Microstructure of Cured Urea-Formaldehyde Resins Modified by Rubber Latex Emulsion after Hydrolytic Degradation

Nuryawan, Arif; Park, Byung‐Dae

doi:10.5658/wood.2014.42.5.605

Cited by 2 publications

(1 citation statement)

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“…Some studies focused on the mechanism by which the hydrolysis of UF resins was achieved via the loss of bond strength and the release of formaldehyde (FE) in neat cured UF resin [10,11,12,13,14,15,16] and UF resin-bonded wood panels [17,18,19,20]. Recently, the hydrolysis of cured UF resins using acid was undertaken to determine the micro-morphology of the sample with the aid of scanning electron microscopy (SEM) [21], transmission electron microscopy (TEM) [22], and Confocal laser scanning microscopy (CLSM) [23]. The results of this investigation indicated that the cured UF resins were composed of amorphous regions which were removed under acid etching and crystalline parts that underwent decomposition after extended reaction periods.…”

Section: Introductionmentioning

confidence: 99%

Hydrolysis of particleboard bonded with urea-formaldehyde resin for recycling

Nuryawan

Rahmawaty

Tambun

et al. 2020

Heliyon

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In this study, the removal of urea-formaldehyde (UF) resin adhesives from waste wood particleboards (PBs) via hydrolysis was discussed, particularly the use of this application to combat environmental issues often encountered in recycling projects. Herein, the conditions required for producing PBs with poor binding properties were examined. Additionally, we determined the appropriate formaldehyde: urea (F/U) mole ratios, namely, 0.95, 1.05, and 1.15, required for generating UF resins that can be characterized and used as PB binders. The resulting values were compared with those obtained for a high mole ratio of UF resin (F/U ¼ 2.0) as well as a commercially available PB sample for binding. Aqueous hydrochloric acid (HCl) solutions of various concentrations and water were used to leach the adhesive from the wood residues, and the effectiveness of these leaching agents was determined using a combined scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) technique in addition to the Kjeldahl method. Swelling tests were performed on the UF resins to measure the sol fraction (ω sol ) and evaluate the network behavior of the resulting resins. Our results showed that factors, such as solid content, density, viscosity, and gel time, were necessary for generating an effective adhesive; herein, we determined that a solid content between 37.17 and 56.57%, density between 1.45 and 1.54 g/cm 3 , viscosity ranging from 115-444 MPa.s, and gel time between 8.50 and 13.13 min were feasible. Whereas the physical properties of the resulting PB (i.e., the density and moisture content) fulfilled the criteria established by the Japanese Industrial Standard, as laid out in the document entitled JIS A 5908: Particleboards (2003), the mechanical properties failed to pass the aforementioned standard as low bending strength and weak internal bonding were noted for the PBs produced. The use of hydrolyzing agents successfully decomposed the UF resin adhesives by altering their nitrogen (N) content; confirmation of this was obtained through SEM-EDS analysis along with the Kjeldahl method. Swelling tests showed that despite containing a reasonable amount of nitrogen owing to its dissolution in either HCl or water, the ω sol parameter was heavily influenced by the concentration of the hardener and type of F/U mole ratio adhesive used for the PB under investigation. These results indicate that wood residues can be used as raw materials for recycling PBs.

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