Microfibrillar Structure Research Articles

In situ micro-fibrillization and post annealing to significantly improve the tribological properties of polyphenylene sulfide/polyamide 66/polytetrafluoroethylene composites

Self-lubricating polyphenylene sulfide (PPS)-based composites were achieved by in-situ construction of ordered polyamide 66 (PA) microfibrillar structure coupling with the addition of polytetrafluoroethylene (PTFE) powders as solid lubricants, using high shear injection moulding technique. The influence of annealing temperature on the in-situ formed PA microstructure and properties such as crystalline structure, mechanical as well as tribological performance of corresponding composites was studied in detail. Results suggested that PPS (56 wt%)/PA (24 wt%)/PTFE (20 wt%) composites exhibited the best tribological properties after annealing at 150 °C for 1h. The lowest friction coefficient and specific wear rate are as low as 0.139 and 4.372 × 10−6 mm3/Nm which are nearly 80% and 1.83 × 103 times lower than pure PPS, respectively. This work provides a facile method to reduce both friction and wear properties of self-lubricating thermoplastic polymers which are critical for weight reduction and energy saving in industrial fields.

Highly reinforcing effect of polycarbonate/poly(ethylene terephthalate) blends by formation of orientation microfibrillar structure

AbstractHighly oriented microfibrillar polycarbonate/poly(ethylene terephthalate) (PC/PET) blends were prepared. Before orientation, the molecular chains of the blends were mostly randomly arranged with a low crystallinity, and low mechanical properties were obtained. Under stress, it was difficult for molecular chains of the amorphous PC phase in blends to form an oriented crystalline structure. With increasing draw ratio, the crystallinity and orientation degree of the PET phase increased, forming a dense lamellar structure with reduced crystalline and amorphous layer thickness, while with increasing PET content the crystalline orientation degree of the PET phase increased with larger sized lamellae. Moreover, the cross‐section of the oriented sample showed an obvious ordered microfibrillar bundle structure, which arranged compactly and orderly along the drawing direction. The tensile strength and modulus of the oriented PC/20 wt% PET sample were up to 126.01 and 7170.10 MPa, which were 66.48% and 317.49% respectively higher than those of pure PC. Therefore, the stress‐induced oriented microfibrillar structure of the PET phase exhibited a highly reinforcing effect on the PC phase and the blend. © 2021 Society of Industrial Chemistry.

Formation of microfibrillar structure of polypropylene/copolyamide blends in the presence of nanoparticles of metal oxides

The influence of nanoparticles made of ifferent metals oxides (ZnO, Al2O3, TiO2, and ZnO/Al2O3) on the in situ formation of microfibrils by the components of a dispersed phase was studied in a thermodynamically incompatible blend of polypropylene/copolyamide (PP/CPA). The viscosity of the melts was determined by capillary viscometry method. Elastic properties were evaluated by the degree of extrudate swelling. The morphology of the compositions was studied by optical polarization microscopy. The method of image analysis was used to quantify the structural characteristics of the blends. It was established that the introduction of 1.0 wt.% of nanoparticles of the studied oxides made from different metals allows tuning the microstructure of the melt of the PP/CPA blend, which is realized in the course of extrusion. More perfect morphology is formed in nanofilled systems: the average diameter of PP microfibrils decreases and their mass fraction increases. The modifying effect of oxide nanoparticles is manifested due to their influence on interfacial phenomena and rheological properties of nanofilled PP melt. The viscosity of the PP melts increases and their elasticity decreases in the presence of nanoparticles of the studied metal oxides. The values of the ratio of the viscoelastic characteristics of the dispersed phase and the matrix in nanofilled systems depend on the nature of oxide and indirectly correlate with the microstructure of the extrudate. As these ratios approach unity, the diameter of PP microfibrils decreases and their share increases. The efficiency of the studied oxides to improve the microfibrillar structure increases in the following series: ZnO, Al2O3, TiO2, ZnO/Al2O3. The obtained results demonstrate the possibility to create the microfiber textile and filter materials with improved consumer characteristics by adjusting the phase morphology of the blends.

In Situ Microfibrillation of Polyamide 66 and Construction of Ordered Polytetrafluoroethylene Fibers to Significantly Reduce the Friction Coefficient of Polyphenylene Sulfide

Self-lubricating polyphenylene sulfides (PPS) were obtained by in situ construction of the ordered polyamide 66 (PA) microfibrillar structure and polytetrafluoroethylene (PTFE) fibers, as induced by high-shear force fields in thin-wall injection molding (TIM). The average friction coefficient and specific wear rate of PPS/PA/PTFE20 composites reached 0.114 and 7.149 × 10–6 mm3/Nm, respectively, of which the former is 27.4% lower than that obtained from conventional injection molding. The worn surface of PPS/PA/PTFE composites prepared by TIM displayed a much smoother and more stable transfer film coupling with the homo-dispersed F element, which greatly improves the tribological properties of subsequent moldings. This study provides a novel perspective for improving the tribological performance of engineering plastics by systematically tailoring the microstructure.

Effect of die structure on the properties of self-reinforced polypropylene/noil ramie fiber composites prepared by solid-state extrusion

In this work, the self-reinforced polypropylene (PP)/noil ramie fiber (NRF) composites were prepared by the solid-state extrusion method. And the effect of die structure such as draw ratio and conical angle on the morphology, thermal and mechanical properties of samples was investigated. The results indicated that the solid-state deformation of PP/NRF composites conducted below the melt transition promoted the formation of the orderly arranged microfibrils inside the samples, which arranged along the extrusion direction and could be observed by scanning electron microscopy (SEM). Besides, the increased draw ratio and conical angle both contributed to the higher degree of orientation, which was obvious observed inside the sample prepared at the draw ratio of 5 and conical angle of 20°. The thermal properties tested by differential scanning calorimetry (DSC) also suggested that the intensified orientation of microfibrillar structure not only demonstrated the transformation of the spherulitic crystal into the aligned chain crystals, but also resulted in the enhanced crystallinity and narrowed melting peak. Moreover, the highly oriented fibrillar bundle structure endowed the samples with the excellent tensile strength and flexural strength, which were up to 80.9 MPa and 83.5 MPa respectively and increased by 182.8% and 102.7% compared with the commonly extruded samples.

Effects of Poly(ethylene-co-glycidyl methacrylate) on the Microstructure, Thermal, Rheological, and Mechanical Properties of Thermotropic Liquid Crystalline Polyester Blends.

In this study, a series of thermotropic liquid crystalline polyester (TLCP)-based blends containing 1–30 wt% poly(ethylene-co-glycidyl methacrylate) (PEGMA) were fabricated by masterbatch-assisted melt-compounding. The scanning electron microscopy (SEM) images showed a uniformly dispersed microfibrillar structure for the TLCP component in cryogenically-fractured blends, without any phase-separated domains. The FT-IR spectra showed that the carbonyl stretching bands of TLCP/PEGMA blends shifted to higher wavenumbers, suggesting the presence of specific interactions and/or grafting reactions between carboxyl/hydroxyl groups of TLCP and glycidyl methacrylate groups of PEGMA. Accordingly, the melting and crystallization temperatures of the PEGMA component in the blends were greatly lowered compared to the TLCP component. The thermal decomposition peak temperatures of the PEGMA and TLCP components in the blends were characterized as higher than those of neat PEGMA and neat TLCP, respectively. From the rheological data collected at 300 °C, the shear moduli and complex viscosities for the blend with 30 wt% PEGMA were found to be much higher than those of neat PEGMA, which supports the existence of PEGMA-g-TLCP formed during the melt-compounding. The dynamic mechanical thermal analysis (DMA) analyses demonstrated that the storage moduli of the blends decreased slightly with the PEGMA content up to 3 wt%, increased at the PEGMA content of 5 wt%, and decreased again at PEGMA contents above 7 wt%. The maximum storage moduli for the blend with 5 wt% PEGMA are interpreted to be due to the reinforcing effect of PEGMA-g-TLCP copolymers.

Combined Small-Angle Neutron Scattering, Diffusion NMR, and Molecular Dynamics Study of a Eutectogel: Illuminating the Dynamical Behavior of Glyceline Confined in Bacterial Cellulose Gels.

A deep eutectic solvent (DES) entrapped in a bacterial cellulose (BC) network gives rise to a gelatin-like, self-supported material termed a bacterial cellulose eutectogel (BCEG). Although this novel material holds potential for numerous industrial, environmental, energy, or medical applications, little is known about the structural features or dynamical behavior within a eutectogel. In this work, we employ X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and small-angle neutron scattering (SANS) to probe the structural and diffusive behavior of the prevailing DES glyceline (1:2 molar ratio of choline chloride:glycerol) confined within bacterial cellulose. XRD investigations demonstrate that the bacterial cellulose maintains its crystallinity even as the glyceline content approaches 95 wt % in the BCEG, an outcome corroborated by molecular dynamics (MD) simulations, which suggest minimal changes in the structural features of the cellulose chains due to the presence of glyceline. SANS measurements reveal a significant reduction in the radius of gyration (Rg) for BC in a BCEG compared to its hydrogel analogue, indicating a collapse in the microfibrillar structure that we attribute to removal of waters from the interfibrillar space due to a higher affinity of DES for water than for cellulose. Furthermore, SANS experiments suggest that the vast majority of DES is hosted within large micropores in the BCEG (i.e., mesoscopic confinement). Interestingly, proton NMR experiments disclose faster diffusional rates for choline and glycerol entrapped in a BCEG compared to neat glyceline. MD simulations offer the possible explanation that this diffusional acceleration results from significant migration of chloride from the bulk to cellulose microfibrillar surfaces, thereby reducing hydrogen bonding with choline and glycerol partners. This study provides the first comprehensive investigation into the structure and diffusional dynamics of glyceline within a eutectogel, offering insights into mass transport that should be useful for tailoring these novel materials to potential applications.

Influence of Aluminum Oxide Nanoparticles on Formation of the Structure and Mechanical Properties of Microfibrillar Composites

The effect of nanosize alumina (Al2O3) concentration on the morphology and mechanical properties of microfibrillar composites obtained by processing the thermodynamically incompatible polypropylene/ copolyamide (PP/CPA) blend was studied. It was established that composite monofilaments exhibited a selfreinforcing effect due to the in situ formation of PP fibrils (microfibers) in the CPA matrix. The tensile strength and the initial elastic modulus of the filaments studied depended on their structure and correlated with dimensional characteristics of the disperse phase component. It is shown that the introduction of Al2O3 nanoparticles in an amount of (0.1-3.0) wt.% allows one to adjust the structure formation process of the dispersed phase component to obtain composites with a thin homogeneous morphology. The maximum performance was achieved for filaments formed from a composition containing 1.0 wt.% alumina. In this case, microfibers were the predominant type of structure, and their diameters were minimum. The increasing ability of the jets of nanofilled melts of PP/CPA blends to the longitudinal deformation was due to the formation of a more perfect microfibrillar structure during extrusion. This makes it possible to obtain filaments from such blends on already existing extrusion equipment.

Phragmites australis as a new cellulose source: Extraction, characterization and adsorption of methylene blue

The aim of this study was to investigate potential use of Phragmites australis in the production of cellulose microfibrils with chemical extraction process. Characterization of the natural P. australis and extracted fibrils were examined by FT-IR, XRD, FE-SEM, TGA, zeta potential and particle size distribution analyses indicating that amorphous polymer parts have been successfully moved away from the plant structure and cellulose content of P. australis was increased from 39.92% ± 0.78% to 91.45 ± 0.49%. Extracted cellulose samples showed microfibrillar structure based on FESEM images. The usability of cellulose microfibrils extracted from P. australis as an adsorbent was investigated in dye removal studies due to its abundant, eco-friendly and low-cost properties. Therefore, Methylene blue (MB) removal capacity of cellulose microfibrils from aqueous solution was tested and the effects of adsorption process parameters were evaluated in a controlled batch system. Maximum adsorption capacity (qmmax) was found to be 54.9 mg/g and the microfibrils allowed MB removal over a wide pH range. Experimental data fit the both Langmuir and Freundlich isotherm models indicating multilayer adsorption. The adsorption process was better described with pseudo second-order kinetic model. In conclusion, P. australis is a good candidate in high purity cellulose microfibrils production as a natural material. Cellulose microfibrils are a potential alternative source which can be used as an adsorbent for wastewater treatment especially for cationic dye removal. Moreover, it can be used for production of cellulose microfibrils in various industrial applications.

Microcrystalline Cellulose from Fruit Bunch Stalk of Date Palm: Isolation and Characterization

Present study deals with the extraction and isolation of microcrystalline cellulose (MCC) from date palm fruit bunch stalk (DPFS) of date palm tree (Phoenix dactylifera L.) through integrated chemical method. To facilitate comparative study, each DPFS-treated, DPFS-pulp and DPFS-MCC samples were produced through respective bleaching, alkaline and acid hydrolysis treatments. The obtained samples were characterized in aspects of structural, morphological, elemental, crystallinity and thermal properties. From physicochemical analysis, fourier transform infrared ray (FTIR) and X-ray diffraction (XRD) showed the improved cellulose crystalline structure from DPFS-treated to DPFS-MCC. Morphology analysis revealed that the isolated DPFS-pulp and DPFS-MCC samples had microfibrillar structure, which achieved through the fibre disintegration by a series of chemical treatments. Moreover, the rigidity was also found the highest for isolated DPFS-MCC with 79.4% crystallinity degree. Further, the DPFS-MCC sample manifested better thermal properties for its high weight loss (84.15%), low residual weight (15.44%) and high decomposition temperature (364.2 °C) compared to the other fibre samples. Also, the DSC analysis showed the thermal behaviour which is in line with the thermal decomposition of those fibre samples. Therefore, in view of the overall result, the isolated DPFS-MCC could act as potential filler for reinforcing polymeric materials in composite field of applications.

Вплив добавок нанорозмірного оксиду алюмінію на структуру та реологічні властивості суміші поліпропілен/співполіамід

Investigation of the effect of the concentration of aluminum oxide nanoparticles on the micro- and macro-rheological properties of the melt of a polypropylene / copolyamide (PP / CPA) mixture to control the morphology of nanofilled composites. The starting polymers and nano-additive were melt blended on a worm-disk extruder. The degree of dispersion of the component of the dispersed phase in the matrix was evaluated by micrographs of cross sections of the extrudates of the mixtures. The types of PP structures and their dimensional characteristics were studied using an optical microscope. The effective viscosity of the melts was determined on an MB-2 micro viscometer, and elasticity was calculated as the ratio of the extrudate and die diameters. It is shown that the introduction of a PP / CPA mixture (0.1÷3.0) mass. % Al2O3 nanoparticles makes it possible to control the process of structure formation of the component of the dispersed phase. In this case, the average diameter of PP microfibrils decreases and their mass fraction increases. The maximum effect was achieved when the content of nanoparticles 1.0 mass.%. It has been established that the macro-rheological properties of melts of nanofilled systems are determined by their morphology. The formation of anisotropic structures (PP microfibrils) with smaller diameters causes a decrease in viscosity and an increase in the elasticity of the melts of mixtures, in contrast to similar indicators for PP and CPA. It was shown that Al2O3 nanoparticles do not affect the type of morphology of the thermodynamically incompatible PP / CPA mixture - in nanofilled compositions, as in the initial one, a microfibrillar structure is formed. The modifying effect of nanoadditives is manifested in the formation of a larger number of PP microfibrils and a decrease in their dimensional characteristics. The studied nanoparticle does not interfere with the stable processing of the PP / SPA mixture into fibers and films on extrusion equipment and does not complicate the process of extraction of the matrix polymer from composite extrudates. The introduction of Al2O3 nanoparticles will make it possible to obtain composite products and fine-fiber materials with improved characteristics due to the regulation of phase morphology.

The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids.

Suberin fatty acids were extracted from outer bark of Silver birch (Betula pendula Roth.) using an isopropanolic sodium hydroxide solution. Laboratory sheets composed of lignocellulosic fiber networks were prepared from unbleached and unrefined softwood kraft pulp and further impregnated with suberin fatty acid monomers and cured with maleic anhydride in ethanol solution. The treatment resulted in hydrophobic surfaces, in which the contact angles remained over 120 degrees during the entire measurement. The fiber network also retained its water vapor permeability and enhanced fiber–fiber bonding resulted in improved tensile strength of the sheets. Scanning electron microscopy (SEM) images revealed that the curing agent, together with suberin fatty acids, was evenly distributed on the fiber surfaces and smoothing occurred over the wrinkled microfibrillar structure. High concentrations of the curing agent resulted in globular structures containing betulinol derivates as revealed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Also, the larger amount of suberin fatty acid monomers slightly impaired the optical properties of sheets.

Physicochemical Structure Analysis of Chitin Extracted from Pupa Exuviae and Dead Imago of Wild Black Soldier Fly (Hermetia illucens)

Chitin is the second most widely available natural fiber with diverse applications. Insect chitin is gaining popularity over the last decade. Black soldier fly is a widely known insect with waste management potential. In this study, chitin was isolated from Black soldier fly (Hermetia illucens) pupae exuvia (BSFE) and imago (BSFI). The chitin content was found to be 9% and 23% for pupae exuviae and imago respectively. Both the chitins were α-chitin. The degree of acetylation (DA) confirms that BSFE chitin has higher purity than BSFI chitin. The BSFE chitin is more amorphous than BSFI chitin. The crystallinity index (CrI) for BSFE and BSFI chitin was 25.20% and 49.4%, respectively. Both the chitins had good thermal stability with a maximum degradation (DTGMax) of BSFI and BSFE chitin at 363 °C and 371 °C, respectively. The Brunauer–Emmett–Teller (BET) study showed that chitin from BSFI was mesoporous with well defined cylindrical pore channels while the chitin from BSFE was non-porous. The surface area of BSFE and BSFI chitin was 1.63 and 23.00 m2/g respectively. Both the chitin had a smooth microfibrillar structure with repeating units. Based on the physicochemical characteristics of the BSF-derived chitin it can find promising commercial applications in tissue engineering, textile industry and as an adsorbent in water and wastewater treatment.

Tensile test for hydrated gel-films of bacterial cellulose

Bacterial cellulose (BC) finds multiple applications due to unique physicochemical properties and biocompatibility. The mechanical characteristics of hydrated BC such as Young modulus, tear strength, and tensile elongation under maximum load are crucial in some instances. The diversity of test methods does not allow correct comparison of the results of BC thermomechanical analysis (TMA) obtained by different researchers. However, current standards for determination of the mechanical characteristics are not intended for highly hydrated samples and do not take into account conditions for their use. The goal of the study is to develop a tensile test method for hydrated gel films of bacterial cellulose and to compare their relative elongation when tested in air and in an aqueous medium. Test samples were produced in a synthetic nutrient broth using Medusomyces gisevii Sa-12 symbiont. Physico-mechanical analysis was performed on a TMA-60 thermomechanical analyzer. The loading rate was selected proceeding from the requirement that the specimen will not dry out when tested in air. The microfibrillar structure of BC samples was studied before and after stretching using scanning electron microscope (JSM-840). The results showed that at different loading rate, tensile strength varies by a factor of 16, Young’s modulus, and elongation at maximum load by a factor of 1.3 and 1.5, respectively. The maximum tensile elongation of hydrated BC in an aqueous medium (51.4%) is 3.1 times larger compared to that determined for the test specimen tested in air. The recommended loading rate is 20 g/min. The BC structure changes during tension: after testing the BC fibers line up along the load vector and thus structured bacterial cellulose acquires the anisotropic properties.

Bacterial Cellulose and Pullulan from Simple and Low Cost Production Media

In this study, the production rate of both water-insoluble EPS, bacterial cellulose, and water-soluble EPS, P, was improved through сultivation of their producers on a nutrient media containing industrial wastes, and their material properties were analyzed. The growth rate and productivity of Gluconoacetobacter xylinus C3 strain on media with industrial wastes was investigated. An optimal nutrient medium based on molasses was selected for the bacterial cellulose producer. The nutrient medium contains 2% molasses, 1% yeast extract and peptone in a 1: 1 ratio, 0.3% sodium hydrogen phosphate, 0.1% citric acid and 1% ethanol. Cultivation of Gluconoacetobacter xylinus C3 strain on this medium for 7 days at 25–30 °С ensures its high productivity – 8.21 g/L. The composition of the optimized medium with molasses provides high mechanical properties (tensile strength – 37.12 MPa and relative elongation at break – 3.28%) of bacterial cellulose and does not affect the polymer microfibrillar structure. A modified Czapek-Dox medium with 10% molasses and 1% peptone is preferable for the exopolysaccharide accumulation by A. pullulans C8 strain. The optimized media has an advantage over the traditionally used media in terms of the efficiency of exopolysaccharide accumulation and cost reduction. The pullulan yield in media was 10.08 g/l, that is 1.5 times higher than in a standard Czapek-Dox medium. The surface morphology and microstructure of the pullulan samples obtained on different media showed minor changes. Therefore, the replacement of carbon source for molasses in a Czapek-Dox media for pullulan production did not alter the polymer content and viscosity.

QCM-D study of electrochemical synthesis of 3D polypyrrole thin films for negative electrodes in supercapacitors

Polypyrrole (PPy) is a conducting polymer widely investigated for many purposes, including as an electroactive material in supercapacitors. In this work, we studied the electropolymerization of PPy using methyl orange as a template to obtain thin films of PPy hydro-sponges. The growth of the films was performed by cyclic voltammetry and potentiostatic steps coupled with a quartz crystal microbalance measuring changes in frequency and energy dissipation. We found that methyl orange does not have an impact on the electropolymerization process in addition to its role in determining the microfibrillar structure, resulting in microfibers with diameters ranging from 500 to 900 nm, which is larger than the microfibers obtained in the chemical route with methyl orange. Changes in frequency and energy dissipation indicated that the film growth is similar when 0.45, 0.50 or 0.6 V vs Ag/AgCl NaCl 3M is applied, However, the chronoamperometric measurements show a larger increase in current density for the highest potential, suggesting that the growth of microfibers increases the surface area, which is responsible for the higher current density. Measurement of roughness using Atomic Force Microscopy for different chronoamperometry durations confirmed the increase in surface area as more PPy hydro-sponge is electropolymerized. Supercapacitors were assembled using an electrode of PPy hydro-sponge electropolymerized onto stainless steel as a negative electrode and activated carbon as a positive one. The capacitance of the PPy hydro-sponge electrode was estimated to be approximately 100 F g−1, while the two-electrode cell achieved 17 F g−1 while operating at 0.1 A g−1.

Construction of Dual Orientation Crystalline Structure in Poly(vinyl alcohol)/Graphene Oxide Nano-Composite Hydrogels and Reinforcing Mechanism

Oriented poly(vinyl alcohol) (PVA)/graphene oxide (GO) nanocomposite hydrogels with different draw ratios were prepared by stretching during a freezing/thawing process. The PVA/GO samples with a draw ratio of 200% had significantly enhanced mechanical properties by formation of a microfibrillar structure, while the tensile strength and compressive modulus respectively reached as high as 11.60 and 4.05 MPa, outperforming the unoriented samples with an increase of 167% and 540%, respectively. During the freezing/thawing process under stress, the orientation factor, crystallinity, and cross-linking density (υe) of PVA/GO samples increased steadily, while the regularly arranged fibrillar bundle structure increasingly formed, and the size of the porous structure decreased. Besides that, additional PVA crystals formed with decreasing long period (L), crystalline region (Lc), and lamellae size (Llateral). Due to the synergic orientation of GO sheets and nucleation effect, the oriented PVA/GO samples showed an or...

Study of the influence of Medusomyces gisevii Sa-12 inoculum dosage on bacterial cellulose yield and degree of polymerisation

Bacterial cellulose (BC) consists in a highly crystalline nanopolymer whose potential for application in both traditional and new industries is significant due to its unique physico-mechanical properties. In scaled BC biosynthesis processes, the use of microorganism consortia characterised by their adaptability and synergistic effects when coordinating substrate consumption appears to be promising. In the present work, the effect of inoculum dosage on BC yield during Medusomyces gisevii Sa-12 symbiotic culture on a glucose medium under optimal conditions is studied in detail. Two available methods were chosen for quality control of the BC: scanning electron microscopy, presenting an express method for confirming the origin of cellulose; and the degree of polymerisation in terms of a common method for controlling the quality of cellulose. Four experiments were carried out for the producer introduction with a dosage of 5, 10, 15 and 20% vol.. Use of the Medusomyces gisevii Sa-12 symbiotic culture provided the greatest number of acetic acid bacteria and the highest BC yield (7.5–8.0%) with an inoculum dosage of 10–20% vol. At the same time, an inoculum dosage of 20% vol. allowed the culture time to be halved, while an inoculum dosage of 5% vol. appears to be insufficient. All inoculum dosage variants were determined to provide the same three-dimensional cross-linked microfibrillar structure of BC samples. The degree of polymerisation (DP) of BC samples was first established to depend on the dosage of the inoculum and the duration of BC biosynthesis. Thus, the biosynthesis process can be controlled using such a simple parameter as inoculum dosage and BCs can be synthesised directionally with a given DP. The inoculum dosage of 10% vol. was established as providing the highest possible DP of BC (value of 5000), decreasing slightly during prolonged culture.

Use of mechanically ground lignocellulosic native fines (LF) in the all-cellulosic composite filaments: fines properties and plasticizers

The influence of the physical and colloidal properties of W-stone ground lignocellulose native fines (LF) on the properties of lignocellulosic composite filaments was investigated. W-stone ground LF is a low-cost material exhibiting a microfibrillar structure with the chemical structure of native wood. The physical properties of manufactured LFs were investigated by utilising SEM imaging, turbidity measurements and image-based particle analysis using a Kajaani fibre analyser. The properties of LFs were varied by adjusting the process energy input that altered the produced material’s particle size and shape and subsequent fractionation with a wire. The reduction in particle size was observed to increase the colloidal stability of produced LFs, but no significant changes in the chemical profile of the LFs were observed. The effect of the properties of LF on the manufacture of composite filaments with carboxymethyl cellulose (CMC) was studied by using a dry-jet wet spinning approach. The smaller particle size had a positive effect on the mechanical properties of composite filaments (tenacity increased from 5.5 to up to 7.6 cN/tex). The compatibility of different plasticisers with LF–CMC composite filaments was also studied. It was observed that the number of free hydroxyls per a monomer unit of the plasticiser had a positive correlation with the plasticisation effect in the LF–CMC composite filaments. Regenerated cellulose filaments are often rather expensive to be used in many applications such as composites. The investigated filaments could thus be used in low-cost applications requiring a fully biodegradable material profile. Here, the presence of lignin may increase the structural compatibility of the produced matrix.Graphical abstract

SPECIFICITY OF CHANGE IN SORPTION CAPACITY OF FLAX FIBER UNDER REGULABLE BIO-CATALYTICAL DESTRUCTION OF NEUTRAL CARBOHYDRATES

Evaluation of the nano sizes of hydrosols from homogeneous cellulosic and industrial products was made using dynamic light scattering method. The influence of the size of the globule of protein catalysts and the duration of their action on the roving of carded flax fiber was compared. The correlation between the change in the equilibrium absorption of sorption marker (methylene blue) and residual content in the fiber of hemicelluloses was monitored. On the basis of a comparative analysis of the efficiency of biocatalysts in industrial homogeneous and cellulosic preparations it was revealed that globule size influences on the efficiency of sorption properties of flax fibers. The use of homogeneous enzymes with differing sized parameters has allowed isolating the contribution of the target enzymatic modification as in the microfibrillar structure of elementary fibers and for modification the hemicelluloses in the binding substance fixing the elementary fibers in the bast bundles (the linen fibrous complexes). The principles of selection of biocatalysts to increase sorption capacity in flax fiber sorbents were revealed. It was found that the sorption capacity of flax fiber sorbents increases due to the development of mezopore space in elementary fibres and regulable amorphization of interfiber binders in the structure of the linen complex. The research revealed that the the amorphization of flax fiber took place only when the cellulases was used. The size of their globules enables the penetration of these enzymes into mesopores of elementary flax fibres. It was established experimentally that the presence of large isoforms of cellulases or hemicellulases can promote as the development of the internal volume into the fibre binders and also conservation the permissible level of reduction of the hemicelluloses amount in flax fibres is not less than 10 mass.%.Forcitation:Aleeva S.V., Lepilova O.V., Kurzanova P.Yu., Koksharov S.A. Specificity of change in sorption capacity of flax fiber under regulable bio-catalytical destruction of neutral carbohydrates. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 80-85