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The application of distributed fiber optic strain and temperature measurement can be utilized to address a multitude of measurement tasks across a diverse range of fields, particularly in the context of structural health monitoring in the domains of building construction, civil engineering, and special foundation engineering. However, a comprehensive understanding of the influences on the measurement method and the sensors is essential to prevent misinterpretations or measurement deviations. In this context, this study investigated the effects of moisture exposure, including various salt solutions and a high pH value, on a distributed strain measurement using Rayleigh backscattering. Three fiber optic sensors with different coating materials and one uncoated fiber were exposed to five different solutions for 24 h. The study revealed significant discrepancies (∼38%) in deformation between the three coating types depending on the surrounding solution. Furthermore, in contrast to the prevailing literature, which predominantly describes swelling effects, a negative deformation (∼−47 μ ε ) was observed in a magnesium chloride solution. The findings of this study indicate that corresponding effects can impact the precision of measurement, potentially leading to misinterpretations. Conversely, these effects could be used to conduct large-scale monitoring of chemical components using distributed fiber optic sensing. [ABSTRACT FROM AUTHOR]

This investigation aims to use Sabai grass fiber as a substitute reinforcement in epoxy-based composite systems, which is environment friendly and performs similarly to other natural fibers. Composite laminates are prepared with treated and untreated Sabai fibers reinforcement layered in different orientations using vacuum resin transfer molding method. Fabricated composite laminates have been evaluated for their mechanical properties (tensile strength, flexural strength, and impact strength). The effect of varying concentrations (3%, 5%, 7%, and 9 wt.%) of NaOH treatment and fiber reinforcement angle on Sabai fiber-reinforced composite laminates on its physical and mechanical properties are experimentally evaluated. The specimen made with 5 wt.% of NaOH-treated has shown maximum tensile properties because of the higher fiber concentration in the composite laminate. The thickness of fibers gets reduced as the central voids contract after the treatment. The treated strand reinforced (0°/0°/0°/0°) composite laminate has maximum tensile (103.15 MPa) and flexural strength (143 MPa). In addition, it has a higher density (1.20 g/cm3) and less porosity contents (0.70%). The untreated reinforcement has a higher impact strength. The adhesion mechanism at the fiber matrix interface has been studied using field emission scanning electron microscopy by analyzing the fiber surface morphology after treatment and in the fractured samples. The correlation of the mechanical properties of the laminate has been discussed with consideration of interfacial adhesion mechanism, fiber pull-outs, and fiber-matrix cracking phenomenon. FTIR analyses confirm the removal of the peak at around 1735 cm−1 that belongs to the acetyl group of hemicellulose attributed to C=O stretching vibration, and the peak at 1253 cm−1 is associated with the lignin, which is in close agreement with chemical analysis. [ABSTRACT FROM AUTHOR]

In recent years, the use of natural fibers has increased in manya applications, particularly in automotive industry, owing to their lightweight, high specific strength, recyclability, and ecological properties. This study aims to investigate the influence of copper filler on fiber-coated hybrid composite through mechanical and machining (CNC milling) characterization. Initially, the copper filler was characterized using the energy dispersive X-ray (EDX), particle size analysis (scanning electron microscope), and component analysis (X-ray diffraction (XRD)). Four coated natural fiber/wire mesh hybrid composite designs were developed and identified as hemp/mesh/ramie composite [HMR (1-4)]. In this work, 16 experiments were designed by central composite design (CCD) using Design Expert 13, considering the spindle speed, feed rate, and composite type as input parameters. The results indicate that copper filler particle proportion influenced the tensile strength and impact resistance of the HMR hybrid composite (16% & 15.42%). A fiber coating with a higher infill percentage reduces water absorption. The responses were estimated based on the resultant force and surface roughness, which were influenced by the weight percentage of the filler. In all the spindle speeds, the resultant forces are increased with raise in feed rates (120–600 mm/min). [ABSTRACT FROM AUTHOR]

The application of distributed fiber optic strain and temperature measurement can be utilized to address a multitude of measurement tasks across a diverse range of fields, particularly in the context of structural health monitoring in the domains of building construction, civil engineering, and special foundation engineering. However, a comprehensive understanding of the influences on the measurement method and the sensors is essential to prevent misinterpretations or measurement deviations. In this context, this study investigated the effects of moisture exposure, including various salt solutions and a high pH value, on a distributed strain measurement using Rayleigh backscattering. Three fiber optic sensors with different coating materials and one uncoated fiber were exposed to five different solutions for 24 h. The study revealed significant discrepancies (∼38%) in deformation between the three coating types depending on the surrounding solution. Furthermore, in contrast to the prevailing literature, which predominantly describes swelling effects, a negative deformation (∼−47 με) was observed in a magnesium chloride solution. The findings of this study indicate that corresponding effects can impact the precision of measurement, potentially leading to misinterpretations. Conversely, these effects could be used to conduct large-scale monitoring of chemical components using distributed fiber optic sensing.

The demands for fiber-reinforced polymer material (FRPM) have rapidly grown over the years. Nevertheless, it has many hurdles in enhancing electrical properties. The electrical properties of the FRPM have been extensively investigated by researchers for various reinforcement, matrix, coating, and chemical treatments. However, the past surveys fail to elaborate on different electrical property measurements and the behavior of various FRPMs. So, the current study aims to critically review the FRPM fabrication methods, measuring techniques, and electrical performances. The electrical performance indexes are assessed by the dielectric constant (permittivity), dissipation factor, dielectric loss factor, electrical resistivity/ conductivity, and EMI shielding effectiveness (absorption, reflection, and multiple reflections). Also, this study compiles the effect of performance influencing factors such as fiber loading, matrix type, chemical treatment, size/loading filler, and coating. Finally, the study indicates the pathway and directions for sustainable fiber-reinforced polymer sensor development for textile, agriculture, and biomedical applications. [ABSTRACT FROM AUTHOR]

A lack of dimensional stability of worsted fabrics when laundering leads to a rapid increase in wool textile waste. Dry cleaning is thus highly recommended; however, it requires solvent(s), which are not eco-friendly. The aim of this study was to produce a machine-washable, 100% worsted wool woven as an outer fabric for men's suit jacket that is also water-repellent in order to reduce the number of washes required during use. Chemical treatments were applied through successive paddings, using a blend of aqueous dispersion of polyurethane and polysiloxane (PUPX) for shrink-proofing/dimensional stability, followed by a second blend of an aqueous emulsion of fluorotelomer methacrylate and paraffin/hydrocarbon waxes (C6PW) polymers for water-repellency. The dimensional change of the finished fabric did not exceed 2%, meeting Woolmark requirements AW-1. Zeta potential measurements confirm that the fabric coated with PUPX has an overall anionic nature, which allows the good adhesion of the successive cationic C6PW polymer blend used in the second padding. Additionally, Scanning Electron Microscopy (SEM) analysis confirmed the good adhesion of the first blend (PUPX) to the wool fiber surface and inter-fiber bonding. After the application of (C6PW) resin, the fabric exhibited durable water repellency with a 5/5 spray test rating after 10 washes and dimensional stability, as well as high resistance to wear and abrasion, while retaining a soft feel and good flexibility. [ABSTRACT FROM AUTHOR]

In this work, resin‐derived carbon coating was prepared on carbon fibers by polymer impregnation pyrolysis method, then silicoboron carbonitride powder was prepared by mechanical alloying, and finally carbon fiber‐reinforced silicoboron carbonitride composites were prepared by hot‐pressing process. The effects of sintering densification and fiber coating on microstructure, mechanical properties, thermal shock resistance, and failure mechanisms of the composites were studied. Fiber bridging hinders the sintering densification, causing more defects in fiber‐dense area and lower strength. However, higher sintering temperature (1800–2000°C) can improve mechanical properties significantly, including bending strength, vickers hardness, and elastic module, because further sintering densification enhances matrix strength and fiber/matrix bonding strength, while the change of fracture toughness is not obvious (2.24–2.38 MPa·m1/2) due to counteraction of higher debonding resistance and less pull‐out length. However, fiber coating improves fracture toughness greatly via protecting carbon fibers from chemical corrosion and damage of thermal stress and external stress. Due to lower coefficient of thermal expansion, lower fiber loading ratio, less stress concentration at the fiber/matrix interface, and better defect healing effect, lower sintering temperature favors thermal shock resistance of composites, and thermal shock recession mechanisms are the damage of interface. [ABSTRACT FROM AUTHOR]

• Hexagonal boron nitride coatings on SiC fibers via a wet-chemical coating. • Continuous roll-to-roll coating process. • Pyrolysis process for hexagonal and near-stoichiometric BN from the raw materials boric acid and urea. • Fiber coatings for CMC reinforcement. Hexagonal BN fiber coatings and BN powders were prepared by pyrolysis of the raw materials boric acid and urea in an atmosphere consisting of hydrogen and nitrogen. The powders were used to determine the appropriate mixing ratio of the raw materials to produce BN with the desired composition and crystal structure. The pyrolysis of boric acid and urea in a molar mixing ratio of 1:2 resulted in a BN that was hexagonal and had a near-stoichiometric composition. To prepare a solution for the coating of fibers, boric acid and urea were dissolved in an ethanol-water mixture. The coating was then applied to SiC filaments using a continuous roll-to-roll dip-coating process. It could be shown by SEM/EDS that BN layers were applied to the fibers. No significant bridging in the fiber bundle was found. Furthermore, it could be demonstrated by grazing incidence x-ray diffraction that the layers were crystalline. [ABSTRACT FROM AUTHOR]

A new approach to improving the interfacial compatibility of SiCf/Ti-6Al-4V composites by using fiber coating coupled with subsequent heat treatment was presented. The SiCf/Ti-6Al-4V composites with C-coated and C/Mo-coated fibers were prepared using the foil-fiber-foil method and subsequently heat treated in vacuum at 750 °C to obtain several kinds of the SiCf/Ti-6Al-4V composites with different interfacial characteristics. Interfacial microstructures of these composites were systematically characterized by means of scanning electron microscopy and X-ray energy dispersive spectroscopy to investigate the interfacial microstructure evolution and reaction dynamics. The effects of interfacial microstructures on interfacial mechanical properties were also investigated using thin-slice fiber push-out tests. The results show that the brittle interfacial reaction layer of TiC in the C-coated SiCf/Ti-6Al-4V composites was obviously thickened and some microvoids even formed near the matrix with increasing heat treatment durations, whereas the matrix adjacent to Mo coating in the C/Mo-coated SiCf/Ti-6Al-4V composites gradually transformed into a ductile β-Ti layer. Interfacial shear strengths of the C/Mo-coated composites were slightly increased with increasing the heat treatment time, while those of the C-coated composites were remarkably improved. Critical issues on modifying interfacial compatibility of the SiCf/Ti composites for further improving the mechanical behavior of the composites were discussed.

We demonstrate a record net gain of 11-dB in a 34-cm fiber length for 300-nm broadband single-mode Cr-doped crystalline core fibers (CCFs) fabricated by precise laser-heated pedestal growth (LHPG) and tetrahedral chromium (Cr4+) optimization. The core composition of the CCF is a Cr4+-doped: yttrium aluminum garnet (YAG). The record gain achieved is mainly due to (1) precise LHPG of the CCFs to fabricate a longer fiber length of 34-cm employing a novel predictive control to constantly maintain conical molten-zone shape in the growth process and (2) the Cr4+ concentration optimization up to 150% utilizing thicker dielectric coating and thermal annealing and then the Cr4+ optimization by polarization pumping. The net gains of 6.4 and 11-dB are measured with and without Cr4+ optimization, respectively. The 72% of net gain improvement is directly related to Cr4+ optimization in the CCFs, as evidenced by SQUID and EPMA measurements, whereas the optimized thicker coating of the Cr4+ concentration provided the dominant net gain improvement of 33% in the CCFs. The development of the CCF is essential for practical use in the next-generation broadband fiber amplifier applications. [ABSTRACT FROM AUTHOR]

Oxide ceramics have excellent high temperature performance, superior thermal and chemical stability, which can be used in high temperature oxidizing environments, while oxide ceramics generally have low toughness and are prone to catastrophic damage... Oxide ceramics can be reinforced by high performance ceramic fibers to improve the fracture strength and fracture toughness, thus expanding its application in high-temperature components such as aero-engine combustion chambers and tail nozzles. The interface between fiber and matrix is an important factor that determines the performance of the composites. By tailoring the interface, the energy dissipation mechanisms such as fiber debonding and fiber pull-out can be brought into play to avoid the catastrophic damage of the composites. This review paper summarizes the recent research progress of the oxide fiber/oxide ceramic matrix composites interface. The mechanical properties of the interface and the design principles of the interface engineering are discussed, and types of interfaces and coating preparation methods are reviewed. [ABSTRACT FROM AUTHOR]

Diffusion of the analytes across the diffusion boundary layers and subsequently through the fiber coatings determines the extraction kinetics of solid‐phase microextraction in aqueous matrices. Besides, the matrix effects can distort the behaviors of the analytes transferring across the diffusion boundary layers. However, these processes were always studied via certain simplification, which often left the mass transfer through the fiber coatings unconsidered and the matrix effects partially investigated. Herein, a comprehensive study on the mass transfer processes in direct immersion solid‐phase microextraction was presented. Under different agitation speeds, it was determined that the mass transfer coefficients across the diffusion boundary layers were three to six orders larger than those through the fiber coatings. However, the mass transfer across the diffusion boundary layers was generally the major rate‐limiting step. In addition, the shuttle effect and the barrier effect, which were responsible for accelerating and retarding the extraction kinetics, respectively, were found to be the dominant matrix effect alternately under different agitation speeds. This study comprehensively illustrated the major rate‐limiting step and the dominant matrix effects through recording the mass transfer coefficients. [ABSTRACT FROM AUTHOR]

There is an urgent need to develop efficient and reliable coating materials for solid phase microextraction (SPME), in order to quantify and monitor pollutants in environmental waters. Herein, a highly graphitized porous carbon/reduced graphene oxide (PC/rGO) was successfully synthesized by pyrolysis of metal organic framework / graphene oxide precursors, and used as a SPME coating for ultrahigh enrichment of polycyclic aromatic hydrocarbons (PAHs) from water. The as-prepared PC/rGO exhibited high degree of graphitization, abundant number of micro/mesopores along with exceptional thermal stability, making it an ideal SPME coating material. The PC/rGO fiber offered an ultrahigh enrichment factor for PAHs (up to 126057), which could be attributed to the multiple interactions between the PC/rGO and PAHs, including hydrophobic and π - π interactions, partitioning, and mesopore filling effect. In the analysis of PAHs, the PC/rGO fiber showed a wide linearity (0.007–100 ng mL−1), low limits of detection (0.0005–0.005 ng mL−1), and good repeatability (RSDs <10.1%, n = 5) under optimized conditions. The established method was applicable for ultrasensitive determination of PAHs in different environmental waters and showed satisfactory recoveries. This study provides a novel way for constructing thermally stable SPME coating having efficient extraction performance. [Display omitted] • SPME fiber was coated by highly graphitized porous carbon/reduced graphene oxide. • Extraction relied on hydrophobicity and π-π stacking, partitioning and pore filling. • This fiber can ultra-highly enrich and ultra-sensitively determine PAHs in water. • The work offers a promising way for development of stable and efficient fiber coating. [ABSTRACT FROM AUTHOR]

When a thin liquid film flows down on a vertical fiber, one can observe the complex and captivating interfacial dynamics of an unsteady flow. Such dynamics are applicable in various fluid experiments due to their high surface area-to-volume ratio. Recent studies verified that when the flow undergoes regime transitions, the magnitude of the film thickness changes dramatically, making numerical simulations challenging. In this paper, we present a computationally efficient numerical method that can maintain the positivity of the film thickness as well as conserve the volume of the fluid under the coarse mesh setting. A series of comparisons to laboratory experiments and previously proposed numerical methods supports the validity of our numerical method. We also prove that our method is second-order consistent in space and satisfies the entropy estimate. [ABSTRACT FROM AUTHOR]

Fibers are an important form of forensic evidence, but their evidential value can be severely limited when the identified characteristics of the fibers are common, such as blue cotton. Detecting chemical fiber treatments offers an avenue to further classify fibers and to improve their evidential value. In this report, we investigate the potential of fluoropolymer fiber coatings, used to impart oil and water-repellent properties in fabrics, for differentiating between fibers. The thin nature of these fiber surface modifications creates an analytical challenge for their detection on a single fiber, a typical sample size for forensic evidence. Specifically, pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) has shown promising selectivity but the sensitivity of the method is not adequate for single-fiber analysis of fluorinated coatings. To overcome this challenge, we utilize a newly developed elemental ionization source, plasma-assisted reaction chemical ionization (PARCI). The high sensitivity of py-GC-PARCI-MS for elemental fluorine analysis offers selective and sensitive detection of fluorinated pyrolysates among the non-fluorinated pyrolysates of the fiber core. As a result, fluoropolymer coatings are detected from 10-mm single-fiber samples. The technique is applied for classification of 22 fiber types, resulting in 4 distinct groups via hierarchical cluster analysis based on similarity of fluorine pyrograms. These results present the first study to classify fibers based on fluorinated coatings, and highlight the potential of py-GC-PARCI-MS for forensic analyses. [ABSTRACT FROM AUTHOR]

In order to develop a practical process for the carbon coating on SiC fiber, high-speed and continuous pyrocarbon (PyC) coating process are under development by using a continuous CVD furnace with open-ends structure. The effects of process gas and winding speed have been investigated. It was revealed that the growth rate of PyC is in proportion to winding speed and the flow rate of process gas. PyC growth rate was reached up to 250 nm/min, which is several hundred higher than those of conventional CVI/CVD methods This results indicates that the mass production of PyC coated SiC fiber without unexpected residual deformation (torsion and curvature) is possible. And, the mass production and practical use of SiC/SiC using PyC coated SiC fiber will be largely promoted. [ABSTRACT FROM AUTHOR]

In spite of the effectiveness of the fiber coatings on interface modification of carbon fiber reinforced magnesium matrix composites, the cost and exclusive equipment for the coatings preparation are usually ignored during research work. In this paper, pyrolytic carbon (PyC) and TiO 2 were coated on carbon fiber surface to study the effects of fiber coatings on interfacial microstructure and mechanical properties of carbon fiber reinforced AZ91D composites (C f /AZ91D composites). It was indicated that both the two coatings could modify the interface and improve the mechanical properties of the composites. The ultimate tensile strength of the TiO 2 -C f /AZ91D and the PyC-C f /AZ91D composite were 333 MPa and 400 MPa, which were improved by 41.7% and 70.2% respectively, compared with the untreated-C f /AZ91D composite. The microstructure observation revealed that the strengthening of the composites relied on fiber integrity and moderate interfacial bonding. MgO nano-particles were generated at the interface due to the reaction of TiO 2 with Mg in the TiO 2 -C f /AZ91D composite. The volume expansion resulting from the reaction let to disordered intergranular films and crystal defects at the interface. The fibers were protected and the interfacial reaction was restrained by PyC coating in the PyC-C f /AZ91D composite. The principle to select the coating of fiber was proposed by comparing the effectiveness and cost of the coatings. [ABSTRACT FROM AUTHOR]

The toughness of geopolymer matrix composites (GMC) has been identified as a limiting factor to their use in structural applications. Advanced ceramic matrix composites (CMC), which also are limited by brittle behavior, have shown gains in toughness through careful tailoring of the interface between fiber and matrix. This can create various crack dissipating mechanisms and prevent premature composite failure. Such interface modification has already been applied to a fiber reinforced geopolymer and while the resulting composite showed a reduction in brittle behavior, the modified interface produced an unacceptable loss in modulus without any other well-defined quantitative gains. Information gathered from other studies suggests the large decrease in modulus observed in the GMCs with the weakened interface may have been the result of poor matrix properties stemming from an inadequate cure. Therefore, this current study explores the effects of initial cure time on composite performance by measuring the mechanical properties GMCs with a modified interface. GMCs containing unidirectional Nextel 610 fiber were cured under two different sets of process conditions to better understand the influence of matrix properties. Additionally, specimens consisted of cleaned and carbon coated fiber surfaces, in an attempt to evaluate extremes of interfacial strength. Mechanical properties were then evaluated for comparison to determine if improved geopolymer matrix properties would allow a weakened interface to yield performance gains more in keeping with expectations based on CMC's. The results of the study indicate that specimens with carbon coating benefited from the longer initial cure time. The average increase in flexural modulus and strength over samples with one hour initial cure time was ~65% and ~170% respectively. Stress-strain behavior of the carbon-coated specimens with an extended cure time also indicated a greater degree of damage tolerance as compared to those without interphase. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) alloy is widely studied as a potential biodegradable implant material in clinical orthopedics. However, its uncontrollable corrosion rate under physiological conditions has severely limited its development. To enhance the corrosion resistance and biocompatibility of AZ31 Mg alloys substrate, the polycaprolactone/collagen/cerium-hydroxyapatite (PCL/Col/Ce-HA) fiber coating is prepared by employing the electrospinning technique. The scanning electron microscope reveals that the PCL/Col/Ce-HA fiber coating with 5 wt% of Ce-HA exhibits the densest surface with a uniform fiber size of 396 nm, which provides a firm physical barrier against the corrosive ions. Furthermore, the enhanced adhesion strength of the PCL/Col/Ce-HA fiber coating will prevent the coating from falling off from the Mg substrate during the long-term immersion periods, and therefore ensures their durability. Electrochemical tests indicate that the annual corrosion rate of PCL/Col/Ce-HA fiber coating with 5 wt% Ce-HA is almost 30 times lower than the bare AZ31 Mg alloy. The lowest hydrogen evolution volume and relatively stable pH variations of the solution also confirm their effective protective ability. In addition, the cell assay indicates that the PCL/Col/Ce-HA fiber coating is beneficial for cell adhesion and growth, reflecting its excellent cell biocompatibility. The lowest hemolysis rate (2.72%) of PCL/Col/Ce-HA fiber coating also meets the biomedical material application requirements. [Display omitted] • The PCL/Col/Ce-HA fiber coating is prepared using the electrospinning technique. • The incorporation of Ce-HA improves the adhesion strength of fiber coatings. • The PCL/Col/Ce-HA fiber coating exhibits enhanced corrosion protection performance. • The PCL/Col/Ce-HA fiber coating shows excellent biocompatibility for MG-63 cells. [ABSTRACT FROM AUTHOR]

Fiber reinforced composites containing a ZrB 2 matrix are prepared by reactive melt infiltration, using a Zr based intermetallic compound. The reactive melt infiltration process is further characterized by determining the contact angle of the different melt and preform elements. Two different methods for boron powder impregnation of the preforms, which form ZrB 2 during Zr 2 Cu melt infiltration, are evaluated. Degradation of fibers and different fiber coatings for Zr 2 Cu melt are evaluated and the microstructure of the infiltrated samples is investigated by means of XRD and SEM. [ABSTRACT FROM AUTHOR]

The coatings of optical fibers are generally characterized by a multi-layer coating structure. In this work, the mathematical modeling of two immiscible non-Newtonian fluids for optical fiber coating inside a straight annular die is developed in the form of a nonlinear differential equation with nonhomogeneous boundary conditions. Two non-Newtonian fluids, namely power law and Phan-Thien-Tanner fluids, are used in the primary and secondary coating dies, respectively. An exact solution is obtained for velocity fields and temperature distributions for the primary and secondary coating resins. The thickness of coated fiber optics is also calculated for both layers. The effect of different emerging parameters on the solution is discussed and sketched. [ABSTRACT FROM AUTHOR]

A metal organic framework-polyaniline (MOF/PANI) nanocomposite was electrodeposited on a stainless steel wire and used as a solid phase microextraction (SPME) fiber coating. The electropolymerization process was carried out under a constant deposition potential and applied to the corresponding aqueous electrolyte containing aniline and MOF particles. The employment of MOFs with their large and small cages and 3-D structures in synthesizing a nanocomposite was assumed to be efficient constitutes to induce more non-smooth and porous structures, approved by scanning electron microscopy (SEM) images. Three different MOFs were incorporated to synthesize the desired nanocomposites and the preliminary experiments showed that all of them, particularly the one containing MOF2, have higher extraction performances in compared with PANI. The applicability of the new fiber coating was examined by headspace-solid phase microextraction (HS-SPME) of some chlorobenzenes (CBs) from aqueous samples. Influencing parameters on the synthesize and extraction processes including the electrodeposition voltage and its duration time, the weight ratio of PANI and MOF, the ionic strength, desorption temperature and time, and extraction time and temperature were optimized. The developed method was validated by analyzing the spiked distilled water and gas chromatography–mass spectrometry (GC–MS). Under optimum condition, the relative standard deviation (RSD%) values for a double distilled water spiked with the selected CBs at 20 ng L −1 were 5–8% ( n = 3) and the detection limits were below 0.2 ng L −1 . The linear dynamic range (LDR) of the method was in the concentration range of 0.5–1000 ng L −1 ( R 2 > 0.9994). The fiber-to-fiber reproducibility was found to be in the range of 4–7%. Eventually, various real-water samples were analyzed by the MOF/PANI-based HS-SPME and GC–MS and the relative recovery values were found to be in the range of 92–98%. [ABSTRACT FROM AUTHOR]

• Functional COF with 3D framework and multiple interactions was proposed for selective SPME. • Good selectivity towards planar, non-coplanar PCBs and organic analogs was achieved. • Efficient adsorption of 15 PCBs was achieved with enhancement factor up to 10305. • Better SPME enhancement factor of PCBs was obtained in the face of commercial fibers and other COFs. • Excellent sensitivity and recovery yields of PCBs in environmental samples were accomplished. Developing functional fiber coating for selective solid phase microextraction (SPME) of trace pollutants is critical in environmental analysis. Herein, the novel covalent organic frameworks (COFs) with three-dimensional (3D) frameworks and multiple interactions were designed and presented for the selective SPME of polychlorinated biphenyls (PCBs). Using tetra (p-aminophenyl) methane (TAM) and 1,3,5-triformylphloroglucinol (Tp) as the monomers, the 3D TpTAM-COF was synthesized and possessed a large specific surface area, high thermal stability, and spatial selectivity toward PCBs. Characterizations such as morphology, XPS, XRD, thermal stability, and enhancement factors (EFs) were studied. Multiple interactions including π-π conjugation, hydrophobic interaction, and selectivity toward non-planar structure were adopted, which resulted in a superior adsorption affinity toward PCBs on TpTAM-COF. Under the optimal conditions, the spatial selectivity toward PCBs, organic analogs (o -dichlorobenzene, biphenyl) and polycyclic aromatic hydrocarbons (naphthalene, pyrene, and anthracene)) was achieved. Efficient and selective adsorption of fifteen PCBs was fulfilled with the highest EF up to 10305. Using the HS-SPME-GC-MS method, the recoveries of PCBs in the river water and soil samples were determined to be 84.8 ± 7.8% ∼ 117.2 ± 8.5% (n = 3) and 84.4 ± 8.6% ∼ 114.7 ± 7.6% (n = 3), respectively. Compared with most commercial SPME fibers and other COFs-based fibers, the resultant TpTAM-COF-coated fibers possessed higher selectivity and EFs of PCBs. It proposed a promising approach for selective SPME of trace PCBs by multiple interactions in the steric structure of 3D COFs. [ABSTRACT FROM AUTHOR]

Owing to the severe toxicity and health hazard of polychlorinated biphenyls (PCBs) to humans, the efficient separation and determination of PCBs in dairy products is highly desirable and challenging. In this study, a new solid-phase microextraction (SPME) fiber was prepared by coating of a new molecularly imprinted phenolic resin (MIPR) in situ using a covalent grafting method. The MIPR coating, synthesized from 4-mercaptophenol and glutaraldehyde, provides rough surface with more adsorption sites; furthermore, the coating has a thickness of 1.0 μm, resulting in rapid equilibration. This new device has the advantages such as less coating peeling from the substrate and selective recognition enhancement of the coating. A highly selective and sensitive SPME-based method was developed using the developed fiber, coupled with GC-MS/MS, for the determination of polychlorinated biphenyls (PCBs) in milk samples. The developed MIPR-HS-SPME-GC-MS/MS method showed low detection limits (0.012–0.066 pg mL−1), good linearity (r ≥ 0.9991), satisfactory recovery (77.5–116.7%), efficient enhancement factors (362–2034 folds) and good reusability (50 cycles). Therefore, this is a simple and efficient strategy for monitoring trace PCBs in complex samples and is a potential alternative for improving the selectivity of SPME fibers by introducing MIPR into the fiber coating. [Display omitted] • A new molecularly imprinted phenolic resin fiber coating was prepared in suit preparation. • As-prepared SPME fiber coating exhibited high selective and enhancement factors for PCBs. • A MIPR-HS-SPME-GC-MS/MS method developed for PCBs detection in complex samples. • Selective enrichment and determination of polychlorinated biphenyls in milk was achieved. [ABSTRACT FROM AUTHOR]

The performance of fiber optic gyroscope (FOG) exhibits temperature dependence due to nonreciprocity phase shift in the fiber coil induced by environmental temperature variation. Research on temperature characteristic is meaningful for high precision FOG working in harsh environment. In this letter, modeling of thermal-induced rate error for FOG with environmental temperature ranging from -40°C to 60 °C is investigated. Temperature dependence of fiber refractive index, thermal expansion of the fiber, and thermal stress of the fiber coating are all considered in our model. Experiments with different temperature change rates between -40°C and 60 °C are performed to verify the effectiveness of the proposed model. Experimental results show great agreement with theoretical values. [ABSTRACT FROM PUBLISHER]

Highlights: [•] A fast and robust DI-SPME–GC–ToFMS method for determination of triazole pesticides in fruits was developed. [•] A newly developed matrix-compatible SPME coating was utilized. [•] No sample pre-treatment required. [•] Very good sensitivity achieved within short extraction time. [•] Accurate quantitative results could be easily achieved. [Copyright &y& Elsevier]

Abstract: This research was aimed to study the potential use of recycled glass fibers-derived three dimensional geomaterial (8FG MAT) obtained from industrial glass fiber wastes to innovate a sustainable, cost-effective geosynthetic for ground improvement in problematic soil applications. The ready availability, high tensile strength, lightweight and non-biodegradable characteristics of glass fibers further elevate their advantages as compared to the presently adopted geosynthetics in soft soil reinforcement condition. In this study, mechanical properties of recycled glass fibers and their ‘8’ shape form samples as well as the pullout resistance force of 8FG MAT were investigated by considering glass fibers' layer thickness, shape formation and orientation in a laboratory scale model. It was observed that the tensile and yield strengths of overall geomaterial samples significantly increase as strip layers thickness increase. Results from both the tensile strength and pullout resistance force indicated similar trend of increasing in strength values with test conducted using other type of geosynthetics in various soil media to simulate the action of different soil conditions at real sites. [Copyright &y& Elsevier]

Abstract: Analytical method for the residues of boscalid in blueberries was developed. Fungicide residues were determined by solid-phase microextraction (SPME) coupled to gas chromatography with micro-electron capture (μ-ECD) detector. The effect of pH values and fiber coatings were studied. The SPME fiber coating selected was 100μm PDMS. The method is selective with adequate precision and high accuracy and sensitivity. Recoveries ranged within the 98–104% range, and detection and quantification limits were 1.33 and 4.42μg/kg, respectively. Statistical parameters indicated the occurrence of matrix effect; consequently calibration was performed on spiked samples. Degradation of boscalid was studied in a blueberry field located in Concordia, Argentina, with fruits from Emerald and Jewel varieties. The degradation of boscalid in both blueberry varieties studied followed a first order rate kinetics and the half-life for boscalid was 5.3 and 6.3days for Emerald and Jewel cultivars, respectively. [Copyright &y& Elsevier]

Abstract: Since the introduction of solid-phase microextraction (SPME) in the 1990s, different types of coating have shown their crucial role in extraction efficiency. In the past decade, unique properties of nanostructured materials (e.g., large surface area, and remarkable thermal, mechanical and chemical stability) led to their application as desirable coatings in SPME. The current review classifies nanomaterial–based SPME coatings as based on carbon, polymer, silica or metal nanoparticles. It also briefly discusses new developments and methods in preparing nanomaterial-based SPME coatings. [Copyright &y& Elsevier]

Abstract: Two kinds of mesoporous cellular foams (MCFs), including mesoporous silica materials (MCF-1) and phenyl modified mesoporous materials (Ph-MCF-1), were synthesized and for the first time used as fiber-coating materials for solid-phase microextraction (SPME). By using stainless steel wire as the supporting core, four types of fibers were prepared by sol–gel method and immobilized by epoxy-resin method. To evaluate the performance of the home-made fibers for SPME, seven brominated flame retardants (BFRs), including tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS) and related compounds were selected as analytes. The main parameters that affect the extraction and desorption efficiencies, such as extraction temperature, extraction time, desorption time, stirring rate and ionic strength of samples were investigated and optimized. The optimized SPME coupled with high performance liquid chromatography (HPLC) was successfully applied to the determination of the seven BFRs in water samples. The linearity range was from 5.0 to 1000μgL−1 for each compound except TBBPS (from 1.0 to 1000μgL−1), with the correlation coefficients (r 2) ranging from 0.9993 to 0.9999. The limits of detection of the method were 0.4–0.9μgL−1. The relative standard deviations varied from 1.2 to 5.1% (n =5). The repeatability of fiber-to-fiber and batch-to-batch was 2.5–6.5% and 3.2–6.7%. The recoveries of the BFRs from aqueous samples were in the range between 86.5 and 103.6%. Compared with three commercial fibers (100μm PDMS, 85μm PA and 65μm PDMS/DVB), the MCFs-coated fiber showed about 3.5-fold higher extraction efficiency. [Copyright &y& Elsevier]

Abstract: Vinyl-SBA-15 mesoporous organosilica was synthesized and used as coating material of solid-phase microextraction (SPME) by two coating techniques (direct coating and sol–gel). The synthesized vinyl-SBA-15 organosilica had highly ordered mesoporous structure, good thermal stability and a specific surface area of 688m2 g−1. The fibers prepared by two methods were evaluated by the extraction of non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene) and polar compounds (phenols). The results showed that the vinyl-SBA-15 fibers prepared by two methods exhibited high thermal stability (310°C for direct-coated and 350°C for sol–gel) and excellent solvent durability in methanol and acetonitrile. The fibers also presented much better extraction performance for both polar compounds (phenols) and non-polar compounds (BTEX), compared to commercial polydimethylsiloxane (PDMS) fiber, as well as wide linear ranges, low detection limits (0.008–0.047μgL−1 for BTEX, sol–gel; 0.15–5.7μgL−1 for phenols, direct-coated), good repeatabilities (RSDs less than 5.4% for BTEX) and satisfying reproducibilities between fibers (RSDs less than 5.8% for BTEX). The self-made fibers were successfully used for the analysis of BTEX and phenols in three aqueous samples including tap water, mineral water and lake water, which demonstrated the applicability of the vinyl-SBA-15 fibers. [Copyright &y& Elsevier]

Abstract: In this work, a molecular sol–gel imprinting approach has been introduced to produce a fiber coating for selective direct immersion solid-phase microextraction (SPME) of caffeine. The polymerization mixture was composed of vinyl trimethoxysilane and methacrylic acid as vinyl sol–gel precursor and functional monomer, respectively. Caffeine was used as template molecule during polymerization process. The prepared fibers could be coupled directly to gas chromatography/mass spectrometry (GC/MS) and used for trace analysis of caffeine in a complex sample such as human serum. The parameters influencing SPME such as time, temperature and stirring speed were optimized. The prepared coating showed good selectivity towards caffeine in the presence of some structurally related compounds. Also, it offered high imprinting capability in comparison to bare fiber and non-imprinted coating. Linear range for caffeine detection was 1–80μgmL−1 and the limit of detection was 0.1μgmL−1. The intra-day and inter-day precisions of the peak areas for five replicates were 10 and 16%, respectively. [Copyright &y& Elsevier]

Abstract: A novel approach was developed for the fabrication of solid-phase microextraction (SPME) fiber by coating stainless steel fiber with a polymeric ionic liquid (PIL) through covalent bond. The stainless steel fiber was sequentially coated with a gold film by replacement reaction between Fe and Au when immerged in chloroauric acid, assembled with a monolayer of 3-(mercaptopropyl) triethoxysilane on the gold layer through the Au–S bond, and coated with a silica layer by the hydrolysis and polycondensation reaction of the surface-bonded siloxane moieties and the active silicate solution. Then, 1-vinyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium chloride ionic liquid was anchored on the silica layer by covalent bond, and the PIL film was further formed by free radical copolymerization between 1-vinyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazdium and vinyl-substituted imidazolium with azobisisobutyronitrile (AIBN) as initiator. Parameters influencing the preparation of PIL fiber were optimized, and the developed SPME fiber has a coating thickness of ∼20μm with good thermal stability and long lifetime. The performance of the PIL fiber was evaluated by analysis of polycyclic aromatic hydrocarbons (PAHs) in water samples. The developed PIL fiber showed good linearity between 0.5 and 20μgl−1 with regression coefficient in the range of 0.963–0.999, detection limit ranging from 0.05 to 0.25μgl−1, and relative standard deviation of 9.2–29% (n =7). This developed PIL fiber exhibited comparable analytical performance to commercial 7μm thickness PDMS fiber in the extraction of PAHs. The spiked recoveries for three real water samples at 0.5–5μgl−1 levels were 49.6–111% for the PIL fiber and 40.8–103% for the commercial PDMS fiber. [Copyright &y& Elsevier]

The influence of fiber coatings on the effectiveness of the propylene-glass copolymerization reaction has been analyzed. The mechanical properties of fiber reinforced composites depend on the effective stress transfer fiber-matrix, which is possible if the adhesion between them is strong. An alternative method to improve the adhesion is the establishment of chemical links between matrix-fiber such as in situ polymerization. The study was carried out on sandwich composite of polypropylene and fiber glass, with and without acrylic coating. Adhesion is analyzed through its influence on the mechanical properties of the composites. The copolymerization reaction acts as an effective bonding agent, when it is carried out on uncoated fibers, making this proposal technological attractive. [ABSTRACT FROM AUTHOR]

Abstract: Two kinds of porous carbon materials, including carbon aerogels (CAs), wormhole-like mesoporous carbons (WMCs), were synthesized and used as the coatings of solid-phase microextraction (SPME) fibers. By using stainless steel wire as the supporting core, six types of fibers were prepared with sol–gel method, direct coating method and direct coating plus sol–gel method. Headspace SPME experiments indicated that the extraction efficiencies of the CA fibers are better than those of the WMC fibers, although the surface area of WMCs is much higher than that of CAs. The sol–gel–CA fiber (CA-A) exhibited excellent extraction properties for non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene), while direct-coated CA fiber (CA-B) presented the best performance in extracting polar compounds (phenols). The two CA fibers showed wide linear ranges, low detection limits (0.008–0.047μgL−1 for BTEX, 0.15–5.7μgL−1 for phenols) and good repeatabilities (RSDs less than 4.6% for BTEX, and less than 9.5% for phenols) and satisfying reproducibilities between fibers (RSDs less than 5.2% for BTEX, and less than 9.9% for phenols). These fibers were successfully used for the analysis of water samples from the Pearl River, which demonstrated the applicability of the home-made CA fibers. [ABSTRACT FROM AUTHOR]

A rapid synthesis of highly ordered phenyl-functionalized MCM-41 (Phen-MCM-41-R) mesoporous silica was performed by using cetyltrimethylammonium bromide as the template and tetraethyl orthosilicate as the silica source under alkaline conditions within 3 h. The samples were characterized by fourier transform infrared (FTIR) spectra, small-angle X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, and thermogravimetric analysis (TGA). It has been found that the resultant material still preserves a desirable two-dimensional P6 mm hexagonal structure and has large specific surface area, large pore volume, and good thermal stability. High extraction efficiency of dibutyl phthalate (DBP) is obtained using the phenyl-MCM-41-R as a fiber coating of solid-phase microextraction. Three hours for the self-assembly step is enough during the process of synthesis and has no unfavorable effect on the extraction behavior of phenyl-MCM-41-R as a mesoporous fiber coating. [ABSTRACT FROM AUTHOR]

Solid-phase microextraction (SPME) has gained widespread acceptance for analyte matrix separation and preconcentration. Recently, the number of publications evaluating new coatings has grown considerably, but relatively few data are currently available dealing with production of fibers with properties to be used for SPME of ionic species. This paper reviews the different approaches of SPME for sample preparation in analysis of ionic species coupled mainly with high-performance liquid chromatography and ion chromatography. Typical SPME applications for the determination of charged species are summarized in terms of fibers used, extraction and desorption conditions, main experimental parameters, and specific examples. [ABSTRACT FROM AUTHOR]

This paper presents the numerical and experimental investigation of fluid flow and mass transfer in an irradiator tube. After applying the synthetic coating material for cushioning and protection, optical fibers or wires are drawn through a glass tube where UV light from the surrounding irradiators cause curing of the coating material. During this curing process, fumes are generated, which needs to be flushed out of the tube before it diffuses to the glass wall and causes tube smoking, a problem faced by the industries. Analytical calculations are first done to study the effect of laminar and turbulent flow, flow rate and tube diameter. Numerical simulation for the purging air flow and mass transfer of the generated chemical species is then done using a computational model and results presented. Irradiator tube flows with regular and enhanced lip at exit and without lip are all simulated. The mass concentration of generated species near the tube wall is found high for regular and extended lip (causes tube smoking), but low for no lip (suggests no smoking and hence desirable). Computations are also done for larger tube diameter, which gives lowest species concentration. Experiments are performed and they support the simulated results. [ABSTRACT FROM AUTHOR]

Abstract: The liquid film remaining on a wire withdrawn from a liquid bath and forced through an annular die is experimentally investigated on a dedicated facility. An optical laser-based technique recently introduced to study liquid-film instabilities on small-radius cylinders allows the measurement of the mean final thickness and wave characteristics. Experimental results are compared to analytical predictions obtained with simple models specifically derived for this configuration and based on liquid-film properties (density, viscosity and surface tension) and operating parameters (wire speed and die dimensions). The experimental measurement of surface-perturbation features (wave amplitude, wavelength and amplification factor) as a function of the operating parameters reveals the presence of a single wavelength for low values of the withdrawing velocity and a progressive wave disappearance for high speeds, in accordance with theoretical predictions. [Copyright &y& Elsevier]

Abstract: Optical fibers are key components in telecommunication technologies. Apart from optical specifications, optical fibers are expected to keep most of their physical properties for 10–20 years in current operating conditions. The reliability and the expected lifetime of optical links are closely related to action of the chemical environment on the silica network. However, the coating also contributes largely to the mechanical properties of the fibers. The aim of this work was to study the strength and the mechanical behavior of the silica optical fibers in an acid environment and with a permanent deformation. A container with ammonium bifluoride acid salt was plunged into hot water at different temperatures (55 and 75°C). This emitted acid vapors which attacked the optical fibers for a period of 1–18 days. An aging study was performed on silica optical fibers with standard polyacrylate coating and with hermetic carbon coating. A dynamic two-point bending bench at different faceplate velocities (100, 200, 400 and 800μm/s) was used. For comparison, the same dynamic measurements were also carried out on non-aged fibers. After acid vapor condensation, salt crystal deposits on the fibers were displayed using an electron scanning microscope. These crystals became visible to the naked eye from the seventh day. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to develop metal coated textile fibres for application in textile electrodes and as a substrate for further functionalisation of the fibres. A polyaramide woven structure was used as substrate and selected because of its excellent mechanical properties and thermal resistivity. Direct plating of copper at this substrate did not give good results, therefore first polypyrrole was deposited chemically. The deposition steps are optimized in this investigation and the obtained layers are characterized with different methods. Typical thicknesses of 0.5 to 3 μm were obtained for polypyrrole and copper layers, which were dependent of the deposition time. The coated fibre structures showed excellent electroconductive properties. [Copyright &y& Elsevier]

Abstract: A liquid atomization method based on meniscus perturbation and a micro air jet was studied. A meniscus on a thin needle with a diameter was constantly perturbed by the sinusoidal oscillation of the needle, and a liquid film was dispersed by the air jet. This atomization method can spray high viscosity media with its print pattern confined to a narrow band of about 1mm at the center of the air jet. [Copyright &y& Elsevier]

Hybrid organic–inorganic fibers and carbon fibers were coated with TiO2 by liquid phase deposition (LPD). Continuous films were easily accessible on untreated carbon fibers after short mineralization times, whereas the density of nucleation sites on the hybrid substrates was increased by hydroxylation. The photocatalytic activity of TiO2 powder prepared by LPD was investigated and the material showed its best performance after heat treatment at 300–400 °C. Due to their better thermal stability at these temperatures, carbon fiber filaments were predominantly used as substrates for LPD TiO2. The photocatalytic activity of the coated fibers per illuminated surface area was found to be higher than that of LPD particles and even higher than that of commercial TiO2 powders normally used in suspension for photocatalytic wastewater treatment. [Copyright &y& Elsevier]

Storage modulus, loss modulus, and loss factor of unidirectional fiber composites of epoxy resin with glass fiber were determined with a Perkin Elmer DMA-7 equipment in three point bending mode. The fibers were coated with two different types of epoxy resins and the relationship between the thickness of coating and the composite viscoelastic properties were determined. A simple micromechanical model was used to analyze the data. [Copyright &y& Elsevier]

The effect of coating-fiber interfacial reaction on the tensile strength and fracture behavior of a squeeze cast 2024Al (Al–4.3wt.%Cu–1.5wt.%Mg) reinforced with Co-coated Al2O3 fiber has been investigated. The Co-coated Al2O3 fibers were exposed at various temperatures, ranging from 300 to 1000 °C, in a vacuum furnace before Al composite manufacture. At higher fiber annealing temperatures, the Co coating reacted with Al2O3 fiber to form Al9Co2 and Co2O3 phases. Substantial improvement in tensile strength and ductility of the Al composites occurred as the fiber annealing temperature increased and this was attributed to an increase in interfacial bonding strength between the coating and the fiber. In-situ fracture study and fractographic analysis of the Al composites suggested that (i) initial failure occurred by fiber cracking; and (ii) further failure included either interfacial debonding or severe matrix deformation, depending on interfacial bonding strength. [Copyright &y& Elsevier]

[Display omitted] • A novel approach to improving the interfacial compatibility based on fiber coating and subsequent heat treatment was presented. • A ductile fiber/matrix interfacial region with relativity lower interfacial shear strength in the SiC f /Ti-6Al-4V composites was obtained. • Interfacial microstructure evolution and reaction dynamics were systematically investigated. • Interfacial microstructures have crucial influence on the interfacial micromechanical properties, interfacial debonding and sliding behaviors. A new approach to improving the interfacial compatibility of SiC f /Ti-6Al-4V composites by using fiber coating coupled with subsequent heat treatment was presented. The SiC f /Ti-6Al-4V composites with C-coated and C/Mo-coated fibers were prepared using the foil-fiber-foil method and subsequently heat treated in vacuum at 750 °C to obtain several kinds of the SiC f /Ti-6Al-4V composites with different interfacial characteristics. Interfacial microstructures of these composites were systematically characterized by means of scanning electron microscopy and X-ray energy dispersive spectroscopy to investigate the interfacial microstructure evolution and reaction dynamics. The effects of interfacial microstructures on interfacial mechanical properties were also investigated using thin-slice fiber push-out tests. The results show that the brittle interfacial reaction layer of TiC in the C-coated SiC f /Ti-6Al-4V composites was obviously thickened and some microvoids even formed near the matrix with increasing heat treatment durations, whereas the matrix adjacent to Mo coating in the C/Mo-coated SiC f /Ti-6Al-4V composites gradually transformed into a ductile β-Ti layer. Interfacial shear strengths of the C/Mo-coated composites were slightly increased with increasing the heat treatment time, while those of the C-coated composites were remarkably improved. Critical issues on modifying interfacial compatibility of the SiC f /Ti composites for further improving the mechanical behavior of the composites were discussed. [ABSTRACT FROM AUTHOR]

This paper is concerned with the study of elasto-plastic deformation of the coating, and consequently, the changes in the states of stress in the constituent phases of a unidirectional fiber reinforced polymer matrix composite (PMC) under uniform thermal, hygral and hygrothermal loadings. A four-phase composite cylinder assemblage (CCA) model has been used for the analysis. The coating interphase between the fiber and the matrix has been taken to be of lower modulus and lower yield stress value than that of the matrix. Only those combinations of temperature and moisture content are considered which give rise to plastic deformation in the coating, other phases still remaining elastic. Plastic behaviour of the coating has been idealized by taking a linear work-hardening constitutive relation. [ABSTRACT FROM PUBLISHER]

Mechanical tensile behaviour studies are reported for discontinuous glassfibers reinforced polypropylene matrix. Samples were prepared by varying fiber/matrix coupling agents. The influence of strain rate on mechanical properties was analyzed in low and moderate (10-sec-1 to 10 sec-1) strain rate ranges. It was found that (1) in the moderate strain rate range, optical extensometry is invaluable in determining the actual specimen strain, (2) a drastic transition of mechanical tensile behaviour occurs with increasing strain rates, and (3) fiber/matrix coupling agents affect particularly stress-strain behaviour in the moderate strain rate range. A strong interfacial bond seems to improve the ability of the fibers to take up load in regions of matrix cracking; this leads to higher tensile strength. [ABSTRACT FROM PUBLISHER]

This study presents the development and characterization of nonwoven fiber mats (NWFs) with stimuli-controlled permeability. An ensemble of membranes was initially constructed by coating the fibers of polypropylene NWFs with a layer of poly ((N-isopropyl acrylamide)-co-(acrylic acid)) (PNIPAm-co-AA) hydrogel. Different coatings were produced by varying the PNIPAm/AA monomer ratio between 3.9 and 18.6. The thermo-responsive layer is expanded at room temperature and contracts when heated above its lower critical solution temperature (LCST). The resulting membranes were first characterized via laser scanning microscopy and fluorescence confocal microscopy to evaluate the thickness and morphology of the hydrogel layer. Microscopy shows uniform coating of the fibers, with a thickness comparable to the fiber diameter, and homogeneous filling of the pore space. The permeability of the NWFs was then evaluated using different solutes, namely an inorganic salt (sodium chloride), an organic acid (citric acid), and an amphiphilic drug (Doxorubicin). These tests consistently show that the flux of the solute is (1) higher at temperatures > LCST, where the hydrogel layer collapses and opens the pore space, and (2) decreases at room temperature (