resumo
This paper presents a study of two crucial synthesis parameters of the alkaline-acid process of UF resin synthesis: condensation formaldehyde/urea (F/U) molar ratio and U feed rate during the methylolation step. The differences in the polymeric structures and the performance of the ensuing resins on particleboards (PBs) properties were analyzed and compared with a standard resin. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatography (GPC/SEC) and the unreacted oligomers by high-performance liquid chromatography (HPLC). The PBs produced were analyzed following European standards for mechanical tests and formaldehyde emission. The data obtained were also submitted to a statistical analysis. The results obtained showed that the use of low molar ratios yield higher internal bond strength (IB) values and lower formaldehyde emissions (F). In turn, the effect of urea feed rate during the methylolation step on IB values depends on the F/U-II molar ratio used: (i) a reduction for the higher final molar ratio used, and no effect for the lowest final molar ratio used. Moreover, the statistical analysis carried out showed that F/UII molar ratio has significance on almost all of the resins' characteristics. The resin used as standard yielded the best results when the final F/U molar ratio was 1.10 and the resulting PBs presented values of internal bond (IB) of 0.51 N mm(-2) and formaldehyde content (F) of 5.1 mg/100 g o.d.b., complying with the market requirements. Additionally, the effect of resin ageing was also studied and the PBs prepared using the best resin upon fifteen days of its production presented similar IB values and even lower F content in relation to those obtained using fresh resin.
palavras-chave
EMISSION; OPTIMIZATION; TEMPERATURE; REACTIVITY; SEPARATION
categoria
Engineering; Materials Science
autores
Goncalves, C; Pereira, J; Paiva, N; Ferra, J; Martins, J; Magalhaes, F; Barros-Timmons, A; Carvalho, L
Grupos
agradecimentos
Carolina Goncalves thanks ENGIQ - Doctoral Programme in Refining, Petrochemical and Chemical Engineering (PDERPQ); FCT and EuroResinas - Industrias Quimicas for the PhD grant PD/BDE/114352/2016. This work was financially supported by: Project POCI-01-0145-FEDER-006939 (Laboratory for Process Engineering, Environment, Biotechnology and Energy -UID/EQU/00511/2013) funded by the European Regional Development Fund (ERDF), through COMPETE2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) and by national funds, through FCT - Fundacaeo para a Ciencia e a Tecnologia; this work was developed within the scope of the project CICECO-Aveiro Institute of Materials, FCT Ref. UID/CTM/50011/2019, financed by national funds through the FCT/MCTES and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement and 2GAR project under PT2020.