Impact of alkaline-acid and strongly acid process on the synthesis of urea-formaldehyde resins and derived composites: a comparison study
authors Gon?alves, C; Pereira, J; Almeida, M; Paiva, NT; Ferra, JM; Martins, JM; Magalhaes, FD; Barros-Timmons, A; Carvalho, LH
nationality International
journal EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS
keywords ADHESIVES; OPTIMIZATION; PERFORMANCE; SEPARATION; ABES; PH
abstract This paper presents the impact of different processes for producing urea-formaldehyde resins and their roles on the physico-mechanical properties and the formaldehyde emission of the resulting particleboards. Five resins were produced: four via the alkaline-acid process (Resin A to D) and one using the strongly acid process (Resin E). The differences between the syntheses are mainly related to different formaldehyde/urea molar ratios during the synthesis, temperatures, and the number of urea load addition. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatography and the unreacted oligomers were followed by high-performance liquid chromatography. The shear strength of adhesive joints was evaluated using automated bonding evaluation system. Particleboards produced with these resins were analyzed according to the usual standards for mechanical tests and formaldehyde emission. The resins differ in some characteristics, namely percentage of unreacted oligomers, chemical composition, viscosity, and reactivity. At a pressing time of 120 s, the internal bond of the particleboards was similar for all the resins produced using the alkaline-acid process (approximate to 0.60 N mm(-2)) but differed from that obtained using the strongly acid process (approximate to 0.40 N mm(-2)). However, formaldehyde emissions were apparently independent of the synthesis process.
publisher SPRINGER
issn 0018-3768
isbn 1436-736X
year published 2019
volume 77
issue 6
beginning page 1177
ending page 1187
digital object identifier (doi) 10.1007/s00107-019-01453-4
web of science category Forestry; Materials Science, Paper & Wood
subject category Forestry; Materials Science
unique article identifier WOS:000496309100018
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journal analysis (jcr 2019):
journal impact factor 1.542
5 year journal impact factor 1.771
category normalized journal impact factor percentile 63.918
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