Diameter variations of irregular fibers under different tensions

The cross-section area of animal fibers varies along the fiber length, and this geometrical irregularity has a major impact on the mechanical properties of those fibers. In practice fibers are often subjected to tensile stresses during processing and application, which may change fiber cross-section area. It is thus necessary to examine geometrical irregularity of fibers under tension. In this study, scoured animal fibers were subjected to different tensile loading using a Single Fiber Analyzer (SIFAN) instrument. The 3D images of the fiber specimens were first constructed, and then along-fiber diameter irregularities of the specimens were analyzed for different levels of tensile loading. The changes in effective fineness of the fiber specimens were also discussed. The results indicate that for the wool fibers examined, there is considerable discrepancy in the fiber diameter results obtained from the commonly used single scan along fiber length and that from multiple scans at different rotational angles, and that the diameter variation along fiber length increases as fiber tension increases. The results also show that when diameter reduction treatments are applied to wool by stretching, the reduced average fiber diameter is associated with an increase in both within-fiber and between-fiber diameter variations. So in terms of effective fineness, the change is much smaller than the difference between the average diameters of the parent and treated wool. These results have significant implications for improving the accuracy of fiber diameter measurement and evaluation.     

Effects ofIn Vitro degradation on the weight loss and tensile properties of PLA/LPCL/HPCL blend fibers

PLA/LPCL/HPCL blend fibers composed of poly (lactic acid) (PLA), low molecular weight poly (ɛ-caprolactone) (LPCL), and high molecular weight poly (ɛ-caprolactone) (HPCL) were prepared by melt blending and spinning for bioabsorbable filament sutures. The effects of blending time and blend composition on the X-ray diffraction patterns and tensile properties of PLA/LPCL/HPCL blend fibers were characterized by WAXD and UTM. In addition, the effect ofin vitro degradation on the weight loss and tensile properties of the blend fibers hydrolyzed during immersion in a phosphate buffer solution at pH 7.4 and 37°C for 1–8 weeks was investigated. The peak intensities of PLA/LPCL/HPCL blend fibers in X-ray diffraction patterns decreased with an increase of blending time and LPCL contents in the blend fibers. The weight loss of PLA/LPCL/HPCL blend fibers increased with an increase of blending time, LPCL contents, and hydrolysis time while the tensile strength and modulus of the blend fibers decreased. The tensile strength and modulus of the blend fibers were also found to be increased with an increase of HPCL contents in the blend fibers. The optimum conditions to prepare PLA/LPCL/HPCL blend fibers for bioabsorbable sutures are LPCL contents of 5 wt%, HPCL contents of 35 wt%, and blending time of 30 min. The strength retention of the PLA/LPCL/HPCL blend fiber prepared under optimum conditions was about 93.5% even at hydrolysis time of 2 weeks.     

Green composites. I. physical properties of ramie fibers for environment-friendly green composites

The surface topography, tensile properties, and thermal properties of ramie fibers were investigated as reinforcement for fully biodegradable and environmental-friendly ‘green’ composites. SEM micrographs of a longitudinal and cross-sectional view of a single ramie fiber showed a fibrillar structure and rough surface with irregular cross-section, which is considered to provide good interfacial adhesion with polymer resin in composites. An average tensile strength, Young’s modulus, and fracture strain of ramie fibers were measured to be 627 MPa, 31.8 GPa, and 2.7 %, respectively. The specific tensile properties of the ramie fiber calculated per unit density were found to be comparable to those of E-glass fibers. Ramie fibers exhibited good thermal stability after aging up to 160°C with no decrease in tensile strength or Young’s modulus. However, at temperatures higher than 160°C the tensile strength decreased significantly and its fracture behavior was also affected. The moisture content of the ramie fiber was 9.9%. These properties make ramie fibers suitable as reinforcement for ‘green’ composites. Also, the green composites can be fabricated at temperatures up to 160°C without reducing the fiber properties.     

The preparation and characterization of conductive poly(ethylene terephthalate)/polyaniline composite fibers using benzoyl peroxide

Conductive polyaniline (PAn)/poly(ethylene terephthalate) (PET) composite fibers were prepared by chemical polymerization of aniline in the presence of PET fibers using benzoyl peroxide (Bz₂O₂) in organic solvent/aqueous hydrochloric acid mixtures. The effects of polymerization conditions such as organic solvent/water ratio, oxidant, aniline and hydrochloric acid concentrations and temperature were investigated on the amount of PAn deposited on PET fiber and the electrical surface resistance of composite fibers. The maximum PAn content and the lowest electrical surface resistance of composite fibers were observed at HCl concentrations of 0.5 mol L⁻¹. The properties of PAn/PET composite fibers such as density, diameter, tensile strength and breaking elongation were also investigated in comparison with those of pure PET. Characterization of conductive composite fibers was carried out by FTIR, TGA, SEM techniques, surface resistance measurements, and cross section images taken by optical microscope.     

Surface modification of okra bast fiber and its physico-chemical characteristics

The effect of chemical treatment i.e. bleaching, alkalization and graft copolymerization on the morphology changes of okra bast fiber has been investigated by means of infrared spectroscopy (IR), scanning electron microscopy (SEM), water absorption and tensile properties measurements. The graft copolymerization reaction of bleached fiber with acrylonitrile monomer (AN) has been carried out under the catalytic influence of K₂S₂O₈ and FeSO₄ redox system. The maximum graft yield (11.43 %) has been found at 70°C temperature, 3×10⁻² mol/l acrylonitrile, 5×10⁻³ mol/l K₂S₂O₈, 5×10⁻³ mol/l FeSO₄ and for 90 min. On the contrary, the fiber has been treated with 10 % NaOH solution, which is much effective to remove the impurities. Based on findings of water absorption, tensile properties and SEM micrograph, the AN-grafted fiber has been showed better properties than bleached and alkali treated fibers. The degree of modification of okra bast fiber by chemical treatment has been evaluated by IR measurement.     

Quantification of degradation and surface morphology of NB7 silk fibers irradiated by 8 MeV electron beam using XRD and SEM techniques

NB7 silk fiber (Bombyx mori) was irradiated with the maximum dose range of 100 kGy using 8 MeV electron beam at room temperature. Irradiation effect in these fibers is quantified in terms of the changes in microstructural parameters employing X-ray diffraction line profile analysis technique. For this purpose we have used three asymmetric distribution functions for column lengths in a crystal. The decreasing trend of crystallite size values (〈N〉 as well as D _s ) and crystallinity with increasing dosage of radiation clearly indicates the degradation of fiber. Of the several factors responsible for such a behavior, we presume that the chain scission of polymer network is a significant one over others and it is well pronounced here, leading to low molecular weight of the samples. This degradation is attributed to many changes in tensile properties of the polymer. Comparison of SEM photographs also confirms the X-ray results.     

Study on damping and mechanical properties of nano-titanium dioxide/acrylonitrile butadiene-rubber hollow fiber

TiO₂/NBR-PVC hollow fibers were spinned by NBR casting solution blended PVC with nano-titanium dioxide (TiO₂). The effect of NBR-PVC hollow fiber damping and mechanical properties aroused by loading TiO₂ were studied. Results showed that the hollow fibers loaded TiO₂ increased in tensile strength, storage modulus, stiffness and glass transition temperature, while decreased in tanδpeak and breaking tensile elongation. The damping of the TiO₂/NRR-PVC hollow fiber were not only linked to the dosage of TiO₂, but also related to the degree of dispersion in matrix.     

The modification of Kevlar fibers in coupling agents by <Emphasis Type="Italic">γ</Emphasis>-ray co-irradiation

Kevlar fibers were treated in three kinds of coupling agents’ solutions by Co⁶⁰ γ-ray co-irradiation. After the treatment, the interlaminar shear strength (ILSS) values of Kevlar fibers/epoxy composites were all improved. Surface elements of the fibers were determined by energy dispersive X-ray microanalysis (EDX). X-ray photoelectron spectroscopy (XPS) indicated that the oxygen/carbon ratio of the treated fibers was increased and Fourier transform infrared (FT-IR) spectrum confirmed the increase in the polar groups at the fiber surface. The tensile strength of the fibers was evaluated by statistical analysis using the Weibull distribution. The wettability of the fiber surface was also enhanced by the treatment. The possible mechanisms of γ-ray co-irradiation treatment are proposed by the radical reactions. The results indicated that γ-ray co-irradiation technique modified the physicochemical properties of Kevlar fibers and improved the interfacial adhesion of its composites.     

Mechanical properties of wool fiber in the stretch breaking process

Short wool fibers obtained by the stretch breaking process can be blended with cotton fibers and processed in a cotton spinning system, which has a high production rate. For the structural property of the wool fiber after stretch breaking, the diameter and length of the wool fiber were measured as a function of time. The diameter of the broken fibers was finer than the diameter of untreated fibers. The fiber diameter at the break point was the finest and was more irregular than the original fiber. The broken fiber showed mechanical properties of increased modulus, decreased breaking strain, and increased breaking strength.     

Preparation and dielectric properties of polyvinyl alcohol (Co,Zn Acetate) Fiber/n-Si and polyvinyl alcohol (Ni,Zn Acetate)/n-Si Schottky diodes

Dielectric properties and ac electrical conductivity (σ _ac ) of Au/PVA(Co, Zn acetate)/n-Si and Au/PVA(Ni, Zn acetate)/n-Si Schottky diodes (SDs) have been investigated in dark and under illumination by using experimental capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements at 1 MHz and room temperature. Experimental results indicate that the change in dielectric constant (ɛ′), dielectric loss (ɛ″), loss tangent (tanδ), the real (M′) and imaginary (M″) parts of electric modulus and ac electrical conductivity (σ _ac ) with illumination were found to change linearly with illumination level (P). On the other hand, the ɛ′, ɛ″, tanδ and σ _ac vs P have positive slope while the M′ and M″ vs P have negative slope. Such behavior of dielectric properties and σ _ac can be attributed to illumination induced electron-hole pairs under illumination effect in the depletion region of SDs. The obtained results under illumination suggest that these devices can be used as a sensor in optical applications.     

Effect of the low and radio frequency oxygen plasma treatment of jute fiber on mechanical properties of jute fiber/polyester composite

We investigated the surface modification of jute fiber by oxygen plasma treatments. Jute fibers were treated in different plasma reactors (radio frequency “RF” and low frequency “LF” plasma reactors) using O₂ for different plasma powers to increase the interface adhesion between jute fiber and polyester matrix. The influence of various plasma reactors on mechanical properties of jute fiber-reinforced polyester composites was reported. Tensile, flexure, short beam shear tests were used to determine the mechanical properties of the composites. The interlaminar shear strength increased from 11.5 MPa for the untreated jute fiber/polyester composite to 19.8 and 26.3 MPa for LF and RF oxygen plasma treated jute fiber/polyester composites, respectively. O₂ plasma treatment also improved the tensile and flexural strengths of jute fiber/ polyester composites for both plasma systems. It is clear that O₂ plasma treatment of jute fibers by using RF plasma system instead of using LF plasma system brings about greater improvement on the mechanical properties of jute/polyester composites.     

The variability of mechanical properties and molecular conformation among different spider dragline fibers

Spider dragline fiber is a high-performance biomaterial that has received much attention. To screen the outstanding spider dragline fibers, the mechanical properties and microstructures of dragline fibers collected from Nephia clavata, Nephia pilipes, Argiope bruennichi and Argiope amoena were investigated. It was found that the mechanical properties of spider dragline fiber were variable. Among the four different species, the larger spiders did not always extrude thicker dragline fibers and produce fibers with the maximum breaking force. The dragline fibers could sustain one to three times the body weight of the spider at a reeling speed of 20 mm/s. N. clavata dragline fiber showed a stronger breaking stress and initial modulus than that of N. pilipes, A. bruennichi and A. amoena. With an increasing reeling speed, the breaking strain decreased; the initial modulus increased in N. clavata, N. pilipes and A. bruennichi, but the breaking stress exhibited a different tendency. The results also revealed that dragline fiber of N. clavata contained the most β-sheet polypeptides and an excellent orientation of β-sheet molecular chains.     

Synthesis and characterization of boron doped alumina stabilized zirconia fibers

Boron doped PVA/Zr-Al acetate nanofibers were prepared by electrospinning using PVA as a precursor. The effect of calcination temperature on morphology and crystal structure was investigated at 250, 500, and 800 °C. The study also establishes the effect of boron doping on the morphology of PVA/Zr-Al acetate nanofibers at various calcination temperatures. The measurements showed that the conductivity, pH, viscosity and the surface tension of the hybrid polymer solutions have increased with boron doping. In addition, the fibers were characterized by FTIR, DSC, XPS, XRD and SEM techniques. The addition of boron did not only increase the thermal stability of the fibers, but also increased the average fiber diameters, which gave stronger fibers. The DSC results indicated that the melting temperature (Tm) of the fibers was increased from 256 to 270 °C with the addition of boron. XRD peak patterns showed that after further heat treatment at 800 °C, zirconia exists in two phases of tetragonal and monoclinic modifications. Moreover, alumina does not transform into the γ-Al₂O₃ and θ-Al₂O₃ phase at 800 °C. The SEM appearance of the fibers showed that the addition of boron resulted in the formation of crosslinked bright surfaced fibers.     

Modification of natural bamboo fibers for textile applications

Natural bamboo fibers have excellent properties suggesting that there is a good potential for them to be used in textiles; however, they have not received the attention that they deserve owing to their coarse and stiff quality. Therefore, a chemical method for extraction and modification of natural bamboo fibers for textile end uses were developed and optimized in this paper. The quality of natural bamboo fibers were characterized by their chemical composition, linear density, and tenacity. Experimental results show that the modified bamboo fibers are finer, with significant lower content of noncellulosic substances. The processing parameters are optimized as: 20 g/l NaOH, 3 g/l Na₅P₃O₁₀, 5 g/l Na₂SO₃, 3 g/l penetrating agent, with a fiber to liquid ratio of 1:10, at 100 °C for 2 h, and the bamboo fiber thus produced has cellulose amount of 73.25 %, fineness of 3.26 tex, average length of 44.5 mm, breaking elongation of 2.8 % and tenacity of 2.41 cN/dtex. The result of this study may offer a possibility of developing natural bamboo fibers into practical applications in textiles.     

The combined tensile and torsional behavior of irregular fibers

Most fibers are irregular, and they are often subjected to combined loading conditions during processing and end-use. In this paper, polyester and wool fibers under the combined tensile and torsional loads have been studied for the first time, using the finite element method (FEM). The dimensional irregularities of these fibers are simulated with sine waves of different magnitude and frequency. The breaking load and breaking extension of the fibers at different twist or torsion levels are then calculated from the finite element model. The results indicate that twist and level of fiber irregularity have a major impact on the mechanical properties of the fiber and the effect of the frequency of irregularity is relatively small.     

Variability in physicochemical and nutritional quality traits of parents,F2 and F3 generations of lentil crosses

Ten physicochemical and nutritional quality traits (100-seedweight, seed volume, seed density, bulk density, hydrationcapacity, hydration index, swelling capacity, protein, tryptophanand energy value) were examined in the seed samples of parents,F₂ and F₃ generations of three microsperma ×microsperma and two microsperma × macrospermacrosses of lentils. Significant variation for different traits wasobserved among the genotypes in both the groups and also amongboth types of crosses in F₂ and F₃ generations. Ranges,means and coefficients of variation (CV %) for various traitsamong parents, F₂ and F₃ generations of different crosses,along with the deviations between F₂ and F₃ generationmeans for various traits in different crosses are discussed. Alsosuggested is a breeding strategy for evolving lentil varieties withimproved seed yield and nutritional quality parameters.     

Preparation and properties of 2-(2-aminoethoxy) ethyl chitosan/cellulose fiber using N-methylmorpholine-N-oxide process

N-methylmorpholine-N-oxide (NMMO) is used widely in the manufacturing of man-made cellulose fibers and functional lyocell fibers due to its environment-friendly advantage. Although chitosan is known as a natural antibacterial polymer it has poor solubility in neutral to basic medium and the antibacterial activity is shown only in acidic medium. Chitosan’s poor solubility in NMMO is the disadvantage for the production of antibacterial lyocell fibers. This paper investigates a more “NMMO soluble” derivative of chitosan, 2-(2-aminoethoxy) ethyl chitosan (AECS). AECS has greatly improved solubility in NMMO hydrate, and stronger antibacterial activity than chitosan. AECS was introduced to modify the lyocell fiber spun in a co-solution of cellulose and AECS in NMMO hydrate. The physical properties and antibacterial activity of the fibers were examined and the results indicated that the modified lyocell fiber, containing more than 2 wt% of AECS, exhibits good antibacterial activity against E. coli and slightly decreased tensile strength compared with unmodified fibers.     

Dynamic mechanical analysis of randomly oriented short bagasse/coir hybrid fibre-reinforced epoxy novolac composites

Hybrid composites of epoxy novolac reinforced with short bagasse fibres and short coir fibres were prepared. The mechanical and dynamic mechanical properties of these bagasse-coir hybrid fibres reinforced epoxy novolac composites were investigated with reference to different layering patterns of the composites. The tensile properties of the tri-layer composites are recorded higher than those of the bi-layer composites, whereas the flexural properties of the tri-layer composites are lower than bi-layer composites. The tensile strength of the intimate mix composite is comparable with trilayer composite having bagasse as skin material. The effect of layering pattern on storage modulus (E′), damping behavior (tan δ), and loss modulus (E″) was studied as a function of temperature and frequency. The E′ values of the bi-layer composites are recorded lower than those of tri-layer (bagasse/coir/bagasse) and intimately mixed hybrid composites. The minimum E′ value is obtained for the composites made with coir as skin layer. Bi-layer composite shows maximum damping property. The theoretical modeling showed good correlation with experimental results at above glass transition temperature (T _g ), while theoretical model deviates experimental data at lower T _g . The Arrhenius relationship has been used to calculate the activation energy of the glass transition of the composites.     

Sound characteristics according to cross-sectional shapes of fibers

In order to investigate the effects of cross-sectional shapes on the sound characteristics of polyester fibers, 10 specimens were woven into a twill structure made of round, hollow, triangular, u-shape, cruciform, and composite cross-sectional (▴/▴, ()/▴,Y y) fibers. Their rustling sounds were recorded, and their sound spectra were obtained from FFT analysis. Physical sound parameters (LPT, ΔL, Δf) and Zwicker’s psychoacoustic parameters of the loudness(Z), sharpness(Z), roughness(Z), and fluctuation strength(Z) were calculated from the sound spectra. According to noncircular cross-section fibers, the hollow shaped fiber had the highest value of LPT, ΔL, loudness(Z), and fluctuation strength(Z). The triangular shaped fiber had a lower value of LPT, ΔL, loudness(Z), and roughness(Z) than those of the round shaped fiber. Among composite cross-section fibers, C1 (▴/▴) and C3 (Y y) had higher values of LPT, ΔL, Δf, and loudness(Z) but C2 (()/▴) had lower values. Also the LPT, ΔL, sharpness(Z), and roughness(Z) values of different denier were similar to each other, but the Δf and loudness(Z) values increased as the denier increased.     

Effect of two bounding walls on the rotational motion of a fiber in the simple shear flow

The effect of two bounding walls on the rotational motion of a freely suspended non-Brownian fiber in the simple shear flow at low Reynolds number was investigated numerically using the lattice-Boltzmann method. Data were reported for the fibers with aspect ratios of 8, 10, and 15 under various ratios of wall gap (2h) to fiber length (L). For 2h/L≥3.0, the time-dependent orientation of the fiber is shown to be in quantitative agreement with the Jeffery’s theory for ellipsoids suspended in an unbounded linear shear flow, and the effect of the walls on the rotational period of the fiber is insignificant for all fibers with different aspect ratios. For 1.8≤2h/L<3.0, the results reveal that the walls have different effects on the rotation of fiber. For 2h/L<1.8, the complete periodical motion of the fiber is suppressed. The fiber rotates to nearly aligning with the flow direction, and then ceases to rotate. In this orientation, the walls have a stabilizing effect on the fiber and this effect is more pronounced for the fibers with large aspect ratio. The fiber finally does not orient with the flow direction, but with a small angle with the flow direction, and the angle is an increasing function of the fiber aspect ratio and dependent on the wall gap.