Nanocomposite polyvinyl alcohol fibers for medical applications

It was investigated how the HAp and SiO₂ nanoadditives introduced into the material of fibers made from polyvinyl alcohol (PVA) affects the structure, sorption, and strength properties of those fibers. The conditions of the fibers' production were selected with the aim of obtaining the nanocomposite PVA fibers which would be soluble in water and in body fluids. These fibers are intended to be used for the production of a biocomposite with another biodegradable polymer. The determination was made of the effect of two different deformations applied at the fiber production stage on the structure and properties of the fibers. Using the WAXS method, the supramolecular structure of the fibers was determined. Nanocomposite PVA fibers obtained in this work have an oriented crystalline structure with a rather low level of crystallinity, reaching 40%, and a relatively high orientation index of crystallites: 0.48–0.54. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The influence of fiber formation conditions on the structure and properties of nanocomposite alginate fibers containing tricalcium phosphate or montmorillonite

The authors devised conditions for the formation of nanocomposite calcium alginate fibers containing tricalcium phosphate (TCP) or montmorillonite (MMT). The rheological, sorptive, and strength properties of these fibers, as well as their porous and supramolecular structures were subjected to analysis. It has been concluded that the presence of nanoadditives in the material of alginate fibers decreases their susceptibility to distortion in the drawing stage. The obtained fibers are characterized by an even distribution of the nanoadditive on the fiber surface. POLYM. COMPOS., 31:1321–1331, 2010. © 2009 Society of Plastics Engineers     

Preparation and characterization of alginate/Hydroxypropyl chitosan blend fibers

Hydroxypropyl chitosan (HPCS) was synthesized from chitosan and propylene oxide under alkali conditions. It was characterized by IR spectroscopy and X-ray diffraction (XRD). We prepared alginate/HPCS blend fibers by spinning their solution through a viscose-type spinneret into a coagulating bath containing aqueous CaCl₂ and ethanol. The structure and properties of the blend fibers were studied with the aid of IR spectroscopy, scanning electron microscopy, and XRD. The results indicate a good miscibility between alginate and HPCS because of the strong interaction of the intermolecular hydrogen bonds. The mechanical properties and water-retention properties were also measured. The best values of the tensile strength and breaking elongation of the blend fibers were obtained when the HPCS content was 30 wt %. The water-retention values of the blend fibers increased as the amount of HPCS increased. Antibacterial fibers, obtained by the treatment of the fibers with an aqueous solution of silver nitrate, exhibited good antibacterial activity to Staphylococcus aureus. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The novel alginate/N‐succinyl‐chitosan antibacterial blend fibers

Alginate/ N‐Succinyl‐chitosan (SCS) blend fibers, prepared by spinning their mixture solution through a viscose‐type spinneret into a coagulating bath containing aqueous CaCl₂, were studied for structure and properties with the aid of infrared spectroscopy (IR) and X‐ray diffraction (XRD). The results indicated a good miscibility between alginate and SCS, because of the strong interaction from the intermolecular hydrogen bonds. The best values of the dry tensile strength and breaking elongation were obtained when SCS content was 30 wt %. The wet tensile strength decreased with the increase of SCS content, and the wet breaking elongation achieved maximum value when the SCS content was 30 wt %. Introduction of SCS in the blend fiber improved water‐retention properties of blend fiber compared to pure alginate fiber. Antibacterial fibers, obtained by treating the fibers with aqueous solution of silver nitrate, exhibited good antibacterial activity to Staphylococcus aureus. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

PAN‐based fibers modified with two‐component ceramic nanoparticles

The authors determined conditions for manufacturing PAN precursor fibers containing a system of two nanoadditives, montmorillonite (MMT), and hydroxyapatite (HAp) in their structure. The PAN precursor fibers thus obtained are characterized by a tenacity of more than 30 cN/tex and a total volume of pores at the level of 0.29 cm³/g. Furthermore, it was found that the use of nanoadditives entails the remodeling of the paracrystalline structure of PAN fibers into a strictly crystalline one. This is accompanied by a decrease in spacing between MMT layers combined with their partial exfoliation. The fibers thus obtained, after being carbonized, will be used for medical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Silver‐loaded lyocell fibers modified by tempo‐mediated oxidation

The purpose of this research was to accomplish antimicrobial properties in lyocell fibers by Ag⁺ ions sorption from aqueous silver nitrate solution. Sorption properties of lyocell fibers were improved by the selective TEMPO‐mediated oxidation, i.e. oxidation with sodium hypochlorite and catalytic amount of sodium bromide and 2,2,6,6‐tetramethylpiperidine‐1‐oxy radical (TEMPO). The most suitable experimental conditions for the selective TEMPO‐mediated oxidation were determined by changing oxidation conditions: concentration of sodium hypochlorite, as well as duration of sorption. The obtained results showed that the maximum sorption capacity (0.809 mmol of Ag⁺ ions per gram of fibers) of modified lyocell fibers was obtained for the sample modified with 4.84 mmol NaClO per gram of cellulose, during 1 h. The antifungal activity of the TEMPO‐oxidized lyocell fibers with silver ions against fungi from the Candida family, Candida albicans (ATCC 24433), and antibacterial activity against two strains: Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922) were confirmed in vitro. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of the structure of polymer and nanosilica additive on the sorption and electric properties of various alginate fibers

Effects of the structure of polymer and nanosilica additive on the sorption and electric properties of various alginate fibers has been investigated. It has been found that regardless of the differences in the chemical structure and the presence of nanosilica, the examined types of alginate fibers show similar values of moisture absorption at relative humidity up to 85%. An exception is the fiber from sodium alginate. It has been found that the electric conductivity and the accompanying polarization processes of various types of alginate fibers depend on the chemical structure of the fiber‐forming polymer. It has been found that the amount of moisture absorbed by the fiber‐forming polymer of alginate fibers exerts a strong influence on their electric properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 686–694, 2006     

Strontium ion substituted alginate-based hydrogel fibers and its coordination binding model

Sr-alginate and Ca-alginate hydrogel fibers were fabricated via microfluidic spinning technology, and various analytical methods were adopted to characterize fibers and disclose the coordination model of Sr²⁺ binding with alginate molecule chain. For both fibers, the more crosslinking sites of Sr²⁺ with alginate molecule were illustrated in comparison with that of Ca²⁺. The more robust mechanical performance of Sr-alginate fibers than Ca-alginate counterpart was a strong indication of the more strong binding of Sr²⁺ with alginate molecular chain. FTIR and electric conductivity disclosed the chelation type of Sr²⁺ with alginate macromolecule being similar to that of Ca²⁺, which was core-shell of the analogous “egg-box” structure. Circular dichroism spectroscopy further certified the extra coordination sites for Sr²⁺ with alginate molecule than Ca²⁺. Research on the coordination model will be more beneficial to optimizing the physicochemical properties of alginate fibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48571.     

Effect of crosslinked structure on SO2 gas sorption properties in amino‐functional copolymers

SO₂ gas sorption properties were examined for poly(styrene‐co‐chloromethyl styrene) functionalized with N,N‐dimethyl‐1,3‐propanediamine (DMPDA). The DMPDA‐functional copolymers were prepared under various reaction conditions. Two types of SO₂ sorption behaviors were observed for these DMPDA‐functional copolymers: SO₂ sorption capacity was very high irrespective of slow sorption/desorption rates (type I), and the sorption/desorption rates were very fast while SO₂ sorption capacity was small (type II). Fourier transform infrared analysis and dielectric loss measurement revealed that the type II sorption behavior was obtained for the highly crosslinked DMPDA‐functional copolymers. The degree of crosslinking was affected by both the solvent used to react DMPDA with the copolymer and the percent conversion of the chloromethyl styrene group. It was confirmed that DMPDA‐functional copolymers having a highly crosslinked structure are suitable materials in quartz crystal microbalance (QCM)‐type polymeric SO₂ gas sensors. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2982–2987, 2003     

Study of nanofiber scaffolds of PAA,PAA/CS,and PAA/ALG for its potential use in biotechnological applications

In recent times, electrospun nanofibers have been widely studied from several biotechnological approaches; in this work, poly(acrylic acid) (PAA) solutions mixed with chitosan and alginate were electrospun and characterized to determine the behavior of these fibers when used in combination with bacteria, different samples were incubated with the bacterial strains: Streptomyces spp., Micromonospora spp., and Escherichia coli and a OD600 test was performed. The formation of nanofibers via electrospinning and the physicochemical properties of the obtained fibers were evaluated. Results showed that the presence of chitosan enhanced the thermal stability of PAA, since PAA/alginate fibers lost 5% of their mass at 41°C, whereas PAA/chitosan lost this amount at around 125°C. The fibers demonstrated suitable characteristics to be used as a bacteria bioreactor.     

Preparation and characterization of alginate/gelatin blend fibers

Alginate and gelatin blend fibers were prepared by spinning their solution through a viscose‐type spinneret into a coagulating bath containing aqueous CaCl₂ and ethanol. The structure and properties of the blend fibers were studied with the aid of infrared spectra, scanning electron micrography, X‐ray diffraction, and thermogravimetric analysis. Mechanical properties and water‐retention properties were measured. The best values of the tensile strength and breaking elongation of blend fibers were obtained when gelatin content was 30 wt %. The water‐retention values of blend fibers increase as the amount of gelatin is raised. The structural analysis indicated that there was strong interaction and good miscibility between alginate and gelatin molecules resulted from intermolecular hydrogen bonds. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1625–1629, 2005     

Structural evaluation and mechanical property of boron nitride fibers during melt‐drawn fabrication process

Boron nitride (BN) fibers were fabricated on a large scale through the melt‐drawn technique from low‐cost boric acid, NH₃, and N₂. Evolution of structure and properties of BN fibers during the fabrication process was studied by Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), scanning electron microscope (SEM), and X‐ray photoelectron spectroscopy (XPS). The mechanical properties of BN fibers were tested and analyzed. The results shown that both the mechanical properties and the crystallinity of BN fibers slightly increased with the temperature from 450 to 850°C, due to the combination of the fused‐B₃N₃. For BN fibers heat‐treated at 850 or 1000°C, the tensile strength (σ^R) and elastic modulus (E) were strongly increased because of the increase in crystallization of the BN phase. The meso‐hexagonal BN fibers with a diameter of 5.0 μm were fabricated at 1750°C, of which the tensile strength (σ^R) and elastic modulus (E) are 1200 MPa and 85 GPa, respectively. BN fibers with excellent mechanical properties and proper diameters were obtained by nitriding of green fibers during their conversion into ceramic.     

Drug‐loaded microparticles prepared by the one‐step deposition of calcium carbonate/alginate onto cotton fabrics

Calcium carbonate (CaCO₃)/alginate inorganic–organic hybrid particles were synthesized and deposited on to the surface of cotton fabrics with a novel one‐step procedure. The effects of the Ca²⁺/CO₃^2?/alginate molar ratio on the cotton matrix were investigated. The optimization of the process resulted in a regular shaped hybrid microparticles, and scanning electron microscopy revealed that the particles were uniformly distributed on the surface of the fibers. Dynamic light scattering showed that the particles were about 2 μm in diameter. Moreover, transmission electron microscopy images demonstrated that the core–shell structure of the particles existed along with CaCO₃ evenly enfolded into the alginate layer. An X‐ray diffraction pattern displayed that the alginate/CaCO₃ hybrid microparticles were a mixture of calcite and vaterite crystal. Fourier transform infrared spectroscopy indicated that CaCO₃/alginate hybrid particles formed in situ were the only deposited materials. The thermogravimetric analysis curve indicated a certain mass ratio of the alginate and CaCO₃ in the hybrid particles. Furthermore, the drug‐loading and drug‐release properties of the hybrid microspheres were studied, and the results show that the water‐soluble diclofenac sodium could be effectively loaded in the hybrid microparticles and the drug release could be effectively sustained. Finally, both of the microparticles and modified fabrics had good cytocompatibility. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42618.     

Material constraint-based laser performance estimation of Yb3+-doped phosphate fibers

Based on the material properties of 47 Yb³⁺-doped phosphate fibers with different sizes and lengths, a laser performance estimation model was established to estimate the laser wavelength just above the threshold (λ_th), the laser threshold (P_th), and the laser slope efficiency (η). This model was solved via a numerical computing method with an accuracy of 0.01. Under the material constraints of this model, λ_th, P_th, and η were investigated by sensitivity analysis and Monte Carlo numerical simulation. The results show that short fibers with a small core diameter may more easily produce a shorter λ_th. Additionally, for constant material properties, fibers with a longer λ_th may have a lower P_th and higher η than other fibers. Verifying the above conjecture, an output power of 8.7 W with 35% enhancement in slope efficiency was obtained from an optimized phosphate fiber for an optical path in which the output of the short-wave laser was inhibited. This model can be extended to simulate the lasing wavelength of multi-composition fibers, providing a theoretical basis for special laser bands, laser material preparation, and fiber structure design.     

Phosphorus sorption in relation to soil properties in some cultivated Swedish soils

Phosphorus (P) sorption properties are poorly documented for Swedish soils. In this study, P sorption capacity and its relation to soil properties were determined and evaluated in 10 representative Swedish topsoils depleted in available P. P sorption indices were estimated from sorption isotherms using Langmuir and Freundlich equations (X_m and a_F, respectively) and P buffering capacity (PBC). X_m ranged from 6.0 to 12.2 mmol kg^–1. All indices obtained from sorption isotherms were significantly correlated with each other (r=0.96^*** to r=0.99^***). Two single-point sorption indices (PSI₁ and PSI₂) were also determined, with additions of 19.4 and 50 mmol P kg^–1 soil, respectively. Both PSI indices were well correlated with X_m (r0.98^***), with PSI₁ giving the highest correlation. As isotherms for determining P sorption capacities involve laborious analytical operations, PSI₁ would be preferable for routine analyses. X_m was significantly correlated with Fe extracted by sodium pyrophosphate and ammonium oxalate, to Al extracted by ammonium oxalate and dithionite-citrate-bicarbonate and to organic c. X_m was also significantly correlated with the sum of Fe and Al extracted by ammonium oxalate. The best prediction of X_m through multiple regression was obtained when Fe extracted in ammonium oxalate and Al extracted in dithionite-citrate-bicarbonate were used. Based on the results obtained, both PSI₁ and oxalate-extractable Fe plus Al can be used for predicting P sorption capacity in Swedish soils.     

Preparation of nanostructured porous carbon composite fibers from ferrum alginate fibers

Nano‐microstructured porous carbon composite fibers (Fe₂O₃@C/FeO@C/Fe@C) were synthesized by the thermal decomposition of ferrum alginate fibers. The ferrum alginate fiber precursors were prepared by wet spinning, and calcined at 300–1000°C in high purity nitrogen. The resulting composite fibers consist of carbon coated Fe₂O₃/FeO/Fe nanoparticles and porous carbon fibers. All the prepared nanostructures were investigated using thermal gravimetry, X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, transmission electron microscope (TEM), and nitrogen adsorption–desorption isotherm. The results show that there are five stages in the decomposition process of the ferrum alginate fibers. Transitions between the five stages are affected by the decomposition temperature. XRD results show that maghemite (Fe₂O₃), wüstite (FeO), martensite (Fe) nanoparticles were formed at 300–500°C, 600–700°C, 800–1000°C, respectively. Scanning electron microscopy and TEM results indicate that the composite fibers consist of nanoparticles and porous carbon. The diameter of the nanosized particles increased from 100 to 500 nm with increasing reaction temperature. The nitrogen adsorption–desorption results also show that the composite fibers have a micro‐ and mesoporous structure. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Moisture sorption/desorption behavior of various manmade cellulosic fibers

The kinetics of dynamic water vapor sorption and desorption on viscose, modal, cotton, wool, down, and polyester fibers and lyocell knit fabrics were investigated according to the parallel exponential kinetics (PEK) model. The total equilibrium moisture regain (M_inf(total)) in all the materials decreased with increasing temperature. However, the partial equilibrium fast sorption, determined by PEK simulation at 60% relative humidity (RH) and 36°C, was larger than that at 20°C, whereas the partial equilibrium slow sorption was smaller. The characteristic times in fast sorption (τ₁) and in slow sorption (τ₂) for lyocell were reduced when the conditions were changed from 60% RH and 20°C to 36°C, whereas those for the other fibers increased. Lyocell exhibited the highest M_inf(total) value and the lowest τ₁ and τ₂ values, and this suggested high equilibrium moisture content and fast moisture uptake/release, that is, high moisture accessibility for lyocell. The relationships between the moisture regain, hysteresis, water retention capacity, and Brunauer–Emmett–Teller surface volume in the materials were also examined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1621–1625, 2005     

Surface Properties of Structural Modified PA 6 Fibers

Fine structure, surface properties (electrokinetic properties) and the accessibility of free adsorption groups determine the sorption behavior of fiber‐forming polymers. The fine structure of such polymers can be explained using a two‐phase model, composed of alternating crystalline and amorphous regions. Different treatments (heat, solutions, ...…) used in fiber production or finishing processes change the fine structure and surface morphology, causing differences in the accessibility of adsorption places. Distinctions in the sorption capacity of modified polymers occur in this manner. In this paper we have carried out an analysis (using PA 6 fibers as an example) of the interdependence between fiber crystalline structure (density determination and X‐ray analysis), surface morphology (using AFM), their electrokinetic character (streaming potential measurements) and their absorption properties (iodine sorption value determination). The structure and adsorption abilities of the PA 6 fibers were modified by annealing in vacuum and treatment in phenol solution. The results show that the modifications of the fibers' fine structure cause changes in both their surface morphology and electrokinetic properties. All these changes are reflected in the different fiber absorption properties. A well‐oriented fibril structure toward the fiber axis could be observed on the surface of the raw sample. Following annealing in a vacuum or treatment in phenol solution the surface fibrils joined together and built up wider fibril bounds with hollow places between them. These surface morphology changes are reflected in the different ZP values in plateau. They can be increased by simultaneous decreasing of the adsorption potential values (Φ, Φ) and the iodine sorption values.     

Modification of dry‐spun Suplon polyimide fibers by mixed‐acid oxidation and their effects on the properties of polypropylene‐resin‐based composites

In this study, the effects of mixed‐acid oxidation on the contents of surface elements, morphology, fiber fineness, mechanical properties, mass change rate, chemical structure, and microaggregate structure of dry‐spun Suplon polyimide (PI) fibers were systematically investigated with wet chemical treatment with HNO₃/H₂SO₄. Experiments investigating both the improvement in the O/C ratio of the fiber surface elements and the changes in other performance features were conducted through the functional modification of the fibers. Meanwhile, the causes of specific changes in the mechanical properties of the oxidized PI‐fiber‐reinforced polypropylene‐resin‐based composites were studied and are discussed. The results of this study demonstrate that the treatment of the fibers with HNO₃/H₂SO₄ mixed‐acid oxidation resulted in significant changes in the properties of the fibers; these changes included an uneven surface, increased specific surface area and surface roughness, a locally etched surface, increased surface energy and O/C ratio, an enhanced wettability, an increased fiber fineness, reduced mechanical properties, and a mass gain in the fibers. Although the chemical structures of the fibers treated by oxidized HNO₃/H₂SO₄ were not significantly changed compared to those of the untreated fibers, the microscopic aggregation of the treated fibers changed to some degree, and the ratio of the amorphous regions significantly increased. Taken together, the functional modification of the PI fiber surface was achieved efficiently through the use of a suitable HNO₃/H₂SO₄ oxidation process and with other performance features of the fibers taken into account. This was favorable for the enhancement of the interfacial properties of the polypropylene fibers and the matrix resins, and thus, the modification improved the mechanical properties of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44932.     

Preparation of alginate/soy protein isolate blend fibers through a novel coagulating bath

Alginate and soy protein isolate blend fibers were prepared by spinning their solution through a viscose‐type spinneret into a novel coagulating bath containing aqueous CaCl₂, HCl, and ethanol. The structures and properties of the fibers were studied with the aids of infrared spectra (IR), X‐ray diffraction (XRD), and scanning electron micrograph (SEM). Mechanical properties and water‐retention properties were measured. And with the sample of AS1 fiber (soy protein isolate weight content was 10%), the effects of the composition of the novel coagulating bath were also studied. The best values of the tensile strength of AS1 were 14.1 cN/tex in the dry state and 3.46 cN/tex in the wet state, respectively. Both the dry state and wet state breaking elongation were also having the best value 20.71% and 56.7% with AS1. Mechanical properties of the AS1 enhanced with the CaCl₂ content increased in the coagulating bath. When the HCl content was 1%, the mechanical property of the fiber was best. Ethanol in the coagulating bath increased the wet mechanical properties of the fiber by 41.2% (tensile strength) and 45.1% (breaking elongation) when the ethanol weight content in the coagulating bath was 50%; but it had little effect on the dry mechanical properties. And the water‐retention value (WRV) of blend fibers decreased as the amount of soy protein isolate was raised. The structure analysis indicated that there were strong interaction and a certain level of miscibility between alginate and soy protein isolate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 425–431, 2006