Flax Shives Research Articles

Flax shives-PBAT processing into 3D printed fluorescent materials with potential sensor functionalities

Incorporation of unused agricultural by-products into materials is a relevant strategy in developing biosourced and economically competitive products that limits the environmental impacts of plastics. Development of 3D printing techniques offers the possibility to design such biomaterials while bringing new functionalities, however, it is critical to characterize and control both the plant material properties and the interactions between the plant material and the polymeric matrix during the whole process, from filament production to 3D printing. In this study, flax shives were selectively milled and then used as a starting material to be grafted to a fluorophore whose fluorescence varies under pH. The resulting fluorescent shives were processed with poly-(butylene-terephthalate) (PBAT) by extrusion to produce a filament reinforced with 10 %-wt of flax shives, which was the subsequently 3D printed. Extensive microstructural characterization (particle size and shape analysis, X-ray microtomography) demonstrated that the flax particles were homogeneously distributed into the 3D printed material. Despite the relatively low content of fluorescent flax shives in the final 3D printed material (1%-wt) and successive heating stages (during extrusion and 3D printing), a strong fluorescent emission could still be measured. This work paves the way for using fluorescent flax shives as reinforcements into composites, thus making 4D materials with potential applications as sensors depending on the fluorophore used.

Performance of particleboards based on annual plant byproducts bound with bio-adhesives

Because the timber market is more and more competitive, the particleboard manufacturers are looking for new sources of plant raw material. In the same time, the use of healthier, safer and more environmentally friendly materials becomes a priority in the building sector. In this context, using bio-based adhesives to bond the particles instead of the synthetic ones is an interesting alternative. In the same time agricultural byproducts as annual plant stems can be a sustainable alternative raw material. These resources are abundant, renewable and safe raw material. Moreover, their porous structure gives them interesting properties for building materials such as lightness and thermal insulation capacity. Two agricultural byproducts abundant in France have been studied: flax shives and sunflower bark. Particleboards were made at laboratory scale by thermocompression of the plant raw particles to a target density of 500 kg m−3. The plant particles were bond by different methods:- * without addition of any adhesive. In that case water was sprayed on the plant particles before the forming process and was evaporated during the thermocompression. It leads to extraction of soluble and lignocellulosic compounds from the agroresources that can act as adhesives.- * with addition of a biobased adhesive based on casein, the protein from bovine milk, or based on a commercial caseinate, added at different ratios to the plant particles.- The effect of the type of agroresources, the particle size, the formulation of the biosourced adhesive, and its application are evaluated testing the physico-chemical properties of the particleboards: mechanical properties (bending test and internal bond), thermal properties, and behavior towards water and fire. Using a biobased adhesive improves the mechanical properties of the particleboards significantly compared to the version without added adhesive. Panels made with flax shives generally showed better properties than with sunflower bark, so flax shives seem more suitable for particleboard manufacturing. But after optimization of the formulation and the process, both raw materials could be used with casein-based adhesive yielding efficient and fully biobased particleboards for applications such as furniture or door panels.

Flax shive as a source of activated carbon for adsorption of methylene blue

The application of carbon as an adsorbent is a well-known method of removal of chemical pollutants, including dyes, from waste waters. However, a lot of attention is now being paid to improving the adsorbent efficiency and searching for cheap precursors for activated carbon (AC) production. In this work, AC is obtained from flax shive by its physical and chemical activation with KOH. The pyrolysis process and mechanism of KOH activation are studied using thermogravimetric analysis. The methods of X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and low-temperature nitrogen adsorption are used to determine the AC characteristics. The AC ability to adsorb the methylene blue (MB) dye is studied. The effect of the properties of the synthesized AC on the MB equilibrium adsorption capacity is analyzed. The maximum BET surface area of the AC is equal to 1832.2 m2/g, which means its values lie in the range typical of industrial activated carbons. The maximum equilibrium adsorption capacity of MB is 464.2 mg/g. The AC adsorption capacity depends on the cellulose content in the flax shive and pore size distribution over the carbon matrix. The use of lignocellulosic biomass, namely flax shive, in the AC production is associated with solving environmental problems, such as agricultural waste recycling and disposal.

Energy optimization of bio-oil production from biomass by fast pyrolysis using microwaves

Microwave fast pyrolysis leads to higher bio-oil production for flax shives than other biomass. An high heating rate and an optimum energy input are required for maximum bio-oil production. Gas and oil composition is stable with operating conditions.

Reductive Catalytic Fractionation of Flax Shive over Ru/C Catalysts

Flax shive is the main waste (up to 70 wt %) in the production of flax fiber. It represents the lignified parts of the flax stem mainly in the form of small straws. Complex processing of such wastes is a significant problem due to the heterogeneity of the chemical structure of lignin. This article presents the results of reductive catalytic fractionation (RCF) of flax shive in ethanol and isopropanol at elevated temperatures (225–250 °C) in the presence of a bifunctional catalyst (Ru/C) and molecular hydrogen. This provides solvolytic depolymerization of lignin and hemicelluloses presented in flax shive. Catalytic hydrogenation effectively stabilizes the formed lignin intermediates and prevents repolymerization reactions producing the lignin fraction with a high degree of depolymerization. RCF of flax shive produces solid products with a high cellulose content and liquid products consisting mainly of monophenolic compounds. Furthermore, the effect of different characteristics (the ruthenium content, particle size, and support acidity) of the bifunctional catalysts containing ruthenium nanoparticles supported on mesoporous, graphite-like carbon material Sibunit®-4 on the yield and composition of the products of hydrogenation of flax shive in sub- and super-critical ethanol has been studied. Bifunctional catalysts Ru/C used in the RCF of flax shive increase its conversion from 44 to 56 wt % and the yield of monophenols from 1.1 to 10.2 wt % (based on the weight of lignin in the sample). Using the best Ru/C catalyst containing 3% of Ru on oxidized at 400 °C carbon support, the high degree of delignification (up to 79.0%), cellulose yield (up to 67.2 wt %), and monophenols yield (up to 9.5 wt %) have been obtained.

Synthesis and characterization of flax shive activated carbon

Concern on dyes-laden effluent has intensified over the years. Dyes are toxic, stable to light hardly bio-degraded and cause irreparable harm to living organisms. Adsorption is widely recognized as an effective way to remove colorants from wastewater. Nevertheless, the search for improving the efficiency of adsorption is constantly being carried out with the help of new cheap activated carbon (AC). For adsorption studies, we used activated carbon obtained by pyrolysis of flax shive activated with K2CO3. Using X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, IR spectroscopy, low-temperature nitrogen adsorption, thermogravimetry, the characteristics of the AC were obtained. The effect of AC characteristics on the equilibrium adsorption capacity of methylene blue (MB) was studied. The maximum BET surface area of the AC equals 1246.1 and 1468.0 m2/g, which means its values are in the range typical of commercial activated carbons. The maximum equilibrium capacity of the obtained AC samples to adsorb the MB dye is 319.1 and 388.5 mg/g. The capacity for the activated carbons depended on the pyrolysis temperature, and cellulose content in flax shive and pore size distribution in carbon matrix. Converting lignocellulosic biomass into activated carbon could solve environmental problems such as agricultural waste and water pollutions control.

High performance electrospun carbon nanofiber mats derived from flax lignin

Flax (Linum usitatissimum) is an abundant source of natural fiber that is industrially cultivated globally for the production of linen as well as for linseed oil. Flax shives isolated from these operations represent a significant source of underutilized biomass. This study reports a novel method to delignify flax shives, describes the characteristics of the isolated flax lignin, and the properties of carbonized fiber derived from the lignin. Knife-milled flax straw was pretreated using a glycerol thermal process that permitted the fractionation of lignin via solvent extraction. The resulting lignin was characterized for its thermal properties, chemical structure, and molecular weight using differential scanning calorimetry, 31P nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and gel permeation chromatography. Additionally, the isolated lignin was transformed into continuous nanofiber mats by electrospinning, using blends of lignin and differing concentrations of polyethylene oxide (PEO). The addition of PEO as a co-processing polymer facilitated the production of uniform nanofibers without defects, such as beading. As-spun nanofiber mats were thermally stabilized in an oxygen environment and subsequently carbonized at 1000 °C. The ensuing nanofiber mats had similar mechanical properties to carbon nanofiber mats spun from softwood kraft lignin, and outperformed those derived from organosolv processed hardwoods.

Effect of flax shives content and size on the hygrothermal and mechanical properties of flax concrete

This paper presents an experimental investigation of the hygrothermal and mechanical properties of green concrete containing different content and size of flax shives. This allows it to respond to different applications in the building domain. Results of microscopic observations by using scanning electron microscopy show that the flax shives have a very complex and porous microstructure. The latter allowed for good hydric and thermal behaviour with a high moisture buffer capacity of which the minimum and maximum were 2.03 and 2.82, respectively. This allows it to be classified as an excellent moisture regulator. Flax concrete with a mass composition of 14.5% of flax shives in bulk, 35% of binder (tradical PF70) and a water-to-binder ratio of 1.45 gave a bio-based material with an average compressive strength of 0.8 MPa; it is, therefore, used as an insulation and filling material in buildings.

The potential of flax shives as reinforcements for injection moulded polypropylene composites

Flax shives (FS) represent approximately 50 % in weight of dry flax stems, making it the main by-product of the flax scutching industry. Being an available and low-added value lignocellulosic resource, flax shives are an interesting candidate for thermoplastic composite reinforcement. In this study, raw flax shives were fragmented by knife milling using two grids of 500 and 250 μm respectively, while a third batch, with a targeted particle size below 50 μm, was obtained by an attrition beads mill. The fragmentation methods used do not modify the biochemical composition of FS but do reduce their crystallinity due to both crystalline cellulose allomorph conversion and amorphization. The poly-(propylene) and 4%-wt maleic anhydride modified poly-(propylene) injection moulded composites produced with these reinforcing materials have a maximum tensile strength that evolves linearly with particle aspect ratio after processing. The tensile Young’s modulus of the composites reinforced by coarser particles is 3268 ± 240 MPa, which is almost 90 % that obtained for a reference 1mm flax fibre reinforced composite. Furthermore, a basic micromechanical model was applied highlighting the reinforcing capacity of cell wall-like small tubular structures (e.g. flax shives). This study underlines the reinforcing potential of low-value by-product flax shives for value-added composite applications.

The influence of oil pollution and carriers of biological product on the agrophysical indicators of sod-podzolic soils

The article presents the results of the influence of various aerating agents, carriers of new generation oil-oxidizing biological product on the agrophysical parameters of sod-podzolic soil highly contaminated with oil (up to 10%), and on the rate of oil decomposition in it. The studies were carried out in a microfield experiment in the conditions of the Udmurt Republic. It was established that during the growing season of 2019 all studied carriers of the biological product had positive effect on these indicators, however, the parameters of the changes were determined by their types. Thus, the application of sawdust, barley straw and flax shive into the soil provided an increase in the structural coefficient by 0.83-0.99 units or 35-43 %. All studied carriers of the biological product statistically significantly reduced the density of the contaminated soil, the greatest effect on this indicator was exerted by flax shive (by 0.42 g/cm3 or 32 %) and sawdust (by 0.34 g/cm3 or by 26 %). The application of vermiculite increased the productive moisture content in the contaminated soil most significantly - by 115 m3 /ha or by 50.7 %. The improvement of agrophysical properties of oil-contaminated soil by carriers of the biological product increased drastically the effectiveness of the preparation for oil decomposition. The greatest effect on this indicator (by 9.9-10.9 mg/kg or 40.2- 44.3 %) was exerted by the biological product in combination with flax shive, lignin and straw. The application of organomineral fertilizers into the contaminated soil also improved the agrophysical properties of oil-contaminated soils significantly and reduced the residual oil content in it by 13.0 mg/kg or 52.8 %.

Thermal conversion of flax shives through slow pyrolysis process: in-depth biochar characterization and future potential use

In this paper, the potential of flax shives use as sustainable materials for environmental and energy applications is assessed. In particular, raw flax shives and their pyrolytic chars produced at three different temperatures (400, 500, and 600 °C) are fully characterized using several analytical techniques including thermogravimetric analysis (TGA), X-ray fluorescence (XRF), scanning electronic microscopy (SEM), CO2 adsorption, Raman spectroscopy, and DRIFT (diffuse reflectance infrared Fourier transform) spectroscopy. Furthermore, thermogravimetric analyses and their derivative (TGA/DTG) during the thermal degradation of the flax shives were used to deduce the corresponding kinetic data. These latter were calculated using three different models: Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The main results indicate that the raw flax shives have high potential in co-firing, which is very close to usual energy vectors in some rural contexts and even more enhanced compared to many other biomasses used in industrial fields. They can also be an attractive carbon source for agricultural soils. Furthermore, the chars derived from flax shives contain important rates of mineral species such as calcium, potassium, magnesium, and phosphorous, which allow their reuse as low-cost amendments for agricultural soils. At the same time, the surface area and the microporous structure of the flax shives biochars are developed enough allowing them to be used as effective adsorbents for pollutants contained in gaseous phase. After an activation step, these biochars’ physico-chemical properties could be significantly improved permitting their application as promising materials for soil bioremediation or wastewater treatment.

High-yield cellulose hydrolysis by HCl vapor: co-crystallization, deuterium accessibility and high-temperature thermal stability

Hydrochloric acid hydrolysis in its gas form was used to produce cellulose nanoparticles from flax shives with a very high yield (> 90%). The efficiency of the transformation was examined by gravimetry, atomic force microscopy and transmission electron microscopy. A novel purpose-built anisotropic line-broadening X-ray diffraction model was used. This XRD method uses a parametric shape in order to address the issue of strongly broadened and overlapping Bragg rays that are characteristic of nano-sized crystallites. This method demonstrated the remarkable stability of the crystallite shapes during hydrolysis and its sensibility was sufficient to detect a minor co-crystallization along the hydrophilic faces. The presence of amorphous material strictosensu in the form of individual and randomly oriented chains was not necessary to describe the diffractograms accurately. Thermal FTIR with isotopic exchange was also performed using deuterium oxide to characterize the accessibility of the materials between 20 and 260 °C. Further, back-exchange experiments were performed in order to quantify the hysteretic amount of deuterium that was trapped by microstructural reorganization. These experiments showed that hydrolysis cancelled any form of deuterium trapping (water-induced co-crystallization). For the first time, thermal FTIR demonstrated that isotopic labelling of cellulose sources can produce false positives when conducted at room temperature and thermal FTIR can unambiguously distinguish between labelled cellulose groups and free deuterium oxide, which is paramount when measuring the higher accessibility of the nanocelluloses. It was also demonstrated that the high-temperature hydrogen bond reorganization and thermal degradation of the cellulose chains strongly depend on the hydrolysis and on the microstructure of the substrate.

Mechanical behavior of flax-lime concrete blocks made of waste flax shives and lime binder reinforced with jute fabric

Due to the increase in production of construction materials, the emission of carbon dioxide levels and the requirement for producing materials with a less environmental footprint is gaining more attention. This paper focuses on the study of a special kind of concrete (without stone aggregates) called flax-lime concrete to decrease amount of environmental footprint via the use of a lime-based binder with a waste material of flax fiber production (i.e. flax shives). Nine flax-lime concrete beam specimens (51 mm × 152 mm x 610 mm) with the same mix proportions were prepared. A layer of jute fabric mesh was also placed at the center of the specimens as a reinforcement. The position and number of layers of the fabric mesh were varied to improve the load capacity and deflection under three-point bending. The physical and mechanical properties (namely: density, load-carrying capacity, failure mode, and load-deflection behavior) of the flax-lime concrete specimens were studied. Overall, the variation in position and number of layers of jute fabric increased the bending capacity and energy absorption in flax-lime concrete blocks. The system can be used in buildings for infilling masonry blocks and filling wall cavities as insulation materials.

Hygrothermal behaviour of flax shives used as insulation material in an attic of a traditional house

Western Europe area is one of the world regions where traditionally flax is grown. Whether in France or Belgium, flax is mainly used for the production of fabrics. When separating the different components of the plant, small woody elements called shives which represented about 50% of the production, are recovered. This work aims to study the behavior of flax shives used as insulation material in an attic of a French Flanders traditional house. Main scientific issues related to the study of heat and mass transfer is to determine the evolution of the thermal characteristics of the material and its durability. First, we propose a laboratory analysis of the hygrothermal behavior of shives by conventional thermal methods for characterizing thermal conductivity and volumetric heat (heat flux method), sorption curve is also determined. Then we focus on an experimental site which is an independent house where the old insulation of the attic in glass wool was replaced by flax shives. The hygrothermal behavior of this new insulation was monitored with humidity and temperature sensors for ten months. The thermal performances determined for a raw form of the shives in the laboratory are encouraging and hygrometric results show advantageous behavior whatever the season.

Structural and thermal insulation products based on vegetable raw materials

The author of the article addresses the issues of obtaining insulation products based on flax shives. The article suggests a systematization method for the flax shives based materials, which takes into account the principle of obtaining construction materials based on flax processing waste on various types of binders. It is based on the literature data and the existing research. The possibility of using flax shives as a large structure-forming aggregate of concrete is determined along with the composition and properties of organic aggregate - flax shives. The article presents the optimal ratios selection of flax and binding bonfires in the preparation of granular materials. The characteristics of granulated aggregates on the basis of flax shives are given. The manufacture of cob granules was carried out in two technological ways: on a complex binder and on mineral binders with “dusting” with portland cement. The the method involving the coating of granules with a cement shell was used to produce a granulated material with higher rates of adhesion to the hardened stone of mineral binders in the concrete composition. The technological parameters of the granulation process are determined for two technological methods.

The technology of producing sorbents from linseed flax shive

Flax processing waste, flax shive is of great importance for producing sorbents from non-wooden materials in Russia. There are more than 700 thousand hectares of linseed flax crops in the country. Linseed flax shive had been burned everywhere until recently as there was no technology of its processing. The waste disposal problem in the linseed flax cultivation regions could be solved by introducing new flax waste recycling and linen producing technologies developed by scientists of the Federal Research Center for Bast Fiber Crops. In 2015-2018 some studies were carried out in research laboratories and on the experi-mental plant of the center as well as on flax-sowing farms of the Udmurt Republic, Rostov region and Krasnodar territory. The research has shown that linseed shive contains 49-51% of cellulose and 23-27% of lignin, on which the sorption capacity of the material depends. The values of flax waste sorbent sorption capacity by the effective sorption of ions in relation to heavy metals are 85-91 %, to oil products - from 3.9 to 17.3 mg/g, to iodine and methylene blue - 222 and 220 mg/g, respectively. These values don’t concede the sorbents from wood and can replace the use of the latter. The developed technology of obtaining sorbent from flax allows to organize the production directly on flax-sowing farms and flax factories applying raw materials ready to use.

Mass Transport and Thermal Conductivity Properties of Flax Shives for Use in Construction Industry

ABSTRACT The paper presents the results of studies concerning raw flax shives obtained from Polish crop of flax as a loose-fill thermal insulation material. The study focusses mainly on measurements of the thermal conductivity and water vapor permeability of material, but on water absorption and capillary rise as well. The shives showed satisfactory lambda values, comparable to traditional thermal insulation materials. They also showed high mass absorptivity and the ability to uptake large amounts of water by capillary action in a short time. The paper presents also an example of the use of the tested material as thermal insulation of the flat roof. The analysis of the heat flow through the flat roof with different thicknesses of flax shives insulation was carried out.

Rice Straw and Flax Fiber Particleboards as a Product of Agricultural Waste: An Evaluation of Technical Properties

Construction materials have a direct impact on the environment, on people, and their health. In addition, building insulation plays a decisive role in terms of energy consumption of buildings and regarding CO2-emissions over their whole life cycle. In order to achieve a holistic concept for green building worldwide, it is necessary to develop ecological insulating materials and to scientifically examine them in terms of their technical properties, as done with particleboards from agricultural waste presented in this article. This study aims to characterize the properties’ tensile and compressive strength, modulus of rupture (MOR), and elasticity (MOE) and thermal conductivity of particleboards affected by parameters, such as waste type (rice straw or flax shives), particleboard density, resin type, and content, as well as the use of treated rice straw. Particleboards made from flax shives had superior properties compared to the rice straw particles. The mechanical properties of the boards increase with an increasing resin content, except for the MOR and MOE, which decrease with an increasing resin content, and reach their peak value at a resin content of 10%.

Hygric Behavior of Cement Composites Elaborated with Flax Shives, a Byproduct of the Linen Industry

The reuse of flax shives, an agricultural waste, in the elaboration of cement composites offers an interesting alternative to meet the challenge of their elimination and solve an environmental problem. The composites studied are developed by adding flax shives to Portland cement and water. Due to their honeycomb structure the flax shives are used as lightweight aggregates and provide insulating properties to the composites. However they are hygroscopic and can release water-soluble molecules responsible for setting retardation, large dimensional variations and low mechanical strengths. In previous works these drawbacks have been reduced by the development of coating processes using lime, linseed oil and paraffin as coating substances. When coated shives are used the composites exhibited compressive strength 8 to 27-fold higher, drying shrinkage two to threefold lower compared to the raw shives composite, and belong to the insulating class of the lightweight concrete. The thermal conductivity of the composites may be negatively affected by environment humidity, so their hygric behavior must be determined. The establishment of the sorption isotherms and the evaluation of the water vapor transport allow the assessment of the hygric behavior. The treatment of the flax shives involves a decrease in the moisture adsorption capacity of the composites up to 48% for a paraffin coating. The composites can be ranked in descending order of hygroscopicity: raw, lime-coated, linseed oil-coated and paraffin-coated shive composites. Only the water vapor permeability and resistance factor of the paraffin-coated shive composite are significantly lower (46%) and higher (73%) compared to those of the raw shive composite. The analytical models (GAB, Janssen and Roels) adjust the experimental results and the influence of flax shives treatment on the composites hygric behavior is demonstrated.

Exploring mechanical properties of fully compostable flax reinforced composite filaments for 3D printing applications

Plant fibres are increasingly used for composite reinforcement, but valorization of by-products such as flax shives still needs to be developed. Also, additive manufacturing, such as Fused Deposition Modelling (FDM), is strongly progressing and can be of great interest to implement biocomposite solutions. The present work focuses on the development of innovative and fully biodegradable filaments for FDM. Three polymer matrices were tested: PLLA, PLLA/PBS 50/50%-wt and PBAT. A filler content of 30-wt% has been achieved using flax shives with PBAT. Flax fibres and shives reinforced 3D printed parts exhibit promising performances and printability, highlighting their potential to successfully develop fully compostable filaments.