# Binderless particleboards from steam exploded woody biomass: chemical and morphological properties relate to their mechanical and physical behavior

Edwige Audibert, Lauriane Ducceschi, Adriana Quintero, Frédéric Martel, Gabriel Paës, Caroline Rémond

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Edwige Audibert, Lauriane Ducceschi, Adriana Quintero, Frédéric Martel, Gabriel Paës, et al. Binderless particleboards from steam exploded woody biomass: chemical and morphological properties relate to their mechanical and physical behavior. Industrial Crops and Products, 2025, 229, pp.120983. 10.1016/j.indcrop.2025.120983. hal-05183862

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# Binderless particleboards from steam exploded woody biomass: chemical and morphological properties relate to their mechanical and physical behavior

Edwige Audibert<sup>a,b</sup>, Lauriane Ducceschi<sup>a</sup>, Adriana Quintero<sup>b</sup>, Frédéric Martel<sup>b</sup>, Gabriel Paës<sup>a,*</sup> (✉), Caroline Rémond<sup>a,*</sup>

## ARTICLE INFO

### Keywords:

- Binderless particleboards

- Lignocellulosic biomass

- Steam explosion

- Physicochemical properties

- Correlation

## ABSTRACT

Wood particleboards are commonly used in the furniture and building sectors and usually contain binders with formaldehyde-based synthetic resins, which raises health and environmental concerns. Pretreatment of wood such as steam explosion allows to modify its chemical and physical structure in order to produce more environmentally friendly binderless particleboards with good bonding-strength and dimensional stability, with an easy processing. In this study, three structurally different wood species (oak, poplar and spruce) were pretreated with pilot-scale steam explosion at different severities by varying temperature and residence time. Particleboards were produced by hot pressing without additives. Mechanical and physical properties were quantified for all particleboards and correlated to structural and morphological properties of pretreated woods. Results highlighted starting material and pretreatment severity impact greatly the mechanical and hygroscopic properties. Overall, the cohesiveness and dimensional ability were improved thanks to the pretreatment compared to the commercial reference. Correlations with physicochemical properties revealed chemical composition and particle size affect internal bonding and thickness swelling of panels while flexural properties are mostly governed by the fibers aspect ratio.

## 1. Introduction

Wood panels or particleboards are commonly used in the construction industry, the furniture industry and insulation (Vitrone et al., 2021). The process to manufacture such particleboards involves hot-pressing of softwood or hardwood chips (Marbun et al., 2023) and to ensure high internal strength, dimensional stability and high bonding between fibers, these panels usually contain binders, such as formaldehyde-based synthetic resins, that are a concern for human and environmental health (Domínguez-Robles et al., 2020). The European Union classified formaldehyde as carcinogen and published new regulations to further control its use based on the amount of formaldehyde released in the air (Commission Regulation (EU) (EU) 2023).

To avoid use of such toxic binders, solutions are being developed with natural and biobased binders, such as Kraft lignin (Gouveia et al., 2018) and lignin-derived compounds (Karthäuser et al., 2021) or protein-based adhesives (Raydan et al., 2021) using soybean for instance

(Li et al., 2022). Research has also been focused on the development of binderless particleboards, with the aim to use constituents already present in the lignocellulosic biomass (LB) matrix as binders thanks to their degradation during the fabrication process (Ge et al., 2020; Ye et al., 2022; Zhang et al., 2015). Such binderless wood panels are also of great interest, especially to facilitate the transfer to an industrial process, as limiting components and production steps lead to reduced manufacturing costs: adhesives represent indeed 15–30 % of the production cost (Lee et al., 2022).

Original process for binderless particleboards was patented by Mason in 1928 consisting in treating wood with steam before pressing at high temperature and high moisture content, referred as the wet-process (Mason, 1928). A dry-process can be traced back to Mobarak et al. in 1982 who studied mechanical properties and water resistance of sugarcane bagasse particleboards (Mobarak et al., 1982). From there, binderless particleboards with interesting mechanical and physical properties were obtained from different raw lignocellulosic biomasses:

<footnote><sup>a</sup> Université de Reims Champagne-Ardenne, INRAE, FARE, UMR A 614, AFERE, Reims, France</footnote>

<footnote><sup>b</sup> Européenne de Biomasse, Pomacle, Paris, France</footnote>

<footnote>* Corresponding authors.</footnote>

<footnote>E-mail addresses: gabriel.paes@inrae.fr (G. Paës), caroline.remond@univ-reims.fr (C. Rémond).</footnote>
kenaf, (Widyorini et al., 2005) wheat straw (Domínguez-Robles et al., 2020) or poplar (Ye et al., 2022). But these panels usually lack stability in wet conditions.

Steam explosion (SE) is a physicochemical pretreatment which consists of putting LB in contact with steam at high pressure (1–3.5 MPa) and high temperature (180–240°C) for several minutes (2–20 minutes) before releasing the pressure and causing the explosion of the lignocellulosic material (Yu et al., 2022). During last decades, SE has been largely studied as a pretreatment step of LB previous to the enzymatic saccharification step to produce second generation bioethanol (Ding et al., 2024; El Hage et al., 2023; Saravanan et al., 2022). In addition, this pretreatment can be used beforehand to enhance the adhesive properties of LB and improve dimensional stability and binding strength in panels, which are two critical points for binderless wood particleboards. Efficiency of steam explosion for this purpose was demonstrated in several studies: particleboards with adequate mechanical and physical properties were obtained from pretreated agricultural residues, such as hemp shives and wheat straw (Tupciauskas et al., 2021), windmill palm fibers (Luo et al., 2018) and banana trunk (Nadhari et al., 2019). Pretreated wood particleboards were also studied, however to a lesser extent: Christy et al. (2020) investigated the potential of gelam wood bark and Cheng et al. (2024) evaluated several processing conditions to optimize production of particleboards from thermally treated poplar. Particleboards with advanced properties were also produced using steam-exploded spruce grafted with phytic acid, resulting in non-flammable panels (Antoun et al., 2024). Yet, based on existing literature, utilization of steam-exploded wood for the production of binderless particleboards without synthetic or natural additives has been put a little to the side for the past years compared to agricultural residues. Moreover, most studies (Anglès et al., 2001; Tupciauskas et al., 2021; Vitrone et al., 2023). present the advantages of using SE pretreatment by quantifying mechanical and physical properties but did not try to relate those properties to physicochemical features of LB and to the impact of SE on these structural and morphological properties to understand how it enables enhanced particleboards properties.

In this study, three wood species (oak, poplar and spruce) were pretreated with pilot-scale continuous SE at different severities and binderless particleboards were manufactured. Mechanical and physical properties of panels were evaluated regarding the severity of pretreatment and confronted to physicochemical properties of pretreated wood in order to establish structure-properties relationships and to better understand the underlying effects of starting materials and SE pretreatment on wood panels properties.

# 2. Materials and methods

## 2.1. Materials and pretreatment

Oak, poplar and spruce were collected in 2022 from forests in the Grand-Est Region in France and were pretreated using continuous steam explosion (SE) at pilot-scale as described previously (Audibert et al., 2025). Wood was first chopped into small pieces using a hammer mill and sieved at 16 mm. Samples entered the SE reactor (initial moisture content between 30 % and 45 %) and were put in contact with steam at three different temperatures (190 – 207.5°C) for three different residence times (5 – 20 min). Nine couples of pretreatment conditions were studied for each wood species and are described in Table 1. Spruce samples were pretreated at slightly higher severities as it is reported to require more drastic conditions than hardwoods to deconstruct the cell wall (Yu et al., 2022). A combined severity factor of pretreatment was calculated for each sample (Overend and Chornet, 1987).

A commercial particleboard Isorel® (Kingfisher, The Netherlands) was purchased to be compared to particleboards manufactured in this study.

<table><caption>**Table 1**
Pretreatment conditions and combined severity factor (CSF).</caption><thead><tr><th colspan="3">Oak / poplar</th><th colspan="3">Spruce</th></tr><tr><th>Temperature (°C)</th><th>Residence time (min)</th><th>CSF</th><th>Temperature (°C)</th><th>Residence time (min)</th><th>CSF</th></tr></thead><tbody><tr><td>190</td><td>5</td><td>3.35</td><td>197.5</td><td>5</td><td>3.57</td></tr><tr><td>197.5</td><td>5</td><td>3.57</td><td>202.5</td><td>5</td><td>3.72</td></tr><tr><td>190</td><td>12.5</td><td>3.75</td><td>207.5</td><td>5</td><td>3.86</td></tr><tr><td>205</td><td>5</td><td>3.79</td><td>197.5</td><td>12.5</td><td>3.97</td></tr><tr><td>190</td><td>20</td><td>3.95</td><td>202.5</td><td>12.5</td><td>4.11</td></tr><tr><td>197.5</td><td>12.5</td><td>3.97</td><td>197.5</td><td>20</td><td>4.17</td></tr><tr><td>197.5</td><td>20</td><td>4.17</td><td>207.5</td><td>12.5</td><td>4.26</td></tr><tr><td>205</td><td>12.5</td><td>4.19</td><td>202.5</td><td>20</td><td>4.32</td></tr><tr><td>205</td><td>20</td><td>4.39</td><td>207.5</td><td>20</td><td>4.47</td></tr></tbody></table>

## 2.2. Particleboards preparation

Before preparation of wood panels, wood powders were stored in a room for several weeks with controlled temperature (20°C) and controlled humidity (50 % relative humidity) to reach a stable moisture content of 7.3 % ± 2.7 %. For each pretreatment conditions, 480 g of wood powder were first uniformly hand-pressed in a 40 cm × 40 cm mold and then hot-pressed at 200°C using a thermo-heating press (Joos, Germany) with the following pressure profile: 1 MPa for 1 min, 0.5 MPa for 1 min, 0.25 MPa for 1 min and 0.06 MPa for 2.5 min to obtain 3 mm thick panels. Manufacturing conditions were chosen after preliminary tests not shown here. Finally, particleboards were cooled at room temperature.

## 2.3. Characterization

### 2.3.1. Mechanical and physical properties of particleboards

Mechanical and physical properties were measured following the European standards: density (EN323 (European Committee for Standardization, 1993a), flexural modulus and flexural strength with 3-point bending tests (EN310 (European Committee for Standardization, 1993b), internal bonding (EN319 (European Committee for Standardization, 1993c) and thickness swelling (EN317 (European Committee for Standardization, 1993d). Testing specimens were obtained from panels using laser-cut with the following dimensions: 5 cm × 15 cm for flexural testing, 5 cm × 5 cm for density, internal bonding and thickness swelling.

The universal testing equipment for flexural measurements (Rycobel, Belgium) used a 10 kN sensor and the bending test speed was set at 10 mm/min. The universal testing equipment for internal bonding measurements (MTS, France) used a 25 kN sensor and the test speed was set at 0.25 mm/min.

Average of 10 measurements (density, flexural testing) or 5 measurements (internal bonding, thickness swelling) per particleboards were reported.

Artificial aging was performed following the standard EN321 (European Committee for Standardization, 2002) consisting of three successive cycles of water soaking (20°C, 70 h), freezing (-20°C, 24 h) and heating (70°C, 70 h) and was followed with characterization of mechanical and physical properties as described above.

### 2.3.2. Pretreated wood powder characterization

Chemical composition (cellulose, hemicelluloses and lignin contents) was determined as previously described (Table 2) (Herbaut et al., 2018). Monomeric sugars were recovered after a two-step acid hydrolysis using H₂SO₄ and were quantified with HPAEC-PAD (ThermoScientific DIO-NEX, USA). Klason lignin was quantified by gravimetry after acid hydrolysis.

Formic acid, acetic acid and furfural contents were quantified using HPLC with UV detection. Total phenolic compounds content was quantified using Folin-Ciocalteu reagent and spectrophotometry (Table 2).
<table><caption>**Table 2**
Chemical composition of untreated and pretreated wood samples (expressed in % dry matter, furfural in mg/kg dry matter). Data extracted from Audibert et al. (2025).</caption><thead><tr><th>Biomass</th><th>CSF</th><th>Cellulose</th><th>Hemicelluloses</th><th>Lignin</th><th>Formic acid</th><th>Acetic acid</th><th>Furfural</th><th>Phenolics</th></tr></thead><tbody><tr><td rowspan="7">Oak</td><td>Untreated</td><td>34.55 ± 1.40</td><td>20.24 ± 1.09</td><td>29.05 ± 0.24</td><td>NA</td><td>NA</td><td>NA</td><td>0.72 ± 0.01</td></tr><tr><td>3.35</td><td>41.38 ± 1.07</td><td>19.29 ± 0.66</td><td>28.89 ± 0.09</td><td>2.78</td><td>0.28</td><td>38.63</td><td>2.61 ± 0.08</td></tr><tr><td>3.57</td><td>39.89 ± 0.53</td><td>15.73 ± 0.37</td><td>30.80 ± 0.11</td><td>2.81</td><td>0.44</td><td>75.19</td><td>2.22 ± 0.17</td></tr><tr><td>3.75</td><td>39.86 ± 0.78</td><td>16.48 ± 0.04</td><td>30.34 ± 0.06</td><td>2.40</td><td>0.67</td><td>100.97</td><td>2.64 ± 0.07</td></tr><tr><td>3.79</td><td>42.58 ± 0.63</td><td>10.77 ± 0.15</td><td>34.12 ± 0.42</td><td>2.67</td><td>0.82</td><td>140.24</td><td>3.38 ± 0.11</td></tr><tr><td>3.95</td><td>41.03 ± 1.90</td><td>13.99 ± 0.14</td><td>32.28 ± 0.88</td><td>2.11</td><td>0.95</td><td>163.55</td><td>3.14 ± 0.30</td></tr><tr><td>3.97</td><td>43.38 ± 1.52</td><td>12.41 ± 0.76</td><td>33.10 ± 1.37</td><td>1.86</td><td>1.45</td><td>172.07</td><td>3.36 ± 0.35</td></tr><tr><td rowspan="7">Poplar</td><td>Untreated</td><td>46.29 ± 0.80</td><td>8.21 ± 0.11</td><td>35.24 ± 0.40</td><td>1.50</td><td>1.44</td><td>256.96</td><td>3.61 ± 0.39</td></tr><tr><td>3.35</td><td>49.22 ± 0.46</td><td>20.64 ± 0.98</td><td>25.02 ± 0.52</td><td>1.29</td><td>0.27</td><td>17.64</td><td>2.20 ± 0.26</td></tr><tr><td>3.57</td><td>49.14 ± 0.40</td><td>17.87 ± 0.15</td><td>25.41 ± 0.43</td><td>NA</td><td>NA</td><td>NA</td><td>1.93 ± 0.19</td></tr><tr><td>3.75</td><td>51.32 ± 0.14</td><td>17.90 ± 0.17</td><td>25.61 ± 0.17</td><td>0.62</td><td>0.52</td><td>22.54</td><td>1.97 ± 0.09</td></tr><tr><td>3.79</td><td>51.64 ± 2.01</td><td>15.71 ± 0.52</td><td>27.51 ± 0.93</td><td>0.58</td><td>0.57</td><td>37.79</td><td>3.22 ± 0.37</td></tr><tr><td>3.95</td><td>53.09 ± 0.81</td><td>14.78 ± 0.08</td><td>27.86 ± 0.97</td><td>0.62</td><td>0.07</td><td>48.36</td><td>2.97 ± 0.51</td></tr><tr><td>3.97</td><td>52.07 ± 1.74</td><td>14.99 ± 0.64</td><td>28.31 ± 0.76</td><td>0.66</td><td>0.72</td><td>49.44</td><td>3.06 ± 0.65</td></tr><tr><td rowspan="7">Spruce</td><td>Untreated</td><td>50.76 ± 0.90</td><td>13.55 ± 0.15</td><td>29.98 ± 1.88</td><td>0.91</td><td>1.05</td><td>74.84</td><td>4.21 ± 0.03</td></tr><tr><td>3.35</td><td>54.71 ± 0.85</td><td>9.34 ± 0.30</td><td>30.49 ± 0.53</td><td>0.77</td><td>0.92</td><td>38.40</td><td>4.04 ± 0.19</td></tr><tr><td>3.57</td><td>58.50 ± 0.28</td><td>5.27 ± 0.07</td><td>32.24 ± 0.24</td><td>1.47</td><td>1.26</td><td>95.65</td><td>4.08 ± 0.25</td></tr><tr><td>3.72</td><td>48.81 ± 0.79</td><td>24.08 ± 0.38</td><td>27.27 ± 0.29</td><td>NA</td><td>NA</td><td>NA</td><td>0.70 ± 0.10</td></tr><tr><td>3.86</td><td>48.71 ± 0.47</td><td>21.76 ± 0.42</td><td>29.68 ± 0.06</td><td>1.75</td><td>0.32</td><td>14.67</td><td>1.54 ± 0.22</td></tr><tr><td>3.97</td><td>48.03 ± 1.57</td><td>18.99 ± 0.40</td><td>30.95 ± 0.82</td><td>1.24</td><td>0.36</td><td>19.76</td><td>1.68 ± 0.28</td></tr><tr><td>4.11</td><td>50.09 ± 0.44</td><td>14.17 ± 0.22</td><td>33.77 ± 0.29</td><td>1.06</td><td>0.92</td><td>57.58</td><td>1.45 ± 0.05</td></tr><tr><td>4.17</td><td>50.12 ± 2.69</td><td>16.00 ± 0.46</td><td>32.92 ± 0.05</td><td>1.18</td><td>0.42</td><td>13.50</td><td>1.51 ± 0.16</td></tr><tr><td>4.26</td><td>49.22 ± 0.61</td><td>12.41 ± 0.13</td><td>34.04 ± 0.55</td><td>1.25</td><td>1.23</td><td>59.07</td><td>1.60 ± 0.07</td></tr><tr><td>4.32</td><td>49.79 ± 2.88</td><td>6.78 ± 0.26</td><td>35.20 ± 2.26</td><td>1.02</td><td>0.94</td><td>61.74</td><td>1.32 ± 0.08</td></tr><tr><td>4.47</td><td>51.08 ± 0.93</td><td>3.44 ± 0.05</td><td>40.64 ± 0.68</td><td>1.39</td><td>1.38</td><td>80.06</td><td>1.58 ± 0.04</td></tr></tbody></table>

Untreated and pretreated wood were observed with a macroscope (Zeiss, Germany) to qualitatively assess the morphology changes occurring with steam explosion pretreatment. Images were acquired under brightfield light, with a 7x magnification and exposure time of 2.251 ms. Field of view, resolution and depth of field were 33 mm, 5.0 µm and 0.47 mm, respectively.

Particle size and shape were assessed with the Qicpic equipment (Sympatec, Germany). Bigger samples were analyzed using the M9 lens (17–33792 µm) and smaller samples were analyzed using the M5 lens (1.8–3755 µm). The median particle length (d50) and the median aspect ratio, corresponding to the width-to-length ratio, were quantified. Calculations were made with automatic image analysis. Particles were defined as cylindric objects and diameters were measured using Feret diameter by automatic images analysis.

## 2.4. Statistical analyses

ANOVA, pair-wise *t*-test and Pearson correlation coefficients were performed using R software.

# 3. Results and discussion

## 3.1. Fibers morphology

Macroscopic observations of pretreated wood samples highlighted the SE effect on the morphology of wood fibers (Fig. 1A). There is a clear reduction of particle size with increasing severity of pretreatment, alongside an evolution of the sample morphology from long fibers to powder with increasing CSF. Morphological changes occur at lower severities for oak compared to poplar and spruce, suggesting variable behavior towards pretreatment depending on wood species. SE is known to cause defibration and different types of fibers can be obtained: semi-opened fibers, fine fibers and fluffy fibers (Zhao et al., 2023). A majority of long semi-opened fibers can be observed for low CSF samples, while for intermediate and high CSF fine fibers predominate as well as fluffy fibers especially for highly pretreated poplar and spruce.

These visual observations were confirmed with the quantification of particle size (Fig. 1B). Median particle length decreased linearly with increasing severity between CSF 3.57 and CSF 4.17 from 6.5 mm to 0.9 mm for poplar (CSF 3.35 was defined as an outlier, maybe due to a finer grinding before pretreatment) and from 5.1 mm to 0.5 mm for spruce, i.e. 86 % and 90 % decrease with R² equal to 0.82 and 0.95, respectively. From CSF 4.17, further increase in pretreatment severity did not lead to significant size reduction (*p* > 0.05). Oak showed a different behavior: particle size dropped earlier from 2.5 mm at CSF 3.35–0.5 mm at CSF 3.57 and slightly linearly decreased until 0.3 mm at CSF 4.39 with no significant differences (*p* > 0.05). Aspect ratio evolved in opposite way in comparison to particle size (Fig. 1C): aspect ratio for poplar and spruce was steady until CSF 4.17 and increased linearly for highest pretreatment severities (R²=0.99 and R²=0.70, respectively). For oak, aspect ratio increased linearly from lowest to highest severity (R²=0.83). Increased aspect ratio means more spherical particles. Given the evolution of particle size and aspect ratio with increasing CSF, it seems that SE first reduces particle length then impacts particle shape.

## 3.2. Particleboards morphology

Before testing for mechanical and physical properties, effect of biomass species and pretreatment severity on particleboards resistance were first observed (Fig. 2A). Oak panels were highly brittle from a mid-range severity of pretreatment, while poplar and spruce panels seemed to be more resistant except for highest pretreatment severities.

Density of the particleboards was measured and it can be noted that standard deviations are high, attesting the heterogeneity of panels (Fig. 2B). Oak particleboards density remained constant with increasing severity of pretreatment, as there were no significant differences between panels (*p* > 0.05). Because of brittleness of oak particleboards, density measurements could not be performed for severities above CSF 4.17. As for poplar and spruce particleboards, a significant effect of pretreatment severity on density was revealed (*p* < 0.001) where density increased especially for high severities. This could be due to lower particle size since lower particle size results in less space between fibers
<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Effect of SE on the morphology of wood particles: macroscopic observations (A), median particle diameter quantification (B) and aspect ratio (C).</figcaption></figure>

and therefore in denser panels.

Lower severity of pretreatment is thus required for oak panels to reach an equivalent density as panels made from highly pretreated poplar or spruce.

### 3.3. Mechanical properties

Mechanical properties, flexural and internal bonding, were determined for most of the wood particleboards. No measurement was possible for oak particleboards from CSF 4.19 and for spruce CSF 4.47 as testing specimens could not be obtained due to high brittleness.

Flexural modulus and flexural strength (Fig. 3A-C) present the same evolution with pretreatment severity. First, an effect of the wood species is observed: the highest resistance and rigidity are achieved for oak particleboards. Maximum values of flexural modulus and flexural strength obtained for oak (1.6 GPa and 6.7 MPa) are twice those obtained for spruce (0.8 GPa and 3.6 MPa).

Second, pretreatment severity has an impact on mechanical flexure properties which differ depending on wood species. Flexural properties

of oak panels are strongly impacted by SE severity while there is no significant effect of pretreatment on poplar and spruce panels, even though some tendencies stand out. For oak (Fig. 3A), particleboards lose rigidity and resistance as demonstrated by the significantly decreasing flexural properties with increasing CSF (p < 0.001). Flexural modulus is divided by two between lowest and highest severity and flexural strength is divided by 3.5.

For poplar (Fig. 3B), no significant differences between panels can be observed until a mid-range severity (before CSF=4), then flexural properties decrease for panels made from highest pretreated poplar. Likewise, spruce particleboards properties (Fig. 3C) show no significant evolution but a tendency to increase until a mid-range severity (CSF=3.97) then decrease at higher CSF.

Like flexural properties, internal bonding (IB) properties (Fig. 3D-F) depend on wood species and pretreatment severity. Oak and poplar panels offer better internal bonding than spruce panels. Maximum values of IB reach 1.44 MPa and 1.59 MPa for oak and poplar, respectively, compared to 0.64 MPa for spruce, i.e. more than twice higher.

Steam explosion severity has different impacts on IB depending on
<figure><img src="image_4.png" /><figcaption>Fig. 2. Representative parts of particleboards obtained from steam exploded wood (A) and evolution of density with increasing CSF (B).</figcaption></figure>
<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /><figcaption>**Fig. 3.** Mechanical properties of pretreated wood particleboards. Flexural properties: flexural modulus and flexural strength (A-C) and internal bonding properties (D-F).</figcaption></figure>

wood species, but its effect is significant for all biomass (*p* < 0.001). IB of oak panels increases until CSF 3.79 from 0.3 MPa to reach 1.3 MPa in average. Then, increasing pretreatment severity does not provide significant changes (*p* > 0.05). For poplar and spruce, evolution with increasing CSF is inverted compared to oak: IB is steady until CSF 3.97 and increases significantly for the higher pretreatment severities.

Overall, the maximum IB is obtained at less drastic conditions of pretreatment for oak panels (CSF 3.79) than poplar panels (CSF 4.39) or spruce panels (CSF 4.32).

### 3.4. Hygroscopic properties

Hygroscopic properties of wood particleboards were evaluated through the measurement of thickness swelling (TS) after 24 h of water impregnation (Fig. 4).

Once more, results differ depending on wood species. Overall, oak panels are more resistant to water than poplar and finally than spruce which displays the greatest TS (42 %).

TS decreases significantly with increasing severity (*p* < 0.001) in accordance with previous study carried out on steam exploded hemp and wheat straw (Tupciauskas et al., 2021): there is a gradual decrease
<figure><img src="image_11.png" /><figcaption>**Fig. 4.** Thickness swelling of pretreated wood particleboards after 24 h of water impregnation.</figcaption></figure>

with the appearance of distinct levels. For oak particleboards, TS at lowest CSF (3.35) is 13 % and drops to 5 % in average for all panels from CSF 3.57. For poplar, three levels are identified: TS reaches 23 % at the three lowest severities, then drops at 9 % for the following three CSF and reduces to 4 % for the three highest severities. For spruce, TS is 42 % at lowest severity, then 13 % until CSF 3.97 and finally 4 % from CSF 4.17.

The minimum value of TS is reached at a lower pretreatment severity for oak particleboards compared to poplar or spruce panels.

### 3.5. Artificial aging

To evaluate particleboards resistance over time, flexural properties and thickness swelling were quantified on poplar panels after artificial aging (Fig. 5). Poplar panels were selected for this study as it was the only species for which panels could be manufactured for all severities of pretreatment.

Flexural properties strongly decrease after artificial aging: flexural modulus displays 80–98 % loss while flexural strength shows 59–91 % loss. Interestingly, a severity threshold appears at CSF 3.79, creating two groups of samples with significantly different properties (p < 0.001): before this threshold, mechanical properties are almost completely lost.

Thickness swelling presents the same tendency with increasing severity before and after artificial aging, but artificially aged particleboards present 69 % in average more swelling compared to unaged panels.

Based on these results, it seems relevant to favor pretreatment severities above CSF 3.79 for the fabrication of wood particleboards in order to limit the loss of mechanical properties and maintain sufficient hygroscopic properties.

### 3.6. Comparison of properties to commercial materials and literature data

Mechanical and physical properties of pretreated oak, poplar and spruce wood particleboards were compared with the commercial reference Isorel®, a high-density fiberboard made from steam treated

<figure><img src="image_12.png" /><figcaption>**Fig. 5.** Mechanical (A) and hygroscopic (B) properties of pretreated poplar particleboards after artificial aging.</figcaption></figure>
wood (Table 3) used for furniture, building and packaging industries. Isorel® flexural modulus and flexural strength were measured in the same conditions as SE-based boards at 2.5 GPa and 25.7 MPa, respectively. IB was 0.15 MPa and thickness swelling 31 %.

Compared to Isorel®, using steam exploded oak, poplar or spruce to produce binderless particleboards greatly improves the internal bonding, which is multiplied by 11 at most (poplar - CSF 4.39). It also considerably decreases the panels thickness swelling, which is divided by 12 at most (oak - CSF 3.95). However, flexural properties are much reduced compared to Isorel®: flexural modulus is divided by 1.5 at best (oak - CSF 3.75) and by 8 at worst (spruce - CSF 3.57), while 74-93 % of flexural strength is lost.

Results from different studies in literature that investigated binderless particleboards made from wood or agricultural residues, pretreated or not, are reported in Table 3 and were compared to properties of steam exploded wood binderless particleboards. Flexural properties of panels from steam exploded wood are globally lower than other studies. This is probably due to the conditions used for the fabrication process. In literature, pressure used for hot-pressing was in the range 5 - 32 MPa, while in this study pressure was 1 MPa. Tupciauskas et al. demonstrated that higher pressure led to increased flexural modulus and flexural strength that met standard requirements for non-load-bearing boards for use in humid conditions (Tupciauskas et al., 2022). Increasing fabrication pressure could therefore help reaching better flexural properties. On the contrary, IB and TS are equivalent or even better to those reported in literature. This demonstrates the potential of steam exploded wood for the production of binderless particleboards. But pressing conditions should be optimized depending on desired applications and required specifications, for example boards used for furniture in dry conditions require less strength than boards used for heavy duty load-bearing in humid conditions (European Committee for Standardization, 2010).

### 3.7. Structure-properties relationships

To understand evolution of mechanical and hygroscopic properties with severity, the corresponding data were combined with morphological and structural data (Table 2) (Audibert et al., 2025). The following physicochemical changes were observed: hemicelluloses degradation and increase in lignin content with increasing pretreatment severity, particle size reduction and increase of the aspect ratio for pretreated oak in opposition to poplar and spruce for which aspect ratio was steady and increased for high severities of pretreatment. Pearson correlation coefficients were calculated to investigate structure-properties relationships (Fig. 6). Observations and correlations were consistent for all biomass species.

Chemical composition of wood strongly impacts mechanical and physical properties of particleboards. For all species, hemicelluloses content is strongly negatively correlated to IB (-0.76 ≤ r ≤ -0.92), while lignin content is strongly positively correlated to IB (0.81 ≤ r ≤ 0.92). Bonding strength is linked to chemical changes (Widyorini et al., 2005) and lignin plasticization (Bouajila et al., 2005) and cross-linking

between lignin and other chemicals such as furfural is reported as the main self-bonding mechanism (Zhang et al., 2015). After steam explosion pretreatment, part of the hemicelluloses are degraded in furfural, while a part of lignin is degraded in reactive hydroxyl phenolics and other radicals are generated, which contribute to improve the self-bonding (Marbun et al., 2023). Degradation products (furfural, phenolics, acetic and formic acids) in pretreated wood samples were previously quantified (Audibert et al., 2025). Phenolic compounds are present in higher quantity in pretreated oak and poplar, almost twice as much as in spruce samples. This could explain the higher IB values for oak and poplar panels. Pretreated oak also contains 2.5 times more furfural, even at low pretreatment severity, than pretreated poplar and spruce, and the furfural content increases with increasing severity, which could also explain better cohesion properties. Moreover, Astari et al. (2024) demonstrated that addition of citric acid to corn stalks particleboards led to improved mechanical properties, both flexural and IB, thanks to the formation of ester linkages between acid and hydroxyl groups in LB. Also, weak organic acids (acetic and formic) are generated during SE. There is twice as much formic acid in low-pretreated oak than in poplar or spruce for the same pretreatment severities, which could lead to higher IB for panels made from oak pretreated below CSF 4 as well as better flexural properties. As from acetic acid, its content increases with increasing severity for all biomass species and could thus enable better panel cohesion with wood pretreated at high CSF.

Hemicelluloses strongly positively correlated to thickness swelling, especially for poplar and spruce panels (0.79 and 0.75, respectively) and lignin strongly negatively correlated to it (-0.91 and -0.69). Hemicelluloses are the most hydrophilic constituents in LB and lignin is hydrophobic: degradation of hemicelluloses during SE leading to increased relative content of lignin thus contributes to more hydrophobic woody biomass and so to reduced swelling of particleboards, providing more dimensional stability.

Morphological properties of pretreated wood also seem to have an impact on the particleboards mechanical and hygroscopic properties. Particle size is highly negatively correlated to IB (-0.78 ≤ r ≤ -0.92): small particles lead to the formation of panels with higher density and less void between particles, which could enable better contact between molecules for self-bonding mechanism. Particle size is also highly correlated to thickness swelling, which is consistent because with small particles, the network of fibers is rendered tighter during hot-pressing and this would prevent water to enter (Ye et al., 2022).

Flexural properties seem mostly governed by the aspect ratio of fibers, which is strongly negatively correlated to flexural modulus (r = -0.73) and flexural strength (r = -0.86) for oak particleboards. While for poplar and spruce, the aspect ratio evolves little similarly to flexural properties and, like oak, properties drop at high pretreatment severities while aspect ratio increases.

### 4. Conclusions

The influence of steam exploded wood species at different severities on the properties of particleboards was highlighted. Pretreated oak

<caption>**Table 3**</caption>

Comparison of mechanical and hygroscopic properties of pretreated particleboards with a reference (Isorel®) and data from literature.

<table><thead><tr><th>Lignocellulosic biomass</th><th>Flexural modulus</th><th>Flexural strength</th><th>Internal bonding</th><th>Thickness swelling</th><th>Ref.</th></tr></thead><tbody><tr><td>Oak, poplar or spruce</td><td>0.3 - 1.6 GPa</td><td>1.7 - 6.7 MPa</td><td>0.06 - 1.59 MPa</td><td>2.6 - 42 %</td><td>This study</td></tr><tr><td>Isorel®</td><td>2.5 GPa</td><td>25.7 MPa</td><td>0.15 MPa</td><td>31 %</td><td>This study</td></tr><tr><td>Poplar</td><td>5.59 GPa</td><td>41.9 MPa</td><td>2.7 MPa</td><td>9.09 %</td><td>Zhong et al. (2024)</td></tr><tr><td>Poplar + Kraft lignin</td><td>11.35 GPa</td><td>84.4 MPa</td><td>2.7 MPa</td><td>8.42 %</td><td>Zhong et al. (2024)</td></tr><tr><td>Poplar</td><td>2.5 - 3.1 GPa</td><td>33 - 50 MPa</td><td>-</td><td>4.2 - 9 %</td><td>Ye et al. (2022)</td></tr><tr><td>Rice straw (twin extrusion pretreatment)</td><td>4.2 - 8.6 GPa</td><td>27.9 - 50.3 MPa</td><td>-</td><td>10.1 - 35.2 %</td><td>Theng et al. (2019)</td></tr><tr><td>Agricultural waster + Kraft lignin</td><td>3 - 6.5 GPa</td><td>20 - 50 MPa</td><td>0.2 - 1.1 MPa</td><td>2 - 10 %</td><td>Mancera et al. (2012)</td></tr><tr><td>Sugarcane bagasse</td><td>0.9 - 6.9 GPa</td><td>6.1 - 43.6 MPa</td><td>-</td><td>9 - 208 %</td><td>Cavailles et al. (2024)</td></tr><tr><td>Corn stalks</td><td>2.5 GPa</td><td>7.34 MPa</td><td>0.013 MPa</td><td>108.3 %</td><td>Astari et al. (2024)</td></tr><tr><td>Pine + spruce + steam exploded Arundo donax</td><td>1.2 - 3.5 GPa</td><td>5 - 23 MPa</td><td>&lt; 0.1 MPa</td><td>30 - 110 %</td><td>Vitrone et al. (2023)</td></tr></tbody></table>
<figure><img src="image_13.png" /><figcaption>**Fig. 6.** Correlations between physicochemical properties of steam exploded wood and properties of binderless particleboards. Blue circles show positive correlations; red circles show negative correlations; the higher the correlation, the bigger the circles.</figcaption></figure>

particleboards offer best properties and require less severe conditions of pretreatment to reach optimal properties, making oak economically preferable in terms of OPEX. Likewise, pretreatment severity has an effect on the panels properties. Best flexural properties are obtained at low severity of pretreatment, while internal bonding, thickness swelling and resistance in time are improved with high severities of pretreatment. There is therefore a possibility to define trade-offs between properties and applications so that adapted processes can be developed.

Multimodal characterization revealed which physicochemical properties of pretreated wood were more likely responsible for the mechanical and hygroscopic properties of particleboards. Chemical composition such as hemicelluloses, lignin and steam explosion degradation products contents and particle size have strong impacts on internal bonding and thickness swelling of particleboards, while flexural properties are mostly affected by the aspect ratio of the fibers.

The use of steam exploded wood to produce binderless particleboards with high cohesiveness and dimensional stability was demonstrated. In the case high mechanical flexure properties are desired, process conditions should be optimized to compete with existing fiberboard materials.

### CRediT authorship contribution statement

**Quintero Adriana:** Writing – review & editing, Supervision, Resources. **Martel Frédéric:** Writing – review & editing, Supervision, Resources. **Rémond Caroline:** Writing – review & editing, Supervision, Conceptualization. **Paës Gabriel:** Writing – review & editing, Supervision, Conceptualization. **Audibert Edwige:** Writing – original draft, Methodology, Investigation, Formal analysis, Conceptualization. **Duceschi Lauriane:** Investigation, Formal analysis.

### Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgements

This work was supported by the French National Agency for

Research and Technology ANRT (PhD fellowship to EA) and the company Européenne de Biomasse. The authors thank Sarah Rollet (ARD, France) for carrying out the pretreatment; Alain Lemaitre (UMR FARE, France) for his help to choose the panels manufacturing process; Marie-Laure Antoine, Christine Perrin and Pierre Girods (LERMAB, France) for lending the hot-press and for their assistance on the equipment; Françoise Berzin (UMR FARE, France) for scientific discussion and giving access to the IUT; Idriss Moussa (IUT Reims-Chalons-Charleville, France) for the laser-cut of particleboards and training on the universal testing equipment for bending tests; Elliott Guelzec (ESB Nantes, France) for carrying out the internal bonding tests.

### Data availability

Data will be made available on request.

### References

* Anglès, M.N., Ferrando, F., Farriol, X., Salvadó, J., 2001. Suitability of steam exploded residual softwood for the production of binderless panels. Effect of the pre-treatment severity and lignin addition. *Biomass--*. Bioenergy 21, 211–224. https://doi.org/10.1016/S0961-9534(01)00031-9.

* Antoun, K., Besserer, A., El Hage, R., Segovia, C., Sonnier, R., Brosse, N., 2024. Environmentally-friendly, binder-free, non-flammable particleboard with enhanced properties. *Ind. Crops Prod.* 222, 119578. https://doi.org/10.1016/j.indcrop.2024.119578.

* Astari, L., Belleville, B., Ozarska, B., Umemura, K., Crawford, R., Kusumaningrum, W.B., Ismayati, M., 2024. Performance of self-binding engineered panels made from sweet corn stalks (Zea mays L.) for furniture applications. *Bioresour. Technol. Rep.* 25, 101802. https://doi.org/10.1016/j.biteb.2024.101802.

* Audibert, E., Floret, J., Quintero, A., Martel, F., Rémond, C., Paës, G., 2025. Determination of trade-offs between 2G bioethanol production yields and pretreatment costs for industrially steam exploded woody biomass. *Appl. Energy* 380, 125028. https://doi.org/10.1016/j.apenergy.2024.125028.

* Bouajila, J., Limare, A., Joly, C., Dole, P., 2005. Lignin plasticization to improve binderless fiberboard mechanical properties. *Polym. Eng. Sci.* 45, 809–816. https://doi.org/10.1002/pen.20342.

* Cavailles, J., Vaca-Medina, G., Wu-Tiu-Yen, J., Peydecastaing, J., Pontalier, P.-Y., 2024. Influence of thermocombpression conditions on the properties and chemical composition of bio-based materials derived from lignocellulosic biomass. *Materials* 17, 1713. https://doi.org/10.3390/ma17081713.

* Cheng, D., Ding, H., Xu, B., Li, T., 2024. Suitability of thermally modified wood for binderless particleboard production: effects of temperature and moisture content in hot pressing. *Ind. Crops Prod.* 221, 119376. https://doi.org/10.1016/j.indcrop.2024.119376.

* Christy, E.O., Soemarno, Sumarlan, S.H., Soehardjono, A., 2020. Pilot study on low-density binderless bark particleboards manufacture from gelam wood (Melaleuca sp.) bark. *BioRes* 15, 7390–7403. https://doi.org/10.15376/biores.15.4.7390-7403.
Commission Regulation (EU), 2023. Commission Regulation (EU) 2023/1464 of 14 July 2023 amending Annex XVII to Regulation (EC) No 1907/2006 of the European Parliament and of the Council as regards formaldehyde and formaldehyde releasers, C/2023/4687.

Ding, K., Liu, D., Chen, X., Zhang, H., Shi, S., Guo, X., Zhou, L., Han, L., Xiao, W., 2024. Scalable lignocellulosic biorefineries: technoeconomic review for efficient fermentable sugars production. Renew. Sustain. Energy Rev. 202, 114692. https://doi.org/10.1016/j.rser.2024.114692.

Domínguez-Robles, J., Tarrés, Q., Alcalà, M., El Mansouri, N.-E., Rodríguez, A., Mutjé, P., Delgado-Aguilar, M., 2020. Development of high-performance binderless fiberboards from wheat straw residue. Constr. Build. Mater. 232, 117247. https://doi.org/10.1016/j.conbuildmat.2019.117247.

El Hage, M., Louka, N., Rezzoug, S.-A., Maugard, T., Sablé, S., Koubaa, M., Debs, E., Maache-Rezzoug, Z., 2023. Bioethanol production from woody biomass: recent advances on the effect of pretreatments on the bioconversion process and energy yield aspects. Energies 16, 5052. https://doi.org/10.3390/en16135052.

European Committee for Standardization, 1993a. EN323. Wood-based panels - Determination of density.

European Committee for Standardization, 1993b. EN310. Wood-based panels - Determination of modulus of elasticity in bending and of bending strength.

European Committee for Standardization, 1993c. EN319. Paistleboards and fiberboards - Determination of tensile strength perpendicular to the plane of the board.

European Committee for Standardization, 1993d. EN317. Particleboards and fiberboards - Determination of swelling in thickness after immersion in water.

European Committee for Standardization, 2002. EN321. Wood-based panels - Determination of moisture resistance under cyclic test conditions.

European Committee for Standardization, 2010. EN312. Particleboards - Specifications.

Ge, S., Ma, N.L., Jiang, S., Ok, Y.S., Lam, S.S., Li, C., Shi, S.Q., Nie, X., Qiu, Y., Li, D., Wu, Q., Tsang, D.C.W., Peng, W., Sonne, C., 2020. Processed bamboo as a novel formaldehyde-free high-performance furniture biocomposite. ACS Appl. Mater. Interfaces 12, 30824-30832. https://doi.org/10.1021/acsami.0c07448.

Gouveia, S., Otero, L., Fernández-Costas, C., Filgueira, D., Sanromán, Á., Moldes, D., 2018. Green binder based on enzymatically polymerized eucalypt kraft lignin for fiberboard manufacturing: a preliminary study. Polymers 10, 642. https://doi.org/10.3390/polym10060642.

Herbaut, M., Zoglhami, A., Habrant, A., Falourd, X., Foucat, L., Chabbert, B., Paës, G., 2018. Multimodal analysis of pretreated biomass species highlights generic markers of lignocellulose recalcitrance. Biotechnol. Biofuels 11, 52. https://doi.org/10.1186/s13068-018-1053-8.

Karthäuser, J., Biziks, V., Mai, C., Militz, H., 2021. Lignin and lignin-derived compounds for wood applications—a review. Molecules 26, 2533. https://doi.org/10.3390/molecules26092533.

Lee, S.H., Lum, W.C., Boon, J.G., Kristak, L., Antov, P., Pědzik, M., Rogoziński, T., Tagiyari, H.R., Lubis, M.A.R., Fatriasari, W., Yadav, S.M., Chotikhun, A., Pizzi, A., 2022. Particleboard from agricultural biomass and recycled wood waste: a review. J. Mater. Res. Technol. 20, 4630-4658. https://doi.org/10.1016/j.jmrt.2022.08.166.

Li, Y., Cai, L., Chen, H., Liu, Z., Zhang, X., Li, Jingchao, Shi, S.Q., Li, Jianzhang, Gao, Q., 2022. Preparation of a high bonding performance soybean protein-based adhesive with low crosslinker addition via microwave chemistry. Int. J. Biol. Macromol. 208, 45-55. https://doi.org/10.1016/j.ijbiomac.2022.03.059.

Luo, H., Zhang, H., Yue, L., Pizzi, A., Lu, X., 2018. Effects of steam explosion on the characteristics of windmill palm fiber and its application to fiberboard. Eur. J. Wood Prod. 76, 601-609. https://doi.org/10.1007/s00107-017-1259-7.

Mancera, C., El Mansouri, N.-E., Pelach, M.A., Francesc, F., Salvadó, J., 2012. Feasibility of incorporating treated lignins in fiberboards made from agricultural waste. Waste Manag. 32, 1962-1967. https://doi.org/10.1016/j.wasman.2012.05.019.

Marbun, S.D., Dwianto, W., Meliala, S.B.P.S., Widyorini, R., Augustina, S., Hiziroglu, S., 2023. Dimensional stability mechanisms of binderless boards by heat or steam treatment: a review. Cellulose. https://doi.org/10.1007/s10570-023-05429-9.

Mason, W.H., 1928. Press-dried structural insulating board and process of same. US1663504A.

Mobarak, F., Fahmy, Y., Augustin, H., 1982. Binderless lignocellulose composite from bagasse and mechanism of self-bonding. Holzforschung 36, 131-136. https://doi.org/10.1515/hfsg.1982.36.3.131.

Nadhari, W.N.A.W., Danish, M., Nasir, M.S.R.M., Geng, B.J., 2019. Mechanical properties and dimensional stability of particleboard fabricated from steam pre-treated banana trunk waste particles. J. Build. Eng. 26, 100848. https://doi.org/10.1016/j.jobe.2019.100848.

Overend, R.P., Chornet, E., 1987. Fractionation of lignocellulosics by steam-aqueous pretreatments. Philos. Trans. R. Soc. Lond. A 321, 523-536. https://doi.org/10.1098/rsta.1987.0029.

Raydan, N.D.V., Leroyer, L., Charrier, B., Robles, E., 2021. Recent advances on the development of protein-based adhesives for wood composite materials—a review. Molecules 26, 7617. https://doi.org/10.3390/molecules26247617.

Saravanan, A., Senthil Kumar, P., Jeevanantham, S., Karishma, S., Vo, D.-V.N., 2022. Recent advances and sustainable development of biofuels production from lignocellulosic biomass. Bioresour. Technol. 344, 126203. https://doi.org/10.1016/j.biortech.2021.126203.

Theng, D., Arbat, G., Delgado-Aguilar, M., Ngo, B., Labonne, L., Mutjé, P., Evon, P., 2019. Production of fiberboard from rice straw thermomechanical extrudates by thermopressing: influence of fiber morphology, water and lignin content. Eur. J. Wood Prod. 77, 15-32. https://doi.org/10.1007/s00107-018-1358-0.

Tupciauskas, R., Rizhikovs, J., Andzs, M., Bikovens, O., 2022. Influence of manufacturing conditions on binder-less boards from steam-exploded hemp shives and wheat straw. Materials 15, 3141. https://doi.org/10.3390/ma15093141.

Tupciauskas, R., Rizhikovs, J., Brazdausks, P., Fridrihsone, V., Andzs, M., 2021. Influence of steam explosion pre-treatment conditions on binder-less boards from hemp shives and wheat straw. Ind. Crops Prod. 170, 113717. https://doi.org/10.1016/j.indcrop.2021.113717.

Vitrone, F., Brinker, S., Ramos, D., Ferrando, F., Salvadó, J., Mai, C., 2023. Approaching self-bonded medium density fiberboards made by mixing steam exploded Arundo donax L. and Wood Fibers: a comparison with pMDI-bonded fiberboards on the primary properties of the boards. Materials 16, 4343. https://doi.org/10.3390/ma16124343.

Vitrone, F., Ramos, D., Ferrando, F., Salvadó, J., 2021. Binderless fiberboards for sustainable construction. Materials, production methods and applications. J. Build. Eng. 44, 102625. https://doi.org/10.1016/j.jobe.2021.102625.

Widyorini, R., Xu, J., Watanabe, T., Kawai, S., 2005. Chemical changes in steam-pressed kenaf core binderless particleboard. J. Wood Sci. 51, 26-32. https://doi.org/10.1007/s10086-003-0608-9.

Ye, H., Wang, Y., Yu, Q., Ge, S., Fan, W., Zhang, M., Huang, Z., Manzo, M., Cai, L., Wang, L., Xia, C., 2022. Bio-based composites fabricated from wood fibers through self-bonding technology. Chemosphere 287, 132436. https://doi.org/10.1016/j.chemosphere.2021.132436.

Yu, Y., Wu, J., Ren, X., Lau, A., Rezaei, H., Takada, M., Bi, X., Sokhansanj, S., 2022. Steam explosion of lignocellulosic biomass for multiple advanced bioenergy processes: a review. Renew. Sustain. Energy Rev. 154, 111871. https://doi.org/10.1016/j.rser.2021.111871.

Zhang, D., Zhang, A., Xue, L., 2015. A review of preparation of binderless fiberboards and its self-bonding mechanism. Wood Sci. Technol. 49, 661-679. https://doi.org/10.1007/s00226-015-0728-6.

Zhao, W., Zhang, J., Zhang, W., Yuan, S., Chen, H., Wu, A., 2023. Effect of bamboo unit morphology on the preparation of bamboo fibers by steam explosion. Ind. Crops Prod. 202, 117066. https://doi.org/10.1016/j.indcrop.2023.117066.

Zhong, Y., Ren, Y., Yang, Y., Huo, H., Zhang, L., Zhang, J., Yue, K., Zhang, Z., 2024. Formaldehyde-free environmentally friendly lignocellulosic composites made from poplar and lignin obtained from paper mills. Ind. Crops Prod. 208, 117907. https://doi.org/10.1016/j.indcrop.2023.117907.