Obtenção e caracterização de compósito sanduíche de poliamida 11 e fibra de juta

Aliando boas propriedades mecânicas e de isolação térmica. Para isso, a poliamida 11 (PA 11) foi utilizada como matriz e a fibra de juta, como reforço. A PA 11 é um polímero termoplástico de origem renovável, fabricado a partir de óleo de mamona, conhecida por suas propriedades contra agentes químicos. A fibra de juta é a segunda fibra natural mais cultivada no mundo e é igualmente barata. O material compósito sanduíche foi criado a partir de uma termoprensa. A malha de juta foi utilizada pré-impregnada de PA 11 em alguns casos. Diversos compósitos foram criados, variando-se a pressão, tempo e temperatura. Após a caracterização, notou-se um aumento do módulo em flexão, tensão em flexão e módulo de Young de todos os compósitos em relação à uma referência, a pré-impregnação da juta também resultou em maior rigidez dos compósitos. O compósito sanduíche apresentou ganhos de no mínimo 3 vezes em tensão na flexão máxima em comparação à referência, e módulo em flexão teve também um aumento dessa proporção, mostrando que o compósito é promissor

The twin-screw extruder, a continuous liquid/solid extractor and separator during sunflower (Helianthus annuus L.) biorefinery

Biorefinery of sunflower whole plant can be conducted with water using a nine modules Clextral Evolum HT 53 twin-screw extruder (TSE). Aqueous extraction of oil is an environmentally cleaner alternative technology to solvent extraction. TSE carries out three unit operations: conditioning and grinding, liquid/solid (L/S) extraction and L/S separation. The compressing action by the reverse screws (CF2C) is essential for L/S separation. Positioned in module 9, CF2C screws push part of the mixture upstream against the general movement in TSE, and this counter pressure ensures the L/S separation efficiency above the metal filter, located in eighth position. Oil is extracted in the form of two emulsions, stabilized by phospholipids and proteins, and usable as co-emulsifiers in cosmetic industry. An aqueous extract containing water-soluble components from whole plant is also generated; it could be recycled. As a mixture of fibers and proteins, the cake can be moulded by thermo-pressing into boards, usable in the furniture and building industries. In this study, fractionation was conducted from next inlet flow rates: 54 kg/h solid and 183 kg/h water (3.4 L/S ratio). The screw speed varied from 249 to 124 rpm, corresponding to a filling coefficient (ratio of the solid inlet flow rate to the screw speed) from 217 to 436 g/h rpm. The filling coefficient directly affects the L/S separation efficiency. The latter can be estimated from next experimental data: the outlet flow rates of both cake and filtrate, the cake moisture content, the residual contents of oil and water-soluble components in the cake, and the extraction yields in dry matter, lipids and water-soluble components. For low filling coefficients (i.e. high screw speed), the L/S mixture compression in CF2C screws is insufficient, not allowing a satisfactory L/S separation. Conversely, for high filling coefficients (i.e. low screw speed), solid particles accumulate more upstream from the pressing zone, obstructing part of the filtering screens and thus reducing the filtration surface. A less efficient L/S separation is then observed. From the experimental data evolution, optimal screw speed was estimated at 182 rpm using a second order polynomial regression, corresponding to a filling coefficient of 297 g/h rpm. Extraction yields in dry matter, lipids and water-soluble components were 22%, 49% and 40%, respectively. Such filling would lead to a specific mechanical energy of 103 W/h kg whole plant processed

New insulation fiberboards from sunflower cake with improved thermal and mechanical properties

New insulation fiberboards from sunflower cake with improved thermal and mechanical properties were produced by pressing at ambient temperature. Best compromise between mechanical and heat insulation properties (λ = 77.6 mW/m K at 25°C) was a starch-based board with 20% binder content. Because of its promising heat insulation properties, this new fiberboard could be positioned on walls and ceilings for thermal insulation of buildings. The bulk cake was an even better insulation material (only 62.0 mW/m K for thermal conductivity at 25°C): usable as loose fill in the attics of houses

Thermopressed Binderless Fiberboards from Post-Harvest Tomato and Maize Plants

Post-harvest tomato plants were used to manufacture fireboards by thermopressing. Four plant materials were investigated: exhausted tomato plants ground to 5-10 mm (PHTr), tomato (PHT) and maize (PHM) plants ground to <0.5 mm, composted tomato plants (CPHT). These materials had significantly different chemical composition, which significantly influenced the fireboards mechanical properties. The PHM fireboards containing the highest amount hemicellulose and water soluble sugars, and the lowest minerals‘ amount, performed best. The data allow estimating the role of each plant proximate in determining board mechanical behavior. Moreover, the findings of the work prospect a desirable integration of municipal and agriculture biowastes as a step forward toward the valorization of renewable organic matter and the realization of the zero waste objective

Comparison between two different pretreatment technologies of rice straw fibers prior to fiberboard manufacturing: Twin-screw extrusion and digestion plus defibration

The present work compares two different pretreatment technologies, i.e. twin-screw extrusion, and steaming digestion plus defibration, for producing a thermo-mechanical pulp from rice straw for fiberboard manufacturing. Five liquid/solid ratios from 0.43 to 1.02 were tested for twin-screw extrusion pretreatment, while liquid/solid ratios from 4 to 6 were used for digestion pretreatment. Energy consumption, and characteristics of the extrudates (twin-screw extrusion) and pulps (digestion) (including fiber morphology, chemical composition, thermal properties, apparent and tapped densities, as well as color) were the analyzed parameters for the resulting lignocellulosic fibers. The results showed that liquid/solid ratio had influence on energy consumption of the equipment for both defibrating methods For the twin-screw extrusion method, a lower liquid/solid ratio required more energy while for the digestion plus defibration the effect was the opposite. The corresponding total specific energy consumption ranged from 0.668 kW h/kg to 0.946 kW h/kg dry matter for twin-screw extrusion, and from 6.176 kW h/kg to 8.52 kW h/kg dry matter for digestion plus defibration. Thus, the pulping method consumed about nine times more energy than that of the twin-screw extrusion. In addition, for twin-screw extrusion, the liquid/solid ratio did not have a substantial effect on fiber characteristics with similar chemical compositions and thermal properties. For twin-screw extrusion, the energy consumption was 37% reduced when the liquid/solid ratio was increased from 0.43 to 1.02. Instead, for digestion plus defibration, the energy increase was 38% when the liquid/solid ratio increased from 4 to 6

Innovative low-density blocks from amaranth pith for the thermal insulation of buildings

Amaranth is an annual herb native to temperate and tropical regions. Cultivated by Native Americans for the nutritional properties of its seeds, the latter are very digestible and also an interesting source of starch and proteins. For the future, amaranth appears as a promising raw material for the biorefinery of whole plants, all parts of the plant being potentially usable for different food and non-food applications. This study especially aims to investigate the possible uses of pith from stems for material applications. For that, plants from the Amaranthus cruentus variety were cultivated in 2018 near Auch (Gers, France). Stems were manually harvested at plant maturity. Representing up to 90% w/w of the aerial part of amaranth plant, stems were then dried in a ventilated oven to facilitate their conservation. They are composed of a bark on their periphery and a pith fraction in their middle. The structure of stems was studied from ten samples, and the pith fraction was estimated manually to 27% w/w. Due to the difference in density between bark and pith fractions, a fractionation process associating grinding and blowing steps made possible the continuous separation between bark and pith. As for sunflower and corn, amaranth pith particles have an alveolar (i.e. a microporous) structure similar to that of expanded polystyrene, and they reveal a very low bulk density (e.g. 48-52 kg/m3 for 4-16 mm particle size, and 58-61 kg/m3 for 1.25-2.50 mm particle size), making them a promising raw material for the thermal insulation of buildings. Cohesive and low-density insulation blocks were successfully obtained from amaranth pith, primarily mixed with a starch-based binder, through compression moulding at ambient temperature. Different operating conditions were tested, especially including (i) the size distribution of amaranth pith particles, (ii) the binder content, and (iii) the filling level of the mould. All produced samples were then characterized in terms of (i) density, (ii) bending and compression properties, and (iii) thermal insulation properties (measured through the hot wire method). All insulation blocks revealed low density, ranging from 90 to 140 kg/m3. Such innovative materials could be sustainable and viable options for the thermal insulation of buildings

Extraction of hemp fibres for load bearing composites. Minimisation of the extraction impact of processes such as scutching or “all fibre” extraction devices on the fibres mechanical properties

With the view to minimise the impact on the environment of composite materials all along their life cycle, numerous studies and reviews investigate the potential of renewable and recyclables fibres. Among them, bast fibres such as flax received a wide attention and commercial reinforcement products are now available on the market and are used in different composite load bearing applications (automotive, sport, furniture etc…). This is not the case of textiles based on hemp because the extraction techniques (hammer mills) are not adapted to minimise their impact on the fibres and severely reduce their properties

Post-harvest tomato plants and urban food wastes for manufacturing plastic films

Poly(vinyl alcohol-co-ethylene) was compounded with 2-10% post-harvest tomato (PHT) plant powder and processed by single-screw extrusion to yield composite films. Upon increasing the filler content, the values of the mechanical properties indicators were found to decrease as follows: Young's modulus from 1797 to 750 MPa, stress at yield from 36 to 15 MPa, maximal stress from 39 to 15 MPa, stress at break from 35 to 14 MPa, and strain at break from 6.6 to 4.3%. The results are discussed in comparison with other composite films containing poly(vinyl alcohol-co-ethylene) and water soluble biopolymers obtained by alkaline hydrolysis of fermented municipal biowastes, and with other commercial materials, such as starch based and low density polyethylene mulch films. Depending on the intended application, the post-harvest tomato blend films may be competitive for cost, performance and sustainability

Continuous mechanical extraction of fibres from linseed flax straw for subsequent geotextile applications

Linseed flax is a multipurpose crop. It is cultivated for its seeds and particularly for its oil. The main contributors for this crop are Canada, France and Belgium. In general, straws of linseed flax are buried in the fields or burnt. However, these solutions are not good practices for the environment and from an economical point of view. In this study, straws of linseed flax (six batches in total) with different dew retting durations and harvesting techniques were studied to possibly use them for producing innovative geotextiles. Two different fibre extraction processes were investigated. A first process (A) involved horizontal breaker rollers and then a breaking card. A second one (B) consisted in using vertical breaker rollers, and an “all fibre” extraction device (fibre opener) followed by sieving. The chemical composition of fibres in parietal constituents appeared to be globally equivalent to the one of textile flax with a pectic content decreasing as a function of the dew retting duration. This contributed to an increase in the cellulose content. The fibre content was situated in a range from 29% to 33%, which corresponds to a good yield for linseed flax fibre. The level of purity can reach values of up to 90% for method A (without extra-sieving) and 96% for method B (with extra-sieving), and the length of the fibres (larger for method A than for method B) and their tensile properties make them suitable for structural geotextile yarn manufacturing

The coriander straw, an original agricultural by-product for the production of building insulation materials

Straw represents 60-80% of the aerial part of coriander. It is cheap (90 €/ton including harvesting, bunching and transportation) and has an availability of 250 tons/year. However, the latter will grow strongly in the next five years due to the increasing use of vegetable oil from the fruits for food, cosmetics or the chemical industry. Due to its high lignocellulose content (62%), coriander straw is an interesting crop by-product for the production of bio-based building materials. Two types of insulating materials are presented here. Firstly, it is possible to produce bulk materials by thermo-mechano-chemical refining of straw with water using a twin-screw reactor. According to the applied liquid/solid ratio (0.4-1.0), it is possible to control the fiber aspect ratio of the refined straw (22.9-26.5) and thus the tapped density of the resulting bulk material (110-61 kg/m3). For the lowest density, the thermal conductivity was 47.3 mW/m K, corresponding to a 1.06 m2 K/W resistance for a 5 cm thickness of extrusion-refined straw. Twin-screw refining was also successfully conducted with an aqueous borax solution, allowing fire-proofing of the straw. When used as loose fill in housing, refined coriander straw is a promising solution for building insulation. Medium-density insulation blocks can also be manufactured using compression molding by combining coriander straw (milled or extrusion-refined) and a starch-based binder. The use of a milled straw (7.5 mm sieve) mixed with 15% binder, cold pressed (87 kPa, 30 s) and then dried, resulted in cohesive blocks with a 155 kg/m3 density and a 55.6 mW/m K thermal conductivity, corresponding to a 0.90 m2 K/W resistance for a 5 cm thickness. Similarly, such blocks could be used for the thermal insulation of buildings, including the filling of walls, interior partitions, etc