Showing papers in "Fibers and Polymers in 2014"

Effect of reinforcement and chemical treatment of fiber on The Properties of jute-coir fiber reinforced hybrid polypropylene composites

Abstract: Present research investigates the mechanical properties of jute-coir fiber reinforced hybrid polypropylene (PP) composite with fiber loading variation and observes the effect of chemical treatment of fiber on property enhancement of the composites. Composites were manufactured using hot press machine at four levels of fiber loading (5, 10, 15 and 20 wt%). Fiber ratio’s were varied (jute:coir=1:1, 3:1 and 1:3) for 20 % fiber loaded composites. Both jute and coir fiber was treated using 5 % and 10 % NaOH solutions. Composites were also prepared using treated fiber with jute-coir fiber ratio of 3:1. Tensile, flexural, impact and hardness tests and Fourier transform infrared spectroscopic analysis were conducted for characterization of the composites. Tensile test of composite showed a decreasing trend of tensile strength and increasing trend of the Young’s modulus with increase in fiber loading. During flexural, impact and hardness tests, the flexural strength, flexural modulus, impact strength and hardness values were found to be increased with increase in fiber loading. All these properties enhanced with the enhancement of jute content except impact strength. 5 % NaOH treatment provided an improving trend of properties whereas, 10 % NaOH treatment showed the reverse one. The FTIR analysis of the composites indicated decrease of hemicelluloses and lignin content with alkali treatment.

Binary catalyst system dye degradation using photocatalysis

Abstract: In this paper, soy meal hull activated carbon (SMHAC) and titania nanoparticle (TiO2) were used as catalysts to degrade dyes. Activated carbon was prepared using soy meal hull. Degradation of dyes using single and binary catalyst systems was studied. Textile dyes were used as model pollutants. Photocatalytic dye degradation and mineralization were studied using UV-Vis spectrophotometer and ion chromatography (IC). The effects of pH, initial dye concentration, and salt on dye degradation were investigated. Dye solutions were decolorized completely (100 %). The presence of salts decreased dye degradation rate. Degradation of dyes followed first order kinetics model. Formate, acetate, and oxalate were detected as dominant aliphatic intermediates during dye degradation process. Nitrate, sulfate, and chloride anions were detected as dye mineralization products.

Bio-composites: Development and mechanical characterization of banana/sisal fibre reinforced poly lactic acid (PLA) hybrid composites

Abstract: The work focuses on the influencing effect of fiber surface treatment by BP towards mechanical properties of BSF reinforced PLA composites. BSF were treated by BP to improve the adhesion between fibres and matrix. BSF (30 wt %) reinforced PLA (70 wt %) hybrid composites were fabricated by means of twin screw extrusion followed by injection molding process. Tensile strength, flexural strength and modulus were tested by means of UTM. The morphological analysis of the untreated and treated BSF reinforced PLA composites in comparison with virgin PLA was carried out by SEM to examine the existence of interfacial adhesion between BSF and PLA. The resultant data reveals that treated BSF restricts the motion of the PLA matrix due to better wettability and bonding. Consequently, mechanical properties like tensile and flexural moduli of BSF reinforced PLA composites were enhanced in comparison to virgin PLA and untreated BSF reinforced PLA composites. The results are discussed in detail.

Experimental Investigation of Mechanical behavior of Jute-Flax Based Glass Fiber Reinforced Composite

Abstract: Present technological development and innovation needs a better class of material that meets all the practical applications along with its environmental friendly nature and economical value. Hybrid natural fiber composites, a sector of natural composites meets these requirements. This paper deals with fabrication, mechanical characterization of a hybrid (Jute+Flax+GFRP) composite and also the comparison of it with the (Jute+GFRP) based composite. These composites are fabricated using hand lay-up technique. The arrangement of hybrid composite is such that a layer of vertically laid flax fiber is flanked between layers of horizontally laid jute fiber. Epoxy resin alongside with HY951 hardener is used as the binding agent throughout the layer. Glass fiber laminates are used on both sides for improving the surface finish and surface hardness. The volumetric fraction is such that one third of total volume is occupied by Jute and Flax fibers. Test results shows that the hybrid natural composite has excellent properties under tensile, flexural loading. At last failure morphology analysis is done using Scanning Electron Microscope (SEM) and the internal structure of the broken specimen is discussed.

Mechanical and thermal properties of epoxy composites containing graphene oxide and liquid crystalline epoxy

Abstract: The graphene oxide (GO) sheets are chemically grafted with γ-etheroxygentrimethoxysilane (KH560) and liquid crystalline epoxy (LCE) is synthesized from 4,4′-bis(2-hydroxyhexoxy)biphenyl (BP2) and epichlorohydrin before being incorporated into epoxy matrix. Then we present a novel approach to the fabrication of advanced polymer composites from epoxy matrix by incorporation of two modifiers, which are grafted GO (g-GO) and LCE. The mechanical properties of epoxy composites are greatly improved by incorporating LCE/g-GO hybrid fillers. For instance, the addition of 3 wt% hybrid filler (2 wt% g-GO and 1 wt% LCE) into the epoxy matrix resulted in the increases in impact strength by 132.6 %, tensile strength by 27.6 % and flexural strength by 37.5 %. Moreover, LCE/g-GO hybrid fillers are effective to increase thermal decomposition temperature, glass transition temperature, and storage modulus by strong affinity between the fillers and epoxy matrix.

Chemical stability of basalt fiber in alkaline solution

Abstract: The chemical stability of basalt fiber in alkaline solution is investigated by the means of weight retention and tensile strength retention. It has been observed that the basalt fiber immersed in weak alkaline solution is very stable whereas the basalt fiber immersed in strong alkaline solution shows poor weight retention due to the high dissociation constant. On the other hand, the tensile strength of basalt fiber in alkaline solutions is drastically decreased regardless of alkaline solution concentrations. Also basalt fiber in saturated Ca(OH)2 solution, which is similar to the alkaline environment of cement hydration, shows very low weight loss and high stability even after 3 months of immersion compared to glass fiber in the same condition.

Preparation and properties of pineapple leaf fiber reinforced poly(lactic acid) green composites

Abstract: Green composites from Pattawia pineapple leaf fiber (PALF) and poly(lactic acid) (PLA) were prepared. The mechanical method was chosen to extract PALF from fresh leaves due to this method gave high yield of fiber, short extraction time, and environmental friendly. Tensile and thermal properties, together with morphology of the fibers were disclosed. The fibers were conducted into a specified length of 1-3 mm and blended with PLA, using a twin screw extruder, with the PALF content of 10-50 wt%. Tensile testing, morphology investigation and thermogravimetric analysis were applied. Preliminary results showed that tensile modulus of the composites depended on PALF content. The tensile modulus and elongation at break of the composite containing 40 % PALF was about 48 %, and 111 % increase, respectively, compared with that of PLA. With addition of maleic anhydride coupling agent, such the composite showed the tensile modulus of 5.1 GPa, which was 34 % higher than that of the non-coupling agent composite, and about 104 % higher than that of PLA. Although the elongation at break of the composite containing 40 % PALF was found to dramatically increase by 111 %, the introduction of maleic anhydride in such the composite caused only 57 % increase in the elongation at break compared with that of PLA. Finally, a pilot product of square boxes was produced successfully from the proposed composite, by conventional injection molding process.

Preparation and characterization of cellulose nanofiber reinforced thermoplastic starch composites

Abstract: In the present study, cellulose nanofibers composite films were manufactured based on thermoplastic starch. Nanofibers were extracted from rice straw employing a developed chemo-mechanical method. In the chemical step, almost all of non-cellulosic components were removed and a white pulp of cellulose microfibers was obtained. Then, a diluted suspension of fibers was ultrasonicated to destruct intermolecular hydrogen bonds achieving nanofibers networks. Afterward, bio-nanocomposites were prepared by film casting. In order to study the effect of nanofibers content on the composite properties, the mechanical and dynamic mechanical properties, morphology, humidity absorption, and transparency of films were investigated. The yield strength and Young modulus of nanocomposites were satisfactorily enhanced compared to the pure thermoplastic starch film. The glass transition temperature of films was shifted to higher temperatures by increasing nanofibers contents. The uniform dispersion of the nanofibers was investigated using SEM images. The humidity absorption resistance of films was significantly enhanced by using 10 wt% cellulose nanofibers. The transparency of the nanocomposites was reduced compared to the pure starch films.

Dyeing of meta-aramid fibers with disperse dyes in supercritical carbon dioxide

Abstract: Dyeing characteristics of meta-aramid fibers were investigated in supercritical carbon dioxide by employing three disperse dyes and a carrier. The effects of dyeing temperature, pressure, time, dye concentration, CO2 flow, and carrier concentration on dyeing properties were investigated. The results showed that meta-aramid fiber could be dyed in supercritical carbon dioxide. Its color depth was improved with increasing dyeing temperature, pressure, time, dye concentration, CO2 flow, and carrier concentration. Moreover, the color depth could be significantly improved by adding the carrier. The dyeing procedure of supercritical carbon dioxide fluid did not influence the chemical structure and antistatic properties of the meta-aramid fiber. The maximum decomposition temperature and breaking strength of the dyed meta-aramid fiber are slightly increased. The dyed meta-aramid fiber in supercritical carbon dioxide had good fastness, which was rated at 4–5.

Mechanical and thermal properties of polypropylene (PP) composites filled with CaCO3 and shell waste derived bio-fillers

Abstract: The clam shell (CS) waste was first modified by furfural and hydrochloric acid to prepare fillers FCS and ACS, which were then used as fillers in polypropylene (PP), as well as the commercial calcium carbonate (CC). These fillers were characterized and analyzed by means of X-ray diffraction (XRD), atomic force microscopy (AFM), particle size analyzer, Fourier transformed infrared spectroscopy (FTIR) and contact angle measurement. The mechanical and thermal properties of PP composites were investigated as well. XRD analysis indicated that the major crystalline phase of CC was calcite; of shell waste derived fillers, calcite and aragonite. The CC was fully hydrophobic, while the shell derived fillers were amphiphilic. Mechanical property studies showed that the incorporation of FCS played the role mainly of toughening the PP; of CC, CS and ACS, that of reinforcing. The optimum filler contents of CS, ACS and FCS could reach 5, 7 and 15 wt.%, respectively, to obtain a good balance between fracture toughness and stiffness of the PP composites. Polarized optical microscopy (POM) observation indicated that the inclusion of these fillers could promote the heterogeneous nucleation of PP.

PAN fiber diameter effect on the structure of PAN-based carbon fibers

Abstract: The oxidation reaction mechanism during the thermal stabilization process of polyacrylonitrile(PAN) fibers was studied to investigate why the skin-core structure formed easily after the thermal stabilization of PAN fibers was elaborated. And it was found that the heterogeneity of the fibers was poor. In order to achieve a uniform structure after the stabilization treatment, the fiber diameter was systematically reduced. Three PAN fiber samples with different diameters were selected, and they were treated by thermal stabilization and carbonized under the same conditions. The stabilized samples and carbon fiber samples with different diameters were analyzed by differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, and elemental analysis. The results show that: the skin-core structure of the PAN fiber with the smallest diameter was completely eliminated by stabilization, and the heterogeneity was better. Meanwhile, C | N bonding also decreased, and the cross-linking reaction was easier to happen to form a large network molecular structure in the fiber with smaller diameter. The degree of graphitization of carbon fibers was higher when the diameter of fibers was reduced, and the relative carbon content increased. Crystallite size parameters were also affected when the diameter of fibers was reduced, with larger d002, lower Lc and increased La. In addition, the graphitization degree, as well as the carbon content was higher in the carbon fiber with smaller diameter.

CuBTC metal-organic frameworks enmeshed in polyacrylonitrile fibrous membrane remove methyl parathion from solutions

Abstract: A method is presented to immobilize Cu-BTC metal-organic framework (MOF-199) particles by enmeshing them in nonwoven polyacrylonitrile (PAN) nanofibers creating a fibrous membrane with the potential ability to remove chemical warfare agents or pesticides from solution. These membranes were shown to effectively adsorb methyl parathion, an organophosphate pesticide. Based on solubility theory and experimental results, partitioning was determined to be the main mechanism of removal. After 2 hours, the PAN/MOF-199 membranes removed 88 % more methyl parathion than the unmodified PAN membranes and 62 % as much as the MOF-199 crystal powder. Since the MOF particles were enmeshed in the PAN fiber mats, the MOF particles were in a workable and flexible substrate. Potential applications of these functionalized fibrous membranes include protective clothing for agricultural workers or military personnel as well as filtration media.

A simultaneous measurement method to characterize touch properties of textile materials

Abstract: Touch feels of textile materials are major factors related to the clothing comfort. We could perceive touch feels through contacts between skin and fabrics. Latest researches concluded there were four types of touch information including thermal, proprioceptive, cutaneous, and irritant and pains. There is a clear gap between current measurement methods on fabric touch feels and latest theoretical research outputs. This report introduced a new characterization method of textile touch feels. It simultaneously measured four categories of physical properties of textiles. Fabric Touch Tester (FTT), the reported instrument, included four modules as thermal, compression, bending and surface. Measuring time of one complete test on this instrument only took about 5 minutes. Output of FTT contained comprehensive descriptions on the physical properties of samples in both directions (warp/wale and weft/course). Experiment results showed that FTT could measure and distinguish these fabrics with good repeatability and reproducibility. Correlation study between FTT results and subjective evaluation scores showed there were significant correlations between them. Initial findings were concluded on the effect of thermal properties on other tactile perceptions as well as the interactions between different physical parameters.

Properties of alkali treated short flax fiber reinforced poly(lactic acid)/polycarbonate composites

Abstract: The main focus of this study is to investigate the properties of alkali treated flax fiber reinforced poly(lactic acid)/polycarbonate (PLA/PC) composites. Characterization of these composites was performed by conducting tensile strength, dynamic mechanical analysis (DMA), differential scanning calorimeter (DSC) and scanning electron microscope (SEM) analyses. Tensile strength results revealed that the highest mechanical performance was observed for 2 % sodium hydroxide (NaOH) treated flax fiber reinforced PLA/PC composites. DMA analysis also supported the results of the tensile tests. Tan delta (δ) curves were used for evaluating the fiber-matrix adhesion in flax fiber reinforced composites. The lowest peak magnitude and consequently the best fiber-matrix adhesion were also observed for 2 % NaOH treated flax fiber reinforced composites. DSC results showed that slight changes occurred in glass transition and melting temperature values. Moreover, crystallinity of PLA was affected by the flax fiber reinforcement. The maximum crystallinity value was observed in 2 % NaOH treated flax fiber reinforced composites. Furthermore, SEM analysis showed that 2 % NaOH treated flax fibers have better interfacial bonding with PLA/PC matrix among the flax fibers.

Effect of Molecular Weight and Concentration on Crystallinity and Post Drawing of Wet Spun Silk Fibroin Fiber

Abstract: Wet spun silk fibroin (SF) filaments have attracted considerable attention because of their potential in biotechnological applications including surgical sutures, tissue engineering and wound dressing. Although the molecular weight (MW) of polymers is one of key factors affecting the wet spinnability of dope along with the structural characteristics and properties of wet spun filament, no related study has been conducted. In this study, regenerated SFs with different MWs and concentrations were prepared by wet spinning. The effects of the SF concentration and MW on 1) wet spinnability and rheology of silk dope solution and 2) crystallinity index and post drawing performance of wet spun silk filament were examined. Their relationships were also investigated. The rheological measurements showed that an 80 mPa·s viscosity is needed to obtain a continuous wet spun SF filament. As the MW of SF increased, the peak position of the maximum draw ratio shifted to a lower SF concentration with a concomitant increase in the maximum draw ratio value at the peak. Interestingly, the crystallinity index obtained from Fourier transform infrared spectroscopy (FTIR) revealed a similar trend to the maximum draw ratio suggesting that the post drawing ability is strongly affected by the quantity of short-ordered crystalline regions in wet spun SF filaments. On the other hand, X-ray diffraction did not detect any crystallinity change in the SF filament produced from the formic acid solvent system. It was concluded that MW strongly affected the dope solution viscosity and the crystallinity index from FTIR and these determined the fiber formation of dope and post drawing performance of fiber.

Antibacterial finishing of cotton fabric via the chitosan/TPP self-assembled nano layers

Abstract: In this study, chitosan and pentasodium tripolyphosphate (TPP)-based bilayers were fabricated on the cationized woven cotton fabrics via layer-by-layer (LBL) self-assembly technique. The initial cationic charges on cotton fabric were produced through the aminization procedure involving the covalent attachment of reactive dye to cotton fabric and subsequent reductive cleavage of the dye to free amine. Different numbers of bilayers (1, 5, and 10) consisting of chitosan/TPP have been deposited on the fabrics. The surface morphology, cationic group content, chemical surface modification, whiteness index, surface tension and antibacterial properties of the modified cotton samples were investigated using scanning electron microscopy (SEM), methylene blue test, FTIR, reflectance spectroscopy, water contact angle measurements and antibacterial test, respectively. The bacterial inhibition experiments demonstrated that the modified cotton fabric with the addition of chitosan/TPP bilayers can increase the degree of inhibition on E. coli and S. aureus bacteria. The utilized LBL method was an easy and cost-effective procedure for developing of novel antibacterial textiles with the highly attractive feature in the medical and hygienic products.

Scaling up the production rate of nanofibers by needleless electrospinning from multiple ring

Abstract: Mass production of nanofibers is crucial in both laboratory research and industry application of nanofibers. In this study, multiple ring spinnerets have been used to generate needleless electrospinning. Multiple polymer jets were produced from the top of each ring in the spinning process, resulting in thin and uniform nanofibers. Production rate of nanofibers increased gradually with the increase of the number of rings in the spinneret. Spinning performance of multiple ring electrospinning, namely the quality and production rate of the as-spun nanofibers, was dependent on experimental parameters like applied voltage and polymer concentration. Electric field analysis of multiple ring showed that high concentrated electric field was formed on the surface of each ring. Fiber diameter together with production rate of needleless electrospinning was dependent on the strength and distribution of the electric field of the spinneret. Needleless electrospinning from multiple ring can be further applied in both laboratory research and industry where large amount of nanofibers must be employed simultaneously.

Preparation and Properties of Nanodiamond/Poly(lactic acid) Composite Nanofiber Scaffolds

Abstract: Nanodiamonds (NDs) were employed for the first time to enhance the mechanical properties of poly(lactic acid) (PLA)-based nanofiber scaffolds. Uniform ND/PLA composite nanofibers can be electrospun at <1 wt% loading of NDs. The introduction of NDs improved the thermal stability of PLA-based nanofibers. Fourier transform infrared spectroscopy results demonstrated good adhesion between ND nanofillers and PLA matrix. Following the addition of NDs, the four mechanical indicators, tensile strength, Young’s modulus, elongation at break and fracture toughness of ND/PLA composite nanofiber membranes increased accompanied by the later decrease with the rise of ND content. The four indicators achieved their respective maximum value at 1 wt% ND content, which revealed 2.4 fold increase of tensile strength, 1.6 fold augment of Young’s modulus, 1.4 fold elevation of elongation at break, and 4.8 fold growth of fracture toughness, respectively. Compared with the tensile strength and Young’s modulus of neat PLA, ND nanofillers exhibited the best reinforcing ability for PLA-based composite nanofibers, which was attributed to the effective interfacial adhesion between PLA and rigid ND particles and the good dispersion of NDs in PLA matrix. The ND/PLA composite nanofiber membranes with improved mechanical properties possess potential application in biomedical engineering.

Colour fading effect of indigo-dyed cotton denim fabric by CO2 laser

Abstract: In this study, denim fabric was treated with CO2 laser under different combination of laser process parameters, i.e. resolution and pixel time, in different irradiation directions, i.e. warp and weft directions. Experimental results revealed that the laser power increased with increment of resolution and pixel time. The colour fading effect was increased with the increase of laser power but an optimum colour fading effect was achieved. Meanwhile, the colour levelness of the laser treated denim fabric was good according to quantitative measurement. However, it was noted that the direction of laser irradiation did not affect the colour fading effect and colour levelness.

The application of gas plasma technologies in surface modification of aramid fiber

Abstract: Gas plasma technologies have been utilized to improve the surface properties of fibers in many applications from textiles to fiber-reinforced composites since the 1960s. This review discusses the feasibility and characteristics of gas plasma technologies applied to aramid fiber. The influence of various plasma treatments on the chemical and mechanical properties of aramid fibers as well as fiber-reinforced composites is described. The moisture regain is emphasized to achieve good bonding between aramid fibers and polymer matrix and to enhance the surface modification of aramid fiber and mechanical properties of the composites. More sophisticated technologies such as plasma-initiated graft polymerization are also discussed to highlight very recent developments.

Evaluation of effective electrospinning parameters controlling gelatin nanofibers diameter via modelling artificial neural networks

Abstract: The aim of this work was to evaluate the effective parameters for prediction of the electrospun gelatin nanofibers diameter using artificial neural network (ANN) technique. The various sets of electrospinning process including temperature, applied voltage and polymer and solvent concentrations were designed to produce pure gelatin nanofibers. The obtained results by analyzing Scanning Electron Microscopy (SEM) images indicated that the produced nanofibers diameter was in the range of 85 to 750 nm. Due to the volume of the data, k fold cross-validation method was used for data setting. Data were divided into the five categories and trained and tested using ANN technique. The results indicated that the network including 4 input variables, 3 hidden layers with 10, 18 and 9 nodes in each layers, respectively, and one output layer had the best performance in the testing sets. The mean squared error (MSE) and linear regression (R) between observed and predicted nanofibers diameter were 0.1531 and 0.9424, respectively. The obtained results demonstrated that the selected neural network model had acceptable performance for evaluating involved parameters and prediction of nanofibers diameter.

Synthesis of silver nanoparticles with sericin and functional finishing to cotton fabrics

Abstract: This research presents a novel strategy to fabricate multi-functional cotton textiles. In this study, silver nanoparticles-sericin (Ag NPS-sericin) hybrid colloid has been prepared using sericin as reducing agent and dispersing agent. Cotton fabrics was oxidized selectively with sodium periodate (NaIO4) to generate oxidized cotton fabrics, and which has then been finished using Ag NPS-sericin hybrid colloid prepared to obtain multi-functional cotton textiles. The finished cotton fabric not only possessed excellent antibacterial activity, but also it was modified functionally by sericin protein, which endowed antibacterial cotton fabrics relatively smooth surface and good wear ability. Fourier transform infrared spectrogram confirmed that sericin protein was grafted onto cellulose fibers. Ag NPs were characterized by UV-Vis spectroscopy, transmission electron microscope (TEM) and X-ray powder diffraction (XRD). The results of SEM, X-ray photoelectron spectroscopy (XPS) and EDS confirmed that silver nanoparticles and sericin been loaded successfully on the surface of cotton fabrics. The antibacterial experiments showed bacterial reduction rates of S.aureus and E.coli were able to reach above 99 %. After washing 20 times, it showed still good antibacterial activity at over 95 % against S.aureus and E.coli.

Production of carboxymethylcellulose fibers from waste lignocellulosic sawdust using NaOH/NaClO2 pretreatment

Abstract: In this study, waste lignocellulosic sawdust was converted to carboxymethylcellulose (CMC) by the combination process of an inorganic base (NaOH) and a weak acid (monochloroacetic acid, MCA). Optimum conditions for the pretreatment were studied on the basis of lignin and hemicellulose removal. NaOH and MCA concentration, reaction time, and operating temperature were the parameters studied to acquire the optimized conditions for the production of CMC. Degree of substitution (DS) and solubility were greatly influenced by the changes in the experimental conditions. DS increased on increasing the concentration of NaOH and MCA but the effect was more profound during the NaOH loading. A maximum DS of 0.5 was obtained on the treatment with 20 % NaOH and 20 % MCA concentration at 50 °C, 150 rpm for 4 h. 1.28 g CMC/g cellulose was obtained at the optimized set of conditions. Structural information of cellulose and CMC was obtained using IR spectroscopy and the surface morphology was studied using field emission scanning electron microscopy (FESEM). Carboxymethylcellulose showed lower crystallinity than the native cellulose extracted from sawdust which was studied using X-ray diffraction.

Synthesis, structure and thermal protective behavior of silica aerogel/PET nonwoven fiber composite

Abstract: In recent years, flexible, mechanically strong and environmental friendly thermal insulation materials have attracted considerable attention. In this work, silica aerogel/polyethylene terephthalate (PET) nonwoven fiber composite with desirable characteristics was prepared via a two-step sol-gel process followed by an ambient drying method through immersing the PET nonwoven fiber into silica sol. The silica aerogel particles were characterized by FTIR, FE-SEM, TGA and nitrogen adsorption analysis. The morphology and hydrophobic properties of neat PET nonwoven fiber and its silica aerogel composite were also investigated. For studying thermal protective properties, the thermal diffusivity was calculated from temperature distribution curves. The mean pore size of 11 nm, the surface area of 606 m2/g and the total pore volume of 1.77 cm3/g for the silica aerogel particles in the composite are obtained from nitrogen adsorption analysis, indicating the aerogel can maintain its high porosity in the nonwoven composite structure. Silica aerogel particles were efficiently covered the surface of the PET fibers and completely filled the micron size pores of the nonwoven fiber leading to a stronger hydrophobicity and higher thermal insulation performance in the aerogel composite samples compared to the neat PET nonwoven. In this regard, an almost 64 % decrease in the thermal diffusivity was achieved with 66 wt% silica aerogel.

Polyamide-grafted-multi-walled carbon nanotube electrospun nanofibers/epoxy composites

Abstract: Multi-walled carbon nanotubes were grafted by polyamide via Friedel-Crafts acylation and in-situ polymerization routes using γ-Phenyl-e-caprolactone to obtain MWCNT-PA. Poly(azo-naphthyl-imide) (PI) was also prepared in this work. Afterward, electrospun nanofibers were prepared using grafted nanocarbon fibers in two different polymers; polyimide (PI) and PI/polyaniline (PANI). The obtained nanofibers were used to reinforce an epoxy resin. Scanning and transmission electron microscopy revealed fibrous nature of these composites. The tensile modulus of epoxy composites reinforced by electrospun PI/PANI nanofibers (25.3 GPa) was considerably higher than PI nanofibers (19.8 GPa). In addition, thermal stability of PI/PANI nanofiber composites was superior as having 10 % gravimetric loss at 623–671 °C and glass transition temperature of 289–297 °C relative to MWCNT-PA/PI nanofiber-based system. The addition of 1 to 3 wt% MWCNT-PA/PI/PANI filler content enhanced the electrical conductivity of DGEBA/MWCNT-PA/PI/PANI from 3.33 to 5.99 S cm−1.

Mechanical properties and water absorption of short snake grass fiber reinforced isophthallic polyester composites

Abstract: Natural fiber composite replaces the conventional and synthetic materials in many fields especially in light weight applications. The randomly oriented short snake grass fiber reinforced isophthallic polyester composites are prepared by hand lay-up technique and finally compression molded. The various length and weight fraction of fiber are used in composite fabrication. The mechanical properties and water absorption under various climatic conditions are examined according to the prescribed standard. SEM image revealing the fiber pullout and breakage of the tensile and impact fractured composite specimens has been analysed and compared with control through scanning electron microscope. The result shows that the mechanical properties increase with increase in fiber length and weight fraction of the composites. The rate of water absorption increases with increase in temperature and time. Obtained experimental tensile strength of the composite is compared with various theoretical models such as Series, Hirsch’s, Halpin-Tsai, Modified Halpin-Tsai and Modified Bowyer & Brader’s and the obtained inferences are discussed.

Electrospinning and microwave absorption of polyaniline/polyacrylonitrile/multiwalled carbon nanotubes nanocomposite fibers

Abstract: Electrical conductive nanocomposite fibers were prepared with polyaniline (PANI), polyacrylonitrile (PAN) and multi-walled carbon nanotubes (MWCNTs) via electrospinning. The morphology and electrical conductivity of the PANI/PAN/MWCNTs nanocomposite fibers were characterized by scanning electron microscope (SEM) and Van De Pauw method. Electrical conductivity of nanocomposite fibers increased from 1.79 S·m−1 to 7.97 S·m−1 with increasing the MWCNTs content from 3.0 wt% to 7.0 wt%. Compared with PANI/PAN membranes, the mechanical property of PANI/PAN/MWCNTs nanocomposites fiber membranes decreased. The microwave absorption performance of composite films was analyzed using waveguide tube, which indicated that with the thickness increasing the value of RL reduced from −4.6 to −5.9 dB.

Effect of peroxide and softness modification on properties of ramie fiber

Abstract: Ramie fiber is one of the natural cellulose fibers that have undergone rapid development due to its good performance. This study confirmed that hydrogen peroxide and isopropyl alcohol can be used as very efficient agents for simultaneous removal of non-cellulosic substances and improvement of ramie fiber properties. The factors influencing the properties of modified fiber with combined chemicals were investigated. Optimum treatment conditions were achieved at 85 °C, 60 min, pH 11.0, hydrogen peroxide concentration 7 %, and isopropyl alcohol concentration 4 %. SEM, XRD, and FT-IR were used to elucidate the effects of preparation and modification. Results showed that fiber preparation and chemical modification process in the same bath solution could successfully remove most of the gummy materials. The treated fibers demonstrated improved softness, elongation, and fineness properties as compared to the alkali or peroxide method.

Fabrication of conductive fabric as textile electrode for ECG monitoring

Abstract: To develop textile electrodes for electrocardiogram (ECG) monitoring, cotton woven fabric was coated with polypyrrole via electrochemical polymerization process A two-step polymerization process was conducted, ie via chemical polymerization to make cotton fabric electric conductive and then electrochemical polymerization Evaluations of the electrodes in terms of electrical resistance and electrochemical impedance spectroscopy were made to examine the progress of electric performances after each processing step The results show that, after electrochemical polymerization process, the conductivity of the electrode is increased and the quality in transferring electrical signals improved

Aerogel based nanoporous fibrous materials for thermal insulation

Abstract: In this research work, the thermo physiological properties of polyester/polyethylene nonwoven composite wraps of varying thicknesses impregnated with aerogel were studied and compared. The SEM images were also taken to compare the physical configuaration of the aerogel based fibrous composites. Specific thermal properties like thermal conductivity, thermal resistance, thermal diffusivity and thermal absorptivity were measured using alambeta instrument. The air permeability of the thermal wraps was measured in air permeability tester. The relative water vapor permeability and absolute water vapor permeability was measured in Permetest. These tests were conducted to understand thermal properties, air and water vapor permeability of flexible aerogel based composites with nanoporous structure. The results of the experiments were statistically analyzed and found to be within confidence intervals.