Modified Polyacrylonitrile Fiber Research Articles

Dye-free coloration and flame retardancy of surface-modified polyacrylonitrile fibers

In this study, polyacrylonitrile (PAN) fibers were modified with triethylenetetramine (TETA) and subsequently treated with sodium hydroxide (NaOH). The influence of TETA and sodium hydroxide concentration, sodium hydroxide treatment temperature and time on the color and structure of the PAN fibers is discussed. It is shown that when treated with sodium hydroxide, the TETA-modified PAN fibers exhibit excellent flame retardancy and good colorfastness properties. Fourier transform infrared spectrometry analysis of the modified PAN fibers shows a gradual decrease in the characteristic –CN absorption peak at 2243 cm−1, while new absorption peaks for –C=N, –C–N and –NH2 functional groups appear at 1650, 1560 and 3600–3300 cm−1, respectively, confirming changes in the chemical structure of the fibers. In addition, the powder X-ray diffraction data show damage to the physical structure of the fibers in the form of decreased crystallinity and crystal completeness, while the scanning electron microscopy data indicate a significant increase in fiber diameter and surface roughness. These results demonstrate that enhanced flame retardancy and dye-free coloration of PAN fibers can be obtained by TETA and sodium hydroxide modification.

Modification of Polyacrylonitrile Fibers by Coupling to Thiosemicarbazones.

This work reports the modification of Polyacrylonitrile (PAN) fibers by coupling to thiosemicarbazones to achieve the biological activity for the applications in the food product packaging. After modification, seven thiosemicarbazone compounds were synthesized. The as-synthesized thiosemicarbazone compounds were bonded to PAN fibers via covalent coupling, which was confirmed using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy. The mean graft efficiency of the compounds was about 1.92%, and the antibacterial efficiency was 88.6% and 45.1% against Staphylococcus aureus (S-aureus) bacteria. All the seven thiosemicarbazone compounds exerted excellent tyrosinase activity, low cytotoxicity, excellent metal ion chelation ability, and anti-bacterial behavior against both gram-positive and negative bacteria. The mechanical properties of the fibers have been maintained without significant damage after the chemical modification. The break strength test and elongation at the break test were done to measure the fracture strength of the modified fibers. Overall, the promising properties of the modified PAN fibers show potential applications in food packaging materials for fruits and vegetables, which require long-term anti-browning effects during their transportation and storage.

Carbon-dot modified polyacrylonitrile fibers: Recyclable materials capable of selectively and reversibly adsorbing small-sized anionic dyes

Amine-rich carbon dot (CD) functionalized polyacrylonitrile fibers (PANF-g-CDs) were prepared by a facile hydrothermal method. These fibers are fluorescent and contain nano-sized pores. Dye adsorption experiments demonstrated that PANF-g-CDs preferred to adsorb small-sized anionic dyes with high aspect ratio, such as methyl orange (MO). The maximum adsorption capacity for MO reached 422 mg/g. The adsorption kinetics satisfied the pseudo second-order adsorption model, and the adsorption behavior was monolayer uniform adsorption. After adsorption, PANF-g-CDs could be separated conveniently just by taking it out from the solution. Moreover, the used PANF-g-CDs could be regenerated in an alkaline aqueous solution very rapidly within 30 min. Its adsorption performance was so stable that it did not show obvious performance loss even after ten adsorption-desorption cycles. In addition, the fluorescence of the fiber exhibited periodical change during the adsorption-desorption processes. Thus, this CD modified fibers with the combined advantages of simple synthesis, high dye-adsorption efficiency and selectivity, moderate dye-adsorption rate, fast dye-desorption, easy recyclability, stable adsorption performance and photoluminescent nature could be promising adsorbents for practical dyestuff wastewater treatment.

Study of adsorption performance and adsorption mechanism for U(VI) ion on modified polyacrylonitrile fibers

The modified polyacrylonitrile fibers (ACPAN fibers) was synthesized by oximation reaction and alkaline hydrolysis. ACPAN fibers was characterized by means of SEM, FTIR, XPS and elementary analysis. The effects of contact time, solid–liquid ratio, pH, ionic strength, initial concentration and temperature on U(VI) adsorption onto ACPAN fibers was studied and the adsorption mechanism was also discussed. The experimental data fitted well pseudo-second-order kinetics model and Freundlich and D–R models, and thermodynamic process was an endothermic and spontaneous reaction. The maximum adsorption capacity was 163 mg/g, and U(VI) and ACPAN fibers possible formed more stable penta-coordination complexation. This paper highlighted ACPAN fibers as a good adsorbent to remove efficiently and economically uranyl from radioactive wastewater.

Graphene modified polyacrylonitrile fiber as high-performance cathode for marine sediment microbial fuel cells

The goal of this study is to make a high-performance cathode in a simple way, so that it can better serve marine sediment microbial fuel cells. We design a cathode by combining graphene with carbon fiber through a binder, and apply it for the first time to these cells, to improve the electrochemical performance of these cells while increasing the specific surface area of the cathode. This cathode shows excellent performance in a laboratory simulated marine environment. The specific surface area of graphene modified polyacrylonitrile fiber cathode reaches 41.13 m2/g, 1.5 times larger than that of the blank cathode (26.98 m2/g). Its capacitance and exchange current density are 6.1 times and 16.4 times higher than that of theblank cathode, respectively. The anti-polarization ability of the modified cathode was significantly improved, and the maximum power density of the cell equipped with the G/P cathode (2.12 kW/kg) is 6.24 times that of the blank (0.34 kW/kg). In terms of stability, it is quite resistant to prolonged seawater immersion or scouring. This excellent mechanical stability can extend the cells’ life and reduce replacement costs.

Synthesis of Polyacrylonitrile Fiber Aminated with Ethylenediamine in Aqueous Solution and the Vapor Phase

Modification of polyacrylonitrile fiber by ethylenediamine in aqueous solution and the vapor phase was investigated. The optimum process conditions were determined. The process was found to be significantly enhanced if the gaseous amine was used rather than its aqueous solution. FTIR spectra confirmed the structure of polymer fiber produced under these conditions.

A new polyacrylonitrile fiber for direct carbonization without oxidation

Polyacrylonitrile (PAN) was cyclized by heating in an inert atmosphere and then dissolved in sulfuric acid and oxidized by nitric acid, resulting in product named OCPAN. The OCPAN was dissolved along with PAN and spun into fibers, getting modified PAN fiber (MPAN), to realize self-crosslinking and direct carbonization. The chemical structure of the OCPAN and its compatibility and co-carbonization effects with PAN were characterized through characterization methods of optical microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The structure and properties of the resultant carbon fibers were investigated by scanning electron microscope and monofilament strength tester. The results show that ketone aromatic heterocycles are produced in OCPAN, which are able to promote the formation of a stable structure of carbon network and produce crosslinking with PAN molecules. The carbon yield of the MPAN fiber after direct carbonation under 900 °C temperature in nitrogen is 23% higher than that of the PAN fiber without oxidation carbonized under the same condition, while the strength of the final carbon fiber is a bit lower than that derived from the PAN fiber through pre-oxidation. Therefore, the direct carbonation of PAN fiber is basically realized.

A novel biomimetic catalyst constructed by axial coordination of hemin with PAN fiber for efficient degradation of organic dyes

A novel biomimetic catalyst was synthesized by supporting hemin onto the amidoximated polyacrylonitrile (PAN) fiber and then used for the oxidative degradation of organic dyes by H2O2 activation. SEM, FTIR and XPS results suggested that the OH and NH2 in amidoxime groups were responsible for hemin immobilization through axial coordination bonds. The fibrous support significantly enhanced the catalytic activity and pH tolerance of pure hemin, and the prepared catalyst also exhibited excellent recycling capability. In addition, the effect of axial ligands on the catalytic mechanism was clarified by employing the modified PAN fiber with amidrazones groups as the support of hemin, and the possible catalytic mechanism was proposed and discussed based on the ESR measurement combined with a series of designed experiments. It is found that OH and NH2 as axial ligands of hemin might induce H2O2 activation through two different pathways, corresponding to the generation of Fe(IV)=O and ·OH species, respectively.

Modified polyacrylonitrile fiber as a renewable heterogeneous base catalyst for Henry reaction and Gewald reaction in water

ABSTRACTA polyacrylonitrile fiber catalyst with high polar surface micro‐environment (C‐PANF‐Na) was conveniently synthesized and characterized by elemental analysis, Fourier‐transfer infrared spectroscopy, UV–vis spectroscopy, scanning electron microscopy, X‐ray diffraction, and breaking strength test. The catalytic performance of the fiber was tested by Henry reaction and Gewald reaction in water and favorable results were obtained in terms of high yields, mild conditions, extensive applicability, superior catalytic recyclability, and renewability. It also has advantages of easy preparation, high functional degree, good stability in acid and base, high strength, and good flexibility, and so on. In addition, a high solvent selectivity phenomenon was found in this catalytic system and the reason was explained by proposing a high polar micro‐environment effect. Furthermore, the fiber catalyst performed well in scaled‐up experiment and flow chemistry experiment, which shows tremendous potential in industrial catalyst as an ideal material for packed bed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45992.

Study of flame‐resistant acrylic fibers reinforced by poly(vinyl alcohol)

ABSTRACTAcrylic fibers [polyacrylonitrile (PAN) fibers] have excellent flame‐retardant properties after they are modified by hydrazine hydrate and metal ions; however, their widespread applications are restricted because of poor mechanical properties. To improve the mechanical properties of these modified PAN fibers, poly(vinyl alcohol) (PVA) was added to the spinning solution of PAN as an effective reinforcing agent. The structure of the fibers before and after modification was studied by Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive spectroscopy, and wide‐angle X‐ray diffraction. The mechanical properties and flame resistance of the fibers after treatment were also tested by a single‐fiber tensile tester and a limiting oxygen index (LOI) analyzer, respectively. We found that the LOI of the modified fibers was reduced from 54.7 to 29.1 after the introduction of 50 wt % PVA; however, the tensile strength was dramatically improved from about 1.50 cN/dtex to more than 4.00 cN/dtex. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43006.

Preparation and properties of polyacrylonitrile fibers with guanidine groups

The polyacrylonitrile (PAN) fibers grafted with guanidine groups were prepared by hydrolyzing with sodium hydroxide solution followed by reacting with polyhexamethylene guanidine hydrochloride (PHGC). The grafting degree could be controlled by changing the treatment time of hydrolyzed PAN fibers with PHGC. The chemical composition and morphology of the modified PAN fibers were characterized by Fourier transform infrared spectroscopy (FTIR), Elemental analysis (EA), X-ray photoelectric spectroscopy (XPS) and scanning electron microscope (SEM). The results showed that the guanidine groups were effectively grafted on the fibers. The water contact angle of the surface modified PAN fibers was reduced and moisture regain was improved significantly with the immobilization of PHGC on the fibers. Furthermore, the modified PAN fibers exhibited favorable acid dyeability at low temperature (50 °C) over a wide pH range and good mechanical properties. The simple and applicable synthesis process provides a new avenue for modification of PAN fibers with improved hydrophilicity and acid dyeability.

Preparation and performance of polyacrylonitrile fiber functionalized with iminodiacetic acid under microwave irradiation for adsorption of Cu(II) and Hg(II)

Polyacrylonitrile fiber immobilized with iminodiacetic acid (IDA) was prepared under microwave irradiation and was used to adsorb Cu(II) and Hg(II) in aqueous solution. Synthesis conditions such as time, temperature and ratio of solvents were exploited systematically by orthogonal experiment and the properties of this fibrous absorbent were characterized by fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), scanning electron microscopy (SEM). The adsorption performances, in both thermodynamic and kinetic conditions, were investigated strictly and the experimental data fitted the Langmuir model (R2>0.99) and pseudo-second-order equation very well. The effect of pH on the adsorption capacity of metal ions was discussed and the optimal value for Cu(II) and Hg(II) was found to be 5.0 and 2.0, respectively. Thermodynamic parameters reveal the spontaneous and endothermic nature of the adsorption process, due to the negative value of standard free energy (ΔG) and the positive value of standard enthalpy (ΔH). The adsorption capacities toward Cu(II) and Hg(II) on the modified polyacrylonitrile fibers under microwave irradiation are higher than those on other adsorbents through conventional heating. The less consumed time and high grafting rate of the functional groups may be attributed to thermal effect as well as non-thermal effect of microwave irradiation.

Polyacrylonitrile Fiber Modified by a Quaternary Ammonium Salt

The preparation of acrylonitrile, methylacrylate, and 2-acrylamido-2-methylpropanesulfonic acid terpolymer fiber and its dyeing by anionic dyes were examined. The stability of the dye in modified polyacrylonitrile fiber was studied. It was shown that the modified fiber had bactericidal properties. The fiber physicomechanical properties changed insignificantly as a result of the modification and coloring.

Preparation and Application of Modified Polyacrylonitrile Fiber as a Adsorbent for Precious Metals

Polyacrylonitrile fiber ( PAN ) was used as the starting material, after precrosslinked respectively by hydrazine hydrate, ethylenediamine and diethylenetriamine, the products reacted with sodium sulfide with N,N-dimethyl formamide ( DMF ) as solvent under slight alkaline conditions. The reaction temperature was controlled at 70 °C and the reaction time was 6h to prepare three kinds of sulfamide modified polyacrylonitrile fiber (SAPAN), the sulfur content of which could come up to 6.8mmol/g ( dry fiber). The structure of modified polyacrylonitrile fiber was characterized by the means of IR, EA, TG and gravimetric analysis, etc., meanwhile, the preparation conditions as well as adsorption property of the fiber for precious metal ions were researched.

Heterogeneous Fenton degradation of azo dyes catalyzed by modified polyacrylonitrile fiber Fe complexes: QSPR (quantitative structure peorperty relationship) study

The amidoximated polyacrylonitrile (PAN) fiber Fe complexes were prepared and used as the heterogeneous Fenton catalysts for the degradation of 28 anionic water soluble azo dyes in water under visible irradiation. The multiple linear regression (MLR) method was employed to develop the quantitative structure property relationship (QSPR) model equations for the decoloration and mineralization of azo dyes. Moreover, the predictive ability of the QSPR model equations was assessed using Leave-one-out (LOO) and cross-validation (CV) methods. Additionally, the effect of Fe content of catalyst and the sodium chloride in water on QSPR model equations were also investigated. The results indicated that the heterogeneous photo-Fenton degradation of the azo dyes with different structures was conducted in the presence of the amidoximated PAN fiber Fe complex. The QSPR model equations for the dye decoloration and mineralization were successfully developed using MLR technique. MW/S (molecular weight divided by the number of sulphonate groups) and NN=N (the number of azo linkage) are considered as the most important determining factor for the dye degradation and mineralization, and there is a significant negative correlation between MW/S or NN=N and degradation percentage or total organic carbon (TOC) removal. Moreover, LOO and CV analysis suggested that the obtained QSPR model equations have the better prediction ability. The variation in Fe content of catalyst and the addition of sodium chloride did not alter the nature of the QSPR model equations.

Synthesis of palladium dendritic nanostructures on amidoxime modified polyacrylonitrile fibers through a complexing-reducing method

Abstract In this paper, three-dimensional fern-leaf-like palladium (Pd) dendritic nanostructures were successfully synthesized on amidoxime modified polyacrylonitrile fibers via a simple and efficient complexing-reducing method. The influence of reaction time, temperature, and concentrations of N2H4 and Fe3+ on the morphology and structure of Pd nanostructures was investigated. The results indicate that the supply rate of metallic Pd atoms plays a crucial role in the formation of the dendritic nanostructures. The formation mechanism of Pd dendritic nanostructures was proposed.

Gold nanoparticles immobilized in hyperbranched polyethylenimine modified polyacrylonitrile fiber as highly efficient and recyclable heterogeneous catalysts for the reduction of 4-nitrophenol

Hyperbranched polyethylenimine (HPEI) modified polyacrylonitrile fiber (PANF) was prepared through a water mediated hydrolysis and amidation reaction in an autoclave. The grafting amount of HPEI onto PANF could be modulated conveniently by varying the preparation conditions, such as reaction temperature, reaction time and the feed ratio of HPEI to PANF. The Young's modulus of the PANF decreased with the grafting of HPEI, especially when more HPEIs were grafted. As for the PANF-g-HPEI with low HPEI content, the Young's moduli were similar before and after loading of AuNPs, whereas the loading of AuNPs obviously deteriorated the strength of the fibers with high HPEI content. From the nitrogen adsorption and desorption isotherms, it could be seen that PANF contained nanometer sized pores, and the grafting with HPEI did not affect the pore size, but did reduce the surface area. Moreover, the loading of AuNPs into PANF-g-HPEI also did not influence the pore size, but decreased the surface area. FTIR and XPS analyses demonstrated that the obtained PANF-g-HPEI not only contained a large amount of amino groups from the HPEI moiety, but also many carboxylate ions due to the hydrolysis of the cyano groups of PANF. XRD characterization proved that the inner crystal region of PANF was partially broken by the introduction of HPEI moieties. SEM showed that the PANFs swelled up after grafting with HPEI, and the increase of the grafting efficiency led to a larger average diameter of the fibers. When the grafting amount of HPEI onto PANF reached as high as 97%, the surface of the fibers was severely impaired. The obtained PANF-g-HPEIs could be successfully used as supporters and stabilizers in the preparation of small-sized AuNPs. TEM characterization showed that the mixing time of PANF-g-HPEIs with HAuCl4 aqueous solution affected the size and size distribution of the formed AuNPs, and the optimal mixing time was around 0.5 h. The average diameter of the obtained AuNPs was around 3.0 nm at a feed ratio of amino groups of PANF-g-HPEI to Au atoms ([N] : [Au]) of 200, independent of HPEI content of the PANF-g-HPEIs used. Reducing the [N] : [Au] feed ratio increased the average size of the obtained AuNPs. The AuNPs supported by PANF-g-HPEIs could be used as efficient catalysts for the heterogeneous catalytic reduction of 4-nitrophenol by NaBH4. The PANF-g-HPEI with lower HPEI content endowed the supported AuNPs with a slightly higher catalytic rate. These heterogeneous AuNP catalysts could be conveniently recovered and reused many times, especially the AuNPs supported by the PANF-g-HPEIs containing a low content of HPEI. The turnover number (TON) values of the AuNPs supported by PANF-g-HPEI0.31 and PANF-g-HPEI0.58 could reach more than 5 × 104, which is unprecedented in the catalytic reduction of 4-nitrophenol.

Applied Research on Modified Polyacrylonitrile Fiber with Collagen

The surface modification process for polyacrylonitrile fiber which was hydrolyzed first, and then grafted with collagen was studied. The optimum process was as follows: concentration of alkaline 12%, time 10min, temperature 80°C, ratio of water and PAN fiber was 100:1. The method for surface modification of polyacrylonitrile fiber was determined from comparative analysis, and the optimum process: collagen solution concentration at 5%, pick-up at 900%, pre-baking 15min at 70°C, baking 15min at 110°C. Compared with original polyacrylonitrile fiber，the breaking strength and elongation of collagen modified polyacrylonitrile fiber decreased, while the moisture regain increased from 2% to 6.1%.

Characterization and Hydrolization of PAN by Sodium Hydroxide

An polyacrylonitrile fiber is one that contains at least 85% by mass of acrylonitrile comonomer in the polymer chain. The nitrile group (-C≡N) in polyacrylonitrile fiber is converted to carboxyl group(–COOH) after hydrolysis in NaOH aqueous solution.This research explores the hydrolysis of copolyacrylonitrile fiber in sodium hydroxide solution and characterization by chrome yellow method. The optimum hydrolytic technology is sodium hydroxide mass fraction is 12%, the time of hydrolysis is 10min, the temperature of hydrolysis is 80°C. In addition, the surface morphology of the polyacrylonitrile fiber and the modified polyacrylonitrile fiber were observed by SEM. The strength of the hydrolysed fiber is decline and the moisture regain is increased compared with the polyacrylonitrile fiber.

Some properties of modified polyacrylonitrile fibres

Fibre-forming copolymers of acrylonitrile and a monomeric quaternary ammonium salt, β-methacryloylhydroxyethyl-(N-dimethyl,methylene)ammonium iodide, were obtained by wet spinning and their physicomechanical and structural properties were investigated. It was found that the modified fibres have a set of valuable properties in comparison to the industrial fibre Nitron.