Determination of formaldehyde/urea molar ratio in amino resins by near‐infrared spectroscopy |
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Authors: | Ana Henriques Paulo Cruz Jorge Martins João M Ferra Fernão D Magalhães Luisa H Carvalho |
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Affiliation: | 1. LEPAE—Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200‐465 Porto, Portugal;2. ARCP—Rede Competência de Polímeros, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200‐465 Porto, Portugal;3. Euroresinas—Industrias Químicas, S.A., 7520‐195 Sines, Portugal;4. DEMad—Departamento de Engenharia de Madeiras, Instituto Politécnico de Viseu, Campus Politécnico de Repeses, 3504‐510 Viseu, Portugal |
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Abstract: | New processes for synthesis of urea‐formaldehyde (UF) and melamine‐fortified urea‐formaldehyde (mUF) resins have been developed in the last years, motivated by the current concerns about the effects of formaldehyde on human health. All these formulations are quite susceptible to possible operation error, which can significantly influence the characteristics of the final product. The main objective of this work was to implement chemometric techniques for off‐line monitoring of the product's formaldehyde/urea (F/U) molar ratio using near infrared (NIR) spectroscopy. This allows the timely implementation of the necessary corrections in case the product is off‐specification. Calibration models for F/U molar ratio were developed taking into account the most relevant spectral regions for these resins, individually or in combination (7502–6098 cm?1 and 5000–4246 cm?1) and using different preprocessing methods. When the appropriate spectral range and preprocessing methods are selected, it is possible to obtain calibration models with high correlation values for these resins. The best preprocessing methods were identified for three cases: UF resin (produced by strongly‐acid process), mUF resin (alkaline‐acid process), and a combined model that involves both UF and mUF resins. It was concluded that significantly better accuracy is obtained when a new model is developed for each particular resin system. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 |
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Keywords: | urea‐formaldehyde resins spectroscopy partial least‐squares regression chemometrics |
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