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Polyacrylonitrile (PAN) fiber modification can promote the stabilization efficiency and mechanical properties of the subsequent carbon fibers; however, it could cause damage to the fibers to some extent. In this article, the effects of NaIO4 treatment on the chemical and physical properties of PAN fibers were investigated. After NaIO4 modification, the cyclization reaction has partially occurred, owing to the FTIR revealed that the C≡N peak was weakened, but the C=N stretching vibration peak, the –N = C=O stretching vibration peak, the C=O stretching vibration absorption peak, and the short sequence conjugate C=N characteristic peak were enhanced simultaneously, indicating a successful cyclization and dehydrogenation reaction. Moreover, owing to more oxygen-containing functional groups successfully attached to the PAN fibers and the cyclization reaction taking place, the initial temperature, peak temperature, and heat release of cyclization decreased, which means a more efficient and safer stabilization process. X-ray diffraction (XRD) showed that the (100) crystal plane microcrystal size was the smallest at 40 °C of the modification temperature, whereas the (002) crystal plane microcrystal size was the largest at 60 °C. The modified stabilized PAN fibers presented lower crystallinity and a more aromatic structure compared with untreated fibers. Raman spectra revealed a significant increase in the intensity of the G peak after NaIO4 modification; the R-value decreased from 1.65 to 1.43, demonstrating a transformation of the sp3 hybrid carbon structure into a more graphite-like sp2 hybrid C=C structure. Meanwhile, scanning electron microscopy (SEM) images disclosed additional grooves and cracks on the fiber surface after modification. [ABSTRACT FROM AUTHOR]

This study aims to develop highly hygroscopic bio-based co-polyamides (CPs) by melt co-polycondensation of polyamide (PA) 56 salt and PA66 salt with varying molar fractions. The functional groups and the chemical structure of the prepared samples were determined by Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The relative viscosity was determined with an Ubbelohde viscometer. The melting behavior and the thermal stability of CPs were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Furthermore, the water absorption behavior of CP hot-pressed film was studied. The results reveal that the melting point, the crystallization temperature and the crystallinity of CPs firstly decrease and then increase with the molar fraction of PA66 in CPs. The copolymerization of PA56 with PA66 leads to an obvious increase in water absorption. The CPs with PA66 molar fraction of 50% possess a high saturated water absorption rate of 17.6%, compared to 11.6% for pure PA56 and 7. 8% for pure PA66. [ABSTRACT FROM AUTHOR]

The effects of KBrO3 modification on polyacrylonitrile (PAN) precursor fibers at different modification temperatures were studied. The mechanical properties, chemical structure, aggregation structure, morphological structure, and thermal behavior of PAN precursor fibers were analyzed. The mechanical properties of PAN precursor fibers are essentially unaltered after KBrO3 modification, although oxygen-containing functional groups are introduced. KBrO3 can ionize bromate ion in aqueous solution, which has good nucleophilicity and can attack the positively charged carbon atom in C≡N, so that the cyclization proceeds according to the ionic mechanism, allowing the transformation of C≡N to C = N in the PAN precursor fibers generated a cyclic trapezoidal structure containing primary aromatic amine, which reduced the peak temperature of the cyclization reaction from 284.5 °C to 275.1 °C and decreased the heat release. The sp3-hybridized carbon structure changes into a sp2 hybridized C = C structure with increasing aromatization, according to XRD and Raman data, and the KBrO3 alteration accelerates the degradation of the original microcrystalline structure and transforms into a new polycyclic aromatic structure. The degree of conjugation and aromatization of the system rapidly increased with the rise in modification temperature. The stabilized fibers were discovered to have the lowest R-value, the highest aromatization, the smoothest surface, and the fewest flaws at impregnation temperature of 60 °C. [ABSTRACT FROM AUTHOR]

In recent years, natural polymer‐based electrospun fibers (EFs) with huge specific surface area, good biocompatibility, and biological activity obtained from electrospinning process exhibit tremendous vitality in the field of biomedical areas. Herein, the parameters of electrospinning from two perspectives, polymer solution such as solvent, polymeric relative molecular mass, concentration, viscosity, and conductivity of the solution, and electrospinning process such as spinning voltage, spinning flow rate, needle tip to collector distance, temperature, and humidity are first detailed. Next, the raw materials consisting of polysaccharides such as cellulose, hyaluronic acid, alginate, and chitosan as well as proteins such as collagen, gelatin, silk fibroin, and keratin are summarized. The preparation method and related characteristics of EFs with multistage structures such as porous, core–shell, Janus, bamboo‐like and other structures are introduced. The biomedical applications of these natural polymer‐based EFs mainly including tissue engineering, drug sustained release, wound dressings, and biomedical sensors are systematically recapitulated. Finally, the outlook on natural EFs is further proposed. [ABSTRACT FROM AUTHOR]

As a recently developed biobased polyamide, polyamide 56 (PA56) has great potential in the field of fibers and textiles due to its high strength, high moisture absorption, and easy dyeing. However, the application of PA56 is restricted due to its flammability. Flame‐retardant PA56 copolymers (FRPA56s) have been designed and successfully synthesized by the introduction of 2‐carboxyethyl(phenyl)phosphinic acid (CEPPA) monomer. The thermal properties and thermal stability of FRPA56s have been evaluated using DSC and TGA, respectively. The flammability behavior of the resultant copolymer has been investigated using UL94 vertical burning and cone calorimetry tests. The crystallization temperature (Tc), melting temperature (Tm), and crystallinity (Xc) of FRPA56s are reduced and the degradation pathway for PA56 is changed with the introduction of CEPPA. In addition, FRPA56 containing 7.8 mol% CEPPA may be characterized by a V‐0 rating in the UL94 vertical burning test and its total heat release is reduced 20% than that of PA56, reflecting the high flame‐retardant efficiency of CEPPA. Based on the analysis of the residual char and the gas‐phase pyrolysis products for combustion of FRPA56s, it is concluded that the flame‐retardant modes of action for this material mainly include flame inhibition, dilution effect and charring. [ABSTRACT FROM AUTHOR]

One-hundred percent stereo-complexation in poly( l-lactide) (PLLA)/poly( d-lactide) (PDLA) fibers with non-equivalent molecular weights could be achieved via thermal treatment. Stereo-complexed polylactide (sc-PLA) fibers exhibited excellent hydrolysis resistance and thermal resistance. Till now, preparation of sc-PLA fibers with satisfactory qualities required both PLLA and PDLA with equivalently high molecular weights. Moreover, the high-molecular-weight PDLAs are expensive, restricting industrial-scale production and applications of sc-PLA products. In this study, equal-weight mixtures of low-molecular-weight PDLA (L-PDLA) and high-molecular-weight PLLA (H-PLLA) were melt spun into sc-PLA fibers and then completely stereo-complexed via thermal treatment. The hydrolysis resistance of L3/D1 fibers [PLLA ( M = 3.0 × 10)/PDLA ( M = 1.0 × 10)] was similar to that of L3/D3 fibers [PLLA ( M = 3.0 × 10)/PDLA ( M = 3.2 × 10)], but much higher than that of L3 fibers [PLLA ( M = 3.0 × 10)]. Melting temperature and softening temperature of L3/D1 fibers (223 and 126 °C) were also similar to those of L3/D3 fibers (224 and 131 °C), but higher than that of L3 fibers (172 and 72 °C). Utilizing H-PLLA and L-PDLA to prepare sc-PLA fibers with excellent performance is conducive to the wide industrial application of sc-PLA. [ABSTRACT FROM AUTHOR]

ABSTRACT Cotton stalk bark fibers (CSBF) were prepared using combined steam explosion and laccase treatment (explosion-laccase). CSBF have been applied to reinforce thermoplastic composites, but were difficult to be spun into yarns due to their inferior fineness and high stiffness. In order to improve the fineness and flexibility with a green method, explosion-laccase treatment was used to separate bark of cotton stalks. The results indicated that steam explosion at 1.7 MPa for 3 min effectively facilitated laccase penetration into the lignocellulose complex to enhance delignification without negative effects on activity of laccase. Compared with CSBF after explosion, CSBF after explosion-laccase had better fineness (31 dtex), higher aspect ratio (1110), higher tensile strength (2.81 cN/dtex), higher flexibility (321 twist/(m·dtex)), and better thermal stability, which meets the requirement of textile fibers. CSBF had higher water retention (127%) and moisture regain (10.3%) than cotton. Explosion-laccase is an effective and eco-friendly method of preparing CSBF for textiles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45058. [ABSTRACT FROM AUTHOR]

In this study, composite membranes were prepared from mixed solution of polyvinylidene fluoride (PVDF) and cellulose via the non-solvent-induced phase separation (NIPS) method. N, N-dimethylacetamide (DMAc) and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) were used as the solvent for PVDF and cellulose, respectively. SEM and in situ scanning techniques were used to investigate the morphology of the prepared membranes. The results showed that viscose cellulose/[Bmim]Cl solution acted as a porogenic agent during the membrane preparation process. Hydrophilicity of the composites was evaluated by water contact angle, moisture regain and equilibrium water uptake, which demonstrated that the wettability of the membranes was associated with the hydrophilic group and the roughness of the surface. Most importantly, the α → β transformation in PVDF matrix was demonstrated from the results of WAXD, FT-IR and DSC. The quantitative analysis indicated that the β-phase content in PVDF reached 90.1% when cellulose content was 5%, which is higher than many published references and was ascribed to the cooperation of cellulose and ionic liquid. Besides, the crystallinity, thermal stability and mechanical properties of the composite membranes were studied as well. [ABSTRACT FROM AUTHOR]

Chicken feather, a potential source of keratin, is often disposed as waste material. Although some methods, i.e., hydrolysis, reduction, and oxidation, have been developed to isolate keratin for composites, it has been limited due to the rising environmental concerns. In this work, a green solvent N-methylmorpholine N-oxide (NMMO) was used to extract keratin from chicken feather waste. Eighty-nine percent of keratin was extracted using 75% NMMO solution. However, the result from size exclusion HPLC showed that most of the keratin degraded into polypeptide with molecular weight of 2189 and only 25.3% regenerated keratin was obtained with molecular weight of 14,485. Analysis of amino acid composition showed a severe damage to the disulfide bonds in keratin during the extraction procedure. Oxidization had an important effect on the reconstitution of the disulfide bonds, which formed a stable three-dimensional net structure in the regenerated keratins. Besides, Raman spectra, NMR, FT-IR, XRD, and TGA were used to characterize the properties of regenerated keratin and raw chicken feather. In the end, a possible mechanism was proposed based on the results. [ABSTRACT FROM AUTHOR]

ABSTRACT Keratin particles with microscale are prepared by ball mill and its influences on the chitosan membrane is evaluated. Composite membranes with various content of keratin are fabricated, and their physical and chemical properties such as morphology, wettability, crystallization, thermal stability, tensile strength, and break elongation are investigated. Optical microscope and situ topographic scan mode of nano-test system are used to examine the dispersion and aggregation of keratin on the surface of chitosan membrane. The result of contact angle (CA) and mechanical testing show that the incorporation of keratin particles decrease the CA from 98.1° to 58.2°. Tensile strength and break elongation of the composite membrane reaches a maximum of 65 ± 8 MPa and 15% when the keratin content is 6%, an increase of 80% and 88% compared with the pristine chitosan membrane. Both the increase in tensile strength and break elongation is result of the incorporation of keratin particles known for their excellent compatibility between keratin and chitosan matrix. These kind of composite material combines the antibacterial properties of chitosan with cell culture preference of keratin which may have potential biomedical application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44667. [ABSTRACT FROM AUTHOR]

ABSTRACT In the present study, regenerated cellulose membrane with 'imprinted morphology' and low crystallinity was fabricated from the crystal cellulose/[Bmim]Cl solution. Spherulites of 1-butyl-3-methilimidazolium chloride ([Bmim]Cl) and cellulose/[Bmim]Cl solution were observed using polarized optical microscopy under certain condition. The fabricated cellulose membranes presented some particular characteristics compared with the membrane prepared from traditional cellulose/[Bmim]Cl solution. All the fabricated membranes were characterized by optical microscope, Wide-angle X-ray diffraction (WAXD), thermo-gravimetric analysis, and mechanical testing. The images showed that the resulting membranes prepared from crystal cellulose/[Bmim]Cl solution were 'imprinted' with patterns which originated from the crystalline structure of [Bmim]Cl. The results of WAXD showed that the obtained cellulose membrane exhibited low diffraction peaks and crystallinity of approximately 24.57%. Furthermore, the low crystallinity led to the low mechanical property (27.5 MPa), thermal stability (315.4 °C), and high moisture regain (9.5%). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43798. [ABSTRACT FROM AUTHOR]

In this research, keratin was extracted from the disposable chicken feather using l -cysteine as reducing agent. Then, it was re-dissolved in the sodium carbonate-sodium bicarbonate buffer, and the pure keratin membrane and fiber were fabricated by doctor-blade casting process and wet spinning method, respectively. Scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to characterize the chemical and physical properties of resulting powder, membrane and fiber. Compared with the raw chicken feather, the regenerated keratin materials retain its chemical structure and thermal stability, their relative crystallinity is a little different depend on the shaping method, which leads to the difference in moisture regain. The mechanical results show that tensile strength of the keratin membrane researches 3.5 MPa, have potential application in biomedical fields. However, the keratin fiber presents low tenacity, i.e. 0.5cN/dtex, this problem should be solved in order to apply the new fiber in textile and material science. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, rod-like chitin whisker was used as a filler to reinforce the chitosan membrane, and a series of composite membranes were prepared by casting–evaporation method. Mechanical testing shows that tensile strength of the resulting composite membrane with 3wt% chitin whisker content reaches up to 110.3MPa, which is about 2.8times than that of neat chitosan membrane (38.5MPa), and moisture regain of all composite membranes presents a decreasing tendency with increasing content of chitin whisker. Furthermore, SEM was used to investigate the morphology difference between neat chitosan membrane and composite membranes, to understand the reinforce mechanism of chitin whisker. Wide angle x-ray diffraction and Fourier transform infrared spectroscopy were used to visualize the structure change before and after the compositing processes. Besides, the bacterostatic test shows that this composite membrane presents effective inhibitory effect on Staphylococcus aureus, Escherchia coli and Corinebaterium michiganence respectively, which indicates it a promising material for packaging and wound dressing. [Copyright &y& Elsevier]

Strippable film is effective for removing radioactive contamination. However, it still has some limitations, such as the long curing time (about 30 min~24 h) and the requirement of organic solvents. To address these issues, we report a simple protocol to prepare strippable decontamination films using liquid polybutadiene (LPB) and tert-butyl acrylate (TBA) as the raw materials without solvent and using camphorquinone/ethyl 4-dimethylaminobenzoate (CQ/EDB) as a photoinitiator, where the film was formed under household LED panel light or daylight irradiation for about 540 s. After a thorough study of viscosity, real-time Fourier transform infrared (RT-FTIR spectra), gel and volatile organic compound (VOC) contents, mechanical properties and decontamination efficiency, the optimum composition and curing conditions were determined for the decontamination strippable film. VOC content is as low as 12.7 ± 0.7% and the resultant strippable film exhibits good mechanical performances with a tensile strength of up to 5.4 ± 0.4 MPa and elongation of up to 66.6 ± 13%. Most important, the decontamination efficiencies of this strippable film for 133CsCl on glass, ceramic and metal surfaces reach up to 98.1%, 94.3% and 97.6%, respectively. [ABSTRACT FROM AUTHOR]

Inthis paper, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) was synthesizedand used as solvent to dissolve bamboo pulp. Dimethylsulfoxide (DMSO)was selected as cosolvent to adjust the solution viscosity. As comparedwith the bamboo pulp/[Bmim]Cl system, the addition of DMSO decreasesthe solution viscosity dramatically. Afterward, cellulose hollow fibermembranes were prepared by dry-wet spinning process using 75 wt %[Bmim]Cl + 25 wt % DMSO as solvent. Scanning electron microscope (SEM),mechanical testing, pure water permeability, and retention rate wereused to characterize its properties, respectively. The SEM resultshows that the prepared cellulose hollow fiber membrane presents densesurface structure, which leads to a relative high tensile strengthand retention rate to bovine serum albumin, i.e. 28 MPa and 98%, respectively,but a relative low pure water permeability, i.e. 83 L/m2·h. In the end, the [Bmim]Cl is recovered by azeotropy, andthe recycling yield reaches 99 wt %. [ABSTRACT FROM AUTHOR]

The aim of this paper is the preparation and characterization of cellulosechitin blend filaments over the experimental blend ratio scope i.e., 2.89 and 6.46 ww 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 crosssection 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 Xray, 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 cellulosechitin 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 michiganenceaccording to different testing standards. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article discusses a study on the preparation and characterization of cellulose/chitin blend filaments obtained from cellulose/chitin xanthalate blend solution over an experimental blend ratio. The study showed that chitin xanthalate addition into cellulose xanthalate resulted in an increase of intermittence rate. It also concluded that the degree of crystallinity, density and accessibility of blend filaments decreases with increasing chitin content.

The article examines the rheological properties of cellulose and chitin xanthate and their blend solutions and the properties of the prepared fibers to provide data for further fiber spinning. The researchers measured the viscosity, fluidity, filtering and mechanical properties of the solutions. Results showed the dependence of rheological properties on the solutions' composition and temperature. It showed the relationship between temperature and viscosity in the activation energy of flow.