The authors would like to express their sincere gratitude to R&#233;gion Occitanie (France) that funded this research through ERDF (GEOFIBNET project, grant number MP0013559).

1. Prepare the raw materials
<ol>
	<li>Use oleaginous flax shives, which are the result of a preliminary stage of mechanical extraction of the bast fibers from straw in an &#34;all fiber&#34; extraction device51. Use a vibrating sieve to remove short textile fibers that they may still contain. 
	NOTE: As the removal of these short textile fibers may be difficult, do not hesitate to repeat this sieving operation as many times as necessary. Here, the objective is to improve the flow of the oleaginous flax shives in the hopper of the weight feeder, and, therefore, facilitate their dosing before their introduction into the twin-screw extruder.</li>
	<li>Use a plasticized linseed cake, obtained by destructuring/plasticizing of the proteins according to the methodology described by Rouilly et al.18. 
	NOTE: By doing so, the proteins show better thermoplastic and adhesive aptitudes.</li>
	<li>Grind the agro-granulates of plasticized linseed cake using a hammer mill fitted with a 1 mm grid, and then sieve the grinded material obtained to retain only the particles smaller than 500 &#181;m.</li>
</ol>
2. Check the proper functioning of the constant weight feeders and the piston pump
<ol>
	<li>For the flow rates at which the operator works during production, chosen to avoid the clogging of the machine (15 kg/h for oleaginous flax shives (OFS), and from 1.50 kg/h to 3.75 kg/h for plasticized linseed cake), check the correspondence between the set value entered to the two constant weight feeders and the solid flow rates really distributed by these dosing devices. 
	NOTE: The actual solid flow rate is determined experimentally by weighing the mass of the solid distributed by the constant weight feeder for a known period of time (5 min). If there is a significant deviation between the set value and the actual measured flow rate, this may indicate a malfunction of the weigh feeder. To prevent this, the entire dosing unit should be thoroughly cleaned, with particular emphasis on the area where the weighing device is located. In fact, the cause of this type of malfunction is very often a poor cleaning of the device, as traces of previously used solids can be found in the smallest corners of the dosing unit. If the problem persists, it will then be necessary to check the correct gauging of the balance itself and, if necessary, recalibrate it.</li>
	<li>Calibrate the piston pump to establish a relationship between the electrical power of the motor and the actual water flow rate distributed by the pump. 
	NOTE: For each tested electrical power, the actual water flow rate is determined experimentally by weighing the mass of the water distributed by the piston pump for a known period of time (5 min). Five different electrical powers are tested to draw the calibration curve. The highest electrical power tested is chosen so that it delivers a higher water flow rate than that chosen during production.</li>
	<li>Once the calibration of the pump has been carried out, check for the water flow rate at which the operator works during production (15 kg/h to avoid the clogging of the machine while preserving the length of the extrusion-refined fibers) the correspondence between the set value given to the piston pump for the engine power and the water flow rate actually distributed.</li>
</ol>
3. Prepare the twin-screw extruder
<ol>
	<li>Correctly arrange the twin-screw extruder modules (AB1-GG-8D, FER, and ABF types) by connecting them one after the other (by means of two half clamps) in the correct order according to the machine configuration to be used:
	<ol>
		<li>Set up the configuration for which only the fiber defibration takes place (Figure 1A).</li>
		<li>Alternatively, set up the configuration which is completed with the addition of the natural binder (Figure 1B). 
		NOTE: For both configurations, the first module is used for the introduction of oleaginous flax shives. This is a type AB1-GG-8D module, which has an 8D length, D corresponding to the screw diameter (i.e., 53 mm). The large upper opening of this module is primarily intended to facilitate the introduction of the shives. Modules 2 to 8 are temperature controlled. They are closed modules (type FER), except module 5 in the case of configuration (step 3.1.2), which is of ABF type (i.e., module equipped with a side opening to ensure the connection of the side feeder used to force the introduction of the plasticized linseed cake inside the main barrel). The side feeder consists of two co-rotating and co-penetrating Archimedean screws of constant pitch and conjugated profile.</li>
	</ol>
	</li>
	<li>Position the water inlet pipe laterally at the end of module 2 to connect the piston pump to the machine.</li>
	<li>Set aside the screw elements (Figure 2) that will be needed to set up the screw profile, either the one used for configuration (step 3.1.1) or the one used for configuration (step 3.1.2) (Figure 3). 
	NOTE: Make sure that these are the correct screw elements by carefully checking their type (T2F, C2F, C1F, CF1C, BB, or INO0), length, pitch (for the conveying and reverse screw elements), and their staggering angle (for the BB mixing blocks).</li>
	<li>Set up the screw profile (Figure 3) by inserting the screw elements along the two splined shafts, from the first pair to the last one. 
	NOTE: The screw profiles used for the two configurations tested, are different and both result from prior optimization25,26,27.</li>
	<li>When assembling the screw profile, make sure that the threads of the screw elements just inserted on the splined shafts are always perfectly aligned with the previously assembled elements.</li>
	<li>Once the entire screw profile is assembled, screw by hand the screw points at the end of the two shafts, completely close the barrel of the machine and then tighten the two screw points to the tightening torque recommended by the manufacturer (30 daN m for the twin-screw extruder used in this study) using a torque wrench.</li>
	<li>With the barrel of the machine partially reopened, i.e., with the shafts retracted into the barrel over a distance of approximately 1D, turn the screws at low speed (25 rpm max) to ensure that the entire screw profile is correctly fitted. 
	NOTE: In the case of incorrect installation of the screw elements (e.g., the misalignment for one of them), accelerated wear of the screw elements will be inevitably observed. When testing the rotation of both shafts with the barrel of the machine almost fully open, this results in the shafts touching each other at the point of the incorrectly positioned screw element.</li>
	<li>Completely close the barrel of the machine so that both shafts are entirely trapped inside the barrel.</li>
	<li>Once the barrel is closed, clamp it to the machine with half clamps, and make sure with the help of a level tester that the barrel is perfectly horizontal. 
	NOTE: If the barrel of the twin-screw extruder is not perfectly horizontal, this may lead to premature wear by abrasion of the screw elements and/or the inner walls of the barrel.</li>
	<li>Position the peripherals (the weight feeders for the two solids to be introduced, and the piston pump for the water to be injected) at the required places along the barrel: above module 1 for the feeder used for the oleaginous flax shives, above the hopper of the side feeder (itself connected laterally to module 5) for the one used for the plasticized linseed cake (case of configuration (step 3.1.2) only), and at the end of module 2 for the water injection.</li>
</ol>
4. Carry out the twin-screw extrusion treatment according to configuration (step 3.1.1) or configuration (step 3.1.2)
<ol>
	<li>From the supervision of the machine, enter the set temperatures of each of the modules and start the temperature control of the barrel: for configuration (step 3.1.1), 25 &#176;C for the feeding module (module 1) and 110 &#176;C for the following ones; for configuration (step 3.1.2), 25 &#176;C for module 1, 110 &#176;C for the refining zone (modules 2 to 4), and 80 &#176;C for the premixing one (modules 5 to 8). 
	NOTE: The temperature control of the barrel is carried out separately from one module to another by (i) heating with two resistive half clamps fixed around each module, and (ii) cooling by circulating cold water inside the module. A 25 &#176;C is privileged for the feeding module. For an efficient refining of the fibers, a 110 &#176;C temperature is preferred. An 80 &#176;C temperature is sufficient for the premixing operation. Since the refining and premixing zones are both located along several modules, all modules in the same zone are assigned the same set temperature.</li>
	<li>Wait for the stability of the measured temperatures and make sure that these temperatures are equal to the set points. 
	NOTE: The measured temperatures are given on the control panel of the machine. In order to ensure a second control of these temperatures, it is also possible to measure them with an infrared thermometer at the level of each module along the barrel.</li>
	<li>Slowly turn the screws (i.e., 50 rpm max). 
	NOTE: Premature abrasive wear of the screw elements and the inner walls of the barrel can occur if the screws turn too quickly while the machine is empty.</li>
	<li>Gently feed the twin-screw extruder with water (5 kg/h flow rate).</li>
	<li>Wait for around 30 s until water comes out at the end of the barrel.</li>
	<li>Then, start to introduce the oleaginous flax shives in module 1 at a 3 kg/h flow rate, and wait (for around 1 min) for the solid to start coming out of the extruder.</li>
	<li>Gradually increase (at least in three successive steps) the speed of the screws, then the water flow rate and finally the shives flow rate until the desired set points are reached: 150 rpm, 15 kg/h and 15 kg/h, respectively (Table 1). 
	NOTE: These set points were determined in previous studies and result from the optimization of the process25,26,27.</li>
	<li>Wait for the machine stabilization by following the evolution of the electrical current consumed by the engine over time (variation of the electrical current no more than 5% from the 125 A average value). 
	NOTE: The stabilization time is usually in the range of 10 to 15 min.</li>
	<li>For configuration (step 3.1.2) only, start introducing the plasticized linseed cake at 0.50 kg/h once the machine has stabilized in amperage after the shives and water addition to the desired set values. Then, increase the flow rate of the plasticized linseed cake in at least three successive steps up to the desired set point (from 1.50 kg/h to 3.75 kg/h, which corresponds to values between 10% and 25% by mass in relation to the shives) (Table 1).</li>
	<li>Once the electrical current consumed by the twin-screw extruder motor is perfectly stable, make sure that the temperature profile measured along the barrel is conform to the set values given by the operator, and then start sampling the extruded shives for configuration (step 3.1.1) or the premix for configuration (step 3.1.2) at the outlet. 
	NOTE: In order to not clog the unit, the current drawn by the motor must always remain below its limit value (i.e., 400 A for the pilot scale twin-screw extruder used in this study). It should, therefore, be checked that this limit value is not reached during the entire flow ramp-up phase as well as during sampling. During production, if the cooling system of the machine is not able to maintain the temperature of at least one module at its set value, this may be the consequence of an inappropriate screw profile (i.e., too restrictive screw elements at this location),which causes a local self-heating of the treated material. It is then necessary to make sure, e.g., by means of a thermogravimetric analysis (TGA) of the solid being processed, that this temperature does not cause any fiber degradation.</li>
	<li>During the entire sampling process, make sure that the machine feed is trouble-free by regularly checking the effective entry of solids and water into the barrel of the machine. 
	NOTE: A stable amperage of the current drawn by the motor of the twin-screw extruder during the entire sampling time is a confirmation of a stable feeding of the machine.</li>
	<li>At the end of production, switch off the two solid dosing units and the piston pump.</li>
	<li>Empty the machine while gradually reducing the speed of rotation of the screws to 50 rpm.</li>
	<li>When nothing comes out of the barrel end, clean the inside of the barrel of the twin-screw extruder with plenty of water, introduced in large excess from module 1, while the screws are still rotating at 50 rpm. Add water until the solid residues disappear completely at the outlet of the barrel. Then, stop the rotation of the screws and switch off the heating control of the machine.</li>
</ol>
5. Dry and condition the resulting extrudates (i.e., extrusion-refined shives or premix)
<ol>
	<li>When the extrudates are not to be molded into fiberboards immediately after the twin-screw extrusion process, dry them with a hot air stream to a humidity between 8% and 12% before their conditioning. For this purpose, use a simple ventilated oven or, in the case of large quantities of extrudate to be dried, a continuous belt dryer. 
	NOTE: With such humidity, the extrudates can be conditioned without the risk of fungus or mold growth over time. Packaging should be carried out in perfectly sealed plastic bags, which should be stored in a dry place.</li>
	<li>Dry the extrudates with hot air flow to a humidity between 3% and 4% when fiberboard molding takes place immediately after the twin-screw extrusion process. 
	&#8203;NOTE: Previous studies showed that a moisture content of 3% to 4% of the solid to be hot pressed is ideal to limit degassing phenomena at the end of molding. When it occurs and it is not controlled, degassing can generate defects (e.g., blisters or cracks) inside the fiberboard,and these defects have a negative impact on its mechanical resistance26,27,31,32. When hot pressing is carried out after the extrudates have been stored in airtight plastic bags at a moisture content of 8% to 12%, they should be dried further, i.e., up to 3%-4%, before molding.</li>
</ol>
6. Mold the fiberboards by hot pressing
NOTE: The operating conditions for hot pressing have been chosen on the basis of previous studies26,27,31,32.
<ol>
	<li>Pre-heat the mold. Then, position the solid material to be hot pressed inside the mold. Lastly, pre-heat this solid material for 3 min before applying the pressure. 
	NOTE: For all the fiberboards produced, the proportion of shives in the mix to be molded represents a mass of 100 g when the mold used is square in shape and with 15 cm sides.</li>
	<li>Apply a pressure of 30 MPa with the raw shives, and 10 MPa, 20 MPa, or 30 MPa with the extruded ones (Table 2).</li>
	<li>Set the mold temperature to 200 &#176;C. 
	NOTE: Because the temperature greatly influences the quality (especially the bending properties) of the boards obtained9,26,27,28,31,32, it is important to check the mold temperature with an infrared thermometer on both its male and female parts.</li>
	<li>Set the molding time to 150 s.</li>
	<li>Manufacture different fiberboards with different contents of plasticized linseed cake (from 0% to 25%) using the extrusion-refined fibers obtained through twin-screw extrusion via configuration (step 3.1.1) or one of the three premixes obtained via configuration (step 3.1.2) (Table 1 and Table 2).</li>
	<li>As references, also manufacture two additional fiberboards based on the raw OFS, one without the addition of exogenous binder (board number 11) and the other with the addition of 25% (w/w) of plasticized linseed cake (board number 12) (Table 2). 
	&#8203;NOTE: For these two boards, the molding conditions are the same, i.e., 200 &#176;C for the mold temperature, 150 s for the molding time, and 30 MPa for the applied pressure.</li>
</ol>
7. Condition and characterize the fiberboards
<ol>
	<li>Once the fiberboards have been produced, place them in a climatic chamber at 60% relative humidity and 25 &#176;C until a constant weight is achieved. 
	NOTE: The fiberboards will then be conditioned and stabilized in terms of humidity.</li>
	<li>Once equilibrated, cut the fiberboards into test specimens. 
	NOTE: The most suitable tool for cutting fiberboards is a vertical band saw.</li>
	<li>From the test specimens, proceed with the characterization of the fiberboards using standardized tests for bending properties (ISO 16978:2003 standard), Shore D surface hardness (ISO 868:2003 standard), internal bond strength (ISO 16260:2016 standard), and water sensitivity after immersion in water for 24 h (ISO 16983:2003 standard).</li>
	<li>Compare the properties measured for the fiberboards with the recommendations of the French standard dedicated to the specifications for particleboards (NF EN 312) in order to determine their possible uses.</li>
</ol>

The authors have nothing to disclose.

The protocol outlined here describes how to process the extrusion-refining of lignocellulosic fibers before using them as mechanical reinforcement in renewable boards. Here, the twin-screw extruder used is a pilot scale machine. With screws of 53 mm in diameter (D), it is equipped with eight modules, each 4D in length, except for module 1 that has an 8D length, corresponding to a 36D total length (i.e., 1,908 mm) for the barrel. Its length is long enough to apply to the processed material the succession of several elemen...

Extrusion is a process during which a flowing material is forced through a hot die. Extrusion, therefore, permits the forming of preheated products under pressure. The first industrial single-screw extruder appeared in 1873. It was used for the manufacture of metallic continuous cables. From 1930 onwards, single-screw extrusion was adapted to the food industry to produce sausages and past. Conversely, the first twin-screw extruder has first been used for developments in the food industry. It did not appear in the field of synthetic polymers until the 1940s. For this purpose, new machines were designed, and their operation was also modeled1. A system with co-penetrating and co-rotating screws was developed, allowing mixing and extrusion to be carried out simultaneously. Since then, the extrusion technology has developed continuously via the design of new types of screws. Today, the food industry makes extensive use of twin-screw extrusion although it is more expensive than single-screw extrusion as twin-screw extrusion permits access to more elaborated material processing and final products. It is particularly used for extrusion-cooking of starchy products but also the texturing of proteins and the manufacture of pet food and fish feed.
More recently, twin-screw extrusion has seen its field of application extended to the thermo-mechano-chemical fractionation of plant matter2,3. This new concept has led to the development of real reactors capable of transforming or fractionating plant matters in a single step, up to the separate production of an extract and a raffinate by liquid/solid separation2,3,4. Work carried out at the Laboratory of Agro-industrial Chemistry (LCA) has highlighted the multiple possibilities of the twin-screw technology for the fractionation and valorization of agroresources2,3. Some of the examples are: 1) The mechanical pressing and/or &#34;green&#34; solvent extraction of vegetable oil5,6,7,8,9,10. 2) The extraction of hemicelluloses11,12, pectins13, proteins14,15, and polyphenolic extracts16. 3) The enzymatic degradation of plant cell walls for producing second-generation bioethanol17. 4) The production of biocomposite materials with protein18 or polysaccharide19 matrices. 5) The production of thermoplastic materials by mixing cereals, and bio-based polyesters20,21. 6) The production of biocomposites by compounding a thermoplastic polymer, bio-based or not, and plant fillers22,23. 7) The defibration of lignocellulosic materials for producing paper pulp13,24, and fiberboards25,26,27,28,29,30,31,32.
The twin-screw extruder is often considered as a continuous thermo-mechano-chemical (TMC) reactor. Indeed, it combines in a single step chemical, thermal, and, also, mechanical actions. The chemical one results in the possibility to inject liquid reagents in various points along the barrel. The thermal one is possible due to the thermal regulation of the barrel. Lastly, the mechanical one depends on the choice of the screw elements along the screw profile.
For the defibration of lignocellulosic materials to produce fiberboards, the most recent works have used rice straw25,28, coriander straw26,29, oleaginous flax shives27 as well as sunflower30,32 and amaranth31 barks. The current interest of lignocellulosic biomasses for such an application (i.e., mechanical reinforcement) is explained by the regular depletion of forest resources used for producing wood-based materials. Crop residues are inexpensive and may be widely available. In addition, current wood particles are mixed with petrochemical resins which can be toxic. Often accounting for more than 30% of the total cost of current commercial materials33, some resins contribute to formaldehyde emissions and reduce indoor air quality34. Research interest has shifted to the use of natural binders.
Lignocellulosic biomass is mainly composed of cellulose and hemicelluloses, forming a heterogeneous complex. Hemicelluloses are impregnated with layers of lignins that form a three-dimensional network around these complexes. The use of lignocellulosic biomass for the manufacture of fiberboards generally requires a defibration pre-treatment. For this, it is necessary to break down the lignins that protect cellulose and hemicelluloses. Mechanical, thermal, and chemical35 or even enzymatic36,37,38 pre-treatments must be applied. These steps also increase self-adhesion of fibers, which can promote the production of binderless boards27 even if an exogenous binder is most often added.
The primary purpose of pre-treatments is to improve the particle size profile of micrometric fibers. A simple grinding offers the possibility to reduce the fiber size27,39,40. Inexpensive, it contributes to increase the fiber specific surface. The components of the inner cell wall become more accessible and the mechanical properties of the obtained panels are improved. The efficiency of defibration is significantly increased when a thermo-mechanical pulp is produced, e.g., by digestion plus defibration41, from different pulping processes42 or by steam explosion43,44,45,46,47. More recently, LCA has developed an original pre-treatment of lignocellulosic fibers using twin-screw extrusion25,26,27,28,29,30,31,32. After TMC defibration, the extruder also enables the homogeneous dispersion of a natural binder inside fibers. The resulting premix is ready to be hot pressed into fiberboards.
During the defibration of rice straw, twin-screw extrusion was compared to a digestion plus defibration process25. The extrusion method revealed a significantly reduced cost, i.e., nine times lower than the pulping one. Furthermore, the amount of added water is reduced (1.0 max liquid/solid ratio instead of 4.0 min with the pulping method), and a clear increase in the average aspect ratio of refined fibers (21.2-22.6 instead of 16.3-17.9) is observed as well. These fibers present highly improved mechanical strengthening capability. This was demonstrated for rice straw-based fiberboards, in which pure non deteriorated lignin (e.g., Biolignin) was used as a binder (up to 50 MPa for bending strength and 24% for thickness swelling after 24 h immersion in water)28.
The interest of TMC defibration in twin-screw extruder has also been confirmed with coriander straw26. The aspect ratio of refined fibers varies from 22.9-26.5 instead of only 4.5 for simply ground fibers. 100% coriander-based fiberboards were obtained by adding to the extrusion-refined straws a cake from the seed as protein binder (40% in mass). Their flexural strength (up to 29 MPa) and especially their resistance to water (up to 24% thickness swelling) were significantly improved compared to panels made from simply crushed straw. Moreover, these panels do not emit formaldehyde and, as a consequence, they are more environmentally and human-health friendly than medium-density fiberboard (MDF) and chipboard29 classically found in the market.
Similarly, panels entirely based on amaranth31 and sunflower32, combining extrusion-refined fibers from bark as reinforcement and seed cake as a protein binder, were successfully produced. They showed flexural strengths of 35 MPa and 36 MPa, respectively. However, their water resistance was found to be lower: 71% and 87%, respectively, for thickness swelling. Self-bonded panels based on extrusion-refined shives from oleaginous flax straw can also be obtained27. In this case, it is the ligneous fraction, released during the twin-screw TMC defibration, that contributes to the self-bonding. However, hardboards obtained show a lower mechanical strength (only 12 MPa flexural strength), and very high thickness swelling (127%).
All the extruded fiber-based panels presented above can find industrial applications and are, therefore, sustainable alternatives to current commercial wood-based materials. According to the International Organization for Standardization (ISO) requirements48,49,50, their specific applications will depend on their mechanical and water sensitivity characteristics.
In this paper, the procedure to extrude and refine lignocellulosic fibers before using them as mechanical reinforcement in renewable boards is described in detail. As a reminder, this process reduces the amount of water to be added in comparison to traditional pulping methodologies, and it is also less energy consuming25. The same twin-screw machine can also be used for adding a natural binder to fibers.
More specifically, a detailed outline for conducting the twin-screw extrusion-refining of shives from oleaginous flax (Linum usitatissimum L.) straw is presented. The straw used in this study was commercially obtained. It was from the Everest variety, and the plants were cultivated in the South West part of France in 2018. In the same extruder pass, a plasticized linseed cake (used as exogenous binder) can also be added in the middle of the barrel, and then mixed intimately to the refined shives along the second half of the screw profile. A homogeneous mixture having the form of a fluffy material is collected at the machine outlet. The one-step TMC operation is conducted using a pilot scale machine. Our goal is to provide a detailed procedure for the operators to conduct properly the extrusion-refining of shives, and then the cake addition. Following this operation, the obtained premix is ready for subsequent manufacture of 100% oleaginous flax-based hardboards using hot pressing.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Analogue durometer</td>
			<td>Bareiss</td>
			<td>HP Shore</td>
			<td>Device used for determining the Shore D surface hardness of fiberboards</td>
		</tr>
		<tr>
			<td>Ash furnace</td>
			<td>Nabetherm</td>
			<td>Controller B 180</td>
			<td>Furnace used for the mineral content determinations</td>
		</tr>
		<tr>
			<td>Belt dryer</td>
			<td>Clextral</td>
			<td>Evolum 600</td>
			<td>Belt dryer used for the continuous drying of extrudates at the exit of the twin-screw extruder</td>
		</tr>
		<tr>
			<td>Cold extraction unit</td>
			<td>FOSS</td>
			<td>FT 121 Fibertec</td>
			<td>Cold extractor used for determining the fiber content inside solid materials</td>
		</tr>
		<tr>
			<td>Densitometer</td>
			<td>MA.TEC</td>
			<td>Densi-Tap IG/4</td>
			<td>Device used for determining apparent and tapped densities of extrudates once dried</td>
		</tr>
		<tr>
			<td>Double-helix mixer</td>
			<td>Electra</td>
			<td>MH 400</td>
			<td>Mixer used for preparing the solid mixture made of the raw shives and the plasticized linseed cake for producing board number 12</td>
		</tr>
		<tr>
			<td>Fiber morphology analyzer</td>
			<td>Techpap</td>
			<td>MorFi Compact</td>
			<td>Analyzer used for determining the morphological characteristics of extrusion-refined shives</td>
		</tr>
		<tr>
			<td>Gravimetric belt feeder</td>
			<td>Coperion K-Tron</td>
			<td>SWB-300-N</td>
			<td>Feeder used for the quantification of the oleaginous flax shives</td>
		</tr>
		<tr>
			<td>Gravimetric screw feeder</td>
			<td>Coperion K-Tron</td>
			<td>K-ML-KT20</td>
			<td>Feeder used for the quantification of the plasticized linseed cake</td>
		</tr>
		<tr>
			<td>Hammer mill</td>
			<td>Electra</td>
			<td>BC P</td>
			<td>Crusher used for the grinding of granules made of plasticized linseed cake</td>
		</tr>
		<tr>
			<td>Heated hydraulic press</td>
			<td>Pinette Emidecau Industries</td>
			<td>PEI 400-t</td>
			<td>Hydraulic press used for molding the fiberboards through hot pressing</td>
		</tr>
		<tr>
			<td>Hot extraction unit</td>
			<td>FOSS</td>
			<td>FT 122 Fibertec</td>
			<td>Hot extractor used for determining the water-soluble and fiber contents inside solid materials</td>
		</tr>
		<tr>
			<td>Image analysis software</td>
			<td>National Institutes of Health</td>
			<td>ImageJ</td>
			<td>Software used for determining the morphological characteristics of raw shives</td>
		</tr>
		<tr>
			<td>Oleaginous flax straw</td>
			<td>Ovalie Innovation</td>
			<td>N/A</td>
			<td>Raw material supplied for the experimental work</td>
		</tr>
		<tr>
			<td>Piston pump</td>
			<td>Clextral DKM</td>
			<td>Super MD-PP-63</td>
			<td>Pump used for the water quantification and injection</td>
		</tr>
		<tr>
			<td>Scanner</td>
			<td>Toshiba</td>
			<td>e-Studio 257</td>
			<td>Scanner used for taking an image of raw shives in gray level</td>
		</tr>
		<tr>
			<td>Side feeder</td>
			<td>Clextral</td>
			<td>E36</td>
			<td>Feeder used to force the introduction of the plasticized linseed cake inside the barrel (at the level of module 5) for configuration (b)</td>
		</tr>
		<tr>
			<td>Thermogravimetric analyzer</td>
			<td>Shimadzu</td>
			<td>TGA-50</td>
			<td>Analyzer used for conducting the thermogravimetric analysis of the solids being processed</td>
		</tr>
		<tr>
			<td>Twin-screw extruder</td>
			<td>Clextral</td>
			<td>Evolum HT 53</td>
			<td>Co-rotating and co-penetrating pilot scale twin-screw extruder having a 36D total length (D is the screw diameter, i.e., 53 mm)</td>
		</tr>
		<tr>
			<td>Universal oven</td>
			<td>Memmert</td>
			<td>UN30</td>
			<td>Oven used for the moisture content determinations</td>
		</tr>
		<tr>
			<td>Universal testing machine</td>
			<td>Instron</td>
			<td>33R4204</td>
			<td>Testing machine used for determining the bending properties of fiberboards</td>
		</tr>
		<tr>
			<td>Ventilated oven</td>
			<td>France Etuves</td>
			<td>XL2520</td>
			<td>Oven used for the discontinuous drying of extrudates at the exit of the twin-screw extruder</td>
		</tr>
		<tr>
			<td>Vibrating sieve shaker</td>
			<td>RITEC</td>
			<td>RITEC 600</td>
			<td>Sieve shaker used for the sieving of the plasticized linseed cake</td>
		</tr>
		<tr>
			<td>Vibrating sieve shaker</td>
			<td>RITEC</td>
			<td>RITEC 1800</td>
			<td>Sieve shaker used for removing short bast fibers entrapped inside the oleaginous flax shives</td>
		</tr>
	</tbody>
</table>

twin-screw extrusion process to produce renewable fiberboards

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pre-treatment on lignocellulosic biomass before using it as source of mechanical reinforcement in fully bio-based fiberboards was developed. Various lignocellulosic crop by-products have already been successfully pre-treated through this process, e.g., cereal straws (especially rice), coriander straw, shives from oleaginous flax straw, and bark of both amaranth and sunflower stems.
The extrusion process results in a marked increase in the average fiber aspect ratio, leading to improved mechanical properties of fiberboards. The twin-screw extruder can also be fitted with a filtration module at the end of the barrel. The continuous extraction of various chemicals (e.g., free sugars, hemicelluloses, volatiles from essential oil fractions, etc.) from the lignocellulosic substrate, and the fiber refining can, therefore, be performed simultaneously.
The extruder can also be used for its mixing ability: a natural binder (e.g., Organosolv lignins, protein-based oilcakes, starch, etc.) can be added to the refined fibers at the end of the screw profile. The obtained premix is ready to be molded through hot pressing, with the natural binder contributing to fiberboard cohesion. Such a combined process in a single extruder pass improves the production time, production cost, and may lead to reduction in plant production size. Because all the operations are performed in a single step, fiber morphology is better preserved, thanks to a reduced residence time of the material inside the extruder, resulting in enhanced material performances. Such one-step extrusion operation may be at the origin of a valuable industrial process intensification.
Compared to commercial wood-based materials, these fully bio-based fiberboards do not emit any formaldehyde, and they could find various applications, e.g., intermediate containers, furniture, domestic flooring, shelving, general construction, etc.

During the fiber refining of oleaginous flax shives using configuration (step 3.1.1), water was deliberately added at a liquid/solid ratio equal to 1.0. According to previous works25,26,27, such a liquid/solid ratio better preserves the length of the refined fibers at the twin-screw extruder outlet than lower ratios, which simultaneously contributes to an increase in their average aspect ratio. Furthermore, the amount of water a...

Watch this Scientific Journal Video about Twin-Screw Extrusion Process to Produce Renewable Fiberboards at JoVE.com

Twin-Screw Extrusion Process to Produce Renewable Fiberboards

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pretreatment on lignocellulosic biomass was developed, which leads to an increased average fiber aspect ratio. A natural binder can also be added continuously after fiber refining, leading to bio-based fiberboards with improved mechanical properties after hot pressing of the obtained extruded material.

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pre-treatment on lignocellulosic biomass before using it as ...

twin-screw-extrusion-process-to-produce-renewable-fiberboards

Research

JoVE Journal

Engineering

6.2K Views.  Université de Toulouse, INRAE, INPT. A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pretreatment on lignocellulosic biomass was developed, which leads to an increased average fiber aspect ratio. A natural binder can also be added continuously after fiber refining, leading to bio-based fiberboards with improved mechanical properties after hot pressing of the obtained extruded material.

Video: Twin-Screw Extrusion Process to Produce Renewable Fiberboards

How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a stable and continuous operation of the plasma is possible and the plasma torch can be used for many different applications. On one hand, the hot (3,600 K gas temperature) plasma can be used for chemical processes and on the other hand the cold afterglow (temperatures down to almost RT) can be applied for surface processes. For example chemical syntheses are interesting volume processes. Here the microwave plasma torch can be used for the decomposition of waste gases which are harmful and contribute to the global warming but are needed as etching gases in growing industry sectors like the semiconductor branch. Another application is the dissociation of CO2. Surplus electrical energy from renewable energy sources can be used to dissociate CO2 to CO and O2. The CO can be further processed to gaseous or liquid higher hydrocarbons thereby providing chemical storage of the energy, synthetic fuels or platform chemicals for the chemical industry. Applications of the afterglow of the plasma torch are the treatment of surfaces to increase the adhesion of lacquer, glue or paint, and the sterilization or decontamination of different kind of surfaces. The movie will explain how to ignite the plasma solely by microwave power without any additional igniters, e.g., electric sparks. The microwave plasma torch is based on a combination of two resonators &#8212; a coaxial one which provides the ignition of the plasma and a cylindrical one which guarantees a continuous and stable operation of the plasma after ignition. The plasma can be operated in a long microwave transparent tube for volume processes or shaped by orifices for surface treatment purposes.

This movie shows how an atmospheric plasma torch can be ignited by microwaves with no additional igniters and provides a stable and continuous plasma operation suitable for plenty of applications.

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a ...

A Cost-effective and Reliable Method to Predict Mechanical Stress in Single-use and Standard Pumps

Pumps are mainly used when transferring sterile culture broths in biopharmaceutical and biotechnological production processes. However, during the pumping process shear forces occur which can lead to qualitative and/or quantitative product loss. To calculate the mechanical stress with limited experimental expense, an oil-water emulsion system was used, whose suitability was demonstrated for drop size detections in bioreactors1. As drop breakup of the oil-water emulsion system is a function of mechanical stress, drop sizes need to be counted over the experimental time of shear stress investigations. In previous studies, the inline endoscopy has been shown to be an accurate and reliable measurement technique for drop size detections in liquid/liquid dispersions. The aim of this protocol is to show the suitability of the inline endoscopy technique for drop size measurements in pumping processes. In order to express the drop size, the Sauter mean diameter d32 was used as the representative diameter of drops in the oil-water emulsion. The results showed low variation in the Sauter mean diameters, which were quantified by standard deviations of below 15%, indicating the reliability of the measurement technique.

Shear stress investigations on an oil-water emulsion system result in drop breakup over the experimental time. To count drop sizes in pumping processes, the suitability of inline endoscopy was successfully demonstrated in this protocol.

Pumps are mainly used when transferring sterile culture broths in biopharmaceutical and biotechnological production processes. However, during the pumping ...

Integration of Light Trapping Silver Nanostructures in Hydrogenated Microcrystalline Silicon Solar Cells by Transfer Printing

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly known as plasmonic effects, play an important role. Research in this field has, however, been impeded owing to the difficulty of fabricating devices containing the desired functional metal nanostructures. In order to provide a viable strategy to this issue, we herein show a transfer printing-based approach that allows the quick and low-cost integration of designed metal nanostructures with a variety of device architectures, including solar cells. Nanopillar poly(dimethylsiloxane) (PDMS) stamps were fabricated from a commercially available nanohole plastic film as a master mold. On this nanopatterned PDMS stamps, Ag films were deposited, which were then transfer-printed onto block copolymer (binding layer)-coated hydrogenated microcrystalline Si (&#181;c-Si:H) surface to afford ordered Ag nanodisk structures. It was confirmed that the resulting Ag nanodisk-incorporated &#181;c-Si:H solar cells show higher performances compared to a cell without the transfer-printed Ag nanodisks, thanks to plasmonic light trapping effect derived from the Ag nanodisks. Because of the simplicity and versatility, further device application would also be feasible thorough this approach.

A viable transfer printing-based methodology to introduce plasmonic metal nanostructures in solar cells is described. Using nanopillar poly(dimethylsiloxane) stamps, an Ag-based ordered nanodisk array was integrated with standard hydrogenated microcrystalline Si solar cells, which led to improved device performances due to plasmonic light trapping.

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly ...

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their behavior for single stages of a process or even an entire process. For the simulation with occurring particle-particle and particle-wall contacts, the value of the coefficient of restitution is required. It can be determined experimentally. The coefficient of restitution depends on several parameters like the impact velocity. Especially for fine particles the impact velocity depends on the air pressure and under atmospheric pressure high impact velocities cannot be reached. For this, a new experimental setup for free-fall tests under vacuum conditions is developed. The coefficient of restitution is determined with the impact and rebound velocity which are detected by a high-speed camera. To not hinder the view, the vacuum chamber is made of glass. Also a new release mechanism to drop one single particle under vacuum conditions is constructed. Due to that, all properties of the particle can be characterized beforehand.

The coefficient of restitution is a parameter that describes the loss of kinetic energy during collision. Here, a free-fall setup under vacuum conditions is developed to be able to determine the coefficient of restitution parameter for particles in micrometer range with high impact velocities.

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

Challenges in Rheological Characterization of Highly Concentrated Suspensions &#8212; A Case Study for Screen-printing Silver Pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching.
The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. 
Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. 
A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

Challenges in Rheological Characterization of Highly Concentrated Suspensions &amp;#8212; A Case Study for Screen-printing Silver Pastes

A protocol for a robust and application relevant rheological characterization of highly concentrated suspensions is presented. Silver pastes used for screen-printing application in solar cell production are employed as model systems.

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the ...

Fabrication Procedures and Birefringence Measurements for Designing Magnetically Responsive Lanthanide Ion Chelating Phospholipid Assemblies

Bicelles are tunable disk-like polymolecular assemblies formed from a large variety of lipid mixtures. Applications range from membrane protein structural studies by nuclear magnetic resonance (NMR) to nanotechnological developments including the formation of optically active and magnetically switchable gels. Such technologies require high control of the assembly size, magnetic response and thermal resistance. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln3+) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive assemblies such as DMPC/DMPE-DTPA/Ln3+ (molar ratio 4:1:1) bicelles. Introduction of cholesterol (Chol-OH) and steroid derivatives in the bilayer results in another set of assemblies offering unique physico-chemical properties. For a given lipid composition, the magnetic alignability is proportional to the bicelle size. The complexation of Ln3+ results in unprecedented magnetic responses in terms of both magnitude and alignment direction. The thermo-reversible collapse of the disk-like structures into vesicles upon heating allows tailoring of the assemblies&#39; dimensions by extrusion through membrane filters with defined pore sizes. The magnetically alignable bicelles are regenerated by cooling to 5 &#176;C, resulting in assembly dimensions defined by the vesicle precursors. Herein, this fabrication procedure is explained and the magnetic alignability of the assemblies is quantified by birefringence measurements under a 5.5 T magnetic field. The birefringence signal, originating from the phospholipid bilayer, further enables monitoring of polymolecular changes occurring in the bilayer. This simple technique is complementary to NMR experiments that are commonly employed to characterize bicelles.

Fabrication procedures for highly magnetically responsive lanthanide ion chelating polymolecular assemblies are presented. The magnetic response is dictated by the assembly size, which is tailored by extrusion through nanopore membranes. The assemblies&#39; magnetic alignability and temperature-induced structural changes are monitored by birefringence measurements, a complimentary technique to nuclear magnetic resonance and small angle neutron scattering.

Bicelles are tunable disk-like polymolecular assemblies formed from a large variety of lipid mixtures. Applications range from membrane protein structural ...

Predicting Catalyst Extrudate Breakage Based on the Modulus of Rupture

The mechanical strength of extruded catalysts and their natural or forced breakage by either collision against a surface or by a compressive load in a fixed bed are important phenomena in catalyst technology. The mechanical strength of the catalyst is measured here by its bending strength or flexural strength. This technique is relatively new from the perspective of applying it to commercial catalysts of typical sizes used in the industry. Catalyst breakage by collision against a surface is measured after a fall of the extrudates through the ambient air in a vertical pipe. Quantifying the impact force is done theoretically by applying Newton's second law. Measurement of catalyst breakage due to stress in a fixed bed is done following the standard procedure of the bulk crush strength test. Novel here is the focus on measuring the reduction in the length to diameter ratio of the extrudates as a function of the stress.

Here we present a protocol to measure the modulus of rupture of an extruded catalyst and the breakage of said catalyst extrudates by collision against a surface or by compression in a fixed bed.

The mechanical strength of extruded catalysts and their natural or forced breakage by either collision against a surface or by a compressive load in a ...

Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement during previous phase changes and applied shear. To determine the extent of these changes, we have developed a microfluidic device that enables repeated phase transitions induced by exchange of the surrounding fluid and microrheological characterization while limiting shear on the sample. This technique is &#181;2rheology, the combination of microfluidics and microrheology. The microfluidic device is a two-layer design with symmetric inlet streams entering a sample chamber that traps the gel sample in place during fluid exchange. Suction can be applied far away from the sample chamber to pull fluids into the sample chamber. Material rheological properties are characterized using multiple particle tracking microrheology (MPT). In MPT, fluorescent probe particles are embedded into the material and the Brownian motion of the probes is recorded using video microscopy. The movement of the particles is tracked and the mean-squared displacement (MSD) is calculated. The MSD is related to macroscopic rheological properties, using the Generalized Stokes-Einstein Relation. The phase of the material is identified by comparison to the critical relaxation exponent, determined using time-cure superposition. Measurements of a fibrous colloidal gel illustrate the utility of the technique. This gel has a delicate structure that can be irreversibly changed when shear is applied. &#181;2rheology data shows that the material repeatedly equilibrates to the same rheological properties after each phase transition, indicating that phase transitions do not play a role in microstructural changes. To determine the role of shear, samples can be sheared prior to injection into our microfluidic device. &#181;2rheology is a widely applicable technique for the characterization of soft matter enabling the determination of rheological properties of delicate microstructures in a single sample during phase transitions in response to repeated changes in the surrounding environmental conditions.

We demonstrate the fabrication and use of a microfluidic device that enables multiple particle tracking microrheology measurements to study the rheological effects of repeated phase transitions on soft matter.

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement ...

O-cresol Concentration Online Measurement Based On Near Infrared Spectroscopy Via Partial Least Square Regression

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the prediction of the components in industrial processes. The ability to record spectra for solid and liquid samples without any pretreatment is advantageous and the method is widely used. However, the disadvantages of analyzing high-dimensional near-infrared spectral data include information redundancy and multicollinearity of the spectral data. Thus, we propose to use partial least squares regression method, which has traditionally been used to reduce the data dimensionality and eliminate the collinearity between the original features. We implement the method for predicting the o-cresol concentration during the production of polyphenylene ether. The proposed approach offers the following advantages over component regression prediction methods: 1) partial least squares regression solves the multicollinearity problem of the independent variables and effectively avoids overfitting, which occurs in a regression analysis due to the high correlation between the independent variables; 2) the use of the near-infrared spectra results in high accuracy because it is a non-destructive and non-polluting method to obtain information at microscopic and molecular scales.

The protocol describes a method of predicting o-cresol concentration during the production of polyphenylene ether using near-infrared spectroscopy and partial least squares regression. To describe the process more clearly and completely, an example of predicting the o-cresol concentration during the production of polyphenylene is used to clarify the steps.

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the ...

Optimized Sealing Process and Real-Time Monitoring of Glass-to-Metal Seal Structures

Residual stress is an essential factor to keeping the hermeticity and robustness of a glass-to-metal seal structure. The purpose of this report is to demonstrate a novel protocol to characterize and measure residual stress in a glass-to-metal seal structure without destroying the insulation and hermeticity of sealing materials. In this research, a femto-laser inscribed fiber Bragg grating sensor is used. The glass-to-metal seal structure that is measured consists of a metal shell, sealing glass, and Kovar conductor. To make the measurements worthwhile, the specific heat treatment of metal-to-glass seal (MTGS) structure is explored to obtain the model with best hermeticity. Then, the FBG sensor is embedded into the path of sealing glass and becomes well-fused with the glass as the temperature cools to RT. The Bragg wavelength of FBG shifts with the residual stress generated in sealing the glass. To calculate the residual stress, the relationship between Bragg wavelength shift and strain is applied, and the finite element method is also used to make the results reliable. The online monitoring experiments of residual stress in sealing glass are carried out at different loads, such as high temperature and high pressure, to broaden functions of this protocol in harsh environments.

Key procedures to optimize the sealing process and achieve real-time monitoring of the metal-to-glass seal (MTGS) structure are described in detail. The embedded fiber Bragg grating (FBG) sensor is designed to achieve online monitoring of temperature and high-level residual stress in the MTGS with simultaneous environmental pressure monitoring.

Residual stress is an essential factor to keeping the hermeticity and robustness of a glass-to-metal seal structure. The purpose of this report is to ...