1
  • Siti Hanim Sahari
    • 2
  1. 1.Adhesion Laboratory of Forestry and Forest Products Research InstituteIbarakiJapan
  2. 2.Forest DepartmentTimber Research and Technical Training Center, SarawakKuching, SarawakMalaysia

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