Next Article in Journal
Theory of Movement of the Sugar Beet Tops in Loading Mechanism, Taking into Account the Influence of the Air Flow
Next Article in Special Issue
Applying the Artificial Neural Network and Response Surface Methodology to Optimize the Drilling Process of Plywood
Previous Article in Journal
Processability of High-Speed Steel by Coaxial Laser Wire Deposition Technology for Additive Remanufacturing of Cutting Tool
Previous Article in Special Issue
Elemental Compositions of Wood Plastic Pellets Made from Sawdust and Refuse-Derived Fuel (RDF) Waste
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Applied Sciences
Volume 13
Issue 20
10.3390/app132011234
applsci-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Lightweight Solid Wood Panels Made of Paulownia Plantation Wood

by
Marius Cătălin Barbu
1,2,
Helmut Radauer
1,
Alexander Petutschnigg
1,3,
Eugenia Mariana Tudor
1,2,* and
Markus Kathriner
4
1
Green Engineering and Circular Design Department, Salzburg University of Applied Sciences, Markt 136a, 5431 Kuchl, Austria
2
Faculty of Furniture Design and Wood Engineering, Transilvania University of Brașov, B-dul. Eroilor nr. 29, 500036 Brasov, Romania
3
Institute of Wood Technology and Renewable Materials, University of Natural Resources and Life Sciences (BOKU), Konrad Lorenz-Straße 24, 3340 Tulln an der Donau, Austria
4
Controlling Department, Paris Lodron Universität Salzburg, Residenzplatz 9, 5020 Salzburg, Austria
*
Author to whom correspondence should be addressed.
Appl. Sci. 2023, 13(20), 11234; https://doi.org/10.3390/app132011234
Submission received: 12 September 2023 / Revised: 9 October 2023 / Accepted: 11 October 2023 / Published: 12 October 2023
(This article belongs to the Special Issue International Conference Wood Science and Engineering in the Third Millennium - ICWSE 2023)
Browse Figures
Review Reports Versions Notes

Abstract

:
Light Paulownia seamless-edged glued solid wood panels (SWPs), single-layered and three-layered, were analyzed in this study. Both panel types were calibrated at a thickness of 19 mm, a dimension very often in demand on the SWP market, but produced with other wood species (for example, spruce, pine, larch and fir). The panels were bonded with melamine-urea formaldehyde, polyurethane and polyvinyl acetate resins. The panels were tested for their physical (density) and mechanical (modulus of rupture, modulus of elasticity, compressive shear strength and wood breakage rate) properties. For the single-layered panels, the mechanical and physical properties did not differ significantly and were similar to massive Paulownia wood. For the three-layered panels, the adhesive application of polyurethane influenced positively all SWP properties. Considering the differences in density, these composites failed to achieve the performance of one- and single-layered panels made of spruce. The results of these findings recommend Paulownia SWPs to be used as lightweight and sustainable core materials in sandwich structures for the furniture and packaging industry, sport articles or non-load-bearing constructions.

1. Introduction

Lightweight wood materials offer enormous potential for resource-efficient construction systems considering functional, environmental and economic factors [1]. The structure of these products can consist of a lighter material and/or use less material (e.g., hollow construction) [2]. These do not only imply the lower weight of structures, but ensure the load-oriented use of materials, aiming towards more energy efficiency due to decreased thermal conductivity [3]. Lightweight materials are a sine qua non of aircraft performance to allow greater range and speed, where low weight in relation to strength is needed. The emergence of still-lighter materials in the building and furniture sectors plays a significant role in the development of next-generation products [2]. Considering material savings and reduced weight, furniture is expected to use lightweight panels following designers’ recommendations or for portable furniture (for do-it-yourself purposes). Experts expect that hutch furniture will consist no longer 100% of chipboard, but of “hybrid construction”, where the optimal material is used depending on the functional requirements. The fact that light furniture is more likely to be associated with limited durability than heavier furniture speaks to a certain reluctance on the part of end consumers [4]. There are some ways to reduce the weight of composites, e.g., the use of low-density wood species, lower compaction of the wooden mat and filling the core layers of panels with low-density materials (foam or honeycomb structures) for sandwich structures. It is important to note that lightweight wood products are primarily used for applications where structural strength is not a primary concern. These lightweight solutions should consider tailored manufacturing, machinability (connections and the lamination of the edges) and performance (the physicomechanical properties of the composites) [5]. As a consequence of weight reduction, the transportation and material costs are diminished and ecological aspects as efficiency, consistency and sufficiency are considered [4].
Sustainable raw materials for the manufacture of solid wood panels are of great interest and highly demanded nowadays [6]. Solid wood panels (SWPs), single- and multi-layer, are used for both indoor and outdoor applications [4]. Either as an outer covering, with aesthetic quality and original particularities, or for use indoors in furniture construction [7], the request for SWPs develops constantly. The increased interest in prefabricated building requires the use of high-quality SWPs [8]. In the context of significant pressure for carbon emission reduction, prefabricated wood modules exhibit lower footprints and garner widespread interest [9]. For exterior applications, e.g., timber cladding, the wood species selected include Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), European larch (Larix decidua Mill.), Siberian larch (Larix sibirica Ledeb.) and European oak (Quercus robur L.). Coniferous species such as fir (Abies alba Mill.), spruce (Picea abies L. (Karst)) or pine (Pinus sylvestris L.) are considered only partly durable for use unless they are treated for enhanced protection or preservation [10]. Durability is very important also for structural timber. Considering the shortage of this lignocellulosic resource, alternative raw materials from short-rotation plantations can be considered for the manufacture of SWPs.
Lighter wood species such as balsa (Ochroma lagopus Sw.) have been used since the logs in the FSC-certified plantations in Central America have reached harvestable diameters. Special lightweight fittings are usually not necessary in weight-sensitive furniture and vehicle interior fittings. If higher shear strengths are to be achieved, balsa brainwood panels can be used (e.g., for the rotor blades of wind turbines). For many applications, balsa wood products are too expensive, so lightweight wood species such as Paulownia could represent an alternative to balsa [4].
Paulownia, also known as the princess tree, emperor tree, miracle tree or the European balsa [11], has been cultivated on the old continent more extensively in recent decades [12]. Koman and Feher (2020) [13] reported about at least nine sub-species of Paulownia, of which Paulownia tomentosa, Paulownia elongata and Paulownia fortunei (and their hybrids) are most prevalent [14]. It is worth mentioning that short-rotation plantations are not considered forests when the rotation time is less than 20 years [15]. One of the main properties of Paulownia is its low density, which can range from 250 to 350 kg/m3 [11], and other mechanical properties such as modulus of rupture (on average 40 MPa), modulus of elasticity (on average 4400 MPa), and compressive strength (on average 25 MPa) or tensile strength (on average 38 MPa) for Paulownia Clone In Vitro 112 [13], Paulownia COTE-2 [16] and Paulownia tomentosa × elongata from European plantations [11]. But similar to other fast-growing wood species, Paulownia has low performance in its mechanical properties. One of the limitations of the industrial usage of Paulownia timber is due to the influence of its low density on its mechanical properties [14]. This lightweight wood species can be used for the manufacture of particleboard using raw material from Turkey [17], a combination of bio-waste cotton stalks (Gossypium hirsutum L.) and Paulownia wood particles [18], using raw material from Portugal [19] or in non-load-bearing constructions [20]. Moreover, Paulownia represents a solution to replace expensive and rare tropical low-weight/density wood species (i.e., balsa (Ochroma pyramidale Cav. ex Lam) [11].
To the best of our knowledge, solid wood Paulownia panels were studied hitherto in [21] regarding their microscopic changes under thermal compression. The results of this study showed that Paulownia wood resembles balsa with respect to its reduced density and the occurrence of a hexagonal cell shape in its microstructure. The authors emphasise the idea that Paulownia can replace balsa wood as a core material in sandwich structures. It should be mentioned that SWPs with this cellular structure (e.g., honeycomb, Dendrolight®, Bionic Delta, Steinakirchen am Forst, Austria) as industrial established products are not the object of this study. The aim of this study is to analyse the properties of single- and three-layered solid wood panels made of European Paulownia plantations’ wood and to compare them with similar lightweight commercially available SWPs.

2. Materials and Methods

The Paulownia European plantation timber (Paulownia tomentosa × elongata) was provided by Glendor Holding GmbH (Kilb, Austria) and sourced from 5- to 7-year-old trees. The plantation wood from Petrinja, Croatia, was delivered by Moserholz GmbH (Pettenbach, Austria) dried (m.c. = 12%) as rough-sawn lumber of approximately 100 cm length and 20–30 cm width and with a thickness of 20–25 mm. Prior to testing, the raw material was conditioned to constant weight at 20 °C and 65% relative air humidity for at least 14 days, until constant weight was achieved.
For the manufacture of single- and three-layered SWPs with a thickness of 19 mm, two types of lamellae with the following dimensions were cut with a circular saw and planed: 112 × 3.2 × 2.2 cm for the single-layer SWPs and 98 × 6.6 × 1 cm for the 3-layer SWPs. A lamella width of 32 mm (single-layered board) was opted for according to the dimension of the core layer of a standard industrial blockboard from Moralt AG (Hausham, Germany). A lamella width of 66 mm (3-layered board) was chosen after optimising the available raw material in order to obtain the maximum yield.
Both the one- and three-layered SWPs were glued using polyvinylacetate (PVAc) type Pattex® PV/H, category D3 (Pattex, Düsseldorf, Germany); melamine urea formaldehyde (MUF), type Dynea Prefere 4564 with hardener Prefere 5013, at a ratio of 100:8 (Dynea Austria GmbH, Krems, Austria) and polyurethane Kleiberit® PUR 501.0 (Kleiberit SE & Co. KG, Weingarten, Germany). The adhesive amount was as follows: for the PVAc, 330 g/m2, for the MUF, 340 g/m2 and 210 g/m2 for the PUR.
The single-layered SWPs were manufactured with Paulownia lamellae with 12% moisture content [22]. The lamellae were previous glued with PVAc, MUF and PUR and consequently cold-pressed at 0.68 MPa with screw clamps for two hours (Figure 1).
The single-layer panels were calibrated using a wide belt sander, grit 60, to a thickness of 19 mm, a width of 446 mm and a length of 950 mm.
The individual layers of the 3-layer SWP were formatted to 920 × 920 mm and calibrated. The top layers (faces) had a thickness of 5.75 mm and the middle layer (core) 7.5 mm, considering the model of a standard spruce 3-layer panel from Binderholz GmbH (St. Georgen, Austria) of 19 mm thickness (2 × 5.75 + 7.5 mm).
The adhesive was applied to the individual layers of the 3-layer SWP with a notched trowel of tooth size B1 for all the adhesive types (Table 1). The 3-layer SWPs were pressed at 60 °C for 15 min in a veneer press OTT (Lambach, Austria) with a pressure of 0.6 N/m2 for all panel types (bonded with MUF, PUR and PVAc) (Figure 2).
For the manufacture of SWPs, lamellae with different thicknesses (32 and 66 mm) were used, as well as distinct amounts of adhesive (Table 1):
Table 1. Design of experiments for the single- and three-layered Paulownia SWPs.
Table 1. Design of experiments for the single- and three-layered Paulownia SWPs.
Board TypeAdhesive TypeLamellae Width
(mm)		Adhesive Application (g/m2)
Single-layeredMUF32160
Single-layeredPUR32180
Single-layeredPVAc32150
Three-layeredMUF66340
Three-layeredPUR66210
Three-layeredPVAc66 330
The testing specimens were prepared from the 1-layer and 3-layer SWPs according to EN 326-1:2005 [23] and then stored in a standard climate (20 °C and 65% relative air humidity).
For the density determination of the 1- and 3-layer SWPs (Figure 3), 6 test specimens were prepared for each type of board according to EN 323:2005 [24]. The mechanical properties of 3-point flexural strength (MOR) and modulus of elasticity (MOE) in bending were determined from 6 test specimens per board according to EN 310:2005 [25]. In the case of the 3-layer SWPs, 6 test specimens for each board were tested parallel and perpendicular to the grain. To test the quality of the bond for SWP 1 (24 h water storage), 10 test specimens per board were used to determine the compressive shear strength according to EN 13354:2009 [26], as depicted in Figure 4.

3. Results and Discussion

In this section are presented the density, bending strength, modulus of elasticity, compressive shear strength and wood breakage of the samples from single- and three-layered SWPs tested parallel and perpendicular to the grain.

3.1. Density

Table 2 and Figure 5 show the values of the raw density of the Paulownia boards, single- and three-layered. Similar average values of 258 kg/m3 were measured for the single-layered boards bonded with MUF and PVAc, but with different coefficients of variation (CVs) of 0.055 for the panel glued with MUF and 0.019 for the panel with PVAc adhesive application. The single-layered panel bonded with PUR had a density of 249 kg/m3, and a CV of 0.059.
In the case of the three-layered boards, the density [24] exhibited values of about 280 kg/m3 with a minimum of 264 kg/m3 and a maximum of 300 kg/m3, with the smallest CV for the panel with MUF application (0.023), followed by the panel with PVAc application (0.038) and the highest CV of 0.042 for the panel bonded with PUR. It can be observed that the density values for the single-layered panels are consistent with the raw density of Paulownia wood in results from studies concerning plantation wood from Spain, Serbia and Bulgaria [11,14] and Hungary [13,27]. The three-layered SWPs had increased density due to the adhesive application and there was no difference regarding the extraction of samples parallel or perpendicular to the direction of production/or the grain.

3.2. Three-Point Flexural Modulus of Rupture and Modulus of Elasticity

The elastic properties of the Paulownia SWPs are summarised in Table 3. For the single-layered SWPs (Figure 6, left), there is no significant difference between the values of modulus of rupture (MOR) for panels with three types of adhesive application. A clear difference is seen in the CV of the panel with PUR adhesive application, 0.117, compared with 0.082 (for MUF adhesive application) and 0.078 (for PVAc adhesive application).
The MOR [25] was tested for the three-layered SWPs parallel and perpendicular to the grain (Figure 6, middle and right). The MOR values for the samples tested perpendicular to the grain were at least three times lower compared to the other testing direction, parallel to the grain. The highest MOR (Figure 7) was achieved by the boards with PUR application (36 N/mm2). These boards had similar CVs (about 0.09) when tested in both directions. Significant differences in the CV were determined for the panels bonded with PVAc, 0.022 (parallel to the grain) and 0.147 (perpendicular to the grain).
The values for modulus of elasticity [25] are similar for the single-layer SWPs. Again, MUF, PUR and PVAc (Figure 8) have no significant influence on the edge-gluing of a single-layered SWP. The knot-free structure of the Paulownia lamellae [28], straight-grained [21], determines the relative related values for MOE (from 3500 to 3700 N/mm2) for the single-layered SWPs. The CVs are different when the lamellae are bonded with MUF (0.089), PUR (0.121) and PVAc (0.063).
For the three-layered SWPs, the MOE was higher when the samples were tested parallel to the grain and about eight times lower when the testing was performed perpendicular to the grain. For the MUF bonding, the CVs were almost equal in both testing directions (0.09). For PUR bonding, the CVs were 0.070 (parallel) and 0.093 (perpendicular). Higher CV differences were determined for the bonding with PVAc, namely 0.079 (parallel) and 0.104 (perpendicular).
A comparison of the MOR and MOE of Paulownia SWPs with other lightweight wood products (made of balsa, for example) is relatively difficult, as balsa is used in sandwich structures with glass-fibre reinforcements [29] and is mostly composed as end-grain in a setup that consists of two face sheets (skins) and a core structure (e.g., balsa) [30].

3.3. Compressive Shear Strength and Wood Breakage

The highest compressive shear strength [26] after 24 h of water storage (Figure 9) was measured for the single-layered SWPs (about 3 N/mm2), compared to 2 N/mm2 for the three-layered SWPs bonded with PUR and PVAc (Table 4, Figure 10).
The compressive shear strength (Figure 10 and Figure 11) of the multi-layered panels glued with MUF was 20% lower. The coefficients of variance in this case were the lowest when the lamellae were glued with MUF (0.023 for single-layered boards and 0.082 for three-layered boards) and PVAc (0.038 for single-layered boards and 0.078 for three-layered boards). For the MUF gluing, the CVs were 0.042 (single-layered boards) and 0.117 (three-layered boards). These results are consistent with the findings of [31], which studied the shear strength of balsa end-grain solid wood panels for densities ranging from 200 to 300 kg/m3. Although the orientation of the balsa blocks was different compared to the direction of the production of the Paulownia SWPs, the values of the shear strength for balsa panels, including an interval of 0.5 to 2 N/mm2 for both the parallel and perpendicular grain orientations of the testing specimens, are in line with the results obtained for the single- and three-layered Paulownia SWPs. A major difference, however, is in the panel thickness, which was 5-fold higher for the balsa SWPs. Other solid wood composite panels with a thickness of 20 mm, with a mixture of balsa blocks (flat-grain and end-grain) with a side reinforcement of Brazilian fern wood (Schizolobium parahyba (Vell.) Blake), are an industrial product with a shear strength of 4.1 N/mm2 [32].
The wood breakage rate (Figure 12) after testing the compressive shear strength was relatively high for all panel types (more than 95%), with a smaller rate of 80% for the panels bonded with PVAc (Table 4). This is the case when the stress is perpendicular to the longitudinal axis and wood breakage may develop as intercellular failure due to cells being split up and peeling. Cracks are multiplied via the compound middle lamella (which is also called intercellular fracturing) [33].

4. Conclusions

Paulownia SWPs can be processed well with conventional woodworking machines. The basic prerequisites are well-sharpened tools for the production of the lamellae and SWPs, as well as the appropriate settings of the processing machines. Due to the wide annual rings in Paulownia wood, the variance of testing results for mechanical properties such as modulus of elasticity, bending strength and compression shear test, both positive and negative, is increased. Single-layered SWPs have similar properties even if they are bonded with MUF, PUR or PVAc. In the case of three-layered panels, the use of PUR adhesive influences positively the mechanical properties of SWPs. The presence of PUR-based adhesive joints may influence the elasticity and the shear response of the panels.
In order to meet the demand for ecologically compatible binders and the reduction of emissions from adhesives, it is recommended to carry out further series of tests with protein-based binders, such as casein-based adhesives. As further research, it is recommended to carry out further tests on Paulownia solid wood panels with regard to surface treatment, in terms of surface treatment, moisture behaviour and creep behaviour too. Another aspect to consider for the bonding of Paulownia wood can be the examination of the wood surfaces to be bonded. Different production methods are possible for industrially produced lamellae. These can be cut or split and then further processed in this form, or still be planed or sanded. These surface properties influence the quality of the bonding and offer further possibilities for various test arrangements.
The use of Paulownia wood to produce one-layer and three-layer MHPs is certainly possible. The results obtained suggest, among other things, their use in lightweight construction, and they could find a variety of applications in the furniture and door industry, in interior construction or in means of transport. In Europe, however, the availability of Paulownia sawn timber or lamellae for the production of MHPs is still an open question. Furthermore, the issue of the market preparation and market introduction of MHPs made of Paulownia wood still needs to be considered.
Paulownia, the so-called wood aluminium, can serve in sandwich structures as a lightweight core material for three-layered laminates with thin faces. Paulownia wood from European plantations resembles balsa wood and can successfully replace this lightweight wood species in sandwich structures as the core layer or in engineered products such as three-layered solid wood panels. In this way, the footprint of the end product is considerably reduced and the production costs are diminished by using Paulownia instead of balsa wood.

Author Contributions

Conceptualization, E.M.T., H.R. and M.K.; methodology, H.R. and M.K.; validation, M.C.B., E.M.T. and A.P., formal analysis, A.P.; investigation, H.R. and M.K.; resources, H.R. and M.K.; data curation, E.M.T.; writing—original draft preparation, E.M.T.; writing—review and editing, E.M.T.; visualization, M.C.B.; supervision, A.P.; project administration, M.C.B. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors would like to thank to Arien Crul, Glendor Holding GmbH (Kilb, Austria), for providing all the Paulownia lumber from Petrinja, Croatia; DI (FH) Thomas Harreither, Moserholz GmbH (Pettenbach, Austria), for kiln-drying the Paulownia lumber and Ing. T. Wimmer, for his support with the testing of the Paulownia samples.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Nilsson, J.; Ormarsson, S.; Johansson, J. Moisture-related distortion and damage of lightweight wood panels—Experimental and numerical study. J. Indian Acad. Wood Sci. 2017, 14, 99–109. [Google Scholar] [CrossRef]
  2. Barbu, M.C. Evolution of lightweight wood composites. Pro Ligno 2015, 11, 21–26. [Google Scholar]
  3. Švajlenka, J.; Kozlovská, M. Perception of the Efficiency and Sustainability of Wooden Buildings in the Use Phase of the Building. In Efficient and Sustainable Wood-Based Constructions; Švajlenka, I.J., Kozlovská, I.M., Eds.; Springer International Publishing: Cham, Switzerland, 2022; pp. 35–57. ISBN 978-3-030-87574-9. [Google Scholar]
  4. Paulitsch, M.; Barbu, M.C. Holzwerkstoffe der Moderne; DRW-Verlag: Leinfelden-Echterdingen, Germany, 2015; ISBN 3871818917. [Google Scholar]
  5. Monteiro, S.; Martins, J.; Magalhães, F.D.; Carvalho, L. Lightweight Wood Composites: Challenges, Production and Performance. In Lignocellulosic Composite Materials; Kalia, S., Ed.; Springer International Publishing: Cham, Switzerland, 2018; pp. 293–322. ISBN 978-3-319-68695-0. [Google Scholar]
  6. May, N.; Günther, E.; Haller, P. The sustainable use of wood as a regional resource—An ecological assessment of common and new processing technologies for wood poles. Sustain. Manag. Forum Nachhalt. 2019, 27, 177–201. [Google Scholar] [CrossRef]
  7. Ab-Latib, H.; Choon Liat, L.; Ratnasingam, J.; Law, E.L.; Abdul Azim, A.A.; Mariapan, M.; Natkuncaran, J. Suitability of paulownia wood from Malaysia for furniture application. BioResources 2020, 15, 4727–4737. [Google Scholar] [CrossRef]
  8. Wilk, K. The Use of a Prefabricated Mass Timber Structure in the Design of Single-Family Houses in Terms of Sustainable Development. In Environmental Challenges in Civil Engineering II; Zembaty, Z., Perkowski, Z., Beben, D., Massimino, M.R., Lavan, O., Eds.; Springer International Publishing: Cham, Switzerland, 2023; pp. 226–233. ISBN 978-3-031-26878-6. [Google Scholar]
  9. Tenório, M.; Branco, J.M.; Silva, S.M. Application of a Prefabricated Wooden-Based System for Collective Buildings in a Four-Storey Portuguese Building. In Sustainable and Digital Building; Gaspar, F., Mateus, A., Eds.; Springer International Publishing: Cham, Switzerland, 2023; pp. 183–193. ISBN 978-3-031-25794-0. [Google Scholar]
  10. Hill, C.; Kymäläinen, M.; Rautkari, L. Review of the use of solid wood as an external cladding material in the built environment. J. Mater. Sci. 2022, 57, 9031–9076. [Google Scholar] [CrossRef]
  11. Barbu, M.C.; Buresova, K.; Tudor, E.M.; Petutschnigg, A. Physical and Mechanical Properties of Paulownia tomentosa × elongata Sawn Wood from Spanish, Bulgarian and Serbian Plantations. Forests 2022, 13, 1543. [Google Scholar] [CrossRef]
  12. Jakubowski, M. Cultivation Potential and Uses of Paulownia Wood: A Review. Forests 2022, 13, 668. [Google Scholar] [CrossRef]
  13. Koman, S.; Feher, S. Physical and mechanical properties of Paulownia clone in vitro 112. Eur. J. Wood Prod. 2020, 78, 421–423. [Google Scholar] [CrossRef]
  14. Barbu, M.C.; Tudor, E.M.; Buresova, K.; Petutschnigg, A. Assessment of Physical and Mechanical Properties Considering the Stem Height and Cross-Section of Paulownia tomentosa (Thunb.) Steud. × elongata (S.Y. Hu) Wood. Forests 2023, 14, 589. [Google Scholar] [CrossRef]
  15. Nelis, P.A.; Michaelis, F.; Krause, K.C.; Mai, C. Kiri wood (Paulownia tomentosa): Can it improve the performance of particleboards? Eur. J. Wood Prod. 2018, 76, 445–453. [Google Scholar] [CrossRef]
  16. Lachowicz, H.; Giedrowicz, A. Charakterystyka jakości technicznej drewna paulowni COTE−2. Sylwan 2020, 164, 414–423. [Google Scholar] [CrossRef]
  17. Kalaycioglu, H.; Deniz, I.; Hiziroglu, S. Some of the properties of particleboard made from paulownia. J. Wood Sci. 2005, 51, 410–414. [Google Scholar] [CrossRef]
  18. Khanjanzadeh, H. Utilization of bio-waste cotton (Gossypium hirsutum L.) stalks and underutilized paulownia (Paulownia fortunie) in wood-based composite particleboard. Afr. J. Biotechnol. 2012, 11, 8045–8050. [Google Scholar] [CrossRef]
  19. Esteves, B.; Aires, P.; Sen, U.; Da Gomes, M.G.; Guiné, R.P.F.; Domingos, I.; Ferreira, J.; Viana, H.; Cruz-Lopes, L.P. Particleboard Production from Paulownia tomentosa (Thunb.) Steud. Grown in Portugal. Polymers 2023, 15, 1158. [Google Scholar] [CrossRef] [PubMed]
  20. Huber, C.; Moog, D.; Stingl, R.; Pramreiter, M.; Stadlmann, A.; Baumann, G.; Praxmarer, G.; Gutmann, R.; Eisler, H.; Müller, U. Paulownia (Paulownia elongata S.Y. Hu)—Importance for forestry and a general screening of technological and material properties. Wood Mater. Sci. Eng. 2023, 18, 1663–1675. [Google Scholar] [CrossRef]
  21. Dogu, D.; Tuncer, F.D.; Bakir, D.; Candan, Z. Characterizing Microscopic Changes of Paulownia Wood under Thermal Compression. BioResources 2017, 12, 5279–5295. [Google Scholar] [CrossRef]
  22. EN 322:1993; Wood-Based Panels—Determination of Moisture Content. European Committee for Standardization: Brussels, Belgium, 1993.
  23. EN 326-1:2005; Wood-Based Panels—Sampling, Cutting and Inspection—Part 1: Sampling and Cutting of Test Pieces and Expression of Test Results. European Committee for Standardization: Brussels, Belgium, 2005.
  24. EN 323:2005; Wood-Based Panels—Determination of Density. European Committee for Standardization: Brussels, Belgium, 2005.
  25. EN 310:2005; Wood-Based Panels; Determination of Modulus of Elasticity in Bending and of Bending Strength. European Committee for Standardization: Brussels, Belgium, 2005.
  26. EN 13354:2009; Solid Wood Panels (SWP)—Bonding Quality—Test Method. European Committee for Standardization: Brussels, Belgium, 2009.
  27. Koman, S.; Feher, S.; Vityi, A. Physical and mechanical properties of Paulownia tomentosa wood planted in Hungaria. Wood Res. 2017, 62, 335–340. [Google Scholar]
  28. Fos, M.; Oliver-Villanueva, J.-V.; Vazquez, M. Radial variation in anatomical wood characteristics and physical properties of Paulownia elongata × Paulownia fortunei hybrid Cotevisa 2 from fast-growing plantations. Eur. J. Wood Prod. 2023, 81, 819–831. [Google Scholar] [CrossRef]
  29. Goodrich, T.; Nawaz, N.; Feih, S.; Lattimer, B.Y.; Mouritz, A.P. High-temperature mechanical properties and thermal recovery of balsa wood. J. Wood Sci. 2010, 56, 437–443. [Google Scholar] [CrossRef]
  30. Galos, J.; Das, R.; Sutcliffe, M.P.; Mouritz, A.P. Review of balsa core sandwich composite structures. Mater. Des. 2022, 221, 111013. [Google Scholar] [CrossRef]
  31. Osei-Antwi, M.; de Castro, J.; Vassilopoulos, A.P.; Keller, T. Shear mechanical characterization of balsa wood as core material of composite sandwich panels. Constr. Build. Mater. 2013, 41, 231–238. [Google Scholar] [CrossRef]
  32. Bcomp. bCores Qx + Sb; Bcomp: Fribourg, Switzerland, 2023; Available online: https://pdf.nauticexpo.com/pdf/bcomp-ltd/bcores-qx-sb/51016-104454.html#open546181 (accessed on 11 September 2023).
  33. Karinkanta, P.; Ämmälä, A.; Illikainen, M.; Niinimäki, J. Fine grinding of wood—Overview from wood breakage to applications. Biomass Bioenergy 2018, 113, 31–44. [Google Scholar] [CrossRef]
Applsci 13 11234 g001
Figure 1. Pressing a single-layered Paulownia solid wood panel with clamps, where the lamellae were longitudinally bonded (95 × 44.6 × 2.2 cm).
Figure 1. Pressing a single-layered Paulownia solid wood panel with clamps, where the lamellae were longitudinally bonded (95 × 44.6 × 2.2 cm).
Applsci 13 11234 g001
Applsci 13 11234 g002
Figure 2. Pressing of a 3-layer SWP (92 × 92 × 1.9 cm) bonded with PVAc (left); pressing of 3-layer SWP bonded with MUF and PUR (right).
Figure 2. Pressing of a 3-layer SWP (92 × 92 × 1.9 cm) bonded with PVAc (left); pressing of 3-layer SWP bonded with MUF and PUR (right).
Applsci 13 11234 g002
Applsci 13 11234 g003
Figure 3. PVAc adhesive application on a single-layered SWP before layering (left) and three-layered SWP (92 × 92 × 1.9 cm) bonded with MUF, PUR and PVAc (right).
Figure 3. PVAc adhesive application on a single-layered SWP before layering (left) and three-layered SWP (92 × 92 × 1.9 cm) bonded with MUF, PUR and PVAc (right).
Applsci 13 11234 g003
Applsci 13 11234 g004
Figure 4. Cutting plan for the compressive shear strength test of single- and three-layered Paulownia SWPs (the values are in millimetres).
Figure 4. Cutting plan for the compressive shear strength test of single- and three-layered Paulownia SWPs (the values are in millimetres).
Applsci 13 11234 g004
Applsci 13 11234 g005
Figure 5. Density of single- and three-layered Paulownia SWPs (n = 6).
Figure 5. Density of single- and three-layered Paulownia SWPs (n = 6).
Applsci 13 11234 g005
Applsci 13 11234 g006
Figure 6. Modulus of rupture of the single-layered panels (left) and three-layered boards tested parallel to the grain (middle) and perpendicular to the grain (right).
Figure 6. Modulus of rupture of the single-layered panels (left) and three-layered boards tested parallel to the grain (middle) and perpendicular to the grain (right).
Applsci 13 11234 g006
Applsci 13 11234 g007
Figure 7. Testing of the 3-point bending strength of a Paulownia single-layered SWP.
Figure 7. Testing of the 3-point bending strength of a Paulownia single-layered SWP.
Applsci 13 11234 g007
Applsci 13 11234 g008
Figure 8. Modulus of elasticity of the single-layered panels (left) and three-layered boards tested parallel to the grain (middle) and perpendicular to the grain (right).
Figure 8. Modulus of elasticity of the single-layered panels (left) and three-layered boards tested parallel to the grain (middle) and perpendicular to the grain (right).
Applsci 13 11234 g008
Applsci 13 11234 g009
Figure 9. Water storage (for 24 h) for the SWP samples before a compressive shear test.
Figure 9. Water storage (for 24 h) for the SWP samples before a compressive shear test.
Applsci 13 11234 g009
Applsci 13 11234 g010
Figure 10. Compressive shear strength of the single-layered panels (left) and three-layered boards (right).
Figure 10. Compressive shear strength of the single-layered panels (left) and three-layered boards (right).
Applsci 13 11234 g010
Applsci 13 11234 g011
Figure 11. Testing of the compressive shear strength of a single-layered Paulownia SWP.
Figure 11. Testing of the compressive shear strength of a single-layered Paulownia SWP.
Applsci 13 11234 g011
Applsci 13 11234 g012
Figure 12. Wood breakage (98%) of a sample bonded with PUR after testing of compressive shear strength.
Figure 12. Wood breakage (98%) of a sample bonded with PUR after testing of compressive shear strength.
Applsci 13 11234 g012
Table 2. Density of single- and three-layered SWPs made of Paulownia lamellae.
Table 2. Density of single- and three-layered SWPs made of Paulownia lamellae.
Board TypeAdhesive TypeLamellae Width (mm)Density
Mean Value
kg/m3		Density
Min/Max Value, kg/m3
1-layer SWPMUF32258 a (14.04)234/276
1-layer SWPPUR 32249 a (14.86)236/280
1-layer SWPPVAc32258 a (5.13)251/264
3-layer SWP ǁMUF66277 b (6.45)265/284
3-layer SWP ͰMUF66277 b (6.45)265/284
3-layer SWP ǁPUR66283 b (12.00)270/300
3-layer SWP ͰPUR66283 b (12.00)270/300
3-layer SWP ǁPVAc66280 b (10.73)264/298
3-layer SWP ͰPVAc66280 b (10.73)264/298
(a,b values with the same letter are not significantly different: ANOVA, Post Hoc Tukey HSD, α = 0.05) (standard deviation for MOR and MOE for average/mean value in parentheses).
Table 3. Modulus of rupture and modulus of elasticity of the single- and three-layered Paulownia SWPs.
Table 3. Modulus of rupture and modulus of elasticity of the single- and three-layered Paulownia SWPs.
Board TypeAdhesive TypeLamellae Width
mm		MOR
Average Value,
N/mm2		MOR
Min/Max Values
N/mm2		MOE
Average Value, N/mm2		MOE
Min/Max Values, N/mm2
1-layer SWPMUF 3233 a (2.72)29/383733 a (334)3283/4271
1-layer SWPPUR3232 a (3.75)29/403661 a (443)3179/4528
1-layer SWPPVAc3232 a (2.15)29/363539 a (223)3134/3819
3-layer SWP ǁMUF6628 b (4.17)23/343998 b (333)3736/4507
3-layer SWP ͰMUF668 c (1.42)6/10541 c (43)463/595
3-layer SWP ǁPUR6636 a (3.25)31/414604 d (326)4256/5212
3-layer SWP ͰPUR6610 c (0.93)9/11515 c (48)454/587
3-layer SWP ǁPVAc6629 b (0.66)29/314071 d (322)3485/4374
3-layer SWP ͰPVAc669 c (1.34)7/11461 c (48)422/462
(a,b,c,d values with the same letter are not significantly different: ANOVA, Post Hoc Tukey HSD, α = 0.05) (standard deviation for MOR and MOE for average/mean value in parentheses).
Table 4. Compressive shear strength and wood breakage rate of the single- and three-layered Paulownia SWPs.
Table 4. Compressive shear strength and wood breakage rate of the single- and three-layered Paulownia SWPs.
Panel TypeAdhesive TypeLamellae Width
(mm)		Compressive
Shear Strength Average Value, N/mm2		Compressive Shear Strength Min/Max Value, N/mm2Wood Breakage Rate Average Value
%		Wood Breakage Rate Min/Max Value
%
1-layer SWPMUF323.16 a (0.58)1.81/3.8495 a (5)85/100
1-layer SWPPUR322.92 a (0.32)2.27/3.397.5 a (5.12)85/100
1-layer SWPPVAc322.71 b (0.34)2.21/3.2679 b (15.3)50/100
3-layer SWP ǁMUF661.62 c (0.33)1.00/2.0699 a (2)95/100
3-layer SWP ͰMUF661.62 c (0.33)1.00/2.0699 a (2)95/100
3-layer SWP ǁPUR662.03 b (0.17)1.59/2.2398.5 a (2.29)95/100
3-layer SWP ͰPUR662.03 b (0.17)1.59/2.2398.5 a (2.29)95/100
3-layer SWP ǁPVAc661.9 b (0.25)1.5/2.6296 a (4.36)85/100
3-layer SWP ͰPVAc661.9 b (0.25)1.5/2.6296 a (4.36)85/100
(a,b,c values with the same letter are not significantly different: ANOVA, Post Hoc Tukey HSD, α = 0.05) (standard deviation for MOR and MOE for average/mean value in parentheses).
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Barbu, M.C.; Radauer, H.; Petutschnigg, A.; Tudor, E.M.; Kathriner, M. Lightweight Solid Wood Panels Made of Paulownia Plantation Wood. Appl. Sci. 2023, 13, 11234. https://doi.org/10.3390/app132011234

AMA Style

Barbu MC, Radauer H, Petutschnigg A, Tudor EM, Kathriner M. Lightweight Solid Wood Panels Made of Paulownia Plantation Wood. Applied Sciences. 2023; 13(20):11234. https://doi.org/10.3390/app132011234

Chicago/Turabian Style

Barbu, Marius Cătălin, Helmut Radauer, Alexander Petutschnigg, Eugenia Mariana Tudor, and Markus Kathriner. 2023. "Lightweight Solid Wood Panels Made of Paulownia Plantation Wood" Applied Sciences 13, no. 20: 11234. https://doi.org/10.3390/app132011234

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop