Evaluation of post-added ester and/or urea as a formaldehyde scavenger in UF resins used to bond southern pine particleboard

Three-layer particleboards made of southern pine were bonded with urea-formaldehyde resins containing post-added ester and/or urea. The ester was a water-soluble active methylene compound [(2-hydroxyethoxyethyl) acetoacetate], which was added to the face resin over a range of 0.015 to 0.100 percent based on dry face wood weight. A series of panels was also bonded without a scavenger, as a control. For comparison, a series was bonded with resin containing 0.300 percent urea (percent based on dry face wood weight) as a formaldehyde (HCHO) scavenger. The particleboards were physically tested for density, internal bond strength, and HCHO emission. HCHO emission assessment was determined by the 2-hour desiccator test method. The density and internal bond data indicated that the laboratory procedures used for manufacturing the panels were satisfactory. HCHO emission by resin-scavenger type was significant. Only resin-bonded panels with 0.300 percent post-added urea (percent based on dry face wood weight) yielded significantly lower HCHO emission than the control resin-bonded panels with no scavenger. All panels manufactured had HCHO emissions below the maximum level allowed in ANSI/A208.1-1989 Standard on Wood Particleboard (1).

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