Abstract
In recent years, the production and consumption of thermally modified wood (TMW) has been increasing. Offcuts and other waste generated during TMWs processing into products, as well as already disposed products based on TMWs can be an input recycled raw material for production of particleboards (PBs). In a laboratory, 16 mm thick 3-layer PBs bonded with urea-formaldehyde (UF) resin were produced at 5.8 MPa, 240 °C and 8 s pressing factor. In PBs, the particles from fresh spruce wood and mixed particles from offcuts of pine, beech, and ash TMWs were combined in weight ratios of 100:0, 80:20, 50:50 and 0:100. Thickness swelling (TS) and water absorption (WA) of PBs decreased with increased portion of TMW particles, i.e., TS after 24 h maximally about 72.3% and WA after 24 h maximally about 64%. However, mechanical properties of PBs worsened proportionally with a higher content of recycled TMW—apparently, the modulus of rupture (MOR) up to 55.5% and internal bond (IB) up to 46.2%, while negative effect of TMW particles on the modulus of elasticity (MOE) was milder. Decay resistance of PBs to the brown-rot fungus Serpula lacrymans (Schumacher ex Fries) S.F. Gray increased if they contained TMW particles, maximally about 45%, while the mould resistance of PBs containing TMW particles improved only in the first days of test. In summary, the recycled TMW particles can improve the decay and water resistance of PBs exposed to higher humidity environment. However, worsening of their mechanical properties could appear, as well.
Highlights
The aim of this work was to study the effect of the thermally modified particles on the selected physical, mechanical and biological properties of PBs prepared in a laboratory from thermally modified wood (TMW) particles and particles of freshly cut spruce logs
Slovakia, and the chips milled on particles in the grinding SU1 impact cross mill (TMS, Pardubice, Czech Republic) in the laboratories of the Technical University in Zvolen (TUZVO), Slovakia (Figure 1)
Prepared spruce particles were used for the production of reference particleboards (PBs), and for the production of PBs containing different proportions of TMW particles
Summary
Academic Editor: Luis García EstebanReceived: 8 October 2021Accepted: 24 October 2021Published: 27 October 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Licensee MDPI, Basel, Switzerland.Attribution (CC BY) license (https://creativecommons.org/licenses/by/ 4.0/).For the production of particleboards (PBs), nowadays, the trend is to use non-wood lignocellulosic raw materials and especially recycled wood, except of the various traditional forms of fresh natural soft- and hardwood species, as are slabs, edge trimmings, chips, or sawdust. Recycled wood is the subject of much research, especially in terms of the different subtle composition [1]—old wood, e.g., from building constructions, furniture and packaging, and also residual wood from industry. Thermally modified wood (TMW)
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