Synthesis and evaluation of low viscosity melamine urea formaldehyde for bulking treatment of wood
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ORIGINAL ARTICLE
Synthesis and evaluation of low viscosity melamine urea formaldehyde for bulking treatment of wood Rabiatol Adawiah Mohd Ali1 • Zaidon Ashaari1,2 • Mohd Khairun Anwar Uyup3 Edi Suhaimi Bakar1 • Seng Hua Lee2 • Nur Izreen Farah Azmi1
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Received: 16 September 2019 / Accepted: 5 October 2020 Ó Indian Academy of Wood Science 2020
Abstract This study attempted to produce a low viscosity melamine urea formaldehyde (MUF) resin. The MUF resins were diluted into concentration of 20% and 30% based on solid content with different melamine contents (20 to 30%), formaldehyde contents (50 to 60%) and urea contents (15 to 25%). Performance of the formulated resins was evaluated by measuring solid content, viscosity, precuring time, curing time, curing behaviour and molecular weight. The pH values were set to 9.5 to 9.8 during synthesis. A very low viscosity resin was produced with the viscosity ranges from 6 to 9 cp and the solid content ranged from 21 to 36%. The fastest pre-curing time at 70 °C was observed in formulation 1 for both 20% MUF and 30% while the fastest curing time was obtained from 30% MUF (F2) for 22 min. Analysis of differential scanning calorimetry found that 30% MUF (F2) yield the lowest peak temperature at 95.79 °C and the highest peak was obtained from 30% MUF F4 at 109.47 °C. The gel permeation chromatography shows that 30% MUF (F4) had weight average molecular weight (Mw) of 1988 g/mol and number average molecular weight (Mn) of 1769 g/mol.
& Zaidon Ashaari [email protected] & Seng Hua Lee [email protected] 1
Faculty of Forestry and Environment, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
2
Institute of Tropical Forestry and Forest Products, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
3
Forest Products Division, Forest Research Institute Malaysia, 52109 Kepong, Selangor, Malaysia
Keywords Melamine urea formaldehyde Curing behaviour Molecular weight Viscosity
Introduction There are two types of resins, namely natural and synthetic resin. Natural resins are obtained from extraction of plant or animal such as rosin and fossils, while synthetic resins are produced by polymerization of unsaturated monomers (Buschmann et al. 1976). Synthetic resins, for example, urea formaldehyde (UF), phenol formaldehyde (PF) and melamine formaldehyde (MF) and melamine urea formaldehyde (MUF), are the common resins used in bonding plywood, composites or panel products (Magnusson 2015). The amino resins are preferable in composite panel industries due to its excellent bonding performance and cost-effective (Meyer and Ritchie 1980; Pizzi 1994; Fan et al. 2006). In Malaysia, phenol formaldehyde is widely used as a bulking and gluing agent to enhance dimensional stability of low density tropical hardwood, oil palm and bamboo (Zaidon 2017 inaugural lecture). There are few variables that need to be considered to ensure excellent treatability during treatment process such as molecular weight of the resin (Mw), concentration of the resin, impregnation proces
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