Authors: Marek Kalanin, Catherine Rosenfeld, Andreas Weber

Particleboards (PB) and medium-density fibreboards (MDF) are widely used in the furniture and construction industries. Improving the sustainability of these materials requires reconsidering one of their key components: the adhesives used to bind wood fibres into structural boards.

The SUSBOARD project addresses this challenge by developing a fully bio-based and formaldehyde-free adhesive suitable for the industrial production of particleboard and MDF boards. The objective is to provide a sustainable alternative to conventional fossil-based binders while maintaining the technical performance required for modern industrial manufacturing.

Achieving this goal requires collaboration across the entire value chain. SUSBOARD partners include suppliers of renewable raw materials, research organisations, and industrial manufacturers. Within the project, adhesive formulation is developed in Work Package 1 (WP1), while Work Package 2 (WP2) focuses on optimising laboratory-scale board production and evaluating board performance (Figure 1).

Figure 1: WP2 Laboratory board production: optimization and PB/MDF production parameters and board testing by Wood K plus and IHD, supported by Sonae Arauco and Kastamonu Entegre

Processing parameters for particleboard (PB) and medium-density fiber board (MDF) are systematically adjusted and evaluated to assess mechanical properties and overall board performance. These laboratory experiments form the basis for later upscaling to industrial production by the project’s manufacturing partners, Sonae Arauco (for PB) and Kastamonu Entegre (for MDF).

Using the SUSBOARD adhesive formulations developed in WP1, PB boards are produced at laboratory scale by Wood K Plus, while MDF panels are produced by IHD. In both cases, the work is carried out with the support of other project partners involved in the work package (see Figure 1).

To optimise curing conditions for the new adhesive systems, several typical production parameters are varied, including press time, press pressure, temperature, and wood moisture content. These parameters strongly influence the curing behaviour of adhesives and therefore the final mechanical properties of the boards.

Initial MDF trials are carried out using blenders to mix the wood fibres and adhesive system. In later stages of the project, the laboratory defibration unit at IHD will be used, enabling blowline blending under conditions closer to industrial MDF processing.

In subsequent phases of the project, the developed adhesive formulations will also be evaluated in additional wood-based applications beyond PB and MDF.

The laboratory boards produced in WP2 are tested according to European standards in order to determine key mechanical and physical properties such as internal bond strength (IB), bending strength, thickness swelling, and water absorption (see Figure 2). The objective of these investigations is to demonstrate that the SUSBOARD bio-based adhesives, based on polylysine and HMF-containing activated sugars, can achieve performance levels comparable to, or potentially exceeding, those of conventional formaldehyde-based adhesive systems.

Figure 2: Standardised Test setups for SUSBOARD board testing according to EN 312. Left: Swelling test (EN 317), Middle: Strength test (EN319), Right: Bending test (EN310)

An important process parameter in the production of PB and MDF is the press factor, which defines the time required to cure one millimetre of panel thickness during hot pressing. At laboratory scale, press factors typically range from 5 to 12 seconds per millimetre at press temperatures between 180 °C and 240 °C.

Many carbohydrate-based adhesives show slower curing behavior than conventional synthetic resins due to their lower chemical reactivity. As a result, longer press factors may be required to meet the minimum performance requirements defined in the European standard EN 312 for particleboards (see Figure 3).

Internal bond strength (IB) is a key quality parameter defined in EN 312. The minimum requirement for P2 particleboards is indicated as a reference line at 0.35 N/mm² in Figure 3.

Figure 3: Internal bond strength of SUSBOARD PBs, compared to reported literature on carbohydrate – and/or HMF-containing adhesives [1][2][3]

For an initial performance assessment, two SUSBOARD adhesive formulations were tested in the production of laboratory-scale particleboards.

Wood particles supplied by the industrial partner Sonae Arauco were used as raw material, with a recycling content of approximately 50 %. The boards were manufactured as single-layer particleboards with a thickness of 16 mm. A press factor of 8 s/mm and a resin content of 7 % (based on absolutely dry wood mass) were applied.

Mechanical testing was carried out according to EN 319, which specifies the determination of internal bond strength. Already at this early stage of the project, particleboards bonded with SUSBOARD adhesives exceed the P2 requirements of EN 312. Further optimisation and systematic testing of the developed SUSBOARD adhesive formulations are ongoing.

The first MDF trials using the newly developed adhesive systems have also been carried out. Testing according to EN 622-5 showed excellent TS-Values and a high IB, the values were better than the refence with UF.

[1]Rosenfeld, Catherine, Konnerth, Johannes, Sailer-Kronlachner, Wilfried, Rosenau, Thomas, Potthast, Antje, Solt, Pia, & van Herwijnen, Hendrikus W. G. (2020). Hydroxymethylfurfural and its Derivatives: Potential Key Reactants in Adhesives. ChemSusChem, 13(20), 5408-5422. https://doi.org/10.1002/cssc.202001539

[2] Solt, Pia, Konnerth, Johannes, Gindl-Altmutter, Wolfgang, Kantner, Wolfgang, Moser, Johann, Mitter, Roland, & van Herwijnen, Hendrikus W. G. (2019). Technological performance of formaldehyde-free adhesive alternatives for particleboard industry. International Journal of adhesion and adhesives, 94, 99-131. https://doi.org/10.1016/j.ijadhadh.2019.04.007

[3] Rosenfeld, Catherine, Solt-Rindler, Pia, Sailer-Kronlachner, Wilfried, Kuncinger, Thomas, Konnerth, Johannes, Geyer, Andreas, & van Herwijnen, Hendrikus W. G. (2022). Effect of Mat Moisture Content, Adhesive Amount and Press Time on the Performance of Particleboards Bonded with Fructose-Based Adhesives. Materials, 15(23), 8701. https://doi.org/10.3390/ma15238701

Contact:

DIⁱⁿ Dr.ⁱⁿ Catherine Rosenfeld
(WP 2 lead, & Task lead: lab-scale PB production)
Senior Researcher, Area Wood Materials Technologies
Kompetenzzentrum Holz GmbH (Wood K plus)
E-Mail: c.rosenfeld@wood-kplus.at / Homepage: www.wood-kplus.at

DI Andreas Weber
(Task lead: lab-scale MDF production)
Senior Researcher
Institut für Holztechnologie Dresden gemeinnützige GmbH (IHD)
E-Mail: Andreas.weber@ihd-dresden.de / Homepage: www.ihd-dresden.de