Preparation of Porous <Emphasis Type="Italic">m</Emphasis>-aramid/cellulose Blend Membranes with High Moisture and Air Permeability by an Enzymatic Degradation Method

Enzyme degradation method was adopted to prepare porous m-aramid/cellulose blend membranes with high air permeability, water absorbency and moisture permeability. This facile preparation process started by casting a blend membrane from a DMAc/LiCl solution containing m-aramid and cellulose. An enzyme was then used to degrade the cellulose in the blend membrane, resulting in porous structures. Five enzymes including cellulase, chitosanase, papain, lipase, and glucose oxidase, were evaluated and cellulase was found to be optimal. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the miscibility and the morphology of the m-aramid/cellulose blend membranes before and after degradation, respectively. The thermal stability of the blend membranes were characterized by thermogravimetric analysis (TGA). The properties including air permeability, water absorbency and moisture permeability of the m-aramid/cellulose blend membranes greatly improved after degradation as compared to those of the pure m-aramid. This paper provided a new approach to preparing novel textile materials with high comfortability.     

Dyeing and fastness properties of vat dyes on meta-aramid woven fabric

meta-Aramid fibers have an excellent heat-resistant property and are widely used for protective clothings such as fire-fighter suit and racing suit. They can also be used as military uniforms such as flight suit or army uniform. Vat dyes are specially used for military uniforms owing to outstanding fastness properties, earth tone shade, and near infrared (NIR) camouflage. In this study, 100 % meta-aramid woven fabric was dyed with three vat dyes using an exhaustion method and their dyeing and fastness properties were investigated. Color yields of the vat dyes on the meta-aramid fabric were found to be dependent upon dyeing temperature, liquor ratio, amount of reducing agent, and amount of salt. Dyeing behavior of the vat dye on the meta-aramid fiber was very similar to that on cellulose fibers. It was found that the meta-aramid fabric dyed with 1% owf of C.I. Vat Green 1 satisfied the tolerance of the reflectance spectrum of forest green color in the Korean military standard. Thermal stability and mechanical property of the meta-aramid fabric did not significantly affected by the vat dyeing process. Wash and perspiration fastness was generally good but rubbing and light fastness was unsatisfied.     

Properties of basic dyes on polyacrylonitrile treated m-aramid fabrics

Treatment of polyacrylonitrile (PAN) onto m-aramid fabric was carried out by pad-dry-cure method using dimethylformamide (DMF) dissolved acrylic fiber solution. The obtained PAN treated m-aramid fabric was dyed using exhaustion method with basic dyes. The effect of PAN treatment on fabric stiffness property was acceptable with acrylic fiber solutions ranging from 1 wt% to 4 wt%. Whilst, more than 4 wt% PAN treated fabrics exhibited undesirable stiffness. The dyeing results showed that PAN treated m-aramid fabrics exhibited a significant increase in color strength when compared to untreated fabric, arising from an increase in anionic dye sites (styrene SO₃ ^? group). Wash fastness was comparable to that of untreated fabric, indicating the strong interaction between dye molecules and the PAN. Rubbing fastness of treated fabrics was not affected by treatments with PAN concentrations lower than 4 wt%. Further increase in PAN concentration led to poorer rubbing fastness property due to the problem of surface dyeing. For light fastness, the PAN treatment failed to improve the light fastness property which is the main disadvantage of basic dyeing of aramid fabric. Finally, in case of PAN treatments with the range of 1 wt% to 4 wt%, the flame retardancy property of PAN treated m-aramid fabrics was found not affected by the percent add-on. However, above 4 wt% PAN treatment, the flame retardancy performance became deteriorated.     

Surface modification of cellulose fibers by layer-by-layer self-assembly of lignosulfonates and TiO2 nanoparticles: Effect on photocatalytic abilities and paper properties

Depositing of TiO₂ nanoparticles on cellulose fiber surface has potential technological applications in the field of photocatalysis. With this motivation, multilayers composed of lignosulfonates (LS) and TiO₂ nanoparticles were constructed on cellulose fiber surface via layer-by-layer (LBL) self-assembly technique. X-ray photoelectron spectroscopy (XPS), zeta potential measurement and atomic force microscopy (AFM) were used to characterize the LS/TiO₂ multilayers on cellulose fiber surface. Moreover, the photocatalytic activities of modified cellulose fibers (decomposition of methyl orange and antibacterial test) were investigated. The decomposition efficiency of methyl orange for a (LS/TiO₂)₅ multilayer modified cellulose fibers was 74.7 % under 5 h UV irradiation. Photocatalytic decomposition efficiency of methyl orange by LS/TiO₂ multilayer modified cellulose fibers under the same UV irradiation time increased linearly with the number of bilayers. Antibacterial tests results revealed that the cellulose fibers modified with LS/TiO₂ multilayers exhibited excellent antibacterial activity against E.coil. The degree of E.coil growth inhibition for a (LS/TiO₂)₅ multilayer modified cellulose fiber reached as high as 93 %. In addition, the effect of LS/TiO₂ multilayers on properties of handsheets made from modified cellulose fibers was also considered. The air permeability of the handsheet prepared from fibers modified with TiO₂/LS multilayers had 6.1–24.3 % higher compared with that of handsheet prepared from original fibers. The wetting properties measurement results demonstrated that the water contact angle of handsheet oscillated with the increasing number of layers depended on building block which was in the outermost layer.     

Properties of flame-retardant cellulose fibers with ionic liquid

Flame-retardant cellulose fibers were prepared by dissolving cellulose in tetrabutylammonium acetate and dimethyl sulfoxide, and blending with amino silicone oil (ASO). The ASO was used as a novel fabric softener and flame retardant for cellulose fibers. Fourier-transform infrared spectroscopy showed that blending with ASO did not adversely affect the cellulose fibers. The flame retardancy of the cellulose fibers blended with ASO was determined based on the limiting oxygen index (LOI). Cellulose fibers blended with 8 wt% (add-on) ASO gave the best flame retardancy, with an LOI of 28, which was higher than that of the virgin fibers. The thermal properties of the flame-retardant cellulose fibers were investigated using differential scanning calorimetry and thermogravimetric analysis. The results showed that ASO prevented degradation of the cellulose fibers, hindered the formation of volatile species, and favored char formation. The mechanical properties of the flame-retardant cellulose fibers were better than those of virgin cellulose fibers.     

The effect of alkali pre-treatment on formation and adsorption of silver nanoparticles on cotton surface

This study is an attempt to investigate the feasibility of alkali pre-treatment to activate surface hydroxyl groups of cellulose fibers in order to enhance the deposition efficiency of silver nanoparticles (AgNPs) onto cotton fabrics. Cotton samples were pre-treated with various alkali solutions containing different earth metal hydroxides (LiOH, NaOH, and KOH). The as-prepared samples were then treated with aqueous silver nitrate followed by reduction treatment with aqueous ascorbic acid, which caused in situ formation of AgNPs on fiber surfaces. The surface structure of the fabrics was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis, and colorimetric data. The amount of silver was measured by using inductively coupled plasma-optical emission spectrometer (ICP-OES). Antimicrobial activity was measured against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. It was established that alkali pre-treatment had a substantial effect on the formation and adsorption of AgNPs on the fibers. Alkali pre-treated samples were homogeneously coated by AgNPs with high surface coverage. Alkali type had significant effect not only on the amount of AgNPs on the surface but also on its size. High antibacterial activity against both Gram-positive and Gram-negative strains was also demonstrated, even after 10 cycles washing.     

Synthesis of cationized anthraquinone dyes and their dyeing properties for meta-aramid fiber

Due to compact structure of meta-aramid fiber caused by the intermolecular hydrogen bondings of amide groups, the degree of crystallinity increased, thus its poor dyeing properties arises. Among commercial dyes used in many previous researches, the basic dyes showed comparatively higher exhaustion yields as comparing to those of disperse dyes and acid dyes. The anthraquinone moiety was adopted for good performances of light fastness on meta-aramid fiber. In this study, eight of anthraquinone dye was synthesized. The three of them were obtained from chloro-anthraquinone, by Ullmann reactions with the corresponding heterocylic residues such as morpholine and one of them was obtained from lueco quinizarine by condensation with the corresponding heterocylic residues. The others were prepared by quaternization from dyes above. The synthesized disperse and cationic dyes were dyed on meta-aramid fibers and investigated for their build-up dyeing properties and wash fastness.     

Synthesis of silver nanoparticles with sericin and functional finishing to cotton fabrics

This research presents a novel strategy to fabricate multi-functional cotton textiles. In this study, silver nanoparticles-sericin (Ag NPS-sericin) hybrid colloid has been prepared using sericin as reducing agent and dispersing agent. Cotton fabrics was oxidized selectively with sodium periodate (NaIO₄) to generate oxidized cotton fabrics, and which has then been finished using Ag NPS-sericin hybrid colloid prepared to obtain multi-functional cotton textiles. The finished cotton fabric not only possessed excellent antibacterial activity, but also it was modified functionally by sericin protein, which endowed antibacterial cotton fabrics relatively smooth surface and good wear ability. Fourier transform infrared spectrogram confirmed that sericin protein was grafted onto cellulose fibers. Ag NPs were characterized by UV-Vis spectroscopy, transmission electron microscope (TEM) and X-ray powder diffraction (XRD). The results of SEM, X-ray photoelectron spectroscopy (XPS) and EDS confirmed that silver nanoparticles and sericin been loaded successfully on the surface of cotton fabrics. The antibacterial experiments showed bacterial reduction rates of S.aureus and E.coli were able to reach above 99 %. After washing 20 times, it showed still good antibacterial activity at over 95 % against S.aureus and E.coli.     

Functionalization of lyocell fibers with TiO2, SiO2, and GLYMO

In the research self-cleaning coatings based on photocatalytically active nano titanium dioxide (TiO₂) were prepared. When applied directly to cellulose fiber surfaces, TiO₂ coatings form weak bonds with fibers. Therefore 3-glycidooxypropyl-trimethoxysilane was used as a coupling agent. It had been applied on the surface of cellulose fibers before the TiO₂ coating was performed. In this case, the silane is in the interface region, where it can be most effective as an adhesion promoter. Silane coupling agents have unique chemical and physical properties not only to enhance bond strength, but more importantly to prevent de-bonding at the interface during composite aging and use as well. The coupling agent provides a stable bond between two otherwise poorly bonding surfaces. Surface properties of these coatings have been examined, such as surface morphology and surface microstructure. TiO₂ nanoparticles were irreversibly attached to the surface of monodisperse silica (SiO₂) spheres and to the surface of Lyocell fibers coated with an epoxy-containing silane coupling agent. Analysis using scanning electron microscopy showed uniform distribution of nanoparticles in the resulting coatings. Fourier transform infrared spectroscopy revealed changes in the surface microstructure occurring after different modifications. In addition, the influence of photocatalytic activity on the mechanical properties of Lyocell fibers was determined. In addition to that, the results indicated that SiO₂ and the coupling agent provide a protection against high oxidizing power of TiO₂ under exposure to daylight irradiation.     

Extraction, preparation and characterization of cellulose fibres and nanocrystals from rice husk

Cellulose fibres and cellulose nanocrystals were extracted from rice husk. Fibres were obtained by submitting the industrial rice crop to alkali (NaOH) and bleaching treatments. Nanocrystals were extracted from these fibres using sulphuric acid (H₂SO₄) hydrolysis treatment. The material obtained after each stage of the treatments was carefully characterized and its chemical composition was determined. Morphological investigation was performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy showed the progressive removal of non-cellulosic constituents. X-ray diffraction (XRD) analysis revealed that the crystallinity increased with successive treatments. The thermal stability of the rice husk fibres and cellulose nanocrystals was also investigated using thermogravimetric analysis (TGA).     

Dyeing performance of disperse dyes based on 2-aminothiazole for cellulose triacetate and nylon fibers

A series of monoazo disperse dyes based on 2-amino-4-phenylthiazole was prepared using variousN,N-dialkylaniline derivatives as the coupling component. The dyes were characterized by IR spectral studies, visible absorption spectroscopy and elemental analysis. The dyeing performance of these dyes was assessed on cellulose triacetate and nylon fibers. These dyes were found to give a wide range of colour shades varying from bright red to royal blue with very good depth, brightness and levelness on fibers. The dyed fibers showed good to very good light fastness and very good to excellent fastness to washing, perspiration, rubbing and sublimation. The dyebath exhaustion and fixation on the fibers were found to be very good.     

Design and synthesis of peptide-cellulose conjugate molecules —Aspects from energy/steric profiles—

A multipurpose chemical modification of cellulose to yield soluble cellulose derivatives was investigated on the basis of (i) O-acylation of the parent cellulose using N-Boc-protected Gly, αAla, and βAla, and subsequent Boc-removal, (ii) N-acylation of amino acid-modified cellulose in homogenous solution reaction system using Boc-oligopeptides with multiple types of the side-chain functionalities, and (iii) N-acylation of βAla-Cellulose using 10 kinds of simple Boc-oligopeptides. As for the (i), Thermochemical computation to estimate ΔG transition was well coincided with the observed yields in Oacylations. In the case of (ii), beside the similar ΔG-schemes, a strain energy profile, which is coupled with the preferred conformer transition of the amino acid-modified cellulose, was involved to rule out the N-acylation. The symmetric anhydrate in the N-acylating agents in the (iii) are tend to be in torsions due to the β-strand-like steric stabilizations in the peptides, resulting in the highest N-acylation yields as much as 98 %.     

Effect of degree of polymerization on the mechanical properties of regenerated cellulose fibers using synthesized 1-allyl-3-methylimidazolium chloride

1-Ally-3-methylimidazolium chloride ([AMIM]Cl) was successfully synthesized and was used as a green spinning solvent for cellulose. The celluloses of various degrees of polymerization (DP) were dissolved in the [AMIM]Cl to obtain 5 % (w/w) cellulose solutions, which were regenerated to cellulose fibers through wet spinning process. Of three different regenerated cellulose fibers with different DPs, a DP of 2,730 was gave the strongest regenerated fiber without drawing having a tensile strength of 177 MPa and an elongation at break of 9.6 % respectively, indicating that celluloses of higher molecular weight can be entangled and oriented more easily. Also maximum draw ratio of the as-spun fibers increased from 1.2 to 1.7 with increasing degree of polymerization leading to a tensile strength and modulus of 207 MPa and 48 GPa, respectively. Particularly the tensile modulus was substantially higher than those of lyocell and high performance viscose fibers of 20 GPa or less. The higher DP of pristine cellulose was critical in increasing the mechanical properties such as tensile strength and elongation at break of the as-spun fibers coupled with higher tensile modulus after drawing.     

Mercerization mediated modification of cellulosic fibers with NIPAAm and some compounds with antioxidant activity

A two step process was used for the modification of a cellulose/chitin mixed fibers: the first step was an alkali treatment with a NaOH solution (20 %), which was followed by the reaction with one of the reagents such as Nisopropylacrylamide, p-hydroxybenzoic acid, gallic acid, or eugenol. Both the samples activated with the alkali treatment and modified with chemicals were characterized by attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and thermal analysis. Results revealed the morphological and structural changes of the fiber surface after the surface grafting, which significantly altered the cellulose/chitin mixed fiber properties. Thermal analysis results showed an increase in the thermal stability of the treated samples. Antioxidant activity of cellulose/chitin mixed fibers modified with phenolic compounds showed that the efficiency depends on the chemical nature of phenolic compound.     

Structural differences between non-wood plant celluloses: evidence from solid state NMR,vibrational spectroscopy and X-ray diffractometry

Cellulose from flax, hemp, kenaf and sorghum was investigated by solid state NMR and vibrational spectroscopy, and the structural differences found were validated by X-ray diffractometry. All three techniques indicate a notable region of order in the cellulose of both flax and hemp, but the absolute crystallinity values are not directly comparable. CP-MAS ¹³C-NMR and FTIR spectroscopy revealed the presence of Iα and Iβ forms in all the samples. On passing from flax and hemp to kenaf and sorghum the progressive loss in the crystalline phase is evidenced by ¹³C-CPMAS T₁ measurements; ¹H-CPMAS T_1ρ measurement revealed an analogous loss in phase dimension for the ordered phase, but similar dimension values for the paracrystalline and amorphous phases. The FTIR and FTRaman spectra of all the cellulose samples reveal the same chain conformation but a different hydrogen bond pattern, and this accounts for the NMR and X-ray results.     

Dyeing properties and color fastness of 100% <Emphasis Type="Italic">meta</Emphasis>-aramid fiber

Dyeing characteristics and fastness of 100 % m-aramid fiber with some commercial dyes were investigated on various dyeing conditions, such as using a swelling agent and electrolyte as auxiliaries. Among commercial dyes used, the basic dyes showed comparatively higher exhaustion yield comparing to those of disperse dyes and acid dyes. Under acidic conditions in the range pH 3 to 5, preferably between pH 3 and 4, the stability of cationic dyes could be enhanced leading to higher adsorption. Dye exhaustions of trichromatic dyes were increased proportionally to concentration of swelling agents ranging from 1 to 4 g/l. The addition of electrolyte provided increased K/S values after washing process compared with those of blank dyeings, where the greatest effect was observed with NaNO₃.     

Synthesis of non-water soluble polymeric guanidine derivatives and application in preparation of antimicrobial regenerated cellulose

In order to prepare antimicrobial regenerated cellulose fibers from blended spinning solutions, three non-water soluble polymeric guanidine derivatives, polyhexamethylene guanidine dodecyl benzene sulfonate (PHGDBS), polyhexamethylene guanidine dodecyl sulfate (PHGDSA), and polyhexamethylene guanidine laurylsulfonate (PHGLSO) were synthesized. And the chemical structure of these agents was verified by element analysis, Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (¹H-NMR). The antimicrobial activity of the three agents as well as cellulose films containing PHGDBS was also studied. The results showed that the compounds we prepared had strong properties against both bacterial and fungus, including Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Candida albicans, and Aspergillus niger. Moreover, it was found that three antimicrobial agents were insoluble in water but they can dissolve in solvents of cellulose such as 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and N-methylmorpholine-N-oxide monohydrate (NMMO·H₂O). Meanwhile, it was also proved that [BMIM]Cl had little effect on the antimicrobial properties of these agents. The cellulose films containing only 1.0 wt% PHGDBS showed 99.94 % and 96.95 % bacterial reduction rates for S. aureus and E. coli, respectively. Moreover, still over 91 % of bacterial reduction was maintained after 15 laundering cycles. It suggests that the three agents will be suitable to prepare antimicrobial regenerated cellulose fibers or films.     

Preparation of regenerated cellulose fiber via carbonation. I. Carbonation and dissolution in an aqueous NaOH solution

Cellulose carbonate was prepared by the reaction of cellulose pulp and CO₂ with treatment reagents, such as aqueous ZnCl₂ (20–40 wt%) solution, acetone or ethyl acetate, at −5–0°C and 30–40 bar (CO₂) for 2 hr. Among the treatment reagents, ethyl acetate was the most effective. Cellulose carbonate was dissolved in 10% sodium hydroxide solution containing zinc oxide up to 3 wt% at −5–0°C. Intrinsic viscosities of raw cellulose and cellulose carbonate were measured with an Ubbelohde viscometer using 0.5 M cupriethylenediamine hydroxide (cuen) as a solvent at 20°C according to ASTM D1795 method. The molecular weight of cellulose was rarely changed by carbonation. Solubility of cellulose carbonate was tested by optical microscopic observation, UV absorbance and viscosity measurement. Phase diagram of cellulose carbonate was obtained by combining the results of solubility evaluation. Maximum concentration of cellulose carbonate for soluble zone was increased with increasing zinc oxide content. Cellulose carbonate solution in good soluble zone was transparent and showed the lowest absorbance and the highest viscosity. The cellulose carbonate and its solution were stable in refrigerator (−5°C and atmospheric pressure).     

Improved interfacial properties of carbon fiber/unsaturated polyester composites through coating polyhedral oligomeric silsesquioxane on carbon fiber surface

Carbon fibers were coated with E51 plus Methacryl-POSS together in an attempt to improve the interfacial properties between carbon fibers and unsaturated polyester resins matrix. Atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were performed to characterize the changes of carbon fiber surface. AFM results show that the coating of E51 plus POSS significantly increased the carbon fiber surface roughness. XPS indicates that silicon containing functional groups obviously increased after modification. Dynamic mechanical analysis was carried out to investigate the surface energy of carbon fiber. Force modulation atomic force microscopy (FMAFM) and Interlaminar shear strength (ILSS) were used to characterize the interfacial properties of the composites. ILSS was increased by 21.9 % after treatment.     

Synthesis and characterization of cellulose carbamate by liquid-solid phase method

An efficient and environmentally friendly method for the synthesis of cellulose carbamate from a mixture of cellulose pulp or the activated cellulose pulp and urea was presented in this paper. Cellulose carbamate with a nitrogen content of 1.21 % and 3.29 % were successfully synthesized via esterification reaction in the high-boiling aprotic and polar N-methyl-2-pyrrolidone solvents (hereinafter NMP). The structures of cellulose carbamate were characterized by Fourier transform infrared spectroscopy (FTIR), Kjeldahl analysis, thermo-gravimetric analysis, scanning electron microscopy (SEM), X-ray diffractometry (XRD), and ¹³C-solid-state NMR. The results showed that some functional groups of the alkali cellulose were substituted by amino in the high-boiling aprotic and polar solvents, then the cellulose carbamate was prepared with the reduced crystallinity and thermal decomposition temperature. In addition, the product was prepared with uniform substitution and distribution of carbamate group in the cellulose chain, which guaranteed its good solubility in aqueous alkali as well as its spinnability to produce fiber.