Dry jet‐wet spinning of bagasse/N‐methylmorpholine‐N‐oxide hydrate solution and physical properties of lyocell fibres

Sugarcane bagasse, a cheap cellulosic waste material, was investigated as a raw material for producing lyocell fibers at a reduced cost. In this study, bagasse was dissolved in N‐methylmorpholine‐N‐oxide (NMMO) 0.9 hydrate, and fibers were prepared by the dry jet‐wet spinning method with coagulation in an aqueous NMMO solution. The effects of NMMO in 0 to 50% concentrations on the physical properties of fibers were investigated. The coagulating bath contained water/NMMO (10%) solution produced fiber with the highest drawability and highest physical properties. The cross‐section morphology of these fibers reveals fibrillation due to the high degree of crystallinity and high molecular orientation. In the higher NMMO concentrated baths (30 to 50%), the prepared fibers were hollow inside, which could be useful to make highly absorbent materials. The lyocell fibers prepared from bagasse have a tensile strength of 510 MPa, initial modulus of 30 GPa, and dynamic modulus of approximately 41 GPa. These properties are very comparable with those of commercial lyocell fibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cellulose fibers modified by hydrophobic‐type polymer

In the present research, we discuss the influence of a hydrophobic modifier on the properties of cellulose fibers. The commercially available fluorocarbon polymer water dispersion was introduced in different concentration ratios to the spinning dope to change the physical properties of cellulose fibers. Cellulose fibers from N‐methylmorpholine‐N‐oxide were prepared as a direct solvent. The fibers obtained contained up to 15% w/w of fluorocarbon polymer. To observe how the modifier influences the fibers' mechanical and thermal properties, fibrillation tendency and moisture absorption were examined. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 398–409, 2007     

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     

Synthesis and flocculation properties of N‐oxide polymers

N‐oxide polymers possess strong zwitterionic character, high solubility in water, and high chelating properties with various cations. In this work, N‐oxide polymers were synthesized following various routes and their solution properties were determined. Molecular properties of the polymers (molecular weight, square root of the mean‐squared radius, and virial coefficients) were related to their chain expansion in solution by determining the intrinsic viscosity as a function of pH. Viscosity results were correlated with the flocculation ability of the polymers for suspending solids removal. These polymers exhibit dramatic conformation changes as the solution pH is varied, especially at low pH values. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2693–2700, 2002     

Rheological characterization of cellulose solutions in N‐methyl morpholine N‐oxide monohydrate

Three different modes of rheological properties were measured on 11 and 13 wt % solutions of cellulose in N‐methyl morpholine N‐oxide (NMMO) monohydrate, in which concentration range lyocell fibers of much reduced fibrillation are preferably produced. The dynamic rheological responses revealed that the Cox–Merz rule did not hold for these cellulose solutions. Both cellulose solutions showed a shear thinning behavior over the shear rate measured at 85, 95, 105, and 115°C. However, 13 wt % solution gave rise to yield behavior at 85ºC. The power law index ranged from 0.36 to 0.58. First normal stress difference (N₁) was increased with lowering temperature and with increasing concentration as expected. Plotting N₁ vs shear stress (τ_ω) gave almost a master curve independent of temperature and concentration, whose slope was about 0.93 for both cellulose solutions over the shear rate range observed (τ_ω > 500 Pa). In addition, the cellulose solutions gave high values of recoverable shear strain (S_R), ranging from 60 to 100. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 216–222, 2002     

Magnetically active composite cellulose fibers

A process has been developed for manufacturing magnetically active composite fibers of cellulose using N‐methylmorpholine‐N‐oxide as a direct solvent for this natural polymer. Owing to its elasticity and stability, the process made it possible to add considerable quantities of modifier (up to 50% of fiber weight) to spinning solutions. The incorporation of powdered hard ferrites (barium ferrite) into the polymer solution resulted in fibers with magnetic properties, which exhibited a uniform distribution of the modifier. The results of testing the magnetic properties of the fibers obtained have shown that the coercive force of fibers do not depend on the modifier content, while the residual magnetism increases with the content of the ferromagnetic material. The value of fiber remanence is a fraction of the value of magnetic material remanence, corresponding to its volume content in fibers. This may indicate that the modifier used is chemically stable in the spinning solution medium. The thermal analysis of the fibers (DSC and TGA) has shown no negative effect of the modifiers on the fibers' thermal stability. An undesirable influence of the ferromagnetic compound on the fibers is the deterioration of their mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1529–1534, 2006     

Effect of the chain‐transfer‐agent content on the emulsion polymerization process and adhesive properties of poly(n‐butyl acrylate‐co‐acrylic acid) latexes

The effect of water on regenerated silkworm silk fibers has been studied and compared with that of water on natural silkworm silk fibers. Regenerated fibers are spun from an N‐methylmorpholine‐N‐oxide (NMMO) fibroin solution through a wet‐spinning process, leading to fibers with two distinct tensile behaviors, labeled as brittle and ductile, respectively. Regenerated fibers show a significant contraction when immersed in water. Contraction increases further after drying. In contrast, natural silkworm silk fibers show a negligible contraction when submerged in water. Regenerated fibers tested in water are considerably more compliant than samples tested in air, though their stiffness and tensile strength are significantly reduced. It has been shown that the tensile properties of brittle regenerated fibers can be modified by a wet‐stretching process, which consists of deforming the fiber while immersed in water. Regenerated wet‐stretched fibers always show a ductile behavior independent from their initial tensile behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Atomic force microscopy of cellulose membranes prepared from the N‐methylmorpholine‐N‐oxide/water solvent system

Cellulose membranes were obtained by solutions of cellulose being cast into a mixture of N‐methylmorpholine‐N‐oxide (NMMO) and water under different processing conditions. Atomic force microscopy (AFM) was used to investigate the surface structures of the membranes. The AFM method provided information on both the size and shape of the pores on the surface, as well as the roughness of the skin, through a computerized analysis of AFM micrographs. The results obtained showed that the surface morphologies were intrinsically associated with the permeation properties. For the cellulose membranes, increasing the NMMO concentration and the temperature of the coagulation bath led to higher fluxes and lower bovine serum albumin rejection. These were always correlated with higher values of the roughness parameters and larger pore sizes of the membrane surfaces. When the cellulose concentration of the casting solution was 11 wt %, the membrane showed a nodular structure with interconnected cavity channels between the agglomerated nodules. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3389–3395, 2002     

N‐acyl chitosan and its fiber with excellent moisture absorbability and retentivity: Preparation in a novel [Gly]Cl/water homogeneous system

N‐acyl chitosans (such as N‐acetylated, N‐maleyl, and N‐succinyl chitosan), which were synthesized in glycine chloride ([Gly]Cl)/water homogeneous system, were of better moisture‐absorption and moisture‐retention abilities than those from the traditional methods, even better than hyaluronic acid. Moreover, the new method overcame many shortcomings, such as long reaction time, gel formed during the process of reaction, and complex workup procedure. In addition, the new [Gly]Cl solvent system was of the low volatility and no corrosion compared with organic solvent, especially, could be repeatedly used. Therefore, an environmental friendly approach for the synthesis of N‐acyl chitosan was provided. At the same time, the N‐acetylated chitosan fibers by wet‐spinning using N‐acetylated chitosan‐[Gly]Cl as spinning dope solution were firstly reported, and the fibers had smooth surface as well as round and compact structure. More to the point, the N‐acetylated chitosan fibers directly prepared in this study were of excellent mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modification of polyacrylonitrile (PAN) fiber by blending with N‐(2‐hydroxy)propyl‐3‐trimethyl‐ ammonium chitosan chloride

N‐(2‐Hydroxy)propyl‐3‐trimethylammonium chitosan chloride (HTCC) was synthesized by the reaction of glycidyltrimethylammonium chloride (GTMAC) and chitosan. The reaction product was a water‐soluble chitosan derivative, and showed excellent antimicrobial activity. HTCC was blended with polyacrylonitrile (PAN) using an NaSCN aqueous solution as a common solvent. The blend solution was transparent and stable up to 6 months without phase separation. The PAN/HTCC blend fibers were prepared via a wet spinning and drawing process. Thermal, electrical, and mechanical properties as well as antimicrobial activity were investigated. It was found that the antistatic property and antimicrobial activity of the blend fibers could be achieved by adding only a small amount of HTCC. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2258–2265, 1999     

The Online Measurement of Lyocell Fibers and Investigation of Elongational Viscosity of Cellulose N‐methylmorpholine‐N‐oxide Monohydrate Solutions

In this paper, the development of diameter and surface temperature of Lyocell fibers was measured online. The diameter and tensile force on the spin line in the coagulation bath were traced. The velocity, velocity gradient and the tensile stress profiles development of the fibers in the air gap were studied. The apparent elongational viscosity of cellulose N‐methylmorpholine‐N‐oxide monohydrate (NMMO‐MH) solutions was studied by steady‐state melt spinning theory. The decrease of the fiber diameter was mainly taking place near the spinneret, and the decrease of the diameter became more dramatic with increasing taking‐up speed. The surface temperature of the fibers was also dropping faster with increasing taking‐up speed for the heat transfer coefficient increased. The diameter of the Lyocell fibers almost did not change before and after it entered the coagulation bath. The tensile force on the spin line increases with increasing taking‐up speed and coagulation bath length. The velocity and the tensile stress increase slowly near the spinneret, and then accelerate. The apparent elongational viscosity of cellulose NMMO‐MH solutions decreases with increasing temperature at the same elongation rate and decreases with increasing elongation rate at the same temperature. The fiber of the Lyocell process was not really solidified in the air gap and a gel or rubbery state was formed.     

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

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

Preparation of conductive polyaniline fibers by a continuous forming‐drawn processing routine

Polyaniline fibers were prepared with a continuous forming‐drawn processing routine that better met practical production requirements. The continuous forming drawing of the fibers was conducted successfully with the following methods. A reducing agent was added to a polymer solution during the dissolution of a polyaniline emeraldine base in N‐methyl‐2‐pyrrolidinone (NMP). After the entire wet‐spinning process was finished, the fibers were reoxidized and doped to obtain electric conductivity. The as‐spun fibers were predrawn at a low drawing ratio in a warm water bath before a plasticization drawing process on a hot plate. After the fibers were predrawn, some solvent was still kept in the fibers and used as a plasticizer of the fibers so that the plasticization drawing process would be performed successfully. The spinning conditions that affected the mechanical properties and conductivity of the fibers were the content of NMP in the coagulation bath, the coagulation‐bath temperature, the warm‐water‐bath temperature, the predrawing ratio, the hot‐plate temperature, the plasticization drawing ratio, and the reoxidation and protonation treatment time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 956–960, 2004     

Preparation and properties of conductive polyaniline/poly‐ω‐aminoundecanoyle fibers

Historically, polyaniline (PANI) had been considered an intractable material, but it can be dissolved in some solvents. Therefore, it could be processed into films or fibers. A process of preparing a blend of conductive fibers of PANI/poly‐ω‐aminoundecanoyle (PA11) is described in this paper. PANI in the emeraldine base was blended with PA11 in concentrated sulfuric acid (c‐H₂SO₄) to form a spinning dope solution. This solution was used to spin conductive PANI / PA11 fibers by wet‐spinning technology. As‐spun fibers were obtained by spinning the dopes into coagulation bath water or diluted acid and drawn fibers were obtained by drawing the as‐spun fibers in warm drawing bath water. A scanning electron microscope was employed to study the effect of the acid concentration in the coagulation bath on the microstructure of as‐spun fibers. The results showed that the coagulating rate of as‐spun fibers was reduced and the size of pore shrank with an increase in the acid concentration in the coagulation bath. The weight fraction of PANI in the dope solution also had an influence on the microstructure of as‐spun fibers. The microstructure of as‐spun fibers had an influence on the drawing process and on the mechanical properties of the drawn fibers. Meanwhile, the electrically conductive property of the drawn fibers with different percentage of PANI was measured. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1458–1464, 2002     

Ultrafiltration of metal ions by water‐soluble chelating poly(N‐acryloyl‐N‐methylpiperazine‐co‐N‐acetyl‐α‐aminoacrylic acid)

Water‐soluble copolymers of N‐acryloyl‐N‐methylpiperazine and N‐acetyl‐α‐aminoacrylic acid were synthesized by radical polymerization. The copolymerization yield ranged between 60 and 97%. The FTIR and NMR spectra demonstrated that the copolymerization occurred. The copolymer composition was determined from ¹H‐NMR spectra by comparison of methyl groups from both moieties. The copolymers were richest in AAA units. The metal ion retention properties were investigated by the liquid‐phase polymer‐based retention (LPR) technique at different pH and filtration factors. The affinity for the metal ions depended on the copolymer composition, pH, and filtration factor. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2556–2561, 2002     

Preparation and properties of the single‐walled carbon nanotube/cellulose nanocomposites using N‐methylmorpholine‐N‐oxide monohydrate

Single‐walled carbon nanotube (SWNT)/cellulose nanocomposite films were prepared using N‐methylmorpholine‐N‐oxide (NMMO) monohydrate as a dispersing agent for the acid‐treated SWNTs (A‐SWNTs) as well as a cellulose solvent. The A‐SWNTs were dispersed in both NMMO monohydrate and the nanocomposite film (as confirmed by scanning electron microscopy) because of the strong hydrogen bonds of the A‐SWNTs with NMMO and cellulose. The mechanical properties, thermal properties, and electric conductivity of the nanocomposite films were improved by adding a small amount of the A‐SWNTs to the cellulose. For example, by adding 1 wt % of the A‐SWNTs to the cellulose, tensile strain at break point, Young's modulus, and toughness increased ～ 5.4, ～ 2.2, and ～ 6 times, respectively, the degradation temperature increased to 9°C as compared with those of the pure cellulose film, and the electric conductivities at ? (the wt % of A‐SWNTs in the composite) = 1 and 9 were 4.97 × 10^?4 and 3.74 × 10^?2 S/cm, respectively. Thus, the A‐SWNT/cellulose nanocomposites are a promising material and can be used for many applications, such as toughened Lyocell fibers, transparent electrodes, and soforth. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on the acidic hydrolysis process of poly(N‐vinylformamide/acrylonitrile) fiber

A convenient method of preparing chelating fiber with amine groups on the fiber surface was developed. The precursor polymer of Poly(N‐vinylformamide/acrylonitrile) (P(NVF/AN)) was synthesized via solution polymerization, using N‐vinylforaimde as a functional monomer. The solution of P(NVF/AN) was spun through a wet spinning method and the precursor fiber was hydrolyzed in the hydrochloric acid solution to convert formamide moieties to the corresponding amine. The influence of hydrolytic conditions on hydrolysis degree, such as hydrolysis temperature, hydrolysis time, and hydrochloric acid concentrations were examined experimentally. The hydrolysis degree of the precursor fiber was evaluated by potentiometric and conductometric titrations. The changes of the structure and properties of the fibers were characterized through infrared spectroscopy, scanning electron microscopy, and tensile strength tester. The results showed that the hydrolysis degree was limited in acidic hydrolysis because of the electrostatic repulsion among the cationic amine groups and proton. The hydrolysis degree of precursor fiber reached nearly 60%, and the chelating fiber remained the adequate mechanical properties under the suitable hydrolysis condition. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Toughening of cyanate ester resin by N‐phenylmaleimide–N‐(p‐hydroxy)phenyl‐maleimide–styrene terpolymers and their hybrid modifiers

N‐Phenylmaleimide–N‐(p‐hydroxy)phenylmaleimide–styrene terpolymer (HPMS), carrying reactive p‐hydroxyphenyl groups, was prepared and used to improve the toughness of cyanate ester resins. Hybrid modifiers composed of N‐phenylmaleimide–styrene copolymer (PMS) and HPMS were also examined for further improvement in toughness. Balanced properties of the modified resins were obtained by using the hybrid modifiers. The morphology of the modified resins depends on HPMS structure, molecular weight and content, and hybrid modifier compositions. The most effective modification of the cyanate ester resin was attained because of the co‐continuous phase structure of the modified resin. Inclusion of the modifier composed of 10 wt% PMS (M_w 136 000 g mol^?1) and 2.5 wt% HPMS (hydroxyphenyl unit 3 mol%, M_w 15 500 g mol^?1) led to 135% increase in the fracture toughness (K_IC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and glass transition temperature, compared with the values for the unmodified resin. Furthermore, the effect of the curing conditions on the mechanical and thermal properties of the modified resins was examined. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified cyanate ester resin system. © 2001 Society of Chemical Industry     

Thermostability of Lyocell Dopes Modified with Surface‐Active Additives

Summary: Cellulose/N‐methylmorpholine‐N‐oxide monohydrate (NMMO) spinning solutions were modified with surface‐active additives to yield Lyocell fibers with functional properties. Based on cellulose fibers, a new class of materials with tailored adsorption characteristics are produced. Activated charcoal and carbon black used as additives significantly affect the thermostability of the spinning solutions. Considering the degree of filling three general tendencies become evident. It is most obvious that the onset temperature of dope decomposition is shifted towards lower values accompanied by viscosity reduction after annealing at elevated temperatures and an enhanced formation of degradations products. Morpholine, N‐methylmorpholine and formaldehyde as the main degradation products were detected in aqueous distillates by means of HPLC. To study the rate of by‐product formation during preparation of the solution kinetic measurements were carried out. Thermal instabilities are not only initiated by heavy metal ions, especially Fe(II), but also by the particle size and porosity of the charcoal. The nano‐scaled carbon black used causes autocatalytic reactions as revealed by calorimetric measurements.

Relationships between amount of Acc versus onset temperature (T_on) and concentration of N‐methylmorpholine.     

Hemodialysis membrane prepared from cellulose/N‐methylmorpholine‐N‐oxide solution. I. Effect of membrane preparation conditions on its permeation characteristics

Flat hemodialysis membranes were prepared from cellulose/N‐methylmorpholine‐N‐oxide (NMMO) solutions (dope) with different cellulose concentrations (6–8 wt %) by using a phase‐inversion method. The coagulant used was NMMO aqueous solution, of which the NMMO concentration and its temperature were varied in the range of 0 to 50 wt % and 5 to 60°C, respectively. The effects of these preparation conditions on the permeation characteristics, the ultrafiltration rate (UFR) of pure water, and sieving coefficient (SC) of dextran, were investigated. The decrease in cellulose concentration of the dope and the increases in both temperature and NMMO concentration of the coagulant gave a membrane with high UFR. Concerning the SC, the increase of the cellulose concentration and the decreases in both temperature and NMMO concentration gave a good result. Consequently, the membrane having the preferable UFR and SC as a hemodialysis membrane was obtained when the 8 wt % cellulose dope was coagulated in water at 5°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2302–2307, 2002