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

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

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

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

"Natural Fiber Based Composites", edited by Philippe Evon (Printed Edition of the Special Issue Published in Coatings)

This book is a printed edition of the Special Issue "Natural Fiber Based Composites" that was published in Coatings and edited by Dr. Philippe Evon. Dr. EVON is Research Engineer at the Laboratoire de Chimie Agro-industrielle (LCA). He has the habilitation to supervise researches (HDR). He specializes in the valorization of wastes from biomass to produce extracts and to design agromaterials. He is mainly developing studies for using biomass as raw material for: - Producing bioactive extracts through fractionation processes using “green” solvents and the twin-screw extrusion technology as continuous extraction technique. - The manufacture of agromaterials by combining single- or twin-screw extrusion technologies with molding processes (e.g. injection-molding or thermopressing). He is the Manager of the LCA’s Industrial Technological Hall “AGROMAT” dedicated to agromaterial’s (https://www6.toulouse.inra.fr/lca/AGROMAT), which is located in Tarbes (South-West of France)

Procédés compacts pour le bioraffinage intégré de plantes entières : valorisation multi-produit à valeur ajoutée

Né dans les années 90, le concept de bioraffinerie (ou raffinerie du végétal) s’est formalisé autour de plusieurs critères : (i) envisager la transformation globale du végétal par fractionnement de la plante entière (y compris les co-produits de culture) afin de proposer une valorisation pour tous les constituants de la plante, et concevoir un procédé (ii) respectueux de l'environnement et (iii) économe. De nombreux travaux ont été réalisés dans ce sens au Laboratoire de Chimie Agro-industrielle concernant l’extraction, la séparation et la purification des constituants de la matière végétale, pour leur transformation chimique et la transformation en agromatériaux composites. En particulier, mon travail de Thèse de Doctorat (soutenue en Avril 2008) a été consacré au développement d’un nouveau procédé de bioraffinage du tournesol plante entière. De tels travaux se sont poursuivis ou sont en cours aujourd’hui au laboratoire, notamment à partir d’autres plantes oléagineuses comme le neem, le jatropha et la coriandre. Mon souhait pour les années à venir est de poursuivre ces recherches relatives à la raffinerie du végétal. De nouvelles utilisations industrielles pour les produits issus de tels procédés pourront ainsi être identifiées, dans des domaines énergétiques (biocarburants), non énergétiques (polymères, tensioactifs, solvants, lubrifiants, intermédiaires de synthèse, agromatériaux, etc.) et agroalimentaires