The spinning,structure, and properties of cellulose/chitin blend filaments through HWM method

The aim of this paper is the preparation and characterization of cellulose/chitin blend filaments over the experimental blend ratio scope i.e., 2.89 and 6.46% (w/w) chitin content through high wet modulus (HWM) procedure. The spinnability of the invested solutions was found to vary in the following order: chitin < cellulose < 9.5:0.5 blend < 9:1 blend < 8:2 blend < 5:5 blend (9:1 means the mass ratio of cellulose to chitin, so does 9.5:0.5, 8:2, and 5:5). The cross‐section of the blend filaments is of chrysanthemum shape. It was shown through the SEM photographs that there existed grooves on the surface of filaments, which became coarse with increase in chitin content. Based on the data from X‐ray, sonic velocity, intensity, and hygroscopicity, it is concluded that the degree of crystallinity, dry and wet intensity modulus, degree of orientation, and regain rate of the filaments decreased with increase in chitin content in the experiment scope. The mechanical properties of the blend filaments are much higher than those of Crabyon fiber and normal viscose filaments, which proves that the HWM method is an efficient way of preparing cellulose/chitin blend filaments with satisfactory mechanical properties and processing property. The blend filaments prepared have an effective biostatic effect on Staphylococcus aureus, Escherchia coli, and Corinebaterium michiganence according to different testing standards. Copyright © 2009 John Wiley & Sons, Ltd.     

Structure and properties of novel fibers spun from cellulose in NaOH/thiourea aqueous solution

Cellulose was dissolved rapidly in a NaOH/thiourea aqueous solution (9.5:4.5 in wt.-%) to prepare a transparent cellulose solution, which was employed, for the first time, to spin a new class of regenerated cellulose fibers by wet spinning. The structure and mechanical properties of the resulting cellulose fibers were characterized, and compared with those of commercially available viscose rayon, cuprammonium rayon and Lyocell fibers. The results from wide angle X-ray diffraction and CP/MAS 13C NMR indicated that the novel cellulose fibers have a structure typical for a family II cellulose and possessed relatively high degrees of crystallinity. Scanning electron microscopy (SEM) and optical microscopy images revealed that the cross-section of the fibers is circular, similar to natural silk. The new fibers have higher molecular weights and better mechanical properties than those of viscose rayon. This low-cost technology is simple, different from the polluting viscose process. The dissolution and regeneration of the cellulose in the NaOH/thiourea aqueous solutions were a physical process and a sol-gel transition rather than a chemical reaction, leading to the smoothness and luster of the fibers. This work provides a potential application in the field of functional fiber manufacturing.     

Synthesis of intrinsically flame‐retardant copolyamides and their employment in PA6‐fibers

Flame‐retarded polyamide 6.6 (FR‐PA6.6) was prepared by the cocondensation of hexamethylene diammonium adipate (AH‐salt) with the corresponding salts of hexamethylene diamine and two different organophosphorus compounds, namely, 3‐hydroxyphenylphosphinylpropanoic acid (3‐HPP, 1) and 9,10‐dihydro‐10‐[2,3‐di (hydroxycarbonylpropyl]‐10‐phosphaphenanthrene‐10‐oxide (DDP, 2). The incorporation of the phosphorus comonomers and the thermal and physical properties of the resulting copolyamides have been studied. The phosphorus‐modified FR‐PA6.6 possesses high relative viscosities of 2.0 to 2.4, good thermal stability, and was used for the production of polyamide blends by merging FR‐PA6.6 with commercial PA6. This offered access to flame‐retarded PA6 multifilaments, which possess tensile strengths up to 0.7 GPa and elastic moduli up to 6.2 GPa. Knitted fabrics of FR‐PA6 exhibit high limiting oxygen index (LOI) values between 36 and 38 and executed burning tests demonstrate that the incorporation of phosphorus‐based comonomers improve flame retardancy significantly. The approach presented here offers a straightforward access to effective flame retardancy in nylon 6.     

Structure development during melt spinning and subsequent annealing of polybutene‐1 fibers

The structural development during the melt spinning and subsequent annealing of polybutene‐1 fibers was studied with in situ wide‐angle X‐ray scattering techniques. The online spinning apparatus consisted of a vertically translating extruder that allowed different distances from the spinneret to the stationary X‐ray beam to be sampled. For all take‐up speeds examined, phase II crystals mainly were formed, with only a small population of phase I crystals existing. As the take‐up speed was increased, the crystallinity also increased, indicating that strain‐induced crystallization prevailed. The crystalline orientations observed online were very close to perfect alignment with the fiber axis. In addition, annealing studies were performed to study aspects of the gradual phase II to phase I transformation as functions of time and prior processing take‐up speed. This transformation was strongly dependent on the take‐up speed. The dependence appears to be connected to local stress enhancement via chains connecting crystallites. The results also seem to indicate that at low take‐up speeds (17 mpm) there is a series connectivity of amorphous and crystalline components in the fiber, whereas at greater take‐up speeds (100 and 250 mpm), the morphology grows into some type of three‐dimensional network, possibly a shish–kebob‐type morphology. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1872–1882, 2000     

Preparation and characterization of cellulose and konjac glucomannan blend film from ionic liquid

Blend films from cellulose and konjac glucomannan (KGM) in room temperature ionic liquid 1‐allyl‐3‐methylimidazolium chloride were satisfactorily prepared by coagulating with water. The composition of the blend films was gravimetrically analyzed, and the compatibility of the two natural polymers was characterized by Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction. The results indicate good compatibility and strong interactions between cellulose and KGM, resulting in almost no loss of the water‐soluble KGM from the blend films even after the water coagulating and washing. However, microstructure analyses portrayed phase separations in the blend films, namely, egg‐like new phase particles were embedded in a continuous matrix base (MB). Phase diagram analysis and differential scanning calorimetry of the phase inversion coagulation process suggest that relative low molecular mass part of both cellulose and KGM formed the continuous MB, whereas the egg‐like new phase particles were super patterns of relative high molecular mass of both polymers, which played an important role in strengthening the blend material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1686–1694, 2009     

Ionic liquid chemically bonded basalt fibers for in‐tube solid‐phase microextraction

Ionic liquids have been widely used in different fields by advantage of their specific properties. In this work, 1‐methyl‐3‐(3‐trimethoxysilyl propyl)imidazolium chloride was prepared and chemically bonded onto basalt fibers for in‐tube solid‐phase microextraction. Through combining in‐tube extraction device with high‐performance liquid chromatography equipped with a diode array detector, an online enrichment and analysis method for eight polycyclic aromatic hydrocarbons was established under the optimum conditions. A good enrichment factor (52–814), good linearity (0.10–15 and 0.20–15 μg/L), low limits of detection (0.03–0.05 μg/L), and low limits of quantitation (0.10–0.20 μg/L) were achieved using a sample volume of 50 mL. Analysis method was applied to the real samples including the groundwater and wastewater from a chemical industry park, some target analytes were detected and the relative recoveries were in the range of 80.4–116.8%.     

Interactions of Ionic Liquids with Polysaccharides 1. Unexpected Acetylation of Cellulose with 1‐Ethyl‐3‐methylimidazolium Acetate

The homogeneous conversion of cellulose in the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate with 2‐furoyl chloride, p‐toluenesulfonyl chloride, and triphenylmethyl chloride yields surprisingly pure cellulose acetate samples in any case. From NMR spectroscopic studies, it may be concluded that during the homogeneous functionalization reactive intermediates including furane‐2‐carboxylic acid/acetic acid anhydride and acetic acid triphenylmethyl ester are formed leading to the cellulose acetates with DS values in the range from 0.55 to 1.86.

     

Basalt fibers grafted with a poly(ionic liquids) coating for in‐tube solid‐phase microextraction

To improve the durability and extraction efficiency of an ionic liquid coating, 1‐dodecyl‐3‐vinylimidazolium bromide was polymerized and grafted onto basalt fibers for in‐tube solid‐phase microextraction. To develop an extraction tube, basalt fibers grafted with the poly(ionic liquids) coating were filled into a polyether ether ketone tube with a 0.75 mm inner diameter. The extraction tube was connected to high‐performance liquid chromatography system equipped with a sampling pump to build an online enrichment and analysis system. Using four common phthalates as model analytes, the extraction tube was investigated by the online analysis system. Good enrichment performance was exhibited by high enrichment factors ranging from 851 to 1858. Under the optimum conditions, an online analysis method was established, and good linearity (0.03–12 and 0.15–12 μg/L) and low limits of detection (0.01–0.05 μg/L) were achieved. This analysis method was applied to real samples including water in a disposable plastic box and the bottled water, some targets were detected but not quantified, and the relative recoveries spiked at 2, 5 and 10 μg/L were in the range of 86.4–119.5%.     

Oxidation of cellulose fibers mediated by nonpersistent nitroxyl radicals

Three different nonpersistent radicals bearing >NO^? moiety have been used to oxidize the viscose fibers at room temperature and alkaline pH. The generation of the free radical species was achieved in situ, from their corresponding ? OH precursors: 1‐hydroxybenzotriazole, violuric acid, and N‐hydroxy‐3,4,5,6‐tetraphenylphthalimide. Three different routes were used: (i) in the presence of metallic cocatalyst (lead tetraacetate), (ii) under metal‐free conditions (anthraquinone as organic cocatalyst), and (iii) a homolytically scission of ? OH bond through a 365‐nm UV irradiation. The oxidized fibers were subjected to attenuated total reflection FTIR characterization, potentiometric titration, wide angle X‐ray, energy dispersive X‐ray analyses, microscopic investigations, and solid‐state ¹³C‐NMR. The patterns of CP/MAS ¹³C‐NMR spectra revealed that the oxidation occurred at the C6 primary hydroxyl groups of cellulose. Notably, as a result of the introduction of hydrophilic carboxylate groups, the water retention values of the oxidized fibers increased by 35% as compared to the original nonoxidized sample. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

以纤维素/AmimCl溶液制备纤维素气凝胶

利用离子液体AmimCl溶解结合超临界CO2干燥的方法制备了纤维素气凝胶材料.研究了不同初始浓度的纤维素溶液及其在不同凝固浴中制备的纤维素凝胶的流变行为,进一步考察了纤维素溶液浓度和凝固浴种类对纤维素气凝胶材料结构的影响.结果表明,随着初始纤维素溶液浓度的增大,气凝胶的孔结构逐渐致密,比表面积随之减小;凝固浴的组成对纤维素气凝胶的结构也有较大影响.采用适当的制备条件,可以制备出高比表面积的纤维素气凝胶材料.对纤维素气凝胶的热性能进行了表征,结果表明所得到的气凝胶材料具有较好的热稳定性和较高的炭残余含量.     

Structures and cyclization behaviors of gel-spun cellulose/polyacrylonitrile composite fibers

Polyacrylonitrile (PAN)/cellulose composite fibers have been produced by dry-jet gel spinning through their co-solution. The rheological properties of PAN/cellulose/dimethylacetamide/LiCl solutions containing different cellulose contents from 0 to 10 wt% were characterized, and 5 wt% PAN/cellulose composite solution shows the best solution homogeneity. During gel spinning, the cellulose forms elongated particles inside the gelation bath, and the particle diameters depend on the as-spun draw ratio. It was found that the glass transition of PAN fibers shifts to higher temperatures along with the increase of cellulose content, and the glass transition activation energy of PAN chains becomes higher when cellulose particles become smaller. Regardless the changes of cellulose amount (2–10 wt%) and particle diameter (7.1–1.4 μm), the cyclization activation energy of PAN/cellulose composite fibers is 13–17% lower than that of neat PAN fibers. Our experiments suggest that the addition of cellulose in PAN fibers has no direct effect on the cyclization reaction of PAN chains. Instead, the released by-products during the pyrolysis of cellulose at high temperature degradation affect the cyclization reaction of PAN chains.     

Metal adsorption of carboxymethyl cellulose/carboxymethyl chitosan blend hydrogels prepared by Gamma irradiation

Blend hydrogels based on the carboxymethyl cellulose (CMC) and carboxymethyl chitosan (CMCts) were prepared by γ-irradiation of a high concentrated CMC/CMCts aqueous solution. Properties of the hydrogels, such as gel fraction, swelling ratio, gel strength, and metal adsorption for Pb and Au were investigated. The gel fraction increased with increasing dose, while the swelling ratio decreased with increasing it. The obtained blend hydrogels had high adsorption performance which was controlled by adjusting the composition of CMC/CMCts.     

Effects of spinning conditions on the mechanical properties of ultrahigh‐molecular‐weight polyethylene fibers

We investigated the tensile strength and modulus of ultrahigh‐strength polyethylene (UHSPE) fibers obtained by using the special two‐step‐drawing process of as‐spun fiber (ASFs) which were prepared by the so‐called gel‐spinning method. We have found that the higher the ASF's spinning speed is, the higher the attainable tensile strength σ_f and modulus E are. For all the fibers drawn from ASFs with various spinning speed except for 120 m/min, we have found a master curve for the inverse of σ_f which is plotted as a function of T^1/4E^?1/2, where T is the linear density of the drawn fibers, in consistent with the Griffith theory: a thicker fiber obtained with a lower spinning speed exhibits lower strength, although all the AFSs possess the same value of E. This also suggests that a thicker fiber contains more defects which would lead to the Griffith‐type crack propagation breakage. Moreover, from morphological observation of ASFs under transmission electron microscopy, the ASF obtained at a relatively low spinning speed possesses a heterogeneous cross‐sectional morphology, whereas that obtained at relatively high spinning speed possesses a relatively homogenous morphology. We propose that this morphological evidence may account for the experimental findings of the behavior of the mechanical properties described above. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2639–2652, 2005     

Enzyme immobilization to ultra‐fine cellulose fibers via amphiphilic polyethylene glycol spacers

Ultra‐high specific surface cellulose fibers with an average diameter of 500 nm were generated from electrospinning and alkaline hydrolysis of cellulose acetate and used as porous supports for enzyme immobilization. The cellulose fiber surfaces were reacted with polyethylene glycol (PEG) diacylchloride to simultaneously add amphiphilic spacers and reactive end groups for coupling with a lipase enzyme. The quantity of reactive carboxylic acid on the fiber surfaces could be readily controlled by COCl/OH molar ratios and PEG lengths. The highest free acid (COOH) content of 1.0 mmol per gram of cellulose was obtained at 10 COCl/OH ratio with the 600‐Da PEG diacylchloride. Enzyme coupling on such PEG‐attached cellulose was optimal in the presence of a water‐soluble carbodiimide [1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC)] at a very low EDC/COOH molar ratio of 0.2 under acidic condition and at ambient temperature. Whereas the free lipase retained only 25% of its original activity, the fiber‐bound lipase possessed much superior retention of catalytic activity after exposure to cyclohexane (81%) and toluene (62%) and hexane (34%). The fiber‐bound lipase also exhibited significantly higher catalytic activity at elevated temperatures than the free form, that is, 10 times at 70 °C. The ultra‐fine, fibrous, and porous structures were retained throughout alkaline hydrolysis, activation, coupling, and activity assays. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4289–4299, 2004     

Electrospinning of ultrafine cellulose acetate fibers: Studies of a new solvent system and deacetylation of ultrafine cellulose acetate fibers

Electrospinning of cellulose acetate (CA) in a new solvent system and the deacetylation of the resulting ultrafine CA fibers were investigated. Ultrafine CA fibers (∼2.3 μm) were successfully prepared via electrospinning of CA in a mixed solvent of acetone/water at water contents of 10–15 wt %, and more ultrafine CA fibers (0.46 μm) were produced under basic pH conditions. Ultrafine cellulose fibers were regenerated from the homogeneous deacetylation of ultrafine CA fibers in KOH/ethanol. It was very rapid and completed within 20 min. The crystal structure, thermal properties, and morphology of ultrafine CA fibers were changed according to the degree of deacetylation, finally to those of pure cellulose, but the nonwoven fibrous mat structure was maintained. The activation energy for the deacetylation of ultrafine CA fibers was 10.3 kcal/mol. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 5–11, 2004     

Surface methacrylation and graft copolymerization of ultrafine cellulose fibers

Ultrafine fibrous (? from 100 to 450 nm) cellulose membranes were generated by electrospinning of cellulose acetate [degree of substitution (DS): 2.45, weight‐average molecular weight: 30,000 Da], followed by alkaline deacetylation. Reaction of these ultrahigh surface‐area cellulose fibers with methacrylate chloride (MACl) produced activated surfaces without altering the fiber morphology. Surface methacrylation of these fibers was confirmed by the acquired hydrophobicity (θ_water = 84°) as compared to the originally hydrophilic (θ_water = 56°) cellulose. Changing the MACl:OH molar ratios could vary the overall DS of methacrylation. The very low overall DS values indicate the surface nature of the methacrylation reaction. At a DS of 0.17, the thermal properties of the surface methacrylated cellulose resemble those of cellulose derivatives at much higher DS values, an unusual behavior of the ultrafine fibers. The methacrylated cellulose could be further copolymerized with vinyl monomers (methyl methacrylate, acrylamide, and N‐isopropylacrylamide) as linear grafts or three‐dimensional (3D) networks. The morphology of cellulose fibers and the interfiber pore structure were not altered at 15–33% graft levels. This study demonstrates that either linear or 3D networks of vinyl polymers could be efficiently supported on ultrafine cellulose fibrous membranes via surface methacrylation. Through these surface reactions the chemical, thermal, and liquid wetting and absorbent properties of these ultrafine fibrous membranes were significantly altered with no change to the fiber dimensions or interfiber pore morphology. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 953–964, 2003     

Structural development of ultra‐high strength polyethylene fibers: Transformation from kebabs to shishs through hot‐drawing process of gel‐spun fibers

Structural development of ultra‐high strength polyethylene fibers via hot‐drawing processes of as‐spun gel fibers was investigated by means of transmission electron microscopy. It is found that the shish‐kebabs developed in both the as‐spun and drawn fibers can be transformed continuously into the micro‐fibril structure composed mostly of the shish structure through the hot‐drawing process. The structure transformation involves a drastic decrease in diameter of the kebab plus the shish but almost no change in the shish diameter. This result suggests that the chains in the kebabs are incorporated into the shishs and consumed to extend the longitudinal dimension of the shishs during the drawing process. The proposed new deformation model well explains the relationship between the fiber morphology and their mechanical properties: the tensile strength and modulus of the fibers can be determined by the number of the shish in the fiber and the macroscopic diameter of the fiber, which are apriori determined at the spinning process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1861–1872, 2010     

Fiber‐forming blend polypropylene‐polyvinyl alcohol

The preparation of a fiber‐forming blend consisting of polypropylene and polyvinyl alcohol mixed with glycerol and with polypropylene grafted with maleic anhydride were studied. The physical and mechanical properties of blend fibers were also studied. The rheological measurements for semiquantitative evaluation of technological compatibility of the components and for processing the polymeric material in extruding and spinning process were carried out. The experimental results revealed the technological compatibility of the polypropylene‐polyvinyl alcohol blend in the presence of glycerol and polypropylene grafted with maleic anhydride. The colloidal structure of interface layer is assumed to be in a three‐ or four‐component system. The mixture of polyvinyl alcohol with glycerol allows for the preparation of well spun fiber‐forming polypropylene blends. Polypropylene‐polyvinyl alcohol blend fibers consisting of up to 20% polyvinyl alcohol with sufficient mechanical properties, higher porosity and significantly higher sorption of water than polypropylene fibers alone were prepared. Copyright © 2001 John Wiley & Sons, Ltd.