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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 this work, the effect of aluminum trihydroxide (ATH) on the flame retardancy and dynamic mechanical and tensile properties of kenaf/poly(lactic acid) green composites was explored. Prior to comp...

The effect of electron beam treatment on the thermomechanical and flexural properties of chopped silk fiber-reinforced poly(butylene succinate) (PBS) green composites was studied for the first time...

Exfoliated graphite nanoplatelets (EGN) were successfully coated with a liquid rubber amine-terminated poly(butadiene-co-acrylonitrile) (ATBN) at various concentrations. The rubber-coated EGN was incorporated into epoxy resin at different contents. The result revealed that the impact toughness of EGN/epoxy composite was increased by about 18 % with increasing the ATBN coating concentration. The impact strength, the flexural and dynamic mechanical properties, and the thermo-dimensional stability of EGN/epoxy composites were simultaneously enhanced by the incorporation of 1 wt% EGN coated with 10 wt% ATBN rubber into epoxy, which turns out a very small amount of 0.1 wt% ATBN compared to the epoxy resin.

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.

In this study, biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA) fibers were prepared by a melt-electrospinning and treated with plasma in the presence of either oxygen or ammonia gas to modify the surface of the fibers. The effects of processing parameters on the melt-electrospinning of PLGA were examined in terms of fiber morphology and diameter. Among the processing parameters, the spinning temperature and mass flow rate had a significant effect on the average fiber diameter and its distribution. The water contact angle of melt-electrospun PLGA fibers decreased significantly from 123 ° to 55 ° (oxygen plasma treatment) or to 0 ° (ammonia plasma treatment) by plasma treatment for 180 sec, while their water content increased significantly from 2.4 % to 123 % (oxygen plasma treatment) or to 189 % (ammonia plasma treatment). Ammonia gas-plasma enhanced the surface hydrophilicity of PLGA fibers more effectively compared to oxygen gas-plasma. X-ray photoelectron spectroscopy analysis supported that the number of polar groups, such as hydroxyl and amino groups, on the surface of PLGA fibers increased after plasma treatment. Overall, the microfibrous PLGA scaffolds with appropriate surface hydrophilicity and fiber diameter could be fabricated by melt electrospinning and subsequent plasma treatment, without a significant deterioration of fiber structure and dimensional stability. This approach of controlling the surface properties and structures of fibers could be useful in the design and tailoring of novel scaffolds for tissue engineering.

Cellulose-based bamboo fibers were infiltrated with phenolic resin with assistance of vacuum and carbonized at 700, 900, and 1200 °C. The effects of resin infiltration on the chemical composition, thermal shrinkage, weight loss, and the thermal stability of carbonized bamboo fibers were explored. It was noted that phenolic resin infiltration contributed not only to the decrease of thermal shrinkage and weight loss occurring in the furnace during carbonization but also to the increase of carbon contents and thermal stability of carbonized bamboo fibers, with increasing carbonization temperature. The fiber morphology revealed that the cellular structure of bamboo fiber with resin infiltration was retained after carbonization.

In the present study, randomly aligned jute fiber/poly(lactic acid) (PLA) and two-directionally aligned jute fabric/PLA green composites with jute (50% by weight) treated with electron beam at different dosages (0, 5, 10, 30, 50, and 100 kGy) were fabricated by compression molding technique and the effect of electron beam treatment on their thermal properties was investigated in terms of thermal expansion, thermal stability, dynamic mechanical thermal property, and heat deflection temperature (HDT). The dynamic storage modulus and HDT of neat PLA were significantly increased by incorporating jute fibers or fabrics into PLA, whereas the coefficient of thermal expansion (CTE) and the damping property were decreased, reflecting the enhancement in the interfacial adhesion between the jute and the PLA by electron beam treatment with an optimal dosage of 10 kGy and the reinforcing effect by jute. The result exhibited that the thermal stability, storage modulus, and HDT of jute/PLA green composites were highest ...

To investigate the influence of electron beam irradiation on the properties of poly(ϵ-caprolactone) (PCL), PCL films prepared by solvent casting were irradiated with high-energy electron beams. The irradiated PCL films were investigated in terms of degree of cross-linking, mechanical properties, thermal properties, and biodegradability. The degree of cross-linking of the irradiated PCL films was found to be dependent on the absorption dose. The tensile strength of the irradiated PCL films increased with increasing absorption dose, while their elongation-at-break was reduced. The dynamic mechanical analysis results revealed that the irradiated PCL films had a higher glass transition temperature and a wider rubbery state plateau. The melting and thermal decomposition temperatures of the irradiated PCL films gradually decreased with increasing absorption dose. The results of the enzymatic degradation test revealed that the irradiated PCL films were more slowly degraded than the nonirradiated PCL film. These ...

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.

In the present study, the curing behavior of polycardanol prepared by enzymatic oxidative polymerization of thermally treated cashew nut shell liquid, which can be available from naturally renewable resources, was explored in the presence of methyl ethyl ketone peroxide (MEKP) and cobalt naphthenate (Co-Naph). The curing behavior was monitored varying Co-Naph concentration and curing temperature by means of Fourier transform infrared (FT-IR) spectroscopy. The result revealed that the characteristic absorption bands were significantly affected by the given curing condition, resulting mainly from the unsaturated moiety in the polycardanol molecule. The extent of curing of polycardanol strongly depended on curing temperature, showing a typically sigmoidal curve reaching almost 1.0 upon processing at 200°C for 120 min. The thermal curing conditions for preparing polycardanol with an optimal state of cure were provided in the work. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

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.

Green composites that, in general, consist of cellulosebased natural fibers and polymer resins have many advantages like environmentally friendliness, light weight, costeffectiveness, biodegradability and acceptable mechanical properties over conventional glass fiber-reinforced polymer composites. However, natural fibers of hydrophilic character may cause weak interfacial adhesion with a polymeric resin of hydrophobic character, leading to reduction of the properties and performances of resulting green composites. Due to lack of interfacial adhesion between raw natural fibers and polymers, there have been many papers reporting the modification of fiber surfaces and the effect on the interfacial properties of green composites. In order to modify natural fiber surfaces and consequently to enhance the interfacial bonding to a polymer, chemical methods like alkalization and silane coupling and physical methods like electron beam irradiation and plasma treatment are frequently used. Electron beam technique has often been utilized for surface modification and property improvement of polymer materials like fibers, films, plastics and composites for the last decades. It may remove surface impurities and alter surface chemical characteristics at an appropriate irradiation condition. Electron beam processing is a dry, clean and cold method with advantages such as energy-saving, high throughput rate, uniform irradiation and environmental safety. Poly(lactic acid), referred to as PLA, is obtainable from natural resources, thermoplastic and completely biodegradable. As it combines with natural fibers like jute, kenaf, etc., the material would be not only highly reinforced but also ecobenign and biodegradable. The objective of the present work is to explore the effect of jute fiber surface modification on the interfacial shear strength of jute-PLA green composites. The paper deals with the change of single fiber tensile property, fiber surface topology, and chemical composition occurring in jute fibers irradiated at different dosages of electron beam, discussing on their effect on the interfacial adhesion between jute fibers and PLA.

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.

The mechanical stability of titania (TiO2) nanofibers was improved by fabricating TiO2/poly(dimethyl siloxane) (PDMS) composite fibers using a combination of hybrid electrospinning and sol-gel methods, followed by heat treatment at 250°C for 3 h. The compositions (90/10, 80/20, and 70/30, w/w) of the TiO2/PDMS composite fibers were varied by adjusting the flow rate of the PDMS sol with the flow rate of TiO2 sol fixed. There was no significant change in morphology and average diameter of the as-spun TiO2/PDMS fibers after heat treatment. Both the tensile strength and modulus of the TiO2/PDMS composite fibers increased gradually with increasing PDMS content up to 30 wt %. In addition, from the photo-degradation reaction of methylene blue, the photocatalytic activity of TiO2/PDMS composite fibers was strongly dependent on the TiO2 content (%) in the composite fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

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.

Crosslinked poly(dimethyl siloxane) (PDMS) fibers were fabricated by electrospinning in combination with a sol–gel process followed by heat treatment. Before and after heat treatment, the changes in the chemical and thermal properties of the electrospun PDMS fibers were examined by differential scanning calorimetry (DSC), equilibrium swelling tests, and contact angle measurements. There was no significant change in morphology and average diameter of the as-spun PDMS fibers after heat treatment. The tensile properties of the as-spun PDMS fibers mat increased with increasing heat treatment temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

In this study, polycardanol, which was synthesized by enzymatic oxidative polymerization of thermally treated cashew nut shell liquid (CNSL) using fungal peroxidase, was partially or fully cured using methyl ethyl ketone peroxide (MEKP) as initiator and cobalt naphthenate (Co-Naph) as accelerator. The curing behavior of polycardanol was extensively investigated in terms of curing temperature, curing time, concentration of initiator and accelerator, and the monomer-to-polymer conversion of polycardanol by means of differential scanning calorimetry (DSC). The curing behavior significantly depends on the thermal condition given and it was monitored with the change of the exotherms as a function of temperature. The optimal conditions for fully curing polycardanol are 1 wt% MEKP, 0.2 wt% Co-Naph, curing time 120 min, and curing temperature 200 °C. This study suggests that a polycardanol with high monomer-to-polymer conversion would be useful for processing a polycardanol matrix composite under the optimal conditions of curing.

The purpose of this study was to conduct a thermal analysis of the hydrolysis and degradation behavior of biodegradable polymers and bio-composites at 50°C and 90% relative humidity (RH). With increasing hydrolysis time, the thermal stability and degradation temperature of polybutylene succinate (PBS) slightly decreased. The glass transition temperature (Tg) and melting temperature (Tm) of PBS and the anti-hydrolysis agent treated PBS did not vary significantly with increasing hydrolysis time, whereas those of the trimethylolpropane triacrylate (TMPTA)-treated PBS slightly increased. With increasing hydrolysis time, the storage modulus (E’) values of the bio-composites decreased, whereas those of the TMPTA treated bio-composites slightly increased. Also, the tan values of the anti-hydrolysis agent and TMPTA treated PBS-BF bio-composites were slightly lower than those of the non-treated bio-composites, due to the reduction in their degree of hydrolysis. The tanδmax peak temperature (Tg) of the anti-hydrolysis agent treated bio-composites was not significantly changed, whereas that of the TMPTA treated bio-composites was increased.

The surfaces of kenaf fibers were treated with three different silane coupling agents. 3-glycidoxypropyltrimethoxy silane (GPS), 3-aminopropyltriethoxy silane (APS), and 3-methacryloxypropyltrimethoxy silane (MPS). Among them, the most effective one for the property improvement was GPS when it was applied to the kenaf fiber surfaces at 0.5 wt%. Thermoplastic polypropylene (PP) and thermosetting unsaturated polyester (UPE) matrix composites with chopped kenaf fibers untreated and treated at different GPS concentrations from 0.1 wt% to 5 wt% were fabricated using compression molding technique. The present study demonstrates that the interfacial, flexural, tensile, and dynamic mechanical properties of both kenaf/PP and kenaf/UPE composites importantly depend on the GPS treatments done at different concentrations. The greatest property improvement of both thermoplastic and thermosetting polymer composites was obtained with the silane treatment at 0.5 wt% and the mechanical properties were comparable with E-gl...

In the present study, novel biocomposites with chopped jute fibers and thermosetting polycardanol were prepared using compression molding technique for the first time. Prior to biocomposite fabrication, jute fiber bundles were surface-treated at various concentrations using 3-glycidoxypropyltrimethoxy silane (GPS) and 3-aminopropyltriethoxy silane (APS), respectively. The interfacial shear strength, flexural properties and thermal properties of jute/polycardanol biocomposites reinforced with untreated and silane-treated jute fibers were investigated by means of single fiber microbonding test, three-point flexural test, dynamic mechanical analysis, thermogravimetric analysis and thermomechanical analysis. Both GPS and APS treatments played a role in improving the interfacial adhesion, reflecting that the organofunctional groups located at the end of silane coupling agents may contribute to linking between jute fibers and a polycardanol resin. As a result, it gave rise to increased interfacial shear strengt...

【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, the thermal properties of bio-flour-filled, polypropylene (PP) bio-composites with different pozzolan contents were investigated. With increasing pozzolan content, the thermal stability, 5% mass loss temperature and derivative thermogravimetric curve (DTGmax) temperatures of the bio-composites slightly increased. The coefficient of thermal expansion (CTE) and thermal expansion of the bio-composites decreased as the pozzolan content increased. The glass transition temperature (Tg), melting temperature (Tm) and percentage of crystallinity (Xc) of the bio-composites were not significantly changed. The thermal stability, thermal expansion and Xc of the maleic anhydride-grafted PP (MAPP)-treated bio-composites were much higher than those of non-treated bio-composites at 1% pozzolan content due to enhanced interfacial adhesion. X-ray diffraction (XRD) analysis confirmed the crystallinity of pozzolan-added bio-composites. From these results, we concluded that the addition of pozzolan in the bio-composites was an effective method for enhancing the thermal stability and thermal expansion.

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.

Thermal and dynamic mechanical properties of kenaf natural fiber reinforced polypropylene (PP) biocomposites were examined to compare the effects of natural fiber treatment by electron beam irradiation (EBI) and alkalization. The alpha cellulose contents, the functional groups on the surfaces and the thermal stability of the untreated and treated kenaf fibers were studied. Kenaf fiber/polypropylene(PP) biocomposites were fabricated by means of a compression molding technique using chopped kenaf fibers treated with electron beam (EB) dosages of 100, 200, 500 kGy or with NaOH concentrations of 2, 5, 10 wt%, respectively. The thermal stability, the dynamic mechanical and the interfacial properties of untreated and treated kenaf/PP biocomposites were also investigated through a thermogravimetric analysis, a dynamic mechanical analysis and a fractographic observation, respectively. The results show that the characteristics of kenaf fibers and biocomposites depended on the different treatment level with the EB ...

In the present study, natural fibers (jute, kenaf and henequen) reinforced thermoplastic (poly(lactic acid) and polypropylene) and thermosetting (unsaturated polyester) matrix composites were well fabricated by a compression molding technique using all chopped natural fibers of about 10 mm long, respectively. Prior to green composite fabrication, natural fiber bundles were surface-treated with tap water by static soaking and dynamic ultrasonication methods, respectively. The interfacial shear strength, flexural properties, and dynamic mechanical properties of each green composite system were investigated by means of single fiber microbonding test, 3-point flexural test, and dynamic mechanical analysis, respectively. The result indicated that the properties of the polymeric resins were significantly improved by incorporating the natural fibers into the resin matrix and also the properties of untreated green composites were further improved by the water treatment done to the natural fibers used. Also, the p...

In the present study, chopped henequen natural fibers without and with surface modification by electron beam (E-beam) treatment were incorporated into a polypropylene matrix. Prior to composite fabrication, a bundle of raw henequen fibers were treated at various E-beam intensities from 10 kGy to 500 kGy. The effect of E-beam intensity on the interfacial, mechanical and thermal properties of randomly oriented henequen/polypropylene composites with the fiber contents of 40 vol% was investigated focusing on the interfacial shear strength, flexural and tensile properties, dynamic mechanical properties, thermal stability, and fracture behavior. Each characteristic of the material strongly depended on the E-beam intensity irradiated, showing an increasing or decreasing effect. The present study demonstrates that henequen fiber surfaces can be modified successfully with an appropriate dosage of electron beam and use of a low E-beam intensity of 10 kGy results in the improvement of the interfacial properties, fle...

In this work, quasi-carbon fabrics were produced by quasi-carbonization processes conducted at and below 1200°C. Stabilized polyacrylonitrile (PAN) fabrics and quasi-carbon fabrics were used as reinforcements of phenolic composites with a 50 wt %/50 wt % ratio of the fabric to the phenolic resin. The effect of the quasi-carbonization process on the flexural properties, interfacial strength, and dynamic mechanical properties of quasi-carbon/phenolic composites was investigated in terms of the flexural strength and modulus, interlaminar shear strength, and storage modulus. The results were also compared with those of a stabilized PAN fabric/phenolic composite. The flexural, interlaminar, and dynamic mechanical results were quite consistent with one another. On the basis of all the results, the quasi-static and dynamic mechanical properties of quasi-carbon/phenolic composites increased with the applied external tension and heat-treatment temperature increasing and with the heating rate decreasing for the quasi-carbonization process. This study shows that control of the processing parameters strongly influences not only the mechanical properties of quasi-carbon/phenolic composites but also the interlaminar shear strength between the fibers and the matrix resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

In this study, the glass transition, thermal expansion, dynamic mechanical properties, and water-uptake behaviors of diepoxidized polycardanol (DEPC) cured by electron-beam radiation in the presence of cationic photoinitiators were investigated. How the type and concentration of cationic photoinitiators and the electron-beam absorption dose influenced the properties of the cured DEPC was also studied. Two types of cationic photoinitiators, triarylsulfonium hexafluorophosphate (simply referred to as phosphate type or P-type) and triarylsulfonium hexafluoroantimonate (simply referred to as antimonate type or Sb-type), were used. Electron-beam absorption doses of 200, 300, 400, and 600 kGy were applied to the uncured diepoxidized cardanol (DEC) samples, respectively. It was revealed that the Sb-type photoinitiator was preferable to the electron-beam curing of DEC; this led to a lower photoinitiator concentration and/or a lower electron-beam absorption dose compared to that in the phosphate-type photoinitiator. As a result, the variations in the glass-transition temperature, coefficient of thermal expansion, storage modulus, and water uptake of the cured DEPC were quite consistent with each other. We found that the optimal conditions for the enhanced properties of DEPC by electron-beam curing were an Sb-type photoinitiator at 2 wt % and an electron-beam absorption dose of 600 kGy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42570.

Henequen natural fiber reinforced unsaturated polyester biocomposites were fabricated and characterized. Henequen fibers were treated with various electron beam irradiation (EBI) dose or different concentrations of alkali solution. The effects of EBI or alkali treatments on the both henequen fiber and the properties of biocomposites made of unsaturated polyester and henequen fiber were compared by Fourier transform infrared spectra, thermal gravimetric analysis and dynamic mechanical analysis. Characteristics of the henequen fiber surface showed differently depending on the treatments and there is a close relationship between the optimal surface treatment of henequen fiber and the highest performance of the biocomposite resulting from the good adhesion between fiber and matrix.

The fluorescence excitation and emission spectra of a liquid crystal E7 in ethanol have been explored at a variety of concentrations from very dilute solutions ( −7 mol/L) to concentrated solutions (>1.0×10 −2 mol/L) and also for neat E7. The result showed a strong dependence of the steady-state fluorescence behavior on E7 concentration in ethanol. The photophysical behavior has been interpreted in terms of short-range and long-range intermolecular interactions and ground-state molecular association as well as spectral changes of the fluorescence excitation and emission. The short-range intermolecular interaction characterized by the fluorescence emission band with the maximum between 376 and 385 nm gradually increases with increasing E7 concentration. On the other hand, the long-range intermolecular interaction characterized by the emission band with the maximum between 347 and 362 nm gradually decreases with increasing E7 concentration. Consequently, with increasing E7 concentration in ethanol the long-range interaction effect is reduced, whereas the short-range effect is enhanced and the monomer emission completely disappears at concentrations greater than 2.83×10 −5 mol/L.

The dynamic mechanical thermal properties of carbon fiber-reinforced bismaleimide (BMI) composites processed using polyacrylonitrile(PAN)-based carbon fibers unsized and sized with LaRC PETI-5 amic acid oligomer as interphase material at 150°C, 250°C, and 350°C were investigated by means of dynamic mechanical thermal analysis. It was found that the storage modulus, loss modulus, tan δ and the peak temperature significantly depend on the sizing temperature as well as on the presence and absence of LaRC PETI-5 sizing interphase. The result showed that the carbon fiber/BMI composite sized at 150°C had the highest storage modulus at a measuring temperature of 250°C. The storage modulus decreased with increasing sizing temperature from 150°C to 350°C, being influenced by interdiffusion and co-reaction between the LaRC PETI-5 interphase and the BMI matrix resin. The present result is quite consistent with the interfacial result reported earlier in term of interfacial shear strength and interlaminar shear streng...

This article reports the mechanical and thermal properties of poly(butylene succinate) (PBS) biocomposites reinforced with industrially available waste silk fibers, fabricated with varying fiber contents and lengths. The result indicates that use of waste silk fibers may be a potential as reinforcement for effectively improving the static and dynamic mechanical properties of a biodegradable polymer matrix resin, depending on the waste silk fiber content and length in the present biocomposite system. The “as-separated” waste silk/PBS biocomposites showed the maximum tensile and flexural properties at a fiber loading of 40 wt %, and the “chopped” waste silk/PBS biocomposites showed the optimal strength and modulus with waste silk fibers of 12.7 mm length. The chopped waste silk fibers play a more contributing role in improving the mechanical properties of waste silk/PBS biocomposites than the as-separated waste silk fibers at a fixed fiber loading. Above the glass transition temperature, the storage modulus of waste silk/PBS biocomposites was significantly greater than that of PBS resin, especially in the higher temperature region. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4972–4980, 2006

Henequen natural fiber-reinforced poly(butylene succinate) biocomposites were prepared through a resin microdroplet formation on a single fiber and also fabricated by a compression molding technique using chopped henequen fibers, surface-treated with electron beam irradiation (EBI) at various dosages. The effect of EBI treatment on the surface characteristics and dynamic mechanical properties of henequen fibers was investigated using SEM, XPS and DMA methods, respectively. Also, the interfacial behavior of biocomposites was explored through a single fiber microbonding test and fracture surface observations. The result indicates that the interfacial shear strength (IFSS) of biocomposites greatly depends on the EBI treatment level on the henequen fiber surface. This study also suggests that appropriate modification of natural fiber surfaces at an optimum EBI dosage significantly contributes to improving the interfacial properties of biocomposites.

Without polymer additives, ultrafine titania fibres were successfully prepared via the electrospinning technique in combination with the sol?gel process. The viscosity of titania precursor sol for electrospinning was controlled by the evaporation of solvent and contact with moisture in air. The morphology of the electrospun titania fibres was characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface morphology and crystallinity of titania fibres were dependent on the calcination temperature. In particular, the titania fibres showed pure anatase crystalline structure when they were calcined at temperature as low as 250??C for 3?h. Also, the titania fibres calcined at 1300??C for 3?h showed rutile crystalline structure and burl-like wavy surfaces. This wavy surface seemed to be formed by aggregation of crystalline titania particles, which favours the round shape to minimize the surface area.

The influence of chopped fibre length on the mechanical and thermal properties of silk fibre ( Bombix mori) reinforced poly(butylene succinate) (PBS) biocomposites has been investigated in terms of tensile and flexural properties, thermal stability, thermal expansion, and dynamic mechanical properties. The chopped fibre lengths studied were 3.2 mm, 6.4 mm, 12.7 mm, and 25.4 mm. The results demonstrate that chopped silk fibres play an effective role in improving the mechanical properties of PBS in the present system. At a fixed fibre loading of 40 wt%, the tensile strength and modulus of the PBS control were improved by 69% and 228%, respectively, in comparison with those of the biocomposite reinforced with 25.4 mm silk fibres. The flexural strength and modulus of PBS were also greatly improved by 167% and 323%, respectively. The thermal properties of PBS resin increased when incorporating chopped silk fibres in the composite matrix. The biocomposites had much lower linear coefficient of thermal expansion (CTE) values and higher storage moduli than the PBS controls above the glass transition region, especially with reinforcing silk fibres of 25.4 mm long.