Cellulose fibers modified by silicon dioxide nanoparticles

The sol–gel method is one of the most suitable ways for producing glasses, glass films, glass fibers, and glass nanoparticles. The relatively mild reaction conditions and simplicity of the sol–gel method make it an excellent tool for producing substances with precisely tailored properties. This technique opens the possibility for the synthesis of various new compounds, including pH sensors, ion sensors, bioactive nanoparticles, dyes carriers, and so forth. An attempt was made to combine the sol–gel technique with the advanced technology in the production of cellulose fibers in order to obtain fibers with new and unique properties. Cellulose fibers were prepared with N‐methylmorpholine‐N‐oxide as the direct solvent. The obtained fibers contained up to 30% (w/w) silicon dioxide nanoparticles. In order to observe the influence of the modifier on the fibers, their mechanical properties were examined. Modified fibers were also examined by means of thermogravimetry, wide‐angle X‐ray scattering, and ²⁹Si‐NMR solid‐state spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1793–1798, 2005     

Cellulose nanofibers prepared by the N‐methylmorpholine‐N‐oxide method

The process of electrospinning is very suitable for obtaining fibers with a diameter on a nanometer scale. Such fibers can be spun from almost all kinds of known polymers, copolymers, and polymer blends. In this work, we present cellulose nanofibers obtained by the electrospinning process from spinning dopes containing cellulose dissolved in an N‐methylmorpholine‐N‐oxide/water system. Under different electrospinning process conditions, cellulose fibers, a nonwoven fiber network, and a cellulose membrane were obtained. The fibers were examined with scanning electron microscopy. The diameters of the fibers were in the submicrometer range. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1855–1859, 2005     

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     

Preparation and adsorption properties for metal ions of chitin modified by L‐cysteine

A new adsorbent for heavy metal ions, cys‐chitin, was produced by modifying chitin in THF with L ‐cysteine in the presence of sulfuric acid as a catalyst. Its structure was confirmed by elemental analysis and FTIR spectra analysis. The adsorption properties of cys‐chitin for Cu^II, Cd^II, Pb^II, Zn^II, and Ni^II were investigated. The effect of pH value on adsorption and adsorption kinetics was examined. The results indicate that the cys‐chitin has much better adsorption for Cd^II, Pb^II, and Zn^II than chitin itself. The adsorption capacities of cys‐chitin for Cd^II, Pb^II, and Zn^II were 214.6, 351.5, and 107.0 mg/g, respectively. It also had good adsorption properties for heavy metal ions. The adsorption capacities were also affected by the acidity of medium. The adsorbed Cd^II, Pb^II could be eluted by diluted nitric acid. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2575–2579, 2003     

The effect of borax‐modified starch on wheat straw‐based paper properties

This study was focused on the improvement of mechanical strength properties of wheat straw‐based paper through modification of wet‐end cationic starch with borax. Borax has been used extensively in many industrial applications for its unique physical and chemical properties. We investigated the strengthening effect of borax‐modified starch (BMS) as wet‐end paper strength additive on the mechanical strength properties especially the tensile strength of wheat straw‐based paper. Hand‐sheets made of typical wheat straw‐based papermaking furnish were investigated. Experimental results showed that BMS substantially increased the strength properties. Tensile index, elongation, tensile energy absorption, and wet tensile index were increased by 17%, 23%, 20%, and 21%, respectively. A short mill trial was also conducted on papermaking machine in which the impact of BMS on wheat straw‐based low grammage paper (<90 gsm) was investigated. The objective of mill trial was to reduce costly virgin softwood pulp content in wheat straw‐based paper recipe. Mill trial results showed similar trends in strength properties as in case of laboratory studies. Virgin softwood pulp was reduced from 30% to 25% in papermaking furnish. Furthermore, no sheet breaks were reported during trial which often happened due to poor strength of paper web. This study strongly suggests that modification of wet‐end cationic starch with borax holds a tremendous potential as wet‐end strength additive. It can provide significantly improved strength properties, reduction in softwood pulp costs, and better papermaking machine performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Chitin nanocrystal reinforced wet‐spun chitosan fibers

Chitosan (CS) has been extensively studied and found wide applications in the field of biomedicine because of its favorable biological properties. Normal CS fibers are manufactured either by wet‐spinning or by dry‐jet wet‐spinning. However, the poor tensile strength of CS fibers raises much concern. The present study uses chitin nanocrystal (ChiNC), a stiff rod‐like nanofiller, to enhance the mechanical properties of wet‐spun CS fibers. Owing to the good compatibility between CS and ChiNC, the nanoparticles are well distributed in the CS matrix. When the ChiNCs loading is 5 wt %, the optimal mechanical properties of CS fibers are obtained, and the peak stress is 2.2 cN/dtex and modulus is 145.6 cN/dtex, which are increased by 57% and 84.5%, respectively, compared to that of nonfilled CS fibers under the same processing condition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40852.     

Nitrogen and hydrogen adsorption of activated carbon fibers modified by fluorination

In this study, activated carbon fibers (ACFs) were surface modified with fluorine and mixed oxygen and fluorine gas to investigate the relationship between changes in surface properties by nitrogen and hydrogen adsorption capacity. The changes in surface properties of modified activated carbon fibers were investigated using X-ray photoelectron spectroscopy (XPS) and compared before and after surface treatment. The specific surface area and pore structures were characterized by the nitrogen adsorption isotherm at liquid nitrogen temperature. Hydrogen adsorption isotherms were obtained at 77 K and 1 bar by a volumetric method. The hydrogen adsorption capacity of fluorinated activated carbon fibers was the smallest of all samples. However, the bulk density in this sample was largest. This result could be explained by virial coefficients. The interaction of hydrogen-surface carbon increased with fluorination as the first virial coefficient. Also, the best fit adsorption model was found to explain the adsorption mechanism using a nonlinear curve fit. According to the goodness-of-fit, the Langmuir–Freundlich isotherm model was in good agreement with experimental data from this study.     

A gradient anodic oxidation method for treating polyacrylonitrile‐based high‐modulus carbon fibers

We describe a gradient anodic oxidation method. Polyacrylonitrile‐based high‐modulus carbon fibers were treated by the conventional and gradient anodic oxidation methods. The results show that the carbon fibers treated by the gradient method possessed a more stable tensile strength, larger NaOH uptake, shallower striations, flatter fracture surface of composites, and better interlaminar shear strength compared to those treated by the conventional method. This indicated that the gradient method was more effective in restricting the etching reaction and improving the adhesion between the carbon fibers and matrix, and we give a suggested explanation of the mechanisms. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adsorption of organic amines from wastewater by carboxyl group‐modified polyacrylonitrile fibers

In this study, hexamethylenediamine (HMD) and hexamethyleneimine (HMI) were removed from a real wastewater by carboxyl group‐modified polyacrylonitrile (RPFC‐I) fibers. Adsorption of organic amines by fibrous absorbents is a new technique. Adsorption by fibers has advantages of fast kinetic, high adsorption capacity, and efficiency. Moreover, the fibers could be repeatedly used after regeneration. Batch adsorption tests were conducted to investigate adsorption comparison of the three fibers, adsorption kinetic, adsorption isotherms, regeneration, and readsorption stability. The experiments showed that RPFC‐I fibers had excellent adsorption capacity for HMI and HMD. The adsorption equilibrium was achieved very fast within about 5 min, and the removal rate of total nitrogen (TN) was above 99%. The adsorption kinetic could be well fitted by the pseudo‐second‐order equation. And the adsorption isotherm could be well fitted by the Langmuir model. The estimated maximum adsorption capacity was 105.2 mg g^?1, nearly similar with cation exchange capacity (CEC) of RPFC‐I fibers. Results from adsorption stability tests demonstrated that the RPFC‐I fibers could be fully regenerated by HCl and the regenerated fibers could be repeatedly used even after 12 adsorption–desorption cycles. Analyses from Fourier transform infrared and the adsorption tests suggested that chemical reaction between carboxyl groups and organic amines was the main mechanism for removal of HMI and HMD from the wastewater. The RPFC‐I fibers prepared in the current study have a wide application in wastewater treatment and useful substance recovery. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dynamic mechanical behavior of vinylester matrix composites reinforced by Luffa cylindrica modified fibers

Currently, there is a demand for new engineering materials presenting a combination of strength, low density, processing easiness, and reduced costs. In this context, polymer matrix composites reinforced by natural fibers have been studied in recent years due to their ecological and economic advantages. Some fibers are still little explored in literature despite presenting a great potential as reinforcement like Luffa cylindrica. The present work aims at the preparation and characterization of a vinylester thermoset matrix composite material reinforced by fibers of the natural L. cylindrica fruit after modification treatments. In this study, extraction treatments in organic solvents, mercerization, and a quite new esterification with BTDA dianhydrides were used and the results showed that in all cases, the composite materials reinforced by Luffa fibers have showed improvements in mechanical and thermal properties compared to the vinylester matrix. As an example, 50% tensile increase was obtained for the composite reinforced by fibers esterified with benzophenone tetracarboxylic dianhydride when compared with thermoset matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Modified cellulose fibers prepared by the N‐methylmorpholine‐N‐oxide (NMMO) process

Cellulose fibers with modified properties have been prepared from cellulose solutions in N‐methylmorpholine‐N‐oxide (NMMO). Poly(ethylene oxide) as a hydrophilic modifier and polyethylene as a hydrophobic modifier were added to the spinning solution. Based on microscope examination and measurements of such properties of fibers as porosity, moisture absorption, water retention, and tensile strength, structural changes as well as physical and mechanical properties of the resultant fibers depending on the amount of modifier added to the spinning solution were analyzed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 907–916, 2002     

Soy‐filled polyethylene fibers for modified surface and hydrophilic characteristics

By adding soy flour (soy) to linear low‐density polyethylene (LLDPE), soy‐PE fibers with enhanced hydrophilic characteristics were developed. Blends containing only soy and LLDPE had limited draw‐down, and the resulting thick fibers showed poor mechanical properties. When monoglyceride was added as a compatibilizer, thin fibers with good properties could be successfully spun due to improved dispersion of soy agglomerates in the LLDPE melt. Fibers spun from a blend containing 23/7/70 wt % of soy‐monoglyceride‐LLDPE displayed a tensile modulus and strength of 615 ± 38 and 57 ± 8 MPa, respectively. At 30% less synthetic content, these fibers still displayed mechanical properties generally comparable to those of base polyethylene fibers. Contact angle measurements showed that the soy‐based fibers had a hydrophilic surface (contact angle of 33° ± 4°). Moisture absorption studies confirmed that soy‐PE fibers gained about 20 wt % moisture in 1 h, whereas neat LLDPE fibers did not absorb any significant amount (LLDPE is hydrophobic). This hydrophilic behavior of soy‐PE fibers mimics that of natural fibers. Presence small soy agglomerates on the fiber surface also provides a textured surface and a desired tactile feel to the soy‐PE fibers, which coupled with hydrophilic behavior indicates their potential use in disposable nonwovens. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46609.     

A method for controlling the surface morphology of centrifugally spun starch‐based fibers

In the present study, we provide a method for controlling the surface morphology of centrifugally spun starch‐based fibers by adjusting the ratio of amylopectin/amylose in starches and combining with a hot blast temperature. The effects of hot blast temperature, amylopectin, and amylose on fiber surface morphologies are investigated. Scanning electron microscopy is used to characterize the morphology of the prepared fibers. The results show that fibers with burr‐shaped nanostructures on the surface can be fabricated by adding amylopectin to starches and are promoted by increasing the hot blast temperature. However, amylose in starches plays the role of smoothing the fiber surfaces. X‐ray diffraction reveals that the fibers are amorphous. Through Fourier transform infrared spectroscopy analysis, it was found that some physicochemical changes occur during centrifugal spinning. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45810.     

Wet‐spun,photoinitiator‐modified polyacrylonitrile precursor fibers: UV‐assisted stabilization

The role of dilute concentrations (～1 wt %) of a photoinitiator, 4,4 ′ ‐bis(diethylamino)benzophenone, on the processability and properties of the resulting wet‐spun polyacrylonitrile (PAN) fibers are reported. Rheology measurements show no adverse effect on the viscosities of solutions by the addition of the photoinitiator. Fibers containing photoinitiator were successfully wet‐spun from PAN – DMSO solution. FTIR results prove that 4,4 ′ ‐bis(diethylamino)benzophenone was retained in the fibers after coagulation and post‐stretching. SEM micrographs show no deterioration of the post‐stretched fiber microstructure due to the presence of photoinitiator. Tensile testing results show a small reduction in the strain‐at‐break of post‐stretched fibers containing photoinitiator when compared with pure (control) PAN fibers. After UV treatment, fibers with 4,4 ′ ‐bis(diethylamino)benzophenone display a higher tensile modulus compared with the other sets. Wide‐angle X‐ray diffraction results show no significant decrease in interplanar spacing and size of the crystals within the fibers containing photoinitiator, but such fibers retain a higher extent of molecular orientation after being UV treated. Conversion indices were measured from the WAXD spectra and compared with conventional thermal stabilized fibers. This correlation confirms that the addition of 1 wt % photoinitiator to PAN followed by 5 min of UV treatment leads to a conversion index that is observed in control fibers after more than an hour, which could reduce the conventional thermo‐oxidative stabilization time significantly. These results indicate the potential of the dual stabilization route in generating precursor fibers with higher molecular orientation, and possibly reducing the thermo‐oxidation time during carbon fiber processing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2494–2503, 2013     

Syntheses of chemical‐modified cellulose obtained from waste pulp

Chemical‐modified pulps were synthesized from four types of waste pulps (Pulp1–4) and succinic anhydride (SAn) or maleic anhydride (MAn). The solubility of the modified pulps was evaluated in common organic solvents, and their thermal properties were investigated by DSC measurement. The solubility of the modified pulps increased with an increasing degree of substitution (DS). However, no T_g or T_m of these modified pulps was confirmed. Pulps and modified pulps were graft‐polymerized with ε‐caprolactone (CL) in bulk and in DMAc/LiCl. Although the solubility of the graft copolymers was similar to modified pulps, some graft copolymers showed a T_g by the introduction of CL units. In the bulk, graft copolymers obtained from modified pulps and nonmodified pulps showed a T_g of about 75°C and no T_g, respectively. In DMAc/LiCl, the obtained graft copolymers from both modified and nonmodified pulps exhibited a T_g of 95–110°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2059–2065, 2003     

Fabrication and characterization of food‐grade fibers from mixtures of maltodextrin and whey protein isolate using needleless electrospinning

Food‐grade fibers were fabricated from dispersions of maltodextrin and whey protein isolate (WPI) using needleless electrospinning. Two maltodextrins (DE 2) from different starch sources were used and the maltodextrin/WPI ratio was varied. Molecular weight, intrinsic viscosity, entanglement concentration, shear stability, and electrical conductivity were studied as function of maltodextrin type and mixing ratio and correlated to fiber production rate and morphology. The results show that a high molecular weight of the maltodextrin was beneficial to its spinnability. Waxy potato starch maltodextrin (P‐MD) (M_w = 129.6 kDa) and WPI produced fibers with diameters between 1.40 and 1.67 µm at production rates up to 1.65 g/h; while the dispersions with waxy maize starch maltodextrin (M‐MD) (M_w = 85.9 kDa) showed poor spinnability and ruptured fibers. P‐MD/WPI dispersions had a higher viscosity and stronger shear thinning behavior attributed to a stronger entangled polymer network which is beneficial to electrospinning. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46328.     

Directional self‐assembly by electrospun wet fibers

In this study, we examined directional self‐assembly by electrospun wet fibers. The landing point of the wet fibers was controllable as its trajectory was strictly limited by the adjustment of the parameters of electrospinning. The wet fibers would not stack on the grounded plate in an irregular pattern but in the direction of an electric field in sequence. The preliminary wet fibers deposited and erected on the ground plate to form a controllable circle. The subsequent wet fibers traveled to the top of the circle directionally to organize a mesh tube. The apical circle of the mesh tube was the precise landing point of the subsequent wet fibers. With the wet fibers landing continuously, the mesh tube grew longer and longer. Finally, the controllable circle grew to be the growing mesh tube step by step. We discovered that the mesh tube was assembled by fibers spontaneously in the electrostatic field. In this article, we also try to explain the mechanism of self‐assembly and the formation of wet fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43003.     

Cellulose fibers from cellulose/1‐ethyl‐3‐methylimidazolium acetate solution by wet spinning with increasing spinning speeds

Cellulose fibers from cellulose/1‐ethyl‐3‐methylimidazolium acetate solution were prepared by wet spinning with increasing extrusion speeds and draw ratios. The effects of spinning speeds on the structures and mechanical properties of these fibers were investigated by using scanning electron microscopy, wide angle X‐ray diffraction, birefringence, thermogravimetric analysis, tensile‐fineness tester, and wet friction. The results showed that the crystallinity, orientation, and mechanical properties of the fibers were improved with increasing draw ratio. The break draw ratios, degrees of crystallinity and orientation, tenacities, and wet friction time of the cellulose fibers decreased with increasing extruding speeds. The wet friction time decreased with increasing draw ratio and decreased faster under higher extrusion speed. Due to the high dope concentration and the increased draw ratio, the maximum tenacity of the regenerated cellulose fibers reached 2.73 cN/dtex. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40225.     

Preparation of grafted cationic polymer/silver chloride modified cellulose fibers and their antibacterial properties

In this article, we present a simple method for synthesizing antibacterial cellulose fibers that were modified with a cationic polymer and immobilized silver chloride (AgCl) particles. Relatively simple techniques of graft polymerization and onsite precipitation were used to fabricate the composites. Scanning electron microscopy images, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and energy‐dispersive X‐ray spectroscopy confirmed the immobilization of the AgCl particles. The observed inhibition zone of the immobilized AgCl particle composites indicated that the biocidal silver ions were released from the composites in aqueous solution. Compared with cationic‐polymer‐grafted cellulose fibers or AgCl alone, the cationic polymer/AgCl composites showed excellent antibacterial activity against Gram‐negative Escherichia coli and Gram‐positive Staphylococcus aureus. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42092.     

One‐step facile process to obtain insoluble polysaccharides fibrous mats from electrospinning of water‐soluble PMDA/cyclodextrin polymer

Herein, we used an electrospinning process to develop nanofibers based on poly‐cyclodextrin. This article describes a simple and effective method to produce fibers of a water‐soluble hyperbranched polymer based on β‐CD and pyromellitic dianhydride via electrospinning. The obtained fibers were made insoluble in water with a simple thermal crosslinking without the use of further reactive or solvent. After 24 h of dipping in distilled water or phosphate buffer solution morphology and size of fibers remain unaltered as observed in scanning electron microscopy. The crosslinking mechanism was studied with thermogravimetric analysis, attenuated total reflectance–Fourier infrared spectroscopy, and elemental analysis and a reaction mechanism is proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46490.