Bernard Riedl

The development of halogen-free flame-retardant formulations for wood-based panels is a promising strategy to improve both fire safety and environmental performance. In this study, oriented strand boards (OSB) were impregnated with aqueous solutions of sodium borate (SBo) and sodium bicarbonate (SBi) to evaluate their combined effects on fire resistance and mechanical properties. Fire performance was assessed using the ASTM D3806 small-scale tunnel test, while mechanical and physical properties were measured according to ASTM D1037. Significant improvements in fire performance were observed: mass loss (ML) during flammability testing decreased by 38% (from 6.9% to 4.3%), flame spread speed (FSS) was reduced by more than 50% (from 6.8 to 3.3 mm/s), and after-flame times (AFT) dropped from 17.2 s to 0 s. Thermogravimetric analysis (TGA) further confirmed enhanced thermal stability, with increased char residue (from 16.9% in untreated boards to 31.5% in treated ones). Mechanical testing revealed a 16% increase in internal bond (IB) strength (from 0.44 to 0.51 MPa), while modulus of rupture (MOR) and modulus of elasticity (MOE) were only slightly affected (decreased by up to 4.2% and 3.6%, respectively). Interestingly, the two additives exerted contrasting effects: SBo reduced strength and bonding performance, whereas SBi improved internal bond strength and dimensional stability. The optimal balance was obtained with treatment P250-50 (250 g SBi and 50 g SBo), which combined enhanced fire resistance with acceptable mechanical integrity. Overall, the results demonstrate that the synergistic use of SBo and SBi offers an effective halogen-free approach to simultaneously enhance the fire resistance and mechanical performance of OSB panels, highlighting its potential for industrial applications.

We investigated the effects of polymer blend variation on the physical, mechanical, and thermal properties of wood-polymer composites (WPC). We used high-density polyethylene (HDPE) and polypropylene (PP) and a combination of 80% PP, 20% HDPE, and 80% HDPE, 20% PP as polymer blends for WPC formulations to simulate recycled plastics. We used black spruce (Picea mariana Mill.) hammer milled fibers (75–250 μm) at 35 wt% as a filler for all the formulations. A two-step process was used for WPC manufacturing; pellet extrusion followed by test samples injection. Tensile and three bending tests characterized the WPC mechanical properties. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) characterized the WPCs’ thermal properties. Water absorption and contact angle measurements assessed the composite dimensional stability. Infrared spectroscopy (FTIR) and electron scanning microscopy (SEM) investigated the WPCs’ surface chemistry and microstructure. Mechanical properties and dimensional stability varied according to polymer composition, with better performance for WPC containing higher PP proportions. Thermal properties varied with the polymer composition in the WPC, with better thermal stability for the formulation containing higher HDPE proportions. Surface chemistry analysis did not reveal any chemical changes on the WPCs surface. Scanning electron microscopy analysis revealed distinct phases in all WPCs without evidence of interfacial adhesion.

Wood polymer nanocomposites were prepared from solid aspen wood, water-soluble melamine-urea-formaldehyde (MUF) resin, and silicate nanoclays. The nanofillers were ground with a ball-mill before being mixed with the MUF resin and impregnated into the wood. The water-soluble prepolymer was mixed with the nanoclays at a mixing speed of 3050 rpm for 20 min to form impregnation solutions. Wood was impregnated with resin, which polymerized in situ under certain conditions. The physical and mechanical properties of the composite and the effect of ball-milling treatment of nanofillers on these properties were investigated. Significant improvements in physical and mechanical properties, such as density, surface hardness, and modulus of elasticity, were obtained for specimens impregnated with MUF resin and nanoclay-MUF resin mixtures. Ball-mill treatment favors dispersion of the nanofillers into the wood, but also appears to interfere with particle-resin adhesion.

El uso de la corteza externa de abeto blanco en la fabricación de canoas por las primeras naciones de Canadá es un ejemplo de su uso más antiguo. Esto confirma sus características hidrófugas, la cual puede ser explotada mediante su uso en la superficie del panel compuesto de 3 capas para protegerlo de filtraciones de humedad. Estos tableros fueron fabricados con partículas de corteza externa en las capas superficiales, y con partículas gruesas o fibras de madera en el corazón. Un experimento factorial en un diseño de bloque completo hizo posible realizar el diseño de experimento. Los dos grandes factores considerados, fueron el porcentaje de corteza en las capas superficiales con 3 niveles y el tipo de material usado en el corazón, con dos niveles respectivamente (partículas y fibras de madera). Cuatro réplicas fueron hechas para cada panel. Sólo los tableros con partículas gruesas de madera en el corazón pasaron todas las pruebas físicas satisfaciendo los requerimientos del interior de los tableros de partículas. Paneles con 45% de partículas de corteza en la superficie y 55% de partículas de madera en el corazón fueron seleccionados como los mejores, debido a su buena estabilidad dimensional. AbstractThe use of outer white birch bark in canoes is an example of its oldest use by the first nations in Canada. This use confirms the hydrophobic characteristics of this bark, which can be capitalized on by using it in the outer layers of three-layer mixed composite panels in order to protect them from water infiltration from their surface. These panels were made up of outer white birch bark particles in the surface layers with coarse wood particles or wood fibres in the core layer. A factorial experiment used in a complete block design permitted to carry a suitable statistical analysis of measured properties. The two main considered factors were respectively the bark percentages in the surface layers with three levels and the type of material used in the core with two levels. Four replicates were done for each panel. The panels with wood particles in the core layer gave physical and mechanical properties satisfying the indoor requirements for particleboards and those with wood fibres in the core layer passed the requirement of medium fibres density board. Panel with 45% bark particles in the surface and 55% wood particles in the core was selected as the best because of its good dimensional stability.