Abstract
The potential of producing eco-friendly, formaldehyde-free, high-density fiberboard (HDF) panels from hardwood fibers bonded with urea-formaldehyde (UF) resin and a novel ammonium lignosulfonate (ALS) is investigated in this paper. HDF panels were fabricated in the laboratory by applying a very low UF gluing factor (3%) and ALS content varying from 6% to 10% (based on the dry fibers). The physical and mechanical properties of the fiberboards, such as water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), bending strength (MOR), internal bond strength (IB), as well as formaldehyde content, were determined in accordance with the corresponding European standards. Overall, the HDF panels exhibited very satisfactory physical and mechanical properties, fully complying with the standard requirements of HDF for use in load-bearing applications in humid conditions. Markedly, the formaldehyde content of the laboratory fabricated panels was extremely low, ranging between 0.7–1.0 mg/100 g, which is, in fact, equivalent to the formaldehyde release of natural wood.
Highlights
The growing need for sustainable products and the stringent legislative requirements related to the hazardous formaldehyde emissions from wood-based panels have boosted scientific and industrial interest in the production of eco-friendly, wood-based panels [1,2,3,4,5,6,7] and optimal utilization of the available lignocellulosic materials [8,9,10,11,12,13]
Fiberboards are wood-based panels produced by breaking down softwood and hardwood material into fibers, mixing them with wax and a formaldehyde-based thermosetting resin, such as urea-formaldehyde (UF), phenol formaldehyde, or melamine-urea formaldehyde, and forming panels by applying pressure and high temperature in a hot press [14,15]
The results obtained for the free formaldehyde content of the laboratory-produced HDFThpeanreeslus lftrsoombtianindeudstfroiarlthhearfdreweofoodrmfiabledresh, ybdoendcoendtewnitthofUthFerleasbinoraantodrya-mprmodounciuedm HliDgnFopsaunlfeolsnafrtoemadihnedsuivsteri(aDl-h9a4r7dLw),owoedrefibreemrsa, rbkoanbdlyedlowwitahnUdFcarnesbine aconndsaidmemreodnaius ma zleigro- nfoosrumlfaolndaetheyaddehceosnivten(tD[1-9,2447]L. )A, wll elareborreamtoarryk-afbalbyrilcoawtedanHdDcFanpabneeclsonfuslifidlelreeddthase arezqeuriore- fomremnatsldoefhtyhdeesucopnerteEn0t e[1m,2i4ss].ioAnllgrlabdoer(a≤to1r.y5-mfagb/ri1c0a0tegd).HTDheFlpowaneesltsffourlmfiallleddehthyederecqounitreen-t moefn0t.s7o±f t0h.e1 smupg/er10E00 gemwiassioanchgieravdeed (f≤o1r.5thmegH/1D00F gp)a. nTehlebloonwdeesdt fworimtha3ld%ehUyFderecsointaentd o1f00%
Summary
The growing need for sustainable products and the stringent legislative requirements related to the hazardous formaldehyde emissions from wood-based panels have boosted scientific and industrial interest in the production of eco-friendly, wood-based panels [1,2,3,4,5,6,7] and optimal utilization of the available lignocellulosic materials [8,9,10,11,12,13]. The formaldehyde limit values have steadily been lowered, which has led to the development of less toxic, low-emission, eco-friendly, wood-based panels, where conventional synthetic resins have been partially or completely replaced by sustainable, biobased adhesives [40,41,42,43,44,45,46,47] or by adding formaldehyde scavengers to adhesive formulations, such as urea [48], sodium metabisulfite (Na2S2O5), ammonium bisulfite ((NH4)HSO3), other ammonium-containing agents [49,50], Al2O3 nanoparticles [51], etc. The aim of this research work is to investigate the potential of producing eco-friendly HDF panels from hardwood fibers, bonded with UF resin and a novel ALS adhesive, in order to reach the European standard requirements
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