Effect of aluminosilicate powders on the applicability of innovative geopolymer binders for wood-based composites

In this research, a new binder class for wood based composites, named geopolymer binder, was developed based on pozzolanic by-products (e.g. fly ash). Additionally, effects of different amounts of silica fume, as a replacement agent with other aluminosilicate components (e.g. fly ash and metakaolin), have been evaluated in the innovative binder. The Automated Bonding Evaluation System technique was used to characterize the bonding shear strength of the developed geopolymer binder. It was shown that the best shear strength for fly ash based binders was obtained by the lowest press temperature and longest pressing time. The addition of silica fume (from 20% up to 100%) significantly influenced the bonding shear strength in all binder types. Due to the chemical and mineralogical compositions, silica fume displays higher pozzolanic activity than metakaolin whereas fly ash shows lower strength in comparison to metakaolin. The silica fume (100%) based binder has also superior shear strength compared to those of conventional UF resin and other geopolymer binders. Bonding shear strength like that for UF resin was achieved by substituting only 20% silica fume in geopolymer binder compositions.     

Ultra-light particleboard: characterization of foam core layer by digital image correlation

Increasing markets for internet-traded furniture, but also economic concerns are main driving forces to considerably reduce the weight of wood-based furniture panels. Recent research and technological developments have led to an innovative one-step process which simplifies the typical multi-step process for production of foam core panels. Three layered sandwich panels (with particleboard faces and polymeric in situ expanded foam as core layer) can be produced by a one-step process without additional gluing between the face and core layers. As the morphology of the foam and hence its mechanical properties strongly depend on its chemical composition, as well as on the process parameters during expansion, there are no data available, so far, describing the foam of the novel panels. The aim of the proposed project is to determine the elastic properties of in situ expanded foams using 2D digital image correlation. The data can be used later on for the simulation of the elastic behavior of foam core particleboards by means of FEM to describe the short and long term behavior of the panels.     

Evaluation of low density hybrid panels using expandable granules: effect of granules diameter and content

Low density hybrid panels (16 mm thickness) were produced using wood fiber as face layers and a mixture of coarse wood particles and expandable polystyrene (EPS) as core layer. The EPS was foamed (in-situ foaming) in the core layer during the pressing stage. The effects of granules diameter (0.4, 0.8, 1.15, 1.5, and 2.2 mm) and granules content (5, 10, and 15%) on the physical and mechanical properties were evaluated. The results showed that both variables had significantly influenced the panels’ properties. Mechanical properties mostly depended on the level of mechanical inter-locking of EPS with wood particles, while the physical properties were mostly influenced by the EPS distribution. Stronger mechanical inter-locking of EPS with wood particles was achieved by both larger diameter and higher amount of EPS granules (2.2 mm and 15%). A better EPS distribution between the wood particles was observed with the smaller EPS granules and higher amount of EPS (0.4 mm and 15%).     

Fire performances of foam core particleboards continuously produced in a one-step process

For further progress of novel foam core particleboards, their fire performance was examined with cone calorimetry tests (ASTM E 1354-11a). Specimens with varying surface layer thicknesses, foam densities (polystyrene foam), and processing temperatures were tested. Using the initially recommended cone irradiance of 35 kW/m², different flammability parameters were measured. In comparison to particleboards, the foam core panels generally had much higher heat release rates, somewhat higher heat of combustion and much higher smoke production due to the EPS-foam component of tested panels. The time to ignition and total heat release did not vary significantly among the samples, although certain trends could be explained. The effects of variations in specimen foam densities and processing temperatures on the flammability parameters were not very significant. However, the flammability properties improved towards that of the reference particleboard as the surface layer thickness increased from 3 to 5 mm.     

Cone calorimeter testing of foam core sandwich panels treated with intumescent paper underneath the veneer (FRV)

Surfaces of novel foam core sandwich panels were adhered with intumescent fire‐retardant paper underneath the veneers (FRV) to improve their flammability properties. The panels were evaluated by means of cone calorimeter test (ASTM E 1354). Variables tested were different surface layer treatments, adhesives used for veneering, surface layer thicknesses, and processing conditions, having the objective of obtaining similar or better flammability as that of solid particle boards. Previous research showed that sandwich panels without FRV compared to panels with FRV generally had much higher heat release rates, somewhat higher heat of combustion and much higher smoke production due to the polymeric foam component of tested panels. The present study shows that using FRV adhered to the surface layer of sandwich panels dramatically improved flammability properties; the best FRV performance resulted from panels produced with thicker face layer (5 mm) and lower press temperature (130°C) and adhered with an acrylic thixotropic adhesive. Such protected foam core particleboard has heat release rate profiles as low as that is typical of commercially available fire‐retardant–treated plywood, thus implying a low flammability rating when tested in accordance with both single burn item (Euro Class B anticipated) and steiner tunnel (North America Class A anticipated) tests.     

Flat pressed wood plastic composites made of milled foam core particleboard residues

Flat pressed wood plastic composites were produced on a laboratory-scale using residues of lightweight foam core particleboards as raw material. Raw material preparation methods (dry blending and compounding with a twin screw extruder) and the wood flour content (WF) loading, as influencing parameters on the panel properties, were varied, and coupling agents (CA) were added in some variations. The results showed that panels produced with lower WF content (75 %) have better physical and mechanical properties compared to those of higher WF. The CAs only influenced the panel properties when they were added during the compounding of the materials. Due to the assumed higher wood degradation resulting from raw material compounding, the panel properties were inferior to the panels produced with dry blended materials.     

Development of ultra-light foam-core fibreboard for furniture application

European Journal of Wood and Wood Products - Ultra-lightweight foam-core fibreboard with 19 mm thickness was produced with a novel one-step process using resinated wood fibres for the...     

Effect of ingredient ratios of rigid polyurethane foam on foam core panels properties

One‐step manufacturing process (in‐situ foaming) provide great potential for the production of foam core panels. Polyurethane (PU) foam showed good applicability for use for in‐situ foaming. Here, the effect of ingredient ratios of rigid PU foam on foam performance and panel properties is investigated. It was observed that the isocyanate (ISO) content and polyols (PO) type and content significantly change the foam and panel properties. Foam cell density, as the most important factor influencing the foam characteristics, was higher in foams with higher ISO and polyether content. Bending strength, internal bond and screw withdrawal resistance of the foam core panels were significantly enhanced when the ISO and polyether content was increased in the foam formulation. Varying the ISO content had no influence on panel properties with higher content of polyester (60%) in the PO blend. Varying the foam ingredient ratios did not change the thickness swelling, while the water absorption was dependent on the foam components ratios. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44722.