Manufacturing of Carbon Fibers/Polyphenylene Sulfide Composites via Induction-Heating Molding: Morphology, Mechanical Properties, and Flammability.

Conventional thermosetting composites exhibit advantageous mechanical properties owing to the use of an autoclave; however, their wide usage is limited by high production costs and long molding times. In contrast, the fabrication of thermoplastic composites involves out-of-autoclave processes that use press equipment. In particular, induction-heating molding facilitates a quicker thermal cycle, reduced processing time, and improved durability of the thermoplastic polymers; thus, the process cost and production time can be reduced. In this study, carbon fiber/polyphenylene sulfide thermoplastic composites were manufactured using induction-heating molding, and the relationships among the process, structure, and mechanical properties were investigated. The composites were characterized using optical and scanning electron microscopy, an ultrasonic C-scan, and X-ray computed tomography. In addition, the composites were subjected to flammability tests. This study provides novel insights into the optimization of thermoplastic composite manufacturing and thermoset composite curing processes.

Polypyrrole Nanotunnels with Luminal and Abluminal Layered Double Hydroxide Nanosheets Grown on a Carbon Cloth for Energy Storage Applications.

The structural design of transition metal-based electrode materials with gigantic energy storage capabilities is a crucial task. In this work, we report an assembly of thin layered double hydroxide (LDH) nanosheets arrayed throughout the luminal and abluminal parts of polypyrrole tunnels fastened onto both sides of a carbon cloth as a battery-type energy storage system. Electron microscopy images reveal that the resulting electrode (NiCo-LDH@H-PPy@CC, where H-PPy@CC represents carbon cloth-supported hollow polypyrrole fibers) is constructed by combining luminal and abluminal NiCo-LDH nanosheets onto a long polypyrrole tunnel on a carbon cloth. The primary sample shows an excellent specific capacity of 149.16 mAh g-1 at 1.0 mA cm-2, a remarkable rate capability of 80.45%, and comprehensive cyclic stability (93.4%). The improved performance is mainly attributed to the strategic organization of the electrode materials with superior Brunauer-Emmett-Teller (BET) surface area and conductivity. Moreover, an asymmetric supercapacitor device assembled with NiCo-LDH@H-PPy@CC and vanadium phosphate-incorporated carbon nanofiber (VPO@CNFs900) electrodes contributes a specific energy density of 32.42 Wh kg-1 at 3 mA cm-2 with a specific power density of 359.16 W kg-1. When the current density is increased by 6-fold, the specific power density reaches 1999.89 W kg-1 at a specific energy density of 20.06 Wh kg-1. This is a simple, cost-effective, and convenient synthetic strategy for the synthesis of porous nanosheet arrays assimilated into hollow fiber architectures, which can illuminate the ideal approach for the fabrication of novel materials with an immense potential for energy storage.

CoMnO2-Decorated Polyimide-Based Carbon Fiber Electrodes for Wire-Type Asymmetric Supercapacitor Applications.

In this work, we report the carbon fiber-based wire-type asymmetric supercapacitors (ASCs). The highly conductive carbon fibers were prepared by the carbonized and graphitized process using the polyimide (PI) as a carbon fiber precursor. To assemble the ASC device, the CoMnO2-coated and Fe2O3-coated carbon fibers were used as the cathode and the anode materials, respectively. Herein, the nanostructured CoMnO2 were directly deposited onto carbon fibers by a chemical oxidation route without high temperature treatment in presence of ammonium persulfate (APS) as an oxidizing agent. FE-SEM analysis confirmed that the CoMnO2-coated carbon fiber electrode exhibited the porous hierarchical interconnected nanosheet structures, depending on the added amount of APS, and Fe2O3-coated carbon fiber electrode showed a uniform distribution of porous Fe2O3 nanorods over the surface of carbon fibers. The electrochemical properties of the CoMnO2-coated carbon fiber with the concentration of 6 mmol APS presented the enhanced electrochemical activity, probably due to its porous morphologies and good conductivity. Further, to reduce the interfacial contact resistance as well as improve the adhesion between transition metal nanostructures and carbon fibers, the carbon fibers were pre-coated with the Ni layer as a seed layer using an electrochemical deposition method. The fabricated ASC device delivered a specific capacitance of 221 F g-1 at 0.7 A g-1 and good rate capability of 34.8% at 4.9 A g-1. Moreover, the wire-type device displayed the superior energy density of 60.2 Wh kg-1 at a power density of 490 W kg-1 and excellent capacitance retention of 95% up to 3000 charge/discharge cycles.

Comparison of denture base resin reinforced with polyaromatic polyamide fibers of different orientations.

The aim of this study was to evaluate the effect of reinforcing polyaromatic polyamide (aramid) fibers with various orientations on the flexural properties of denture base resin. Aramid fibers with four orientations of unidirectional, woven, non-woven and paper-type were pre-impregnated and placed at the bottom of a specimen mold. Heat-polymerized denture base resin was packed over the fibers and polymerized. A three-point bending test was performed using a universal testing machine at a crosshead speed of 5 mm/min. The flexural strengths and flexural moduli of the unidirectional and woven groups were significantly higher than those of the control and other experimental groups.For the flexural moduli, all experimental groups showed significantly higher reinforcing effects than the control group. In conclusion, the unidirectional group located perpendicular to the direction of the load was most effective in reinforcing the denture base resin, followed by the woven group.

Gankyrin is frequently overexpressed in breast cancer and is associated with ErbB2 expression.

Gankyrin is a subunit of the 26S proteasome, and has been known to degrade p53 and retinoblastoma protein and promote the tumorigenicity and metastasis in some malignancies. However, the role of gankyrin in breast cancer has not been explored. In this study, we investigated the expression of gankyrin in breast cancer and evaluated its effect on breast cancer. Representative cancer tissues including normal breasts from 60 patients with breast cancer were stained immunohistochemically for gankyrin, estrogen receptor, progesterone receptor, and ErbB2. We evaluated the relationship between gankyrin expression and clinicopathologic parameters or prognostic markers. We also attempted to clarify the mechanism of gankyrin involved in breast carcinogenesis by using MCF7 breast cancer cells. Gankyrin was weakly expressed in normal breast epithelial cells, however, tumor regions of 37/60 (61.7%) cases showed an overexpression of gankyrin. Gankyrin overexpression was associated with extensive intraductal carcinoma (p=0.014) and ErbB2 positivity (p=0.031) in invasive ductal carcinoma. In MCF7 breast cancer cells, downregulation of gankyrin was associated with a reduction of cell proliferation and tumorigenicity. In conclusion, gankyrin was identified in normal breasts and overexpressed in invasive breast cancers. The overexpression of gankyrin was associated with extensive intraductal carcinoma and ErbB2 expression in breast cancer.

Ruthenium recovery from acetic acid waste water through sorption with bacterial biosorbent fibers.

A fibrous bacterial biosorbent was developed to bind precious metal-organic complexes in batch and column processes. Polyethylenimine (PEI)-modified bacterial biosorbent fiber (PBBF) was prepared by spinning Corynebacterium glutamicum biomass-chitosan blends, coating them with PEI and cross-linking with glutaraldehyde. When an acetic acid waste solution containing 1822.9mg/L Ru was used as a model waste solution, Ru uptake by the PBBF was 16.5 times higher than that of the commercial ion exchange resin, Lewatit MonoPlus M600. The maximum amounts of Ru uptake were 110.5, 16.0 and 6.7mg/g for PBBF, raw biomass, and Lewatit MonoPlus M600, respectively. In a flow-through packed bed, PBBF exhibited the breakthrough time of 42.32h. Therefore, PBBF can be considered as an alternative sorbent for recovery of anionic metal-organic complexes from waste solutions.

Growth and osteogenic differentiation of alveolar human bone marrow-derived mesenchymal stem cells on chitosan/hydroxyapatite composite fabric.

Scaffolds can be used for tissue engineering because they can serve as templates for cell adhesion and proliferation for tissue repair. In this study, chitosan/hydroxyapatite (CS/HAp) composites were prepared by coprecipitation synthesis. Then, CS and CS/HAp fabrics were prepared by wet spinning. CS fibers with a diameter of 15 ± 1.3 µm and CS/HAp fibers with a diameter of 22 ± 1.2 µm were successfully produced; incorporation of HAp into the CS/HAp fibers was confirmed by X-ray diffraction analysis. Biological in vitro evaluations showed that human mesenchymal stem cells (hMSCs) cultured on CS/HAp fabric showed increased proliferation compared to those cultured on pure CS fabric, which was observed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, DNA content assay, and [(3) H] thymidine incorporation assay. Neither the CS nor CS/HAp scaffold exhibited any cytotoxicity to hMSCs, as shown by viability staining and cytotoxicity fluorescence image assays. After 10 days of culturing, the attachment of cells onto the scaffold was observed by scanning electron microscopy. Furthermore, under osteogenic differentiation conditions, alkaline phosphatase (ALP) activity and calcium accumulation was higher in cells cultured on the CS/HAp scaffold than in cells cultured on the CS scaffold. The mRNA expression of osteoblast markers, including ALP, osteocalcin, Co1Ia1, and runt-related transcription factor 2, was higher in cells cultured on CS/HAp than in cells cultured on the CS fabric. The results of this study indicate that the CS/HAp composite fabric may serve as a good scaffold for bone tissue engineering applications.

Recovery of gold as a type of porous fiber by using biosorption followed by incineration.

This study introduces a new process for the recovery of gold in porous fiber form by the incineration of Au-loaded biosorbent fiber from gold-cyanide solutions. For the recovery of gold from such aqueous solutions, polyethylenimine (PEI)-modified bacterial biosorbent fiber (PBBF) and PEI-modified chitosan fiber (PCSF) were developed and used. The maximum uptakes of Au(I) ions were estimated as 421.1 and 251.7 mg/g at pH 5.5 for PBBF and PCSF, respectively. Au-loaded biosorbents were freeze-dried and then incinerated to oxidize their organic constituents while simultaneously obtaining reduced gold. As a result, porous metallic gold fibers were obtained with 60 µm of diameter. Scanning electron microscopic (SEM) analysis and mercury porosimetry revealed the fibers to have 60 µm of diameter and to be highly porous and hollow. The proposed process therefore offers the potential for the efficient recovery of metallic porous gold fibers using combined biosorption and incineration.

Synthesis of chitin cycloalkyl ester derivatives and their physical properties.

A series of acylated chitin derivatives was prepared by reacting chitin in a solution of trifluoroacetic anhydride and each of the cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl carboxylic acids. The degree of O-acyl substitution was in a range of 1.1-1.4 depending upon the nature of the cyclic acid added, as determined by FT-IR analysis. The solubility of the products in the organic solvents of DMF and THF increased with an increase in the cyclic chain length of the carboxylic acid. Thermal gravimetric analysis indicated that the products were stable up to 220 degrees C for chitin cyclopropanoate and cyclobutanoate, and 250 degrees C for chitin cyclopentanoate and cyclohexanoate. The surface morphology of the products by scanning electron microscopic analysis revealed porous and globular surface for chitin cyclobutanoate, cyclopentanoate, and cyclohexanoate, contrast to the dense and smooth organization for the cyclopropanoate.

The effect of type II collagen coating of chitosan fibrous scaffolds on mesenchymal stem cell adhesion and chondrogenesis.

The biocompatibility of chitosan and its similarity to glycosaminoglycans (GAG) make it attractive for cartilage tissue engineering. We have previously reported improved chondrogenesis but limited cell adhesion on chitosan scaffolds. Our objectives were to produce chitosan scaffolds coated with different densities of type II collagen and to evaluate the effect of this coating on mesenchymal stem cell (MSC) adhesion and chondrogenesis. Chitosan fibrous scaffolds were obtained by a wet spinning method and coated with type II collagen at two different densities. A polyglycolic acid mesh served as a reference group. The scaffolds were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and type II collagen content. Constructs were analyzed after MSCs seeding via live/dead assay, weight and DNA evaluations, SEM, and TEM. Constructs were cultured in chondrogenic medium for 21 days prior to quantitative analysis (weight, DNA, and GAG), SEM, TEM, histology, immunohistochemistry, and quantitative real time polymerase chain reaction. The cell attachment and distribution after seeding correlated with the density of type II collagen. The cell number, the matrix production, and the expression of genes specific for chondrogenesis were improved after culture in collagen coated chitosan constructs. These findings encourage the use of type II collagen for coating chitosan scaffolds to improve MSCs adhesion and chondrogenesis, and confirm the importance of biomimetic scaffolds for tissue engineering.

Effect of collagen II coating on mesenchymal stem cell adhesion on chitosan and on reacetylated chitosan fibrous scaffolds.

The biocompatibility and biomimetic properties of chitosan make it attractive for tissue engineering but its use is limited by its cell adhesion properties. Our objectives were to produce and characterize chitosan and reacetylated-chitosan fibrous scaffolds coated with type II collagen and to evaluate the effect of these chemical modifications on mesenchymal stem cell (MSC) adhesion. Chitosan and reacetylated-chitosan scaffolds obtained by a wet spinning method were coated with type II collagen. Scaffolds were characterized prior to seeding with MSCs. The constructs were analyzed for cell binding kinetics, numbers, distribution and viability. Cell attachment and distribution were improved on chitosan coated with type II collagen. MSCs adhered less to reacetylated-chitosan and collagen coating did not improve MSCs attachment on those scaffolds. These findings are promising and encourage the evaluation of the differentiation of MSCs in collagen-coated chitosan scaffolds. However, the decreased cell adhesion on reacetylated chitosan scaffold seems difficult to overcome and will limit its use for tissue engineering.

Effect of chitosan scaffold microstructure on mesenchymal stem cell chondrogenesis.

Although numerous biomaterials have been investigated as scaffolds for cartilage tissue engineering, the effect of their microstructure on final construct characteristics remains unclear. The biocompatibility of chitosan and its similarity with glycosaminoglycans make it attractive as a scaffold for cartilage engineering. Our objective was to evaluate the effect of chitosan scaffold structure on mesenchymal stem cell proliferation and chondrogenesis. Chitosan fibrous scaffolds and chitosan sponges were seeded with mesenchymal stem cells in a chondrogenic medium. Constructs were analyzed 72 h after seeding via scanning electron microscopy (SEM), weight measurements and DNA quantification. Constructs were cultured for 10 or 21 days prior to confocal microscopy, SEM, histology, quantitative analysis (weight, DNA and glycosaminoglycan (GAG)), and quantitative real-time polymerase chain reaction. Mesenchymal stem cells maintained a viability above 90% on all chitosan scaffolds. The cell numbers in the constructs were similar at 72 h, 10 days and 21 days. However, matrix production was improved in chitosan fibrous constructs based on the GAG quantification and collagen II mRNA expression. Chondrogenesis on chitosan scaffolds is superior on microfibers compared to macroporous sponges.

Crystalline structure analysis of cellulose treated with sodium hydroxide and carbon dioxide by means of X-ray diffraction and FTIR spectroscopy.

Crystalline structures of cellulose (named as Cell 1), NaOH-treated cellulose (Cell 2), and subsequent CO2-treated cellulose (Cell 2-C) were analyzed by wide-angle X-ray diffraction and FTIR spectroscopy. Transformation from cellulose I to cellulose II was observed by X-ray diffraction for Cell 2 treated with 15-20 wt% NaOH. Subsequent treatment with CO2 also transformed the Cell 2-C treated with 5-10 wt% NaOH. Many of the FTIR bands including 2901, 1431, 1282, 1236, 1202, 1165, 1032, and 897 cm(-1) were shifted to higher wave number (by 2-13 cm(-1)). However, the bands at 3352, 1373, and 983 cm(-1) were shifted to lower wave number (by 3-95 cm(-1)). In contrast to the bands at 1337, 1114, and 1058 cm(-1), the absorbances measured at 1263, 993, 897, and 668 cm(-1) were increased. The FTIR spectra of hydrogen-bonded OH stretching vibrations at around 3352 cm(-1) were resolved into three bands for cellulose I and four bands for cellulose II, assuming that all the vibration modes follow Gaussian distribution. The bands of 1 (3518 cm(-1)), 2 (3349 cm(-1)), and 3 (3195 cm(-1)) were related to the sum of valence vibration of an H-bonded OH group and an intramolecular hydrogen bond of 2-OH ...O-6, intramolecular hydrogen bond of 3-OH...O-5 and the intermolecular hydrogen bond of 6-O...HO-3', respectively. Compared with the bands of cellulose I, a new band of 4 (3115 cm(-1)) related to intermolecular hydrogen bond of 2-OH...O-2' and/or intermolecular hydrogen bond of 6-OH...O-2' in cellulose II appeared. The crystallinity index (CI) was obtained by X-ray diffraction [CI(XD)] and FTIR spectroscopy [CI(IR)]. Including absorbance ratios such as A1431,1419/A897,894 and A1263/A1202,1200, the CI(IR) was evaluated by the absorbance ratios using all the characteristic absorbances of cellulose. The CI(XD) was calculated by the method of Jayme and Knolle. In addition, X-ray diffraction curves, with and without amorphous halo correction, were resolved into portions of cellulose I and cellulose II lattice. From the ratio of the peak area, that is, peak area of cellulose I (or cellulose II)/total peak area, CI(XD) were divided into CI(XD-CI) for cellulose I and CI(XD-CII) for cellulose II. The correlation between CI(XD-CI) (or CI(XD-CII)) and CI(IR) was evaluated, and the bands at 2901 (2802), 1373 (1376), 897 (894), 1263, 668 cm(-1) were good for the internal standard (or denominator) of CI(IR), which increased the correlation coefficient. Both fraction of the absorbances showing peak shift were assigned as the alternate components of CI(IR). The crystallite size was decreased to constant value for Cell 2 treated at >or= 15 wt% NaOH. The crystallite size of Cell 2-C (cellulose II) was smaller than that of Cell 2 (cellulose I) treated at 5-10 wt% NaOH. But the crystallite size of Cell 2-C (cellulose II) was larger than that of Cell 2 (cellulose II) treated at 15-20 wt% NaOH.