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Author(s): Carolina Gonçalves
João Pereira
Margarida Almeida
Nádia T. Paiva
João M. Ferra
Jorge Martins
Fernão D. Magalhães
Ana Barros Timmons
Luísa de Carvalho
Title: Impact of alkaline-acid and strongly acid process on the synthesis of urea-formaldehyde resins and derived composites: a comparison study
Issue Date: 2019
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.
Related Information: info:eu-repo/grantAgreement/FCT - Fundação para a Ciência e a Tecnologia/Programa de Financiamento Plurianual de Unidades de I&D/UID/EQU/00511/2019 /Projeto Estratégico do LEPABE - Laboratório de Engenharia de Processos, Ambiente, Biotecnologia e Energia/LEPABE
Document Type: Artigo em Revista Científica Internacional
Rights: restrictedAccess
Appears in Collections:FEUP - Artigo em Revista Científica Internacional

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