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Sines, Portugal

Costa N.,EuroResinas | Amaral S.,EuroResinas | Alvim R.,EuroResinas | Nogueira M.,EuroResinas | And 2 more authors.
Journal of Applied Polymer Science | Year: 2013

The molar ratios of formaldehyde (F) to urea (U) of three resin formulations in the range from 0.90 to 1.49 have been analyzed by means of Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy and Fourier Transform-Near-Infrared (FT-NIR) spectroscopy. Application of Principal Component Analysis (PCA) to the spectra (MIR and NIR) allowed to separate them according to the molar ratio and to distinguish between two groups of resins. Soft Independent Modeling of Class Analogy (SIMCA) allowed classification of new resin samples with high model distances between the classes. Partial Least Squares Regression (PLS-R) models based on MIR (NIR) spectra resulted in high coefficients of determination (R2) values, low errors, and high residual prediction deviations (RPD). To confirm the reproducibility of the process and to carefully evaluate twice all multivariate analysis results obtained, different batches of resins have been prepared to have an additional independent sample set. The number of samples required for MIR and possible applications of MIR and NIR spectroscopy in this context including limitations have been discussed. © 2012 Wiley Periodicals, Inc. Source

Costa N.A.,University of Porto | Pereira J.,University of Porto | Ferra J.,EuroResinas | Cruz P.,EuroResinas | And 6 more authors.
International Wood Products Journal | Year: 2013

This paper reports on different applications of sodium metabisulphite as a formaldehyde scavenger. The reduction in formaldehyde emission and the effect on physicomechanical properties of particleboards were studied. The scavenger was mixed with urea-formaldehyde resins with different formaldehyde to urea molar ratios and added separately in the production of particleboards. Several differences between the formaldehyde content and physicomechanical properties of boards were found. When applied to melamine-formaldehyde resins, the changes in formaldehyde emission were less significant, probably due to the incorporation of sodium bisulphite in polymeric matrix. The type of formaldehyde-based resin and the form of scavenger addition are the major factors affecting formaldehyde scavenging efficiency. © 2013 IWSc, the Wood Technology Society of the Institute of Materials, Minerals and Mining. Source

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