Search

The increasing demand for high-performance materials has led to the development of natural fiber composites as an alternative to synthetic fiber composites. However, the low thermal conductivity of natural fibers limits their use in advanced applications. In this study, we have developed polyaniline-coated natural fiber composites to enhance their thermal properties. The methodology of this study involves the preparation of natural fiber composites using polyaniline-coated natural fibers as a reinforcement and a bio-based resin as a matrix. The composites were then coated with polyaniline, which was synthesized through chemical oxidation of aniline monomer. The coated composites were characterized using various analytical techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis to evaluate their structural, morphological, and thermal properties. The materials used in this study were natural fibers, bio-based resin, aniline monomer, ammonium persulfate, and hydrochloric acid. The gap identification of this study is the low thermal conductivity of natural fiber composites, which limits their application in advanced fields such as aerospace, automotive, and electronics. The problem identification is the lack of a cost-effective and eco-friendly method to enhance the thermal properties of natural fiber composites. The results of this study showed that the polyaniline-coated natural fiber composites exhibited enhanced thermal conductivity compared to the uncoated composites. The improvement in the properties of the composites was attributed to the high conductivity of polyaniline and its ability to form a continuous conductive network throughout the composite matrix. The development of polyaniline-coated natural fiber composites provides a cost-effective and eco-friendly approach to enhance the thermal properties of natural fiber composites. This approach has the potential to expand the use of natural fiber composites in advanced applications, leading to a sustainable and greener future. [ABSTRACT FROM AUTHOR]

The use of virgin and recycled plastic macro fibers as reinforcing elements in construction materials has recently gained increasing attention from researchers. Specifically, recycled fibers have become more attractive owing to their large-scale availability, negligible cost, and low environmental footprint. In this work, we investigate the benefits related to the use of fully-recycled synthetic fibers as dispersed reinforcement in Fiber Reinforced Cement Composites (FRCCs). In light of the reference performance of FRCCs including virgin polypropylene (PP) fibers only, the mechanical response of composites reinforced with polyolefin filaments treated with a sol-gel silica coating and polyethylene terephthalate (PET)/polyethylene (PE) cylindrical draw-wire fibers is here assessed through three-point bending tests. Remarkably, recycled polyolefins lead to a notable enhancement in terms of peak strength and post-crack energy dissipation capability. This improvement is ascribed to both the flattened shape of fibers and the surface coating, which turns out to be very effective at strengthening the fiber-to-matrix bond. On the other hand, PET/PE fibrous reinforcement generally leads to a lower toughness, if compared to the virgin fibers. However, no reduction in terms of peak stress is evidenced. Balancing the significance of mechanical performance and environmental sustainability in the framework of a circular economy approach, both fully-recycled fibers at hand can be regarded as promising candidates for innovative structural applications.

A four-phase concentric cylinder model with interface effect is proposed. Based on the model and surface/interface theory, a generalized self-consistent method is developed for predicting the effective transverse thermal conductivity of nano coated fiber composites. An analytical solution is obtained for effective thermal conductivity by applying complex elastic theory. Comparisons with the finite element analysis (FEA) and other available theoretical methods show the efficiency and the accuracy of the present method. Numerical results show the dependence of the effective thermal conductivity of the nano composites when the size of fiber and coating are on the order of nanometer. The effects of the interface thermal constant and the coating thermal conductivity on the effective thermal conductivity are discussed. The present solutions are useful to the theoretical research and engineering applications of the nano coated fiber composites. [ABSTRACT FROM AUTHOR]

We propose a new splicing technique by precisely aligning and directly connecting coated fibers with a capillary. The assembled splice for 1.3-μm single-mode fibers with an 80 μm cladding and a 125 μm coating can provide a low insertion loss of 0.2 dB and a high return loss of over 46 dB. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1453-1456, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27636 [ABSTRACT FROM AUTHOR]

Food samples are usually analyzed with a preliminary step of sample preparation, because pesticide residues are present in low concentrations and embedded in complex matrixes. Solid phase microextraction (SPME) is a solvent-free extraction technique that is fast, relatively inexpensive, easily automated, and versatile with high sample throughput. Analyte extraction, pre-concentration, and introduction into the analytical instrument are achieved in a single uninterrupted process. SPME uses fibers coated with a polymeric stationary phase that can be either a solid, liquid, or a combination of both. The fiber coating extracts the target analytes from a complex food matrix by absorption in the case of liquid coatings or adsorption in the case of solid coatings. The SPME fiber is then transferred into the analytical instrument for desorption and analysis of the target analytes. The use of sol-gel technology in the production SPME coated fiber has helped to increase the range of pesticide residues that can be extracted with the SPME technique. [ABSTRACT FROM AUTHOR]

Constructional and micro-dynamic process of the water-transferring composite was analyzed. This composite can transmit water to soil with a self-adjustable speed to ensure the survival of seedlings in arid and semi-arid regions when it is embedded in soil around the roots of the seedlings. It is obtained from natural plant fiber coated with a colloid made by mixing a certain proportion of polyacrylamide and montmorillonite. The rules of water being transmitted to soil by the coating under different condition were tested by M-30 quick moisture measure instrument. The process of water-desorption of the coating material was investigated by a Perkin Elmer Diamond S II thermal multi-analyzer. Moreover, the micro-dynamic behavior was detected by a FEIQuanta 2000 environment scanning electron microscope. The results demonstrate that montmorillonite has lower water-desorption energy barrier than polyacrylamide and can lose water more easily. montmorillonite particles bridge up to be the main water-transmit material at low water potential (when the soil relatively dry or when the temperature is high), and they break bridge at high water potential while the polyacrylamide acts as the main water-transmit material. [ABSTRACT FROM AUTHOR]

A statistical constitutive model, which takes into account the effect of strain rate, was presented to describe the stress— strain relationship of unidirectional fiber-reinforced composites (UFRC). To verify its reliability, tensile tests on two kinds of UFRC: a glass fiber-reinforced polyster and a unidirectional SiC/Al composite wire, were carried out at different strain rates, and the stress—strain curves were obtained. The testing results show that the strength and ductility of the two composites all increase with increasing strain rate. Simulated stress—strain curves, derived from the constitutive model, fit the tested results well, which indicates that the model is valid and reliable. [ABSTRACT FROM AUTHOR]

Abstract: A new solid-phase microextraction (SPME) fiber is fabricated through ultra violet irradiation polymerization of ametryn-molecularly imprinted polymer on the surface of anodized–silylated aluminum wire. The prepared fiber is durable with very good chemical and thermal stability which can be coupled to GC and GC/MS. The effective parameters on the fabrication and application procedures such as spraying mode, ultra violet irradiation (polymerization) time, number of sprayings and polymerizations, pH and ionic strength of sample and extraction time were optimized. This fiber shows high selectivity with great extraction capacity toward triazines. SPME and GC analysis of ametryn, prometryn, terbutryn, atrazine, simazine, propazine and cyanazine using the fabricated fiber result in the detection limits of 9, 32, 27, 43, 51, 74 and 85ngmL−1, respectively. The reliability of the prepared fiber in real samples has been investigated and proved by using spiked tap water, rice, maize and onion samples. [Copyright &y& Elsevier]

Abstract: In this study, thermal wave method is applied to predict the non-steady effective thermal conductivity of composites with coated fibers, and the analytical solution of the problem is obtained. The Fourier heat conduction law is applied to analyze the propagation of thermal waves in the fibrous composite. The scattering and refraction of thermal waves by a cylindrical fiber with coating in the matrix are analyzed, and the results of the single scattering problem are applied to the composite medium. The wave fields in different material layers are expressed by using the wave function expansion method, and the expanded mode coefficients are determined by satisfying the boundary conditions of the layer. The theory of Waterman and Truell is employed to obtain the effective propagating wave number and non-steady effective thermal conductivity of composites. As an example, the effects of the material properties of the coating on the effective thermal conductivity of composites are graphically illustrated and analyzed. Analysis shows that the non-steady effective thermal conductivity under higher frequencies is quite different from the steady thermal conductivity. In the region of lower frequency, the effect of the properties of the coating on the effective thermal conductivity is greater. Comparisons with the steady thermal conductivity obtained from other methods are also presented. [Copyright &y& Elsevier]

Abstract: Porous hydroxyapatite (HA) ceramic was fabricated by 3D fiber network. These fibers as channel underprops were treated by surface coating with acidic macromolecule glue. The solidified coated fibers in ceramic block could form run-through channels and also etch stripes on channel walls for cell attachment. The channels formed in sintering process by fibers volatilization may be directed artificially according to beforehand design of structure for ceramic block. The results showed that the pore characteristics and the inner structure of the sample made from this technique have settled for essential requests of porous bioceramic. The channels in sintered scaffold shown in SEM (scanning electron microscopy) micrographs have directional connection, equal distribution, intact configuration and existence of thin stripes on inner walls. All of these characteristics have met requests for tissue cell developing, transplanting and attaching. The samples have appropriate interconnectivity and reasonable structure with equable pore-arranging and uniform size of pore. XRD (X-ray diffraction) patterns of sample indicated no major change of the crystalline structure. [Copyright &y& Elsevier]

Stress and couple stress distributions are determined analytically for a coated fiber in an infinite micropolar matrix, loaded remotely by classical symmetric stresses. The determined stresses are then compared with those predicted by Cauchy theory, a size dependence is predicted in the framework of micropolar theory, and when the fiber’s diameter is much larger than the characteristic length of the matrix, the classical prediction can be recovered. The exact average stress in a fiber for a fiber-matrix system (without interphase) is also compared with that approximately derived by the average equivalent inclusion method (AEIM), based on the micropolar Eshelby tensor given by Cheng and He [Int. J. Eng. Sci. 35 (7) (1997) 659], the results show that the approximate AEIM method can give an accurate prediction for the size dependence of the average stress in a fiber. A micro–macro transition method is also proposed to determine effective in plane moduli of a heterogeneous micropolar material, the effective shear and in plane bulk moduli of a micropolar composite with coated fibers are derived analytically by extending Mori–Tanaka’s method to a micropolar composite, and the effective shear and in plane bulk moduli for a two-phase fiber composite (without interphase) are also obtained as a special case. The results show that the effective in plane bulk modulus is identical to that obtained by Cauchy theory, however the effective shear modulus depends on fiber’s diameter, it increases with decreasing fiber’s diameter at the same fiber volume fraction, and the classical prediction is recovered when the fiber’s diameter becomes large compared to the matrix characteristic length. [Copyright &y& Elsevier]

Infrared silver halide fibers were studied concerning the optical degradation induced by photodarkening. Infrared transmittance decreased notably in the shorter wavelength (near-infrared) region by the exposure to ultraviolet (UV) or visible light below a wavelength of ~600 nm. Black paint was tentatively coated on the unclad fiber for photodarkening protection, but the infrared transmittance of the fiber decreased heavily due to the evanescent wave absorption by the paint. To reduce this absorption loss, a fluorocarbon polymer was coated between the fiber core and the black paint. Consequently, efficient transmission was realized in the infrared region except for the 7-10-μm wavelength range, where the fluorocarbon polymer has a strong absorption band. In the 2-7-μm wavelength range, the fiber that was heated at 100°C in the polymer coating process exhibited higher transmittance than the original uncoated fiber. No optical degradation of the coated fiber was observed, even after irradiation with UV light for a period of 70 h [ABSTRACT FROM PUBLISHER]

The use of virgin and recycled plastic macro fibers as reinforcing elements in construction materials has recently gained increasing attention from researchers. Specifically, recycled fibers have become more attractive owing to their large-scale availability, negligible cost, and low environmental footprint. In this work, we investigate the benefits related to the use of fully-recycled synthetic fibers as dispersed reinforcement in Fiber Reinforced Cement Composites (FRCCs). In light of the reference performance of FRCCs including virgin polypropylene (PP) fibers only, the mechanical response of composites reinforced with polyolefin filaments treated with a sol-gel silica coating and polyethylene terephthalate (PET)/polyethylene (PE) cylindrical draw-wire fibers is here assessed through three-point bending tests. Remarkably, recycled polyolefins lead to a notable enhancement in terms of peak strength and post-crack energy dissipation capability. This improvement is ascribed to both the flattened shape of fibers and the surface coating, which turns out to be very effective at strengthening the fiber-to-matrix bond. On the other hand, PET/PE fibrous reinforcement generally leads to a lower toughness, if compared to the virgin fibers. However, no reduction in terms of peak stress is evidenced. Balancing the significance of mechanical performance and environmental sustainability in the framework of a circular economy approach, both fully-recycled fibers at hand can be regarded as promising candidates for innovative structural applications. [ABSTRACT FROM AUTHOR]

• BNC improve mechanical properties of cement mortars. • Coating polypropylene fibers with BNC improve fiber-cement interactions. • BNC-powder exhibited better behavior compared to BNC-gel. • Cellulosic nano-fibers increase homogeneity by filling the pores. In this study, the potential effect of bacterial nano-cellulose on mechanical properties of cement mortar was evaluated. For this purpose, bacterial nano-cellulose (BNC) directly as powder and gel (0.1, 0.3, and 0.5 wt%), and indirectly as coated onto the polypropylene fibers were used in the preparation of cement paste in order to investigate the effect of each method on the flexural strength, compressive strength and water absorption of specimens. Results indicated that samples containing BNC gel and powder enhanced mechanical properties. However, BNC-gel indicated inferior properties compared to powder. The maximum increase in flexural strength between all samples was observed in the specimens containing 0.5% of BNC powder, which was 104%, compared to the control sample. In addition, utilizing nanofibers decreased the water absorption of cement mortar. The water absorption of specimens containing 0.1% of the gel fibers and 0.3% of powder was decreased by 26% and 37%, respectively. According to scanning electron microscopy (SEM) analysis, the roughness and specific surface of polypropylene fibers coated with BNC were increased. This can improve the interaction of these fibers with the cement matrix. The results show clearly that the application of BNC nanofibers improves the mechanical properties of cement paste and workability of polypropylene fibers. [ABSTRACT FROM AUTHOR]