Thermal degradation studies of poly(o-anisidine) doped with 5-sulfosalicylic acid

Thermal decomposition of the solid state of poly(o-anisidine) (POAN) base (POAN-EB) and salt [doped with 5-sulfosalicylic (SSA) acid] (SSA-doped POAN) forms has been studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) under non-isothermal conditions. The potential (PE) and optimum molecular geometric (OMG) energies of the repeating unit (tetramer form) of investigated matrix were calculated using molecular mechanics (MM+) calculations. These calculations (PE= −3.48×10⁹ and OMG=−122.72 kJ mol⁻¹) indicate that the optimum molecular geometric structure of this matrix is highly stable. The empirical formula of the doped polymer is best represented by [POAN-2SSA.n/6H₂O] and substantiate by elemental analysis and MM+ calculations. The full polymer decomposition and degradation were found to occur in three stages during the temperature increase. The decomposition activation energy (E _d) of both POAN base (POAN-EB) and its doped (SSA-doped POAN) were calculated by employing different approximations. The heating rate of decomposition and the frequency factor (k _o ) as well as kinetic parameters were calculated for doped or base form of this matrix. A remarkable heating rate dependence of the decomposition rate of the SSA-doped POAN matrix was observed.     

Model system for mechanistic study of catalytic bleaching of cotton

We have developed a homogeneous model system to study the mechanism of hydrogen peroxide bleaching using [Mn₂O₃(N,N′,N″-trimethyl-1,4,7-triazacyclononane)₂](PF₆)₂ (MnTMTACN) as catalyst. The primary model pigment examined is morin (3,5,7,2′,4′-pentahydroxyflavone) owing to its presence in native cotton fiber. Additionally, a series of model compounds with systematic structural differences are examined in order to facilitate the development of a mechanistic understanding of the bleaching system. The pigment oxidative degradation reaction is monitored by UV-Vis spectrophotometry. The influence of pH is examined in both homogeneous and heterogeneous model systems. The use of MnTMTACN catalyst enables low-temperature hydrogen peroxide bleaching of cotton fabric at slightly lower pH values.     

Modeling the tensile strains of non-uniform fibers

The maximum strain experienced by the thinnest segment of a non-uniform fiber governs fiber breakage, yet this maximum strain can not be obtained from a normal single fiber test. Only the average strain of the whole fiber specimen can be obtained from a normal single fiber tensile test. This study has examined the relationship between the average strain, the maximum strain and the degree of fiber non-uniformity, expressed in coefficient of variation (CV) of fiber diameters along fiber length. The tensile strain of irregular fibers has been simulated using the finite element method (FEM). Using this method, average and maximum tensile strains of non-uniform fibers were calculated. The results indicate that for irregular fibers such as wool, there is an exponential relationship (i.e.ɛ _ave ɛ _max=ae ^{−b CV} ) between the ratio of average breaking strain and maximum breaking strain (ɛ _ave ɛ _max) and the along-fiber diameter variation (CV). The strain ratio decreases with the increase of the along-fiber diameter variation.     

Synthesis, characterization, and protonation of poly(2-N,N-dimethylamino-4,6-bis(2-furan)-pyrimidine)

A new monomer (2-N,N-dimethylamino-4,6-bis(2-furan)-pyrimidine) was synthesized and its homopolymer was successfully prepared by using ferric trichloride as an oxidant. The structure of monomer and polymer were fully characterized by ¹H-NMR, FT-IR, UV, fluorescent spectroscopy, and X-ray diffraction. The N,N-dimethylformamide solution of the polymer showed a UV-Vis peak at 387 nm and the PL spectrum gave a peak at 517 nm. We have observed that the polymer was sensitive to inorganic acids and the protonation behavior was investigated applying inorganic acids such as HCI and H₂SO₄. The corresponding UV-Vis peaks were observed at 464 and 357 nm, respectively. X-ray diffraction data shows that polymer had a certain crystalline region. The polymer exhibited an [η] value of 0.21 dl/g at 25 °C in H₂SO₄ (w=98 %).     

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.     

The effect of an external electric field on solid-state phase transition of (P(VDF/TrFE)(72/28)

The copolymers of vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)) with VDF content of 50–80 mole % can be applied to the field of nonvolatile ferroelectric polymeric random access memory (FePoRAM) devices, since they exhibit stable ferroelectricβ-phase at room temperature with spontaneous polarization of the C-F dipoles towards an external electric field greater than the coercive field. Many researchers have already reported the molecular structures and dynamics of the ferroelectric (F) crystalline phase and the unique change in chain conformation between polarF phase and non-polar paraelectric (P) phase near their Curie transition temperature (T _c) which is dependent on factors such as VDF content and annealing treatment conditions. The effect of external electric field strength on theF⇔P crystalline phase transition in P(VDF/TrFE)(72/28) random copolymer samples of nanometer thickness was investigated. Capacitance of 250 nm thick sample measured as a function of heating-cooling under varying external electric field strength exhibited increasingT _c’s during heating (T _c ^↑ ) and cooling (T _c ^↓ ) under an applied electric field of more than 0.03 MV/cm. Applying cyclic bias electric field (+1 to −1 MV/cm) for samples kept isothermally at just above theirT _c(T _c ^↓ ) during cooling, we were able to observe the field-inducedP→F phase transition. With increasing cycles of the applied electric field for sample maintained just above (T _c ^↓ ), the bistableC-E hysteresis was observed and the phase change fromP→F is irreversible even after the electric field is removed. However, for samples kept well above (T _c ^↓ ) and nearT _m (100 °C and 120°C respectively) during cooling, theF-phase initially formed through the field-induced phase transition is reversibly transformed to theP-phase when the applied electric field is removed. Drastic changes were observed in both coercive field (E _c) and remanent polarization (P _r) values during heating and cooling near theT _c range due to theF⇔P phase transition and the results are reported in detail here.     

A Comparative study of redox parameters and electrochemical impedance spectroscopy of polycarbazole derivatives on carbon fiber microelectrode

In this study, N-Carbazole and its derivatives (N-Vinylcarbazole, N-Ethylcarbazole, N-Vinylbenzylcarbazole, and N-Benzylcarbazole) were electrochemically polymerized on carbon fiber microelectrodes (diameter ∼7 μm) by cyclic voltammetry within a potential range from 0.0 to 1.4 V. Redox parameters, Scanning electron microscopic (SEM) images were determined and also capacitance behaviors of polymers were examined via electrochemical impedance spectroscopy (EIS). EIS measurements of polycarbazole derivatives were given comparatively. The existence of a capacitance behavior is shown by Nyquist, Bode magnitude, Bode-phase, Admittance plots relationship. Although the highest low frequency capacitance (C_LF=12901 μA cm⁻²) and maximum phase angle of 81.9 ° at a frequency of 1 Hz were obtained for N-Vinylbenzylcarbazole, the lowest anodic and cathodic potential difference (ΔE=0.04 V) and double layer capacitance (C _dl =0.11 μA cm⁻²) were indicated in 0.1 M LiClO₄/PC.     

Carbon dioxide and methane gas permeations in thermally annealed and chemically cross-linked commercial polyimide hollow fiber membrane

Two types of modifications were performed on a commercial polyimide (PI) hollow fiber membrane for carbon dioxide (CO₂) and methane (CH₄) gas permeations. Thermal annealing was conducted between 50- and 200 °C while chemical cross-linking was performed using 0.1- to 1.0 wt% of N, (1-Naphthyl) ethylene-diamine dihydrochloride (NED). Membrane characterization revealed densification of the thermally annealed PIs. But formation of macrovoids was observed in PIs annealed near its glass transition temperature (207 °C). Fourier transform infrared spectroscopy confirmed the successful cross-linking of NED with PI. Highest CO₂ permeance was obtained from pristine PI (P/L=225 GPU) but it also had the lowest selectivity (α=72). The performances of thermally annealed (P/L=160–219 GPU, α=76–106), NED crosslinked (P/L=68–139 GPU, α=65–95) and thermally induced NED cross-linked (P/L=51-91 GPU, α=98–138) PIs varied according to modification conditions. Among the modified membranes, highest CO₂ permeance was obtained from thermally annealed PI at 100 °C (P/L=211GPU, α=106) while thermally induced NED cross-linked PI (100 °C, 0.5 wt% NED) exhibited the highest selectivity (P/L=91, α=138). Both modified membranes are the best candidates for CO₂/CH₄ separation.     

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 collector temperature and conductivity on the chain conformation of nylon 6 electrospun nanofibers

Electrospinning is a versatile process used to prepare micro- and nano- sized fibers from various polymer solution. Here, we dealt with the variation in the morphology of nylon 6 electrospun nanofibers and their polymorphism depending on the type and physical state of the collectors. SEM study showed that the fiber diameter was increased from 80 to 103 nm while it was collected in water bath. Similarly the fiber diameter and bonding was increased 103 to 115 nm with the temperature whereas it was linearly decreased 103 to 90 nm with the conductivity of the water bath. Spectroscopic analysis (FT-Raman, FT-IR) showed that the polymorphism of nylon 6 depended on the types of collector (aluminum sheet and water bath). Nylon 6 electrospun nanofibers display theγ-phase while collected in aluminum sheet andα-phase while collection in water bath. The extent of transformation fromγ- toα-phase was linearly increased with temperature and conductivity of the water bath.     

An adsorption study of alum-morin dyeing onto silk yarn

Silk yarn was dyed with morin (2′,3,4′,5,7-pentahydroxyflavone) by using alum as mordant. In order to optimize the process, three methods of dyeing involving: pre-mordanting, simultaneous mordanting, and post-mordanting were assessed and compared with a mordant-free process. The adsorption of alum-morin dye onto silk fibers indicated that the adsorption capacities were significantly affected by pH, the initial dye concentration, and temperature. The initial dye adsorption rates of alum-morin dye on silk before equilibrium was reached increased with higher dyeing temperatures. The pseudo second-order kinetic model was indicated for alum-morin dyeing (simultaneous mordanting) of silk at pH 4.0 with an activation energy (E _a ) of 45.26 kJ/mol. The value of the enthalpy of activation (ΔH ^#) for alum-morin dyeing on silk at pH 4.0 was −31.29 kJ/mol. Also, the free energy (ΔG ^o) and entropy changes (ΔS ^o) for alum-morin dyeing on silk were −17.73 kJ/mol and −45.7 J/molK, respectively, consistent with a spontaneous and exothermic adsorption process.     

Fabrication and characterization of nano Al<Subscript>2</Subscript>O<Subscript>3</Subscript> filled PVA:NH<Subscript>4</Subscript>SCN electrolyte nanofibers by electrospinning

Present paper reports a method of preparing polymer composite electrolyte nanofiber mat using polyvinyl alcohol (PVA), ammonium thiocynate (NH₄SCN) salt, and aluminium oxide (Al₂O₃) nano particles based on electrospinning technique. Two-stage process of preparation of nanofibers, namely, preparation of nano particles filled PVA electrolyte gel solution followed by its electrospinning has been used. The so obtained nanofibers have been characterized by XRD, DSC, SEM, and Conductivity measurements. XRD patterns affirm the formation of nanocomposite while SEM pictures reveal formation of fibers on a nano scale format (300–800 nm). Fibers of the electrolytes are seen to be thermally stable. Ionic conductivity of electrolyte fiber is seen to improve in the presence of nano filler at room temperature with a maximum at 5.31×10⁻³ Scm⁻¹ for 4 wt% filler concentration, which is comparable to that for corresponding dried gel electrolyte films.     

Polycarbazole modified carbon fiber microelectrode: Surface characterization and dopamine sensor

Electropolymerization of carbazole (Cz) by cyclic voltammetry (CV) onto carbon fiber microelectrodes (CFME) (diameter ∼7 μm) in dichloromethane (CH₂Cl₂) solution of 0.1 mol·dm⁻³ tetraethyl ammonium perchlorate (TEAP) results in the formation of polycarbazole (PCz) thin film coatings. CV results showed that these PCz thin films have reversible redox behavior in monomer-free electrolyte solution. The resulting thin polymer films were characterized using Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) and atomic force microscopy (AFM). Results performed at optimum experimental conditions indicate that electrodes show a reversible and stable behavior over sixty eight days of testing for dopamine in 100 μmol·dm⁻³ buffer solution. A detection limit for PCz thin films as low as 0.1 μM (3S/N) was obtained for the polycarbazole (PCz) thin films formed using CV. Hence, this novel sensor can be considered as promising sensor for dopamine detection.     

Synthesis of thermotropic polyurethanes containing imide units and their mesophase behavior

Thermotropic polyurethanes were synthesized from 1,6-hexane diisocyanate (HDI) as a diisocyanate, 1,6-hexane diol (HD), and rigid diols containing imide unit such as N,N′-bis(4-hydroxyphenyl)-3,4,3′,4′-biphenyl-dicarboxyimide (BPDI) or bis-N-(4-hydroxyphenyl)-4,4′-oxydiphthalimide (ODPI). The effects of structure difference between BPDI and ODPI and composition of HD/BPDI (ODPI) on the thermal and liquid crystalline behavior were studied. Thermotropic polyurethanes with an inherent viscosity of 0.59–0.70 were obtained. The melting temperature of BPDI-based polyurethanes were in the range of 150–290°C, however, those of ODPI-based polyurethanes were in the range of 150–190°C. All the polyurethanes based on ODPI (25–100 mole %) clearly exhibited a stable liquid crystalline phase, and BPDI-based polyurethane having 5–25% of BPDI showed a mesophase. The melting and isotropization temperatures (T _m , T _i ) andΔT(T _i −T _m ) increased with increasing BPDI and ODPI content. The polyurethanes based on BPDI has higher melting points and thermal stability compared to ODPI-based polyurethanes.     

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.     

Weight loss and morphology changes of electrospun poly(<Emphasis Type="Italic">?</Emphasis>-caprolactone) yarns during <Emphasis Type="Italic">in vitro</Emphasis> degradation

In this study, the in vitro degradation of yarns made from PCL electrospun fibers containing various concentrations of ampicillin sodium salt was investigated. PCL fibers were electrospun and collected as well-aligned fiber bundles and then twisted into yarns. Yarn weight loss, morphology changes in the yarns, and morphology changes in the fiber microstructure with degradation were evaluated. Results showed that the electrospun PCL yarns degraded slowly with a weight loss less than 3 % in 12 weeks. The addition of various concentrations of ampicillin salt increased the degradation rate slightly. The morphological changes observed in fiber microstructure suggested that the degradation underwent bulk erosion and the degradation began with the amorphous regions. Revealed by the fiber morphological changes with degradation, the microstructure of electrospun PCL fibers followed the fringed fibril fiber model. The fiber arrangement in the yarn was impaired by the in vitro degradation environment as well.     

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.     

Predicting properties of single jersey fabrics using regression and artificial neural network models

In our previous works, we had predicted cotton ring yarn properties from the fiber properties successfully by regression and ANN models. In this study both regression and artificial neural network has been applied for the prediction of the bursting strength and air permeability of single jersey knitted fabrics. Fiber properties measured by HVI instrument and yarn properties were selected as independent variables together with wales’ and courses’ number per square centimeter. Firstly conventional ring yarns were produced from six different types of cotton in four different yarn counts (Ne 20, Ne 25, Ne 30, and Ne 35) and three different twist multipliers (α _e 3.8, α _e 4.2, and α _e 4.6). All the yarns were knitted by laboratory circular knitting machine. Regression and ANN models were developed to predict the fabric properties. It was found that all models can be used to predict the single jersey fabric properties successfully. However, ANN models exhibit higher predictive power than the regression models.     

Simulation of salt and water movement and estimation of water productivity of rice crop irrigated with saline water

The HYDRUS-ID model was experimentally tested for water balance and salt build up in soil under rice crop irrigated with different salinity water (ECiw) of 0.4, 2, 4, 6, 8 and 10 dS m⁻¹ in micro-lysimeters filled with sandy loam soil. Differences of means between measured (M) and HYDRUS-1D predicted (P) values of bottom flux (Q _o) and leachate EC as tested by paired t test were not found significant at P = 0.05 and a close agreement between RMSE values showed the applicability of the HYDRUS-1D to simulate percolation and salt concentration in the micro-lysimeters under rice crop. Potential ET values of rice as obtained from CROPWAT matched well with model predicted and measured one at all ECiw treatments. The model predicted root water uptake varied from 66.1 to 652.7 mm and the maximum daily salt concentration in the root zone was 0.46, 2.3, 4.5, 6.7, 8.4 and 10.2 me cm⁻³ in 0.4, 2, 4, 6, 8 and 10 dS m⁻¹ ECiw treatments, respectively. The grain production per unit evapotranspiration ( \textWP_{\textET\texta} {\text{WP}}_{{{\text{ET}}_{\text{a}} }} ) value of 2.56 in ECiw of 0.4 dS m⁻¹ treatment declined to 1.31 with ECiw of 2 dS m⁻¹. The \textWP_{\textET\texta} {\text{WP}}_{{{\text{ET}}_{\text{a}} }} reduced to one-fifth when percolation was included in the productivity determination. Similarly, the water productivity in respect of total dry matter production (TDM) was also reduced in different treatments. Therefore, the model predicted values of water balance can be effectively utilized to calculate the water productivity of rice crop.     

Effects of high energy electrons on physical and tensile properties of non-mulberry silk fibers

Tassar silk fiber (Antheraea mylitta) was irradiated with the available maximum dose range upto 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 studied using wide-angle X-ray scattering data (WAXS). The crystal imperfection parameters such as crystallite size (〈N〉), lattice strain (g in %), and surface weighted crystallite size (D_s in Å) have been determined by line profile analysis (LPA) using Fourier method of Warren. For this purpose, exponential, lognormal, and Reinhold functions for column length distribution have been used for the determination of these parameters. These parameters were compared with tensile properties of the fibers. The increasing trend of crystallite size values (〈N〉 as well as D_s in Å) and tenacity (gf/den) with increasing dosage of radiation clearly indicates the cross linking polymer network in fiber. Comparison of SEM photographs also confirms the X-ray results.