Fiber Formation Process Research Articles

Antimicrobial liposomes-in-nanofiber wound dressings prepared by a green and sustainable wire-electrospinning set-up

Increasing prevalence of infected and chronic wounds demands improved therapy options. In this work an electrospun nanofiber dressing with liposomes is suggested, focusing on the dressing’s ability to support tissue regeneration and infection control. Chloramphenicol (CAM) was the chosen antibiotic, added to the nanofibers after first embedded in liposomes to maintain a sustained drug release. Nanofibers spun from five different polymer blends were tested, where pectin and polyethylene oxide (PEO) was identified as the most promising polymer blend, showing superior fiber formation and tensile strength. The wire-electrospinning setup (WES) was selected for its pilot-scale features, and water was applied as the only solvent for green electrospinning and to allow direct liposome incorporation. CAM-liposomes were added to Pectin-PEO nanofibers in the next step. Confocal imaging of rhodamine-labelled liposomes indicated intact liposomes in the fibers after electrospinning. This was supported by the observed in vitroCAM-release, showing that Pectin-PEO-nanofibers with CAM-liposomes had a delayed drug release compared to controls. Biological testing confirmed the antimicrobial efficacy of CAM and good biocompatibility of all CAM-nanofibers. The successful fiber formation and green production process with WES gives a promising outlook for industrial upscaling.

The Influence of Technological Factors and Polar Molecules on the Structure of Fibrillar Matrices Based on Ultrafine Poly-3-hydroxybutyrate Fibers Obtained via Electrospinning

The article examines the regularities of structure formation of ultrafine fibers based on poly-3-hydroxybutyrat under the influence of technological (electrical conductivity, viscosity), molecular (molecular weight), and external factors (low-molecular and nanodispersed substances of different chemical natures). Systems with polar substances are characterized by the presence of intermolecular interactions and the formation of a more perfect crystalline fiber structure. Changes in technological and molecular characteristics affect the fiber formation process, resulting in alterations in the morphology of the nonwoven fabric, fiber geometry, and supramolecular fiber structure. Polymer molecular weight, electrical conductivity, and solution viscosity influence fiber formation and fiber diameter. The fiber structure is heterogeneous, consisting of both crystalline and non-equilibrium amorphous phases. This article shows that with an increase in the molecular weight and concentration of the polymer, the diameter of the fiber increases. At the same time, the increase in the productivity of the electrospinning process does not affect the fiber geometry. The chemical structure of the solvent and the concentration of polar substances play a decisive role in the formation of fibers of even geometry. As the polarity of the solvent increases, the intermolecular interaction with the polar groups of poly-3-hydroxybutyrate increases. As a result of this interaction, the crystallites are improved, and the amorphous phase of the polymer is compacted. The action of polar molecules on the polymer is similar to the action of polar nanoparticles. They increase crystallinity via a nucleation mechanism. This is significant in the development of matrix-fibrillar systems for drug delivery, bioactive substances, antiseptics, tissue engineering constructs, tissue engineering scaffolds, artificial biodegradable implants, sorbents, and other applications.

Insight on the Intracellular Supramolecular Assembly of DTTO: A Peculiar Example of Cell-Driven Polymorphism.

The assembly of supramolecular structures within living systems is an innovative approach for introducing artificial constructs and developing biomaterials capable of influencing and/or regulating the biological responses of living organisms. By integrating chemical, photophysical, morphological, and structural characterizations, it isshown that the cell-driven assembly of 2,6-diphenyl-3,5-dimethyl-dithieno[3,2-b:2',3'-d]thiophene-4,4-dioxide (DTTO) molecules into fibers results in the formation of a "biologically assisted" polymorphic form, hence the term bio-polymorph. Indeed, X-ray diffraction reveals that cell-grown DTTO fibers present a unique molecular packing leading to specific morphological, optical, and electrical properties. Monitoring the process of fiber formation in cells with time-resolved photoluminescence, it isestablished that cellular machinery is necessary for fiber production and a non-classical nucleation mechanism for their growth is postulated. These biomaterials may have disruptive applications in the stimulation and sense of living cells, but more crucially, the study of their genesis and properties broadens theunderstanding of life beyond the native components of cells.

Shape from Shading-Based Study of Silica Fusion Characterization Problems

With the rapid development of AI (artificial intelligence) in recent years, AI has been widely used in the image processing of iron tailings. The main component of iron tailings is silica, which is the most difficult part of the iron tailing composition to fuse. Therefore, the melting behavior of iron tailings can be characterized by the melting behavior of silica. First of all, in the actual production process, the temperature of the high-temperature furnace exceeds 1500 °C, which leads to a short service life of the conventional testing equipment. A line array CCD (charge coupled device) camera system with amplification effect was used to acquire data on silica in a high-temperature melt pool in a non-contact manner. The corundum crucible position is fixed, which can be used to establish a two-dimensional coordinate system to reproduce the object’s motion pattern to solve the problem of the short service life of conventional inspection equipment. The color and wobble problems generated by the Rift Valley CCD system when taking pictures need to be corrected for accurate image processing. Secondly, the change in the center-of-mass position of silica during melting was studied using the temporal images of silica in a high-temperature melt pool, and the edge contour features were extracted from the silica images and filled inside the contours, from which the mass, area and perimeter were obtained. Finally, the volume change of silica in the time series image is calculated after eliminating the effect of background factors, and the 2D image is constructed into a 3D image. We built a SFS (shape from shading) model according to the lighting conditions, and the actual melting rate of silica is calculated accordingly. According to the model calculation results, it can be seen that with the change in time, silica surface area under heat gradually decreases, then the silica melting rate gradually decreases; among them, the faster melting rate is about 0.007 cubic millimeter/second, and the slower melting rate is about 0.0015 cubic millimeter/second. Data support was provided for the blast furnace slag direct fiber formation process. The introduction of the algorithmic model into the actual production process has certain advantages. Therefore, the SFS model established in this paper has some practical value and is worth promoting in related enterprises.

Optimal Entanglement of Polymers Promotes the Formation of Highly Oriented Fibers

Polymer fibers consist of macromolecules oriented along the fiber axis. Better alignment of chains leads to an increased strength of the fiber. It is believed that the key factor preventing formation of a perfectly oriented fiber is entanglement of polymers. We performed large-scale computer simulations of uniaxial stretching of semicrystalline ultrahigh molecular weight polyethylene. We discovered that there is an optimal number of entanglements per macromolecule necessary to maximize chain orientation in a fiber. Polymers that were entangled too strongly formed less oriented fibers. On the other hand, when polymers had too few entanglements per chain, they disentangled during stretching, and the strong fiber was not formed. We constructed a microscopic analytical theory describing both the fiber formation and disentanglement processes. Our work presents a novel view on the role of entanglements during fiber production and predicts the existence of a single universal optimal number of entanglements per chain maximizing the fiber quality: approximately $10^2$ entanglements.

Facile, Energy-Efficient Microscale Fibrillation of Polyacrylamides under Ambient Conditions.

Insight into fiber formation can provide new rationale for the design and preparation of fibers with programmed mechanical properties. While synthetic bioinspired fibers have shown impressive tensile properties, the fiber formation process remains poorly understood. Moreover, these systems are highly complex and their formation is environmentally and economically costly. Controlled fiber formation under ambient conditions from polyacrylamide solutions with properties comparable to natural fibers such as wool and coir is demonstrated. Photopolymerization and subsequent microscale fibrillation of different acrylamides in water/ethanol mixtures yield a simple and energy-efficient route to fiber formation. This strategy reduces required processing energy by two-to-three orders of magnitude. Through extensive experimental elucidation, insight into precise fiber forming conditions of polymeric solutions is achieved. Ethanol is utilized as a chain transfer agent to control the molecular weight of the polyacrylamides, and the entanglement regimes of the solutions are determined through rheological characterization showing fiber formation above the entanglement concentration. Unique from previously reported hydrogel microfibers, it is shown that fibers with good mechanical properties can be obtained without the need for composites or crosslinkers. The reported approach offers a platform for fiber formation under ambient conditions with molecular-level understanding of theirassembly.

Chitin and cuticle proteins form the cuticular layer in the spinning duct of silkworm

Chitin is found in the exoskeleton and peritrophic matrix of arthropods, but recent studies have also identified chitin in the spinning duct of silk-spinning arthropods. Here, we report the presence and function of chitin and cuticle proteins ASSCP1 and ASSCP2 in the spinning duct of silkworm. We show that chitin and these proteins are co-located in the cuticular layer of the spinning duct. Ultrastructural analysis indicates that the cuticular layer has a multilayer structure by layered stacking of the chitin laminae. After knocking down ASSCP1 and ASSCP2, the fine structure of this layer was disrupted, which had negative impacts on the mechanical properties of silk. This work clarifies the function of chitin in the spinning duct of silkworm. Chitin and cuticle proteins are the main components of the cuticular layer, providing the shearing stress during silk fibrillogenesis and regulating the final mechanical properties of silk. Statement of significanceRecent studies have identified chitin in the spinning duct of silk-spinning arthropods. However, the role of chitin in this specific organ remains unclear. This study reports that chitin and cuticle proteins form the cuticular layer, a unique structure of the spinning duct of silkworm. This layer with a precise laminate structure gives the spinning duct flexible properties, provides shearing forces for silk fibrillogenesis, and contributes to silk final mechanical properties. Our work clarifies the component, ultrastructure, and biological significance of the silkworm cuticular layer, describes the specific process of silk fiber formation, and proposes new molecular targets (chitin and cuticle proteins) for the improvement of animal silks.

ANN-based structure-viscosity relationship model of multicomponent slags for production design in mineral wool

The production of mineral wool from waste high-temperature slags is considered eco-friendly and economical. However, this application is facing a great challenge from an unstable production process caused by the variable compositions and properties of slags. Especially, the viscosity of slags, as a significant property, governs the processes of melt homogenization, tapping, and fiber formation. Here, we designed a structure-property relationship model to describe the development of slag viscosity over a broad range of composition and temperature. A feed-forward back-propagation artificial neural network was adopted as the basis to establish quantitative relationships between effective variables and viscosity. A comprehensive database containing 5474 reliable laboratory-based samples was constructed and further developed using the micro-scale structural features. The importance of structural features was evaluated using the statistical connection weight approach and 74 kinds of first-nearest-neighbor pairs and 4 medium-range characteristics (three kinds of oxygen species and the degree of depolymerization of network) were selected and integrated into the model. The results indicated the obtained model exhibited excellent performance, with a testing mean square error of 0.0592 and a testing Pearson’s correlation coefficient of 0.9966. The model was compared with several other common viscosity models and also showed the optimal predictive ability. Furthermore, the model was successfully applied in the production of mineral wool from three complex slags and the high-quality mineral wool product was achieved.

Study of the fracture surface of concretes reinforced with basalt fiber coated with titanium and zirconium dioxides. Fiber-reinforced concrete composites

It is impossible to imagine the development of modern technologies without the use of efficient and affordable fibrous materials based on minerals, glass, and other fibers. The intensive development of the production of fibers and materials based on them worldwide determines the formulation of significant scientific and technical problems of obtaining them with a given set of properties and high-quality indicators, optimization of processing, and rational use. However, the possibility of modifying the composition of the rock with other components that could significantly improve the physical and chemical properties of the fibers is not always taken into account. For the first time, a study was conducted to research the coating of basalt fibers, such as TiO2, ZrO2 and their effect on the physical and chemical characteristics of aluminosilicate melts made from rocks, fiber formation processes, structure, and physical and chemical properties of fibers. Studies have shown that fibers modified with oxides of TiO2 and ZrO2 have higher chemical resistance in aggressive environments compared with unmodified fibers obtained from melts of similar component groups.

ОЦЕНКА ВОЗМОЖНОСТИ ИСПОЛЬЗОВАНИЯ ЗОЛЫ РЕФТИНСКОЙ ГРЭС В ПРОИЗВОДСТВЕ НЕПРЕРЫВНОГО СТЕКЛОВОЛОКНА

The article presents the results of the evaluation of the study of the possibility of using ash and slag waste (ash) of Reftinskaya GRES as a component of the charge used in the production of continuous glass fiber of high-modulus (type E), dielectric resistant (type S) and high-strength, chemically stable basalt (type B) compositions. Since the chemical composition of ash is multicomponent and significantly differs from the compositions of raw materials traditionally used in the production of glass fiber, in order to establish the technological features of its use as a component of the charge, experimental compositions of glasses were designed to achieve their specified physical and mechanical properties, with the maximum possible content of ash in the composition of glass charges. A priori assessment showed that acceptable properties of glass for glass fiber compositions E, S and B can be obtained at the content of 36%, 68% and 64% ash in the charges, respectively, for the listed types of glass. The determination of the glass transition temperature intervals of the experimental charge compositions showed that an increase in the ash content in them increases the temperature that ensures the production of a high-quality melt. Studies of the tendency of experimental glass compositions to crystallization, which prevents the effective process of fiber formation, allowed us to determine that almost all compositions have a reduced tendency to crystallization, therefore, they can be used in the production of glass fibers of types S, E and B.

Investigating the Role of NHE1 in the Regulation of Changes in Cellular Functions Related to the Development of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis is a chronic lung disorder characterized by the thickening, stiffening, and scaring of tissue within the lungs. Affected individuals develop shortness of breath and the progressive reduction of respiratory function. Fibrosis ultimately results in low blood flow and hypoxia in the tissue, a microenvironment which is closely associated with the upregulation of the sodium-hydrogen exchanger isoform 1 (NHE1). NHE1 is a ubiquitously expressed protein that exchanges one extracellular Na+ for one intracellular H+. This regulates intracellular pH and cell progression through the cell cycle. When NHE1 is upregulated it supports increased cell proliferation and migration, indicating that it may play a vital role in the behavior of fibroblasts in the development of idiopathic pulmonary fibrosis. We hypothesized that inhibition of NHE1 activation would decrease cell progression towards a fibrotic phenotype in lung fibroblasts. For this assessment, we compared differences in cellular behavior in three cell lines to evaluate the role of NHE1 in these processes. LL29 cells are human fibroblasts derived from a patient diagnosed with idiopathic pulmonary fibrosis; WI-38 cells which are derived from healthy lung tissue; and PSN cells, which are derived from Chinese hamster lung fibroblasts and express only human NHE1.Transforming growth factor beta 1 (TGF-b1), Lysophosphatidic Acid (LPA) and Serotonin (5-hydroxytryptamine) were evaluated for their ability to alter cell proliferation, stress fiber formation, and myofibroblast differentiation in all three cell lines. TGF-b1 is a cytokine that is a growth factor implicated in the pathogenesis of pulmonary fibrosis and is involved in differentiation, proliferation, and matrix production of fibroblasts. Serotonin (5-HT) is a signaling molecule that binds to G-protein coupled receptors supporting the increase in TGF-b1 and its effects in cells. This hormone is involved in wound healing and stimulating inflammation. LPA is a lipid signaling molecule that plays a role in mediating inflammation and activating TGF-b1 signaling. All experiments were performed in the presence and absence of Ethylisopropylamiloride (EIPA), a potent inhibitor of NHE1, to evaluate the role of NHE1 in fibrotic transformation. In PSN cells, stimulation with 10 µM LPA increased stress fiber formation over 2-fold and this stimulation was absent in cells treated with 10 µM EIPA indicating a role for NHE1 in the regulation of stress fiber formation and related cellular processes.

Swirling Diffused Air Flow and Its Effect on Helical Fiber Motion in Swirl-Die Melt Blowing

In melt blowing, high-velocity air impinges upon a polymer stream and attenuates it into micro-fibrous materials. The structure of the melt-blown die controls the airflow field and determines the process of fiber formation. This work focused on exploring the air swirling diffusion in a particular swirl-die melt blowing. The air swirling diffusion was analyzed by measuring the lateral velocity (vr), and the lateral twisting velocity (vs) by using single- and dual-wire probe hot-wire anemometer. Results showed that the vr had a diffusion boundary, while the distribution of the vs located out of the diffusion boundary of vr. The fiber paths in the swirl-die melt blowing, which was captured by high-speed camera, showed that the cone angle of the fiber path was consistent with the cone angle of vr-diffusion boundary. However, most of the twisting velocity (vs) located out of the region of fiber path, resulting in that the fiber helical motion was initiated just at a critical z-position, rather than in the region further away from the die. This work shows that energy-wasting of vs exists during swirl-die melt blowing, and a more optimized structure of this kind of die should be found.

Surface and Thermal Characterization of Cotton Fibers of Phenotypes Differing in Fiber Length.

Cotton is one of the most important and widely grown crops in the world. Understanding the synthesis mechanism of cotton fiber elongation can provide valuable tools to the cotton industry for improving cotton fiber yield and quality at the molecular level. In this work, the surface and thermal characteristics of cotton fiber samples collected from a wild type (WT) and three mutant lines (Li1, Li2-short, Li2-long, Li2-mix, and liy) were comparatively investigated. Microimaging revealed a general similarity trend of WT ≥ Li2-long ≈ Li2-mix > Li1 > Li2 short ≈ liy with Ca detected on the surface of the last two. Attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy and thermogravimetric measurements also showed that Li2-short and liy were more similar to each other, and Li2-long and Li2-mix closer to WT while Li1 was quite independent. FT-IR results further demonstrated that wax and amorphous cellulose were co-present in fiber structures during the fiber formation processes. The correlation analysis found that the FT-IR-based maturity parameter was well correlated (p ≤ 0.05) to the onset decomposition temperature and all three weight-loss parameters at onset, peak, and end decomposition stages, suggesting that the maturity degree is a better parameter than crystallinity index (CI) and other FT-IR parameters that reflect the thermal stability of the cotton fiber. In summary, this work demonstrated that genetic mutation altered the surface and thermal characteristics in the same way for Li2-short and liy, but with different mechanisms for the other three mutant cotton fiber samples.

Морфологічний стан трофічних виразок венозної етіології після трансплантації стовбурових клітин кордової крові

The aim. The research deals with analysis of the degree of regenerative processes activity in patients with trophic venous ulcers of the lower extremities that do not heal for a long time on the background of cell transplantation of cord blood stem cells and without. The study involved 32 patients with long-term non-healing trophic venous ulcers of venous etiology. Results and discussion. The study results showed that the healing process of the main group patients began in the first days after transplantation to reduce pericellular edema and inflammatory hyperemia of the soft tissues around the ulcer. When examining the histological features of the central skin ulcers of patients in the control group on the fifth day after treatment, we found out that the bottom surface of the ulcers was covered with homogeneous masses of the type of fibrinoid necrosis. Ulcers had a variable depth, in some places reached the fiber, with sweat and sebaceous glands, hair follicles in the course of defects were completely destroyed, in these places there were hemorrhages and young granulation tissue. In patients of the main group, the surface of the bottom of the ulcer was covered with homogeneous masses of fibrinoid necrosis, but the masses of fibrinoid necrosis were visually expressed three times less than in the control group, but the most important was that they always alternated with "veins" consisting of cells type of lymphoid. Immunohistochemical analysis for Willebrand factor in patients of the main group revealed unevenly scattered small compact groups of positively stained cells, which should be evaluated as foci of neoplasms of blood vessels more evenly distributed among the blood vessels of granulation tissue, in contrast to the control group. On the 14th day of the clinical study at the bottom of the ulcer in the main group there were morphological signs of better maturation of granulation tissue, as seen by more uniform and intensive processes of collagen fiber formation (increase in specific volume of collagen fibers) and blood vessels (decrease in specific volume of blood vessels) and the maturation of lymphoid (polypotent) cells into fibroblasts with more complete production of vimentin in them and endothelial cells with more complete production of Willebrand factor in them. It should be noted that there was a more complete resorption of fibrinoid necrosis masses in the main observation group compared to the control group of patients, which should also contribute to faster and more complete healing of the ulcer

Development and Characterization of Weft-Knitted Fabrics of Naturally Occurring Polymer Fibers for Sustainable and Functional Textiles.

This study focuses on the potential uses in textiles of fibers of soy protein (SP) and chitin, which are naturally occurring polymers that can be obtained from agricultural and food processing by-products and wastes. The as-received natural fibers were first subjected to a three-step manufacturing process to develop yarns that were, thereafter, converted into fabrics by weft knitting. Different characterizations in terms of physical properties and comfort parameters were carried out on the natural fibers and compared to waste derived fibers of coir and also conventional cotton and cotton-based fibers, which are widely used in the textile industry. The evaluation of the geometry and mechanical properties revealed that both SP and chitin fibers showed similar fineness and tenacity values than cotton, whereas coir did not achieve the expected properties to develop fabrics. In relation to the moisture content, it was found that the SP fibers outperformed the other natural fibers, which could successfully avoid variations in the mechanical performance of their fabrics as well as impair the growth of microorganisms. In addition, the antimicrobial activity of the natural fibers was assessed against different bacteria and fungi that are typically found on the skin. The obtained results indicated that the fibers of chitin and also SP, being the latter functionalized with biocides during the fiber-formation process, showed a high antimicrobial activity. In particular, reductions of up to 100% and 60% were attained for the bacteria and fungi strains, respectively. Finally, textile comfort was evaluated on the weft-knitted fabrics of the chitin and SP fibers by means of thermal and tactile tests. The comfort analysis indicated that the thermal resistance of both fabrics was similar to that of cotton, whereas their air permeability was higher, particularly for chitin due to its higher fineness, which makes these natural fibers very promising for summer clothes. Both the SP and chitin fabrics also presented relatively similar values of fullness and softness than the pure cotton fabric in terms of body feeling and richness. However, the cotton/polyester fabric was the only one that achieved a good range for uses in winter-autumn cloths. Therefore, the results of this work demonstrate that non-conventional chitin and SP fibers can be considered as potential candidates to replace cotton fibers in fabrics for the textile industry due to their high comfort and improved sustainability. Furthermore, these natural fibers can also serve to develop novel functional textiles with antimicrobial properties.

Research progress of ultrafine alumina fiber prepared by sol-gel method: A review

As a widely used high-performance inorganic fiber material, preparation and application of ultrafine alumina fibers have attracted much attention in last decades. Therein, preparation of ultrafine alumina fibers via sol gel method has the characteristics of simple synthetic procedure, easy regulation of fiber components and well design of fiber structures, etc., which have been developed rapidly in recent years. In this paper, the research progress of ultrafine alumina fibers prepared via sol-gel method is comprehensive reviewed, which mainly focus on the aspects of fiber forming process and the fiber structure construction during sol-gel method. According to the different fiber formation processes during sol-gel method, the centrifugal spinning, electrospinning and electro-blown spinning for preparation of ultrafine alumina fiber are demonstrated respectively. The effects of different fiber forming process on the structure and properties of ultrafine alumina fiber are compared and analyzed. Particularly, the sol-gel ultrafine alumina fibers constructed with porous, hollow and other profiled structures are special described. Furthermore, the sol-gel ultrafine alumina fibers application in the environment protection, energy storage fields and refractory and thermal insulation fields are also summarized. Novel ultrafine alumina fiber based materials emerging in recent years, such as alumina based MOF and three-dimensional alumina aerogels have been concerned. Finally, the future development of sol-gel ultrafine alumina fiber is prospected, which provides some reference value for the further study of ultrafine alumina fiber.

Process hybridization schemes for multiscale engineered tissue biofabrication.

Recapitulation of multiscale structure-function properties of cells, cell-secreted extracellular matrix, and 3D architecture of natural tissues is central to engineering biomimetic tissue substitutes. Toward achieving biomimicry, a variety of biofabrication processes have been developed, which can be broadly classified into five categories-fiber and fabric formation, additive manufacturing, surface modification, remote fields, and other notable processes-each with specific advantages and limitations. The majority of biofabrication literature has focused on using a single process at a time, which often limits the range of tissues that could be created with relevant features that span nano to macro scales. With multiscale biomimicry as the goal, development of hybrid biofabrication strategies that synergistically unite two or more processes to complement each other's strengths and limitations has been steadily increasing. This work discusses recent literature in this domain and attempts to equip the reader with the understanding of selecting appropriate processes that can harmonize toward creating engineered tissues with appropriate multiscale structure-function properties. Opportunities related to various hybridization schemes and a future outlook on scale-up biofabrication have also been discussed. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Expression and characterization of chimeric spidroins from flagelliform-aciniform repetitive modules.

Spiders can produce up to seven different types of silks or glues with different mechanical properties. Of these, flagelliform (Flag) silk is the most elastic, and aciniform (AcSp1) silk is the toughest. To produce a chimeric spider silk (spidroin) FlagR -AcSp1R , we fused one repetitive module of flagelliform silk from Araneus ventricosus and one repetitive module of aciniform silk from Argiope trifasciata. The recombinant protein expressed in E. coli formed silk-like fibers by manual-drawing. CD analysis showed that the secondary structure of FlagR -AcSp1R spidroin remained stable during the gradual reduction of pH from 7.0 to 5.5. The spectrum of FTIR indicated that the secondary structure of FlagR -AcSp1R changed from α-helix to β-sheet. The conformation change of FlagR -AcSp1R was similar to other spidroins in the fiber formation process. SEM analysis revealed that the mean diameter of the fibers was around 1 ~ 2 μm, and the surface was smooth and uniform. The chimeric fibers exhibited superior toughness (~33.1 MJ/m3 ) and tensile strength (~261.4 MPa). This study provides new insight into design of chimeric spider silks with high mechanical properties.

PET/CLOISITE 15A composite fibers - studies on the structure and the flame inhibition mechanism

The improvement of poly(ethylene terephthalate) (PET) fibers flame retardancy is usually achieved by using antipyrenes, which may be incorporated into polyester molecules during polycondensation or are physically mixed with polymer in the fiber formation process. In this article we present an alternative method to reduce the flammability of PET fibers and fabrics which is analogous to dyeing them with a dispersed dyes in a high temperature bath. We have tested this method many times using various modifiers so far. This time, we applied a commercial organophilized montmorillonite Cloisite®15A (C15A). In the presented work, using Limited Oxygen Index (LOI) flammability tests and the thermogravimetric analysis (TGA) method, the effectiveness of the modification used was demonstrated and its optimal variant was determined. Based on Fourier Transform-Infrared Spectroscopy (FT-IR) studies, the existence of interactions between PET macromolecules and the C15A modifier in the entire temperature range of the oxidative degradation was confirmed. Using the Wide-Angle X-ray Scattering (WAXS) and Small-Angle X-ray Scattering (SAXS) methods, the basic parameters of the nanostructure of the studied fibers were determined, and their nanocomposite nature was confirmed. The most important goal, which was successfully achieved, was to explain the mechanism of flame inhibition by the applied modifier C15A.

Migration Effects of Fluorochemical Melt Additives for Alcohol Repellency in Polypropylene Nonwoven Materials.

The use of bulk polymer melt additives provides a facile, industrially relevant approach to tailor properties of polymer surfaces for many different applications. These melt additives, when blended with polymers prior to melt spinning, migrate to the fiber surface and influence surface functionality. While the use of bulk polymer melt additives to impart hydrophilicity or oleophobicity is well studied, the impact of the fiber formation process on additive migration and resultant repellency of nonwoven media products remains largely unexplored. In this study, we produce fluorochemical melt additive containing meltblown nonwovens, and establish methods for characterization of fiber mat surface composition and repellency. Repellency of low surface tension fluids is a significant challenge and is of particular importance in the creation of medical garments such as surgical gowns and masks which must perform as liquid barriers even when exposed to alcohol based solutions. Similarly, melt additives are also used in the production of electret air filtration devices. Electret filters are imbued with charges to enhance particle capture performance, but this charge can be negated through wetting by low surface tension fluids. To address this challenge, the changing composition of fiber surfaces due to the migration of additives is monitored via X-ray Photoelectron Spectroscopy, then related to repellency of alcohol solutions by contact angle analysis. We demonstrate that for the samples tested a fluorine to carbon (F/C) ratio of 0.35 is sufficient to prevent wicking of isopropanol droplets, and higher surface tension fluids could be repelled by fiber mats with lower fluorine content. Through the use of cross-sectional ToF-SIMS analysis, we find that migration of additives is key to the performance of samples with low additive loadings, and that these phenomena are heavily influenced by many nonwoven manufacturing parameters including fiber size, die-to-collector distance, and polymer resin melt flow rates.