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In the present study, how side-feeding of NiCF during twin-screw extrusion processing influences the fiber aspect ratio and thermal, mechanical, electrical, and electromagnetic properties of nickel-coated carbon fiber (NiCF)-reinforced polyamide 6 (PA6) composites was explored. For this, the fiber length distribution, thermal stability, heat deflection temperature, dynamic mechanical property, tensile, flexural, electrical resistivity, and electromagnetic interference shielding effectiveness (EMI SE) properties of NiCF/PA6 composites were extensively investigated. Chopped NiCF was regularly fed via either a main feeder or a side feeder and NiCF/PA6 pellets with different fiber-feeding pathways were prepared. The side-feeding effect of NiCF on the fiber length distribution and the composite properties was studied. The thermal stability, heat deflection temperature, storage modulus, tensile, flexural, and surface resistivity, and EMI SE properties of the NiCF/PA6 composites strongly depended not only on the NiCF content but also on the feeding method (main-feeding or side-feeding) upon extrusion processing, indicating that the fiber length distribution relevant to the fiber aspect ratio was critically important to enhance the composites’ properties. As a result, the NiCF/PA6 composites produced via side-feeding of NiCF exhibited an NiCF distribution longer than that produced via main-feeding, leading to enhancement of the thermal stability, heat deflection temperature, storage modulus, tensile, flexural, and EMI SE properties, strongly depending on the NiCF content.

Dual-sizing effects with either epoxy or polyurethane (PU) on the thermal, mechanical, and impact properties of carbon fiber/acrylonitrile-butadiene-styrene (ABS) composites produced by extrusion and injection molding processes were investigated. The heat deflection temperature, dynamic mechanical, tensile, flexural, and impact properties of the composites reinforced with either (epoxy + epoxy) or (epoxy + PU) dual-sized carbon fiber were higher than those commercially single-sized with epoxy. The result indicated that the dual-sized carbon fiber significantly contributed not only to improving the heat deflection temperature and the storage modulus, but also to improving the tensile, flexural, and impact properties of carbon fiber/ABS composites. The highest improvement of the composite properties was obtained from the composite with (epoxy + PU) dual-sized carbon fiber. The improvement of the mechanical and impact properties was explained by the enhanced interfacial bonding between carbon fiber and ABS matrix and by the length distribution analysis of carbon fibers present in the resulting composites. The fiber–matrix interfacial behavior was qualitatively well-supported in terms of fiber pull-out, fiber breaking pattern, and debonding gaps between the fiber and the matrix, as observed from the fracture surface topography. This study revealed that the properties of carbon fiber/ABS composites prepared by extrusion and injection molding processes were improved by dual-sizing carbon fiber, which was performed after a commercial epoxy sizing process, and further improved by using PU as an additional sizing material.

Waste Expanded polypropylene (EPP) was utilized as recycled matrix for kenaf fiber-reinforced polypropylene (PP) composites produced using chopped kenaf fibers and crushed EPP waste. The flexural properties, impact strength, and heat deflection temperature (HDT) of kenaf fiber/PP composites were highly enhanced by using waste EPP, compared to those by using virgin PP. The flexural modulus and strength of the composites with waste EPP were 98% and 55% higher than those with virgin PP at the same kenaf contents, respectively. The Izod impact strength and HDT were 31% and 12% higher with waste EPP than with virgin PP, respectively. The present study indicates that waste EPP would be feasible as recycled matrix for replacing conventional PP matrix in natural fiber composites.

In the present study, the activated carbon composites containing silver (Ag) nanoparticles (Acc-Ag composites) for the production of highly functional wound-dressing additives were fabricated using a thermal treatment under an inert argon (Ar) atmosphere. During the thermal treatment, Ag+ was successfully changed to metallic Ag nanoparticles, and NO3− with a potential cytotoxicity was simultaneously eliminated. The reduction of the Ag+ was confirmed using the XRD and XPS analyses. The optimal manufacturing condition of the Acc-Ag composites was examined with various Acc/Ag ratios, and the Acc-Ag composites still maintained superior pore properties. The deodorizing activity of the Acc-Ag composites was evaluated with the use of the NH3 gas as the deodorization test gas; compared with the pure Acc, the Acc-Ag composites showed an excellent deodorant effect. Furthermore, the antibacterial activity of the Acc-Ag composites was tested against three types of bacterial strain, and the results indicated that the Acc-Ag composites showed an enhanced antibacterial activity. Therefore, the Acc-Ag composites with excellent antimicrobial and deodorant properties have great potential for the functional wound dressings.

In efforts to characterize and understand the properties and processing of phenylethynyl-terminated imide (LaRC PETI-5, simply referred to as PETI-5) oligomers and polymers as a high-temperature sizing material for carbon fiber-reinforced polymer matrix composites, PETI-5 imidization and thermal curing behaviors have been extensively investigated based on the phenylethynyl end-group reaction. These studies are reviewed here. In addition, the use of PETI-5 to enhance interfacial adhesion between carbon fibers and a bismaleimide (BMI) matrix, as well as the dynamic mechanical properties of carbon/BMI composites, are discussed. Reports on the thermal expansion behavior of intercalated graphite flake, and the effects of exfoliated graphite nanoplatelets (xGnP) on the properties of PETI-5 matrix composites are also reviewed. The dynamic mechanical and thermal properties and the electrical resistivity of xGnP/PETI-5 composites are characterized. The effect of liquid rubber amine-terminated poly(butadiene-co-acrylonitrile) (ATBN)-coated xGnP particles incorporated into epoxy resin on the toughness of xGnP/epoxy composites is examined in terms of its impact on Izod strength. This paper provides an extensive overview from fundamental studies on PETI-5 and xGnP, as well as applied studies on relevant composite materials.

Extrusion processing and properties of fiber-reinforced polymer matrix composites may be influenced by the fiber feeding route upon extrusion. The purpose of the present study was to investigate the effect of fiber feeding route on the fiber length distribution, electromagnetic interference shielding effectiveness (EMI SE), tensile, and flexural properties and heat deflection temperature of resulting composites with different fiber contents. H–NiCF/polypropylene and S–NiCF/polypropylene pellets were produced through two different feeding routes of nickel-coated carbon fiber (NiCF), hopper feeding (H) and side feeding (S) upon extrusion process, respectively. NiCF-reinforced polypropylene (PP) composites were fabricated by means of compression molding using each pellet, respectively. The effect of fiber feeding route on the electromagnetic, mechanical, and thermal properties of the composites with various NiCF contents was studied. S–NiCF/PP composites exhibited the EMI SE, tensile, and flexural properties and heat deflection temperature higher than H–NiCF/PP composites. The improved properties of S–NiCF/PP composites were ascribed to higher aspect ratio and longer fiber distribution of NiCF remaining in the composite than H–NiCF/PP counterparts, due to less shearing and fiber damages during extrusion.

In the present study, exfoliated graphite nanoplatelets (xGnP) with different particle sizes were coated onto polyacrylonitrile-based carbon fibers by a direct coating method. The flex-ural properties, interlaminar shear strength, and the morphology of the xGnP-coated carbon fiber/phenolic matrix composites were investigated in terms of their longitudinal flexural strength and modulus, interlaminar shear strength, and by optical and scanning electron mi-croscopic observations. The results were compared with a phenolic matrix composite coun-terpart prepared without xGnP. The flexural properties and interlaminar shear strength of the xGnP-coated carbon fiber/phenolic matrix composites were found to be higher than those of the uncoated composite. The flexural and interlaminar shear strengths were affected by the particle size of the xGnP, while the particle size had no significant effect on the flexural modulus. It seems that the interfacial contacts between the xGnP-coated carbon fibers and the phenolic matrix play a role in enhancing the flexural strength as well as the interlaminar shear strength of the composites.

In the present work, a multi-functional monomer triallyl isocyanurate (TAIC) of 4 wt.% is incorporated into neat poly(butylene succinate) (PBS) by twin screw extrusion technique and the PBS sheets are irradiated at various electron beam absorption doses. It has been found that electron beam irradiation at an appropriate absorption dose plays an effective role in crosslinking the PBS molecules in the presence of TAIC. As a result, the irradiation influences the gel fraction, glass transition temperature, thermal stability, thermo-dimensional stability, dynamic storage modulus, and tensile properties of PBS, depending on the electron beam absorption dose applied. The improvement of the thermal and mechanical properties of PBS is most significant in the range of 50 to 70 kGy. The results are consistent with each other, supporting the electron beam irradiation effect on the property improvement of PBS. Keywords: Poly(butylene succinate), Multi-functional monomer, Extrusion, Electron beam irradiation, Crosslinking, Properties

To improve photocatalytic efficiency, graphene/Ag/TiO₂ nanotube catalyst was synthesized, and its surface characteristics and photocatalytic activity investigated. For deposition of Ag nanoparticles on the TiO₂ nanotubes, a polymer compound containing CH₃COOAg/poly(Llactide) was utilized, and the silver particles were precipitated by reducing the silver ions during the annealing process. Graphene deposition on the Ag/TiO₂ nanotubes was achieved using an electrophoretic deposition process. Based on the dye degradation results, it was determined that the photocatalytic efficiency was significantly affected by deposition of silver particles and graphene on the TiO₂ catalyst. Highly efficient destruction of the dye was obtained with the new graphene/Ag/TiO₂ nanotube photocatalyst. This may be attributed to a synergistic effect of the graphene and Ag nanoparticles on the TiO₂ nanotubes.

Surface modified carbon felts were utilized as an electrode for the removal of inorganic ions from seawater. The surfaces of the carbon felts were chemically modified by alkaline and acidic solutions, respectively. The potassium hydroxide (KOH) modified carbon felt exhibited high Brunauer-Emmett-Teller (BET) surface areas and large pore volume, and oxygencontaining functional groups were increased during KOH chemical modification. However, the BET surface area significantly decreased by nitric acid (HNO3) chemical modification due to severe chemical dissolution of the pore structure. The capability of electrosorption by an electrical double-layer and the efficiency of capacitive deionization (CDI) thus showed the greatest enhancement by chemical KOH modification due to the appropriate increase of carboxyl and hydroxyl functional groups and the enlargement of the specific surface area.

Background In this study, silk fibroin (SF) composite hydrogels containing hydroxyapatite (HAP) nanoparticles (NPs) for bone tissue engineering were fabricated using gamma-ray (γ-ray) irradiation treatment. During the irradiation, the HAP dispersed SF solution was changed to the chemically crosslinked SF hydrogel. Methods Distribution of HAP NPs in the SF hydrogel was examined by SEM imagery and energy dispersive X-ray spectrophotometry, and the crystalline structure of SF composite hydrogels was also confirmed by X-ray diffractometry. An optimum preparation condition of the SF/HAP composite hydrogels was determined with various HAP contents. For evaluation of the osteogenic differentiation of human mesenchymal stem cells (hMSCs), alkaline phosphatase activity (ALP), HAP nucleation in SBF and in vitro calcium accumulation were measured. Results The results revealed that compared with the pure SF hydrogels, the SF/HAP composite hydrogels improved osteogenic differentiation. Conclusion This paper demonstrates the great potential of the SF/HAP composite hydrogels in terms of the production of the bone tissue engineering scaffolds for which osteogenesis is required.

In this study, various surfactants were added to control the gelation time of silk fibroin (SF) aqueous solution. The gelation behaviors of SF aqueous solution in the presence of surfactant were investigated with attenuated total reflectance infrared, SEM, and a viscometer. When surfactants other than chitooligosaccharide were added into an SF aqueous solution, the gelation time of the solution was decreased under the fixed conditions. Particularly, anionic surfactant was found to be more effective than non-ionic and cationic surfactants in accelerating the gelation of SF. In addition, the conformational changes of SF hydrogel with or without surfactant were investigated in a time-resolved manner using infrared spectroscopy. Conformational transitions of SF nanofibers from random coil to β-sheet forms were strongly dependent on the inherent properties of surfactant, and on the different interactions between surfactant and SF molecules in aqueous solution. This approach to controlling the gelation of SF aqueous solution by the surfactant, and to monitoring their conformational changes on a real-time scale, may be critical in the design and tailoring of SF hydrogels useful for biomedical applications.

Kenaf fiber and corn husk flour were used as reinforcement in a novel biodegradable hybrid bio-composite system. It was investigated how the aspect ratios of kenaf fibers measured before and after passing through extrusion process influence the mechanical properties and the improvement of predicted values obtained by the Halpin–Tsai equation. It was found that considering of the aspect ratio of reinforcement obtained after the extrusion process, the difference between theoretical and experimental values of the tensile modulus was not significant, indicating that the aspect ratio determined after extrusion did not influence the predicted values. Therefore it was pointed out that the initial values of aspect ratio determined before extrusion can be used directly. It was also found that a scale ratio between reinforcements of different aspect ratios may play a role as a controlling factor in optimizing the mechanical properties of a hybrid bio-composite.

In the present study, stabilized rayon fabrics were prepared from fast isothermal stabilization processes, which were carried out within four minutes at . The effects of ultrasonic cleaning and chemical pre-treatment on the chemical composition, physical characteristics, X-ray diffraction pattern, thermal stability and shape of the stabilized rayon fabrics were investigated extensively. In order to reduce the weight loss and thermal shrinkage of rayon fabrics occurring during the stabilization process, ultrasonic cleaning was first conducted and then chemical pre-treatments using , , , and were performed, respectively. The results indicated that both ultrasonic cleaning and chemical pre-treatment influenced the weight loss, thermal shrinkage, microstructure, carbon content, thermal stability and fabric shape of stabilized rayon fabrics. Also the results depended on the fast-stabilization time and the type of chemical pre-treatment agents used.

Cellulose-based rayon fibers or fabrics can be thermally decomposed very fast within a narrow temperature window during stabilization process. Therefore the stabilization stage is critically important for producing rayon-based carbon fibers. Consequently, in the present study the effects of isothermal stabilization and ultrasonic cleaning on the weight loss, chemical composition, microstructure, and fabric texture of cellulose-based rayon fabrics were explored. The temperature of the isothermal stabilization process performed in the range of influenced the processing time, carbon and oxygen contents, cellulose structural change, and fabric texture. The ultrasonic cleaning, which was conducted prior to the stabilization process, played a role in shortening the stabilization time, increasing the carbon contents, decreasing the oxygen contents, and changing the XRD pattern. Also, it was considered that the ultrasonic cleaning contributed to retarding the weight loss, to reducing the thermal shrinkage, and further to reducing the fast physical change of rayon fabrics.

Investigating the effect of electrospun fiber diameter on endothelial cell proliferation provides an important guidance for the design of a fabric scaffold. In this study, we prepared biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA) fibrous nonwoven mats with different fiber diameters ranged from 200 nm to 5 µm using the electrospinning technique. To control the fiber diameters of PLGA mats, 4 mixture solvents [hexafluoro-2-propanol, 2,2,2,-trifluoroethanol:dimethylformamide (9:1), 2,2,2,-trifluoroethanol:hexafluoro-2-propanol (9:1), chloroform] were used. Average diameters were 200 nm, 600 nm, 1.5 µm, and 5.0 µm, respectively. Stereoscopic structure and spatial characterization of fibrous PLGA mats were analyzed using atomic force microscopy and a porosimeter. The mechanical properties of PLGA mats were analyzed using a universal testing machine. The spreading behavior and infiltration of endothelial cells on PLGA mats were visualized by field emission scanning electron microscopy and hematoxylin and eosin staining. Cell proliferation on different PLGA fibers with different diameters was quantified using the MTT assay. Cells on 200 nm diameter PLGA mats showed rapid attachment and spreading. However, the cells did not penetrate the PLGA mat. Cells cultured on 600 nm and 1.5 µm diameter fibers could infiltrate the pores and cell proliferation was dramatically increased after 14 days. Secreted prostacyclin from endothelial cells on each mat was measured to examine the ability to inhibit platelet activation. This basic study on cell proliferation and fiber diameter with physical characterization provides a foundation for studies examining nonwoven fibrous PLGA mats as a tissue engineering scaffold.

Recently, numerous compounds have been studied in order to develop antibacterial agents, which can prevent colonized wounds from infection, and assist the wound healing. For this purpose, novel silver chloride nanoparticles stabilized with chitosan oligomer (CHI-AgCl NPs) were synthesized to investigate the influence of antibacterial chitosan oligomer (CHI) exerted by the silver chloride nanoparticles (AgCl NPs) on burn wound healing in a rat model. The CHI-AgCl NPs had a spherical morphology with a mean diameter of 42 +/- 15 nm. The burn wound healing of CHI-AgCl NPs ointment was compared with untreated group, Vaseline ointment, and chitosan ointment group. The burn wound treated with CHI-AgCl NPs ointment was completely healed by 14 treatment days, and was similar to normal skin. Particularly, the regenerated collagen density became the highest in the CHI-AgCl NPs ointment group. The CHI-AgCl NPs ointment is considered a suitable healing agent for burn wounds, due to dual antibacterial activity of the AgCl NPs and CHI.

In the present work, exfoliated graphite nanoplatelets (EGN) of 1 μm in average particle size, which were prepared by heating at 900°C and then subjected to ultrasonic, ball-milling, and vibratory ball-milling techniques, were uniformly incorporated into phenylethynyl-terminated polyimide (PETI-5) resin. The fracture surface morphology and the electrical resistivity of the EGN/PETI-5 composites were investigated. The results showed that the fracture surfaces and the electrical resistivity strongly depended on the EGN content. The fracture surfaces became more ductile and roughened with increasing EGN and the electrical resistivity was gradually decreased with increased EGN loading, indicating the percolation threshold at 5 wt% EGN.

In this present work, the effect of additional heat-treatment (AHT) in the range from 1800 o C to 2400 o C on the chemical composition, morphology, microstructure, tensile properties, electrical resistivity, and thermal stability of commercial polyacrylonitrile (PAN)-based carbon fibers was explored by means of elemental analysis, electron microscopy, X-ray dif fraction analysis, single fiber tensile testing, two-probe electrical resistivity testing, and ther mogravimetric analysis (TGA). The characterization results were in agreement with each other. The results clearly demonstrated that AHTs up to 2400 o C played a significant role in further contributing not only to the enhancement of carbon content, fiber morphology, and tensile modulus, but also to the reduction of fiber diameter, inter-graphene layer distance, and electrical resistivity of “as-received” carbon fibers without AHT. The present study sug gests that key properties of commercial PAN-based carbon fibers of an intermediate grade can be further improved by proprietarily adding heat-treatment without applying tension in a batch process.

We discuss the influence of few-walled carbon nanotubes (FWCNTs) treated with nitric acid and/or sulfuric acid on field emission characteristics. FWCNTs/tetraethyl orthosilicate (TEOS) thin film field emitters were fabricated by a spray method using FWCNTs/TEOS sol one-component solution onto indium tin oxide (ITO) glass. After thermal curing, they were found tightly adhered to the ITO glass, and after an activation process by a taping method, numerous FWCNTs were aligned preferentially in the vertical direction. Pristine FWCNT/TEOS-based field emitters revealed higher current density, lower turn-on field, and a higher field enhancement factor than the oxidized FWCNTs-based field emitters. However, the unstable dispersion of pristine FWCNT in TEOS/N,N-dimethylformamide solution was not applicable to the field emitter fabrication using a spray method. Although the field emitter of nitric acid-treated FWCNT showed slightly lower field emission characteristics, this could be improved by the introduction of metal nanoparticles or resistive layer coating. Thus, we can conclude that our spray method using nitric acid-treated FWCNT could be useful for fabricating a field emitter and offers several advantages compared to previously reported techniques such as chemical vapor deposition and screen printing.

Kenaf fibers, cellulose-based natural fibers, were used as precursor for preparing kenafbased carbon fibers. The effects of carbonization temperature (700 o C to 1100 o C) and chemical pre-treatment (NaOH and NH4Cl) at various concentrations on the thermal change, chemical composition and fiber morphology of kenaf-based carbon fibers were investigated. Remarkable weight loss and longitudinal shrinkage were found to occur during the thermal conversion from kenaf precursor to kenaf-based carbon fiber, depending on the carboniza tion temperature. It was noted that the alkali pre-treatment of kenaf with NaOH played a role in reducing the weight loss and the longitudinal shrinkage and also in increasing the carbon content of kenaf-based carbon fibers. The number and size of the cells and the fiber diam eter were reduced with increasing carbonization temperature. Morphological observations implied that the micrometer-sized cells were combined or fused and then re-organized with the neighboring cells during the carbonization process. By the pre-treatment of kenaf with 10 and 15 wt% NaOH solutions and the subsequent carbonization process, the inner cells completely disappeared through the transverse direction of the kenaf fiber, resulting in the fiber densification. It was noticeable that the alkali pre-treatment of the kenaf fibers prior to carbonization contributed to the forming of kenaf-based carbon fibers.

Novel unsaturated polyester composites with PAN-based nanofiber, stabilized PAN nanofiber, and carbonized nanofiber webs have been fabricated, respectively, and the effects of the nanofiber web content on their electrical resistivity, the thermal stability, dynamic storage modulus, and fracture surfaces were studied. The result demonstrated that the introduction of just one single layer (which is corresponding to 2 wt.%) of the carbonized nanofiber web to unsaturated polyester resin (UPE) could contribute to reducing markedly the electrical resistivity of the resin reflecting the percolation threshold, to improving the storage modulus, and to increasing the thermal stability above 350oC. The effect on decreasing the resistivity and increasing the modulus was the greatest at the carbonized PAN nanofiber web content of 8 wt.%, particularly showing that the storage modulus was increased about 257~283% in the measuring temperature range of −25oC to 50oC. The result also exhibited that the carbonized PAN nanofibers were distributed uniformly and compactly in the unsaturated polyester, connecting the matrix three-dimensionally through the thickness direction of each specimen. It seemed that such the fiber distribution played a role in reducing the electrical resistivity as well as in improving the dynamic storage modulus.

The hygrothermal effect of poly(butylene succinate) biocomposites reinforced with silk or henequen fibers was investigated. The biocomposites were fabricated using a compression molding method. The biocomposites were maintained in the chamber at 60 °C and 85% RH for 1000 h. The results show that the degradation of PBS matrix is the main cause for the deterioration of biocomposites performance and the biocomposites degraded much slowly than PBS matrix did. The storage modulus for the biocomposites exposed at 60 °C and 85% RH for 1000 h was decreased 20% and 50% with the silk and henequen fibers comparing to the original specimens, respectively.

Special banks primarily using Internet have different properties in transactions with customers, risk management, capital strength, and branch networks with general banks. The success and failure factors of Internet banks have been explained only by the economies of scale, and learning and experience effects of Internet banks based on the perspective of organizational ecologies. In this study, the success factors of Internet banks are investigated based on strategic choice by organizations and resource-based view of the firms instead of organizational ecology perspective. To this end, 31 major Internet banks operating in overseas market have been classified by the size and profitability of banks, and three strategic groups have been derived. three representative company cases were analyzed. critical success factors of Internet banks were derived, and considerable points when operating Internet banks were discussed.

【In the present study, electrospun PAN precursor webs and the stabilized and carbonized nanofiber webs processed under different heat-treatment conditions were characterized by means of weight loss measurement, elemental analysis, scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimentric analysis (TGA), and X-ray diffraction (XRD) analysis. The result indicated that stabilization and carbonization processes with different temperatures and heating rates significantly influenced the chemical and morphological characteristics as well as the thermal properties of the stabilized and then subsequently carbonized nanofiber webs from PAN precursor webs. It was noted that the filament diameter and the carbon content of a carbonized nanofiber web as well as its weight change may be effectively monitored by controlling both stabilization and carbonization processes.】

In this study, commercially available pitch-based carbon fibers of general grade were post-heat-treated using a box- type high temperature furnace at 1800°C, 2000°C, 2200°C, and 2400°C, respectively. The fundamental characteristics of each heat-treated carbon fibers were investigated in terms of chemical composition, morphology, thermal stability, X-ray diffraction, single filament tensile test, and electrical resistivity. The result showed that the fiber properties were significantly influenced by the post-heat-treatment, indicating the greater effect with increasing treatment temperature. The carbon contents, thermal stability, and tensile properties of the carbon fibers used here were further increased by the post-heat-treatment, whereas the d-spacing between graphene layers and the electrical resistivity were reduced with increasing post-heat-treatment temperature.

In the present study, novel short silk fibre (Bombix mori) reinforced poly(butylene succinate) biocomposites have been fabricated with varying fibre contents by a compression molding method and their mechanical and thermal properties have been studied in terms of tensile and flexural properties, thermal stability, thermal expansion, dynamic mechanical properties, and microscopic observations. The results demonstrate that chopped silk fibres play an important role as reinforcement for improving the mechanical properties of PBS in the present system although raw silk fibres are used without any surface modification normally done to enhance the interfacial adhesion between the natural fibre and the matrix. The tensile and flexural properties of PBS matrix resin are markedly improved with increasing the short fibre content in the composites, showing a maximum value at a fibre loading of 50 wt%. Also, the thermomechanical stability of PBS resin is greatly improved by incorporating reinforcing short silk fibres in the composite matrix, showing much lower linear coefficient of thermal expansion and higher storage modulus than PBS control, respectively. The thermal stability of silk/PBS biocomposites is likely to be intermediate between the PBS matrix and the silk fibre depending on the short fibre content. This work also suggests that use of animal-based natural silk fibres as reinforcement in a natural fibre composite system may be potential for effectively improving the properties and performances of biodegradable polymer matrix resins.

Biodegradable poly(lactide-co-glycolide) (PLGA) has found widespread use in modern medical practice. However, the degradation rate of PLGA should be adjusted for specific biomedical applications such as tissue engineering, drug delivery, and surgical implantation. This study focused on the effect of electron beam radiation on nanofibrous PLGA mats in terms of physical properties and degradation behavior with cell proliferation. PLGA nanofiber mats were prepared by electrospinning, and electron beam was irradiated at doses of 50, 100, 150, 200, 250, and 300 kGy. PLGA mats showed dimensional integrity after electron beam irradiation without change of fiber diameter. The degradation behavior of a control PLGA nanofiber (0 kGy) and electron beam-irradiated PLGA nanofibers was analyzed by measuring the molecular weight, weight loss, change of chemical structure, and fibrous morphology. The molecular weight of the PLGA nanofibers decreased with increasing electron beam radiation dose. The mechanical properties of the PLGA nanofibrous mats were decreased with increasing electron beam irradiation dose. Cell proliferation behavior on all electron beam irradiated PLGA mats was similar to the control PLGA mats. Electron beam irradiation of PLGA nanofibrous mats is a potentially useful approach for modulating the biodegradation rate of tissue-specific nonwoven nanofibrous scaffolds, specifically for soft tissue engineering applications.

Poly(amic acid) nanocomposites were synthesized from a dimethylacetamide (DMAc) solution with two organophilic montmorillonites (organo-MMTs). It was then heated at various temperatures under vacuum, yielding 15-20 um thick films of polyimide/organo-MMT hybrid with different clay contents (1-8 wt%). Dodecylamine (C 12 -) and hexadecylamine (C 16 -) were used as aliphatic alkylamines in organo-MMT. The ultimate strength monotonically increased with increasing clay content in the polymer matrix. Maximum enhancement in the initial modulus was observed for the blends containing 2 wt% clay with two kinds of organo-clays, and values did not alter significantly with further increases in clay content. Additions of only 2 wt% C 12 - and C 16 -MMT to the polyimide were shown to cause 94%-95% reduction in oxygen gas permeability. This is caused by the barrier properties of the clay layers dispersed in the composite. In general, C 16 -MMT is more effective than C 12 -MMT in increasing both the tensile property and the gas barrier in a polyimide matrix. Intercalations of the polymer chains in clay were examined through wide-angle X-ray diffraction (XRD) and electron microscopies (SEM and TEM).

This paper presents an extensive study of the ablation properties, microstructural behavior of ablation and thermal stability of various carbon-fiber-reinforced composites composed of four different matrices, a phenolic matrix, a carbonaceous matrix, a carbonaceous matrix containing impregnated resin and a carbonaceous matrix containing pyrocarbon. The ablation properties of the composites used were quantitatively evaluated by performing ablation tests with a plasma torch. The ablation behavior of both the carbon fibers and the composite matrix has been qualitatively interpreted through a scanning-electron-microscopy approach. The thermal stability of the composites was also examined by using a thermogravimetric analyzer both in air and nitrogen gas. The ablation test results reveal that composites with a carbonized matrix only (1C/C) and these with a carbonaceous matrix (1C/C+CVI) containing pyrocarbon infiltrated by a CVI process have the highest ablation resistance. In particular, the ablation resistances of 1C/C and 1C/C+CVI composites are improved by about 61 and 67% on the basis of weight change, respectively, in comparison with carbon/phenolic green composite.

Rapid cell growth and rapid recovery of intact cultured cells are an invaluable technique to maintain the biological functions and viability of cells. To achieve this goal, thermoresponsive polystyrene (PS) nanofibrous mat was fabricated by electrospinning of PS solution, followed by the graft polymerization of thermoresponsive poly(N-isopropylacrylamide)(PIPAAm) on PS nanofibrous mats. Image analysis of the PS nanofiber revealed a unimodal distribution pattern with 400 nm average fiber diameter. Graft polymerization of PIPAAm on PS nanofibrous mats was confirmed by spectroscopic methods such as ATR-FTIR, ESCA, and AFM. Human fibroblasts were cultured on four different surfaces, PIPAAm-grafted and ungrafted PS dishes and PIPAAm-grafted and ungrafted PS nanofibrous mats, respectively. Cells on PIPAAm-grafted PS nanofibrous mats were well attached, spread, and proliferated significantly much more than those on other surfaces. Cultured cells were easily detached from the PIPAAm-grafted surfaces by decreasing culture temperature to 20°C, while negligible cells were detached from ungrafted surfaces. Moreover, cells on PIPAAm-grafted PS nanofibrous mats were detached more rapidly than those on PIPAAm-grafted PS dishes. These results suggest that thermoresponsive nanofibrous mats are attractive cell culture substrates which enable rapid cell growth and recovery from the culture surface for application to tissue engineering and regenerative medicine.

The surface of polyacrylonitrile-based carbon fiber was appropriately coated with dilute phosphoric acid to protect or retard its thermal oxidation occurring during an exposure to high temperatures above 600°C in air. Microscopic behavior on surface damage and size change in the uncoated and coated fibers was compared using thermogravimetric and scanning electron microscopic techniques. The result showed that the state of the carbon fiber surface was found to be remarkably improved by the coated phosphorous compound, minimizing the surface pitting, and size reduction of carbon fiber by high temperature oxidation. The microscopic evidence for the effective protection of carbon fiber from thermal oxidation also indicated that use of this technology may be positively considerable to other related materials.

In the present study, exfoliated graphite nanoplatelets (EGN), which were prepared by means of microwave and ultrasonic processes from graphite intercalation compounds, were coated with a liquid rubber amine-terminated poly(butadiene-co-acrylonitrile) (ATBN) at various concentrations via ultrasonic and deep-freezing methods. The presence of ATBN coating on EGN particles was characterized by using multiple analytical tools such as X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, elemental analysis, X-ray diffractometer, thermogravimetric analyzer, and scanning electron microscope. The level of ATBN coating of the EGN particles strongly depended on the coating concentration, and it was clearly demonstrated. The characterization results were consistent with each other, indicating that the elastomeric coating of EGN with ATBN was performed successfully. The 1 wt% EGN coated with 10 wt% ATBN incorporated into epoxy increased the toughness of epoxy by 18%. It turns out that the elastomeric coating of EGN with ATBN effectively contributed to toughen epoxy with a very small amount of 0.1 wt% ATBN compared to the epoxy. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2013, 32, 21366; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21366

The isothermal crystallization behaviors and kinetics for a hydrogenated diblock copolymer of polybutadiene and isoprene-co-butadiene were studied by means of dilatometry. It was clearly observed and discussed that both primary and secondary crystallization processes co-exist in this crystallization system. The crystallization kinetic parameters, kc and n, determined from two different analytical methods were in good agreement within the experimental temperature range for the stage of primary crystallization. The kinetic parameters determined independently from dilatometry and differential scanning calorimetry for the given polymer were also compared.