Twin-screw extrusion impact on natural fibre morphology and material properties in poly(lactic acid) based biocomposites

Natural fibres from miscanthus and bamboo were added to poly(lactic acid) by twin-screw extrusion. The influence of extruder screw speed and of total feeding rate was studied first on fibre morphology and then on mechanical and thermal properties of injected biocomposites. Increasing the screw speed from 100 to 300 rpm such as increasing the feeding rate in the same time up to 40 kg/h helped to preserve fibre length. Indeed, if shear rate was increased with higher screw speeds, residence time in the extruder and blend viscosity were reduced. However, such conditions doubled electrical energy spent by produced matter weight without significant effect on material properties. The comparison of four bamboo grades with various fibre sizes enlightened that fibre breakages were more consequent when longer fibres were added in the extruder. Longer fibres were beneficial for material mechanical properties by increasing flexural strength, while short fibres restrained material deformation under heat by promoting crystallinity and hindering more chain mobility

Manufacturing of renewable and biodegradable fiberboards from cake generated during biorefinery of sunflower whole plant in twin-screw extruder: Influence of thermo-pressing conditions

The starting material used in this study was a cake generated during thermo-mechanical fractionation of sunflower (Helianthus annuus L.) whole plant in a twin-screw extruder. It was slightly deoiled (16.7% of oil in dry matter). Composed mainly of fibers and proteins, it could be considered as a natural composite and was processed successfully into fiberboards by thermo-pressing. This study aimed to evaluate the influence of thermo-pressing conditions on mechanical and heat insulation properties of fiberboards manufactured from this cake. All fiberboards were cohesive, proteins and fibers acting respectively as binder and reinforcing fillers. Highest cake quantity (1000 mg/cm²) led to the highest breaking load (60.7 N) with a flexural strength at break quite low (2.9 MPa), lowest elastic modulus (216.6 MPa), and highest Charpy impact strength (6.5 kJ/m² for resilience). The increase of pressure applied during molding (from 320 to 360 kgf/cm²) led to an important increase of elastic modulus (from 352.6 to 728.6 MPa). Besides, fiberboard molded at 360 kgf/cm² was the most rigid of this study, and logically revealed the most important Shore D surface hardness (52.6°). Moreover, lowest molding time (60 s) led to the highest flexural strength at break (3.9 MPa). The low density of the fiberboards (less than 0.97) involved promising heat insulation properties. Indeed, thermal conductivity of fiberboards at 25 °C was low (from 103.5 to 135.7 mW/m K), and decreased with the increase of thickness. According to their mechanical and heat insulation properties, fiberboards would be potentially usable as inter-layer sheets for pallets, for the manufacture of biodegradable containers (composters, crates for vegetable gardening) by assembly of fiberboards, or for their heat insulation properties in building industry. Moreover, thermo-pressing was not only a molding operation. It also improved the oil extraction efficiency as a part of residual oil was expressed from cake during molding, and total oil yield reached 79.3% with a pressure applied of 360 kgf/cm²

Thermo-mechanical behaviour of the raffinate resulting from the aqueous extraction of sunflower whole plant in twin-screw extruder: manufacturing of biodegradable agromaterials by thermo-pressing

Biorefinery of sunflower whole plant can be realized using a twin-screw extruder. Thermo-mechanical fractionation and aqueous extraction are conducted simultaneously. A filter section is outfitted along the barrel to collect continuously an extract and a raffinate (cake meal). Oil yield obtained is 53%. Proteins are partly extracted at the same time, just as pectins and hemicelluloses. Protein yield is 46%. Cake meal is relatively moist (66% for the moisture content). It is first dried to make easier its conservation. It is largely composed of lignocellulosic fibres (59% of the dry matter) from depithed stalk. Lipid content is 13% of the dry matter or 35% of the oil in whole plant. Protein content is 7% of the dry matter or 45% of the proteins in whole plant. DSC measurements indicate that denaturation of proteins is almost complete in the cake meal. DMTA spectrum of its milled powder reveals a significant peak at high temperature (between 175 and 200°C). As already observed with industrial sunflower cake meal, it can be associated with the glass transition of proteins. As a mixture of fibres and proteins, the cake meal can be considered as a natural composite. It is successfully processed into biodegradable and value-added agromaterials by thermo-pressing. As for DMTA analysis, the glass transition of proteins in the cake meal is also observed with PVT analysis at around 180°C. It makes easier the choice of the best thermo-pressing conditions to produce panels with higher mechanical properties in bending. These properties increase simultaneously with temperature, pressure and time chosen for molding operation. The highest flexural strength at break (11.5 MPa) and the highest elastic modulus (2.22 GPa) are obtained for the next molding conditions: 200°C and 320 kgf/cm2 during 60 s. Drop angle measurements show that the corresponding panel is also the most resistant to water. No significant transition is observed inside this panel above 0°C and until 200°C with DMTA analysis. Proteins ensure the agromaterial cohesion without any phase change in this temperature range, and fibres entanglement also acts like reinforcement. This panel could be used as inter-layer sheets for pallets or for the manufacturing of biodegradable containers (composters, crates for vegetable gardening) by assembly of panels

Twin-screw extrusion technology for vegetable oil extraction: A review

Vegetable oils present a valuable class of bioresources with applications in both food and non-food industries and a production that has been steadily increasing over the past twenty years. Their extraction from oilseeds is a key process, as it exerts a strong impact on the resulting oil characteristics and quality. In view of the recent pressure towards sustainability, oilseed processing industries are taking renewed interest in thermomechanical pressing as a means to obtain high quality oils. This work focuses on twin-screw extrusion for vegetable oil extraction and reviews recent technological advancements and research challenges for the design and optimization of novel oil extraction processes. It comprises a critical analysis of the application of twin-screw extruders against their more conventional single-screw counterparts. Further, a comprehensive overview of the key parameters influencing the process performance is provided, while considerable attention is given to the development of innovative green extraction processes using twin-screw extrusion

The twin-screw extrusion technology, an original and powerful solution for the biorefinery of sunflower whole plant

The objective of this study was to evaluate the feasibility of an aqueous process for the biorefinery of sunflower whole plant using a twin-screw extruder. Aqueous extraction of oil was chosen as an environment-friendly alternative to the solvent extraction. The extruder was used to carry out three essential unit operations: grinding, liquid/solid extraction, and liquid/solid separation. Wringing out the mixing was effective. However, drying of the cake meal was not optimal. Lixiviation of cotyledon cells was also incomplete. Extraction efficiency depended on operating conditions: screw rotation speed, and input flow rates of whole plant and water. In the best conditions, oil yield was 57%. Residual oil content in the cake meal was 14%. These conditions leaded to the co-extraction of proteins, pectins, and hemicelluloses. The corresponding protein yield was 44%. Oil was extracted in the form of two oil-in-water emulsions. These hydrophobic phases were stabilized by phospholipids and proteins at interface. An aqueous extract containing part of the water-soluble constituents, mainly proteins and pectins, was also generated. As a mixture of fibers and proteins, the cake meal was molded by thermo-pressing. Panels produced had interesting mechanical properties in bending. The obtained fractions may have applications as bases for industrial products

Extraction of oil from jatropha seeds using a twin-screw extruder: Feasibility study

The objective of this study was to evaluate the feasibility of mechanical pressing to extract oil from jatropha seeds using a twin-screw extruder. Experiments were conducted using a co-rotating (Clextral BC 21, France) twin-screw extruder. The influence of operating conditions on oil yield, specific mechanical energy and oil quality was examined. Operating conditions included screw configuration, pressing temperature and screw rotation speed. Generally, it was the screw configuration, or profile, that most affected oil extraction efficiency. The best oil yields, a minimum 57.5%, were obtained with a trituration zone composed of 10 monolobe and 10 bilobe paddles, and a pressing zone composed of 50 mm long, reverse pitch screws with a −33 mm pitch. In addition, oil extraction yield increased with decreasing temperature and screw rotation speed. Highest oil extraction yield (70.6%) with good press cake quality (residual oil content lower than 8%) was obtained under operating conditions of 153 rpm screw rotation speed, 5.16 kg/h inlet flow rate of jatropha seeds, and 80 ◦C pressing temperature. The corresponding expressed oil was inexpensive to produce (71 W h/kg seed processed or 314 W h/kg expressed oil for specific mechanical energy) compared with another continuous technique, i.e. the single expeller press, commonly used for mechanical extraction of jatropha oil. Its quality was also satisfactory for biodiesel production. The acid value, the density and the kinematic viscosity were 5.4 mg of KOH/g of oil, 915 kg/m3 and 36.7×10−6m2/s, respectively

Thermo-pressing of cake meal from sunflower whole plant, one only operation for two actions : expression of residual oil and molding of biodegradable agromaterials

The starting material used in this study was a cake generated during thermo-mechanical fractionation of sunflower (Helianthus annuus L.) whole plant in a Clextral BC 45 (France) twin-screw extruder. It was slightly deoiled (17.6% dry matter for residual oil content), leading to an oil extraction yield of 46.1% (yield based on the residual oil content in cake). As it was a mixture of fibers and proteins, it could be considered as a natural composite that was processed successfully into fiberboards by thermo-pressing. This study aimed to evaluate the influence of thermo-pressing conditions on oil expression yield during molding and on flexural properties of fiberboards manufactured from this cake. An experimental design with three variables was realized: from 250 to 500 kgf/cm² for pressure applied (in 5 levels), from 60 to 300 s for molding time (in 7 levels), and from 600 to 1200 mg/cm² for cake quantity (in 3 levels). Temperature of the aluminium mold positioned between the two plates of the heated hydraulic press (PEI, France) with 400 tons capacity was 200°C. All fiberboards were cohesive. As an internal binder, proteins ensured the agromaterial cohesion, and fibers entanglement also acted like reinforcement. Thermo-pressing was not only a molding operation. It also consisted in increasing the oil extraction efficiency. Oil expression yield during molding increased with the increase of pressure applied, and especially with the increase of molding time. At the same time, it was not so much influenced by the modification of cake quantity. Highest oil expression yield was 58.8% in proportion to the oil that the cake contained, leading to a total oil yield (oil extracted by water in twin-screw extruder, and oil expressed during molding) of 77.8% in proportion to the oil that the sunflower whole plant contained. It was associated with the next thermo-pressing conditions: 469 kgf/cm² for pressure applied, 300 s for molding time, and 697 mg/cm² for cake quantity. Flexural properties of the corresponding fiberboard were 8.1 MPa for flexural strength at break, and 1778 MPa for elastic modulus. Its thickness was 5.40 mm, leading to a mean apparent density of 1.25. Such flexural strength at break was a bit lower (-25%) than the one of the most resistant fiberboard (10.8 MPa), manufactured from the next thermo-pressing conditions: 250 kgf/cm² for pressure applied, 300 s for molding time, and 807 mg/cm² for cake quantity. For such conditions, oil expression yield was 48.0% in proportion to the oil that the cake contained, leading to a total oil yield close (-8%) to the highest yield obtained (71.9% in proportion to the oil that the sunflower whole plant contained instead of 77.8%). Thermo-pressing of cake from sunflower whole plant led to two actions in a single step: the expression of part of residual oil in cake that contributed to the improvement of the oil extraction efficiency, and the molding of biodegradable fiberboards. Their flexural properties were promising. Moreover, because residual oil content in fiberboards was at least 8.0% dry matter, they were not too water-sensitive (i.e. more durable than other thermo-pressed agromaterials). Such fiberboards were value-added agromaterials that may have direct industrial applications. Indeed, they would be potentially usable as inter-layer sheets for pallets, for the manufacturing of biodegradable containers (composters, crates for vegetable gardening), or for their heat insulation properties in building trade

Participation of green organs to grain filling in triticum turgidum var durum grown under mediterranean conditions

In wheat, flag leaf, stem, chaff and awns contribute to grain filling through photosynthesis and/or re-mobilization. Environmental and genetic effects on the relative contribution of each organ were examined by analyzing the consequences of sink-source manipulations (shading and excision) and by comparing carbon isotope discrimination (D) values in dry matter (at maturity) and sap (two weeks after anthesis) in six durum wheat genotypes grown in two contrasting seasons. The contribution of flag leaf, stem, chaff and awns to grain filling, estimated by sink-source manipulations, highly varied with the season. The contribution of ear photosynthesis and re-mobilization from the stem increased with post-anthesis water stress. They showed a large genetic variation that was, however, not clearly associated to morphological characteristics of ear and stem. Isotopic imprints of chaff on grain D were identified as a possible surrogate of the destructive and cumbersome sink-source manipulations to evaluate the contribution of carbon assimilated in ears or re-mobilized from stem. This might facilitate screening of genetic resources and allow the combining of favourable drought tolerance mechanisms in wheat

New thermal insulation fiberboards from cake generated during biorefinery of sunflower whole plant in a twin-screw extruder

The objective of this study was to manufacture new thermal insulation fiberboards by thermo-pressing. The starting material was a slightly deoiled cake (17.6% oil content), generated during the biorefinery of sunflower (Helianthus annuus L.) whole plant in a co-rotating (Clextral BC 45, France) twin-screw extruder. All fiberboards produced were cohesive mixtures of proteins and lignocellulosic fibers, acting respectively as binder and reinforcing fillers in what could be considered as a natural composite. The molding experiments were conducted using a 400 ton capacity heated hydraulic press (Pinette Emidecau Industries, France). The influence of molding conditions on board density, mechanical properties and heat insulation properties was examined. Molding conditions included mold temperature (140-200°C), pressure applied (150-250 kgf/cm²) and molding time (40-76 s), and these greatly affected board density and thus the mechanical and heat insulation properties. Board density increased with increasingly extreme molding conditions, rising from 500 to 858 kg/m³. The mechanical properties increased at the same time (from 52 to 660 kPa for flexural strength at break, from 5.9 to 49.4 MPa for elastic modulus, from 0.5 to 7.7 kJ/m² for Charpy impact strength, and from 19.2 to 47.1° for Shore D surface hardness). Conversely, heat insulation properties improved with decreasing board density, and the lowest thermal conductivity (88.5 mW/m K at 25°C) was obtained with the least dense fiberboard. The latter was produced with a 140°C mold temperature, a 150 kgf/cm² pressure applied and a 40 s molding time. A medium mold temperature (160°C) was needed to obtain a good compromise between mechanical properties (272 kPa for flexural strength at break, 26.3 MPa for elastic modulus, 3.2 kJ/m² for Charpy impact strength, and 37.3° for Shore D surface hardness), and heat insulation properties (99.5 mW/m K for thermal conductivity).The corresponding board density was medium (687 kg/m³). Because of their promising heat insulation properties, these new fiberboards could be positioned on walls and ceilings for thermal insulation of buildings. The bulk cake also revealed very low thermal conductivity properties (only 65.6 mW/m K at 25°C) due to its very low bulk density (204 kg/m³). It could be used as loose fill in the attics of houses

Nouveau procédé de bioraffinage du tournesol plante entière par fractionnement thermo-mécano-chimique en extrudeur bi-vis : étude de l'extraction aqueuse des lipides et de la mise en forme du raffinat en agromatériaux par thermomoulage

L'extraction aqueuse des lipides de la graine de tournesol est étudiée en contacteur agité. La diffusion à l'intérieur des particules est le facteur limitant de l'échange de matière. Les protéines sont impliquées dans l'entraînement et la stabilisation des lipides par l'eau. Le fractionnement de la plante entière est également étudié avec l'eau en extrusion bi-vis. Un extrait et un raffinat sont obtenus séparément et en une seule étape continue. Des rendements d'extraction en huile de 55 % peuvent être obtenus sous forme d'émulsions huile/eau. Leur stabilité est assurée par la présence à l'interface de tensioactifs : les phospholipides et les protéines voire les pectines. Les extraits se composent aussi d'une phase hydrophile. Prépondérante, elle contient des composés hydrosolubles (protéines, pectines…). Riches en fibres, les raffinats présentent une teneur significative en protéines au comportement thermoplastique. Ils peuvent être transformés en agromatériaux par thermomoulage