Fiber Coatings Research Articles

Thermal stability of optical fiber coatings: comparison of experimental thermogravimetric approaches

Thermal decomposition of poly(methyl methacrylate) (PMMA) and four polymer coatings on optical fibers (single acrylate, dual acrylate, polyimide and a hard silicone) was studied via thermogravimetry (TG). Of main interest was the upper use temperature of the fibers, which can be estimated for a given continuous use time, assuming a certain failure criterion. Arrhenius parameters of the decomposition reaction (the activation energy and the pre-exponential factor) were determined via several model-free approaches: isothermal, Modulated TG (MTG) and four non-isothermal isoconversional approaches. The isothermal approach was considered as a benchmark for the other approaches. The MTG results disagreed markedly with the isothermal ones, and the discrepancy appears unrelated to the choice of the decomposition kinetics model. The non-isothermal isoconversion methods provide closer agreement with the isothermal data. Still, in a few examples, substantial discrepancies between the isothermal and non-isothermal data were observed. It is concluded that the isothermal approach is the best one to use for model-free determination of the Arrhenius parameters from TG. The temperatures for observation of the isothermal kinetics should be selected such that the preheating time is short in comparison with the decomposition time of the material under investigation.

Influence of porosity on anisotropic thermal conductivity of SiC fiber reinforced SiC matrix composite: A microscopic modeling study

The effect of porosity on the effective thermal conductivities calculation for continuous SiC fiber reinforced SiC matrix composites (SiCf/SiC) was studied in this work by finite element modeling. A three-dimensional representative volume element (RVE) containing detailed geometric features (fibers, matrix, fiber coatings and pores) was generated to rebuild the microstructure of SiCf/SiC and used to numerically calculate the effective transversal and longitudinal thermal conductivities of SiCf/SiC. Markworth model and parallel model were chosen as theoretical models to calculate the transversal and longitudinal thermal conductivities respectively. The numerical results obtained by RVE models were validated by comparison with the theoretical and experimental results. The results highlight the existing theoretical models cannot well predict the transversal thermal conductivity of SiCf/SiC with the existence of pores. In the analysis of the effect of porosity, real pore structure in SiCf/SiC was investigated to revel the relationship between porosity and the effective thermal conductivities. In the case of longitudinal thermal conductivity, the parallel model plus the linear term of porosity can still be used to predict the longitudinal thermal conductivity. As for the transversal thermal conductivity, a more proper Markworth model for SiCf/SiC transversal thermal conductivity calculation calibrated by incorporating porosity is proposed to efficiently calculate the transversal thermal conductivity at the end of this paper.

Influence of Fiber Coating and Polymer Modification on Mechanical and Thermal Properties of Bast/Basalt Reinforced Polypropylene Hybrid Composites

Natural fibers, such as kenaf, hemp, and flax, also known as bast fibers, offer several benefits such as low density, carbon dioxide neutrality, and less dependence on petroleum sources. Their function as reinforcement in polymer composites offers a great potential to replace a segment of the glass fiber-reinforced polymer composites, especially in automotive components. Despite their promising benefits, they cannot meet the structural and durability demands of automobile parts because of their poor mechanical properties compared to glass fibers. The focus of this research work was the improvement of the mechanical property profile of the bast fiber reinforced polypropylene composites by hybridization with natural high-performance basalt fibers and the influence of basalt fibers coating and polymer modification at the mechanical and thermal properties of the composites. The specific tensile strength of the composite with polymer tailored coating was 39% and the flexural strength was 44% higher than the composite with epoxy-based basalt fibers. The mechanical performance was even better when the bast/basalt hybridization was done in maleic anhydride modified polymer. This led to the conclusion that basalt fibers sizing and polymer modification are the deciding factors in defining the optimal mechanical performance of the composites by influencing the fiber-matrix interaction. The composites were analyzed for their mechanical, thermal, and morphological properties. The comparison of bast/basalt hybrid composite with bast/glass fibers hybrid composite showed a 32% higher specific flexural and tensile strength of the basalt hybrid composite, supporting the concept of basalt fibers as a natural alternative of the glass fibers.

Validation and expanded uncertainty determination of pesticides in water; and their survey on paddy rice irrigation water from Argentina

A solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry method was validated for the simultaneous determination of penconazole, cyproconazole, epoxiconazole, deltamethrin, azoxystrobin and kresoxim-methyl in paddy rice irrigation water. Different SPME fiber coatings and pH values were tested. Polydimethylsiloxane (PDMS) and pH 7 were chosen to optimize extraction. All pesticides presented a recovery percentage between 90.5 and 104.2%; and detection and quantification limits were 0.03 and 0.05 µg/kg for azoxystrobin and cyproconazole, 0.02 and 0.05 µg/kg for deltametrhin and epoxiconazole, 0.02 and 0.03 µg/kg for kresoxim-methyl, and 0.01 and 0.02 µg/kg for penconazole. The expanded uncertainty was estimated for all pesticides showing results lower than 20%. A total of 100 paddy rice irrigation water samples, collected in different rice fields from Argentina, were evaluated. The study showed that 86 of them presented residues. The concentrations exceeded the values that were set by European legislation and the frequencies were higher than 86% so the agricultural practices should be revised.

Molecularly imprinted polymer-based fiber array extraction of eight estrogens from environmental water samples prior to high-performance liquid chromatography analysis

A fiber array extraction method based on molecularly imprinted polymers (MIPs) as fiber coatings for the simultaneous enrichment of three classes of environmental estrogens (EEs) was proposed. The MIP fiber array mainly relies on the selective recognition of MIPs for target analytes and their structural analogs and utilizes the prepared fibers to develop an effective extraction device that can simultaneously adsorb multiple estrogens. The MIP fiber array showed increased adsorption throughput and greatly improved detection sensitivity in comparison with single MIP fiber. The proposed fiber array extraction followed by high-performance liquid chromatography (HPLC) analysis was also used to analyze three types of EEs in environmental water, and satisfactory recoveries of 80.8%-114.1% with the relative standard deviation (RSD) of 0.8%-12.4% were achieved. The detection limits of bisphenols (BPs) and parabens (PBs) were identical at 0.003 μg L−1, and the detection limits of phthalates (PEs) were 0.016 μg L−1. The MIP fiber array is an effective strategy to simultaneously enrich environmental pollutants, especially endocrine disruptors and can be successfully used to identify and quantify multiple estrogens.

Silicon-containing polyimides: synthesis, properties, and application as optical fiber light guide coatings

Organosoluble polyimides with tetramethyldisiloxane fragments in the main chain were synthesized by one-step high-temperature polycondensation and their properties were studied. Heat resistant polymers (Tg = 195–240 °C, T10% = 420–490 °C) were tested as protective coatings for quartz optical fibers. The new developed coatings have high thermal (72 h at 300 °C) and hydrolytic stability.

Metal-organic framework functionalized polymer coating for fiber optical methane sensors

Functional polymer coating integrated with optical fiber is an intriguing approach to develop low-cost point and distributed fiber sensors for large-scale applications. This paper presents the development of gas-sensitive coatings for both single-mode and multi-mode optical fibers through the application of polymer/nanocrystalline metal-organic frameworks (MOFs) composites as methane sensors for monitoring natural gas infrastructure. Silicone polymers based on PDMS with optimized optical and mechanical properties were developed as host materials for the well-known metal organic framework ZIF-8. Integration of ZIF-8 nanocrystals within the PDMS polymer modified the physical properties of the material and led to an enhancement of the CH4 solubility and permeability of the resulting film. The refractive indices, viscosities, and mechanical properties of the ZIF-8 functionalized polymers were optimized by adjusting the ZIF-8/polymer weight ratio and subsequently used as the fiber coating. Both multi-mode and single-mode optical fibers coated with the MOF-functionalized polymers showed scaled changes in transmitted power upon exposure to various concentration of CH4 in a N2 carrier gas. The variations in transmitted power through the fiber were the result of changes in evanescent wave interactions with the sensor coating due to shifts in the polymer cladding refractive index upon CH4 sorption. A methane detection limit of 1 % in nitrogen was achieved using both multimode fiber and D-shaped single mode fibers. Overall, our paper presents a low-cost approach to perform point and distributed sensing for CH4 through an innovative method of functional polymer material integration on optical fiber sensor platforms.

Analysis of 16 phthalate esters in wastewater from textile plants using headspace solid-phase microextraction and gas chromatography with mass spectrometric detection

Solid-phase microextraction (SPME) with a 100-µm polydimethylsiloxane (PDMS) fiber coupled to gas chromatography–mass spectrometry was used to determine 16 phthalate esters (PAEs) in wastewater from textile processing plants. Some of the 16 PAEs that exist as mixtures of isomers were identified and quantified. We investigated the matrix effect and evaluated a qualification and quantitation method for determining trace amounts of PAEs in wastewater from textile processing plants. The major advantages of this approach are the reduced matrix effects from the textile wastewater and the compatibility with the standard addition method (SAM) for PAE quantitation. Moreover, the developed method has low reagent and solvent consumption, does not require clean-up or evaporation steps and involves minimal sample manipulation. Two fiber coatings, 85-µm polyacrylate and 100-µm PDMS, were tested. The variables affecting SPME absorption, such as the sample temperature, extraction time and salt concentration, were studied. The final conditions were an extraction temperature of 95℃, an extraction time of 30 min and a salt concentration of 0.3 g/mL. The SAM was used to analyze and quantify samples. The linear range was between 5 and 20 µg/L, and the limits of detection of the method were between 0.5 and 5 µg/L. Finally, the precision of the phthalate quantitation was also evaluated.

Comparison of different fiber coatings for distributed strain measurement in cementitious matrices

Abstract. Distributed fiber optic strain measurement based on Rayleigh scattering has recently become increasingly popular in automotive and mechanical engineering for strain monitoring and in the construction industry, especially structural health monitoring. This technology enables the monitoring of strain along the entire fiber length. This article addresses integrating optical fibers of different coatings into the concrete matrix to measure the shrinkage deformations. However, previous studies do not give a clear statement about the strain transfer losses of fiber optic sensors in this application. In this context, three different coating types were investigated regarding their strain transfer. The fibers were integrated into fine-grained concrete prisms, and the shrinkage strain was compared with a precise dial gauge. The analysis shows a high correlation between the reference method and the fiber measurement, especially with the ORMOCER® coating. The acrylate coating used is also consistent in the middle area of the specimen but requires a certain strain introduction length to indicate the actual strain. The main result of this study is a recommendation for fiber coatings for shrinkage measurement in fine-grain concretes using the distributed fiber optic strain measurement. In addition, the advantages and disadvantages of the measurement method are presented.

Wet chemical deposition of BN, SiC and Si3N4 interphases on SiC fibers

Fiber coatings based on BN, BN/SiC and BN/Si3N4 were deposited on Hi Nicalon type S SiC fibers. The coating parameters were optimized using a design of experiments study. With optimized parameter sets, the coatings exhibited a high degree of coverage on the fibers and almost no fiber bridging could be observed. The coated fiber bundles are flexible and can be processed further by techniques such as filament winding. In comparison to a non-processed reference sample, the maximum tensile load of the fiber bundles with BN, BN/SiC and BN/Si3N4 coatings was reduced by only 5 %, 13 % and 10 %, respectively. The coated fiber bundles retained their tensile strength after thermal annealing up to 1650 °C in a nitrogen atmosphere for 0.5 h. SiCf/SiC samples with BN/SiC fiber coatings exhibited higher values of bending strength and strain-to-failure as a reference sample without fiber coating indicating the functionality of the fiber coatings.

Magnetohydrodynamic MgO/CuO‐water hybrid nanofluid flow driven by two distinct geometries

AbstractResearch regarding the heat transit mechanism of magnetohydrodynamic hybrid nanoliquid flow over contrasting flow profiles is predominantly employed in transpiration, coolants, fiber coatings, heat exchangers, and so on. Owing to this, we intend to dissect the heat transport behavior of MHD hybrid nanofluid flow past a cone as well as a wedge. For the analysis, we take nonlinear radiation and viscous dissipation into consideration with 30% of ethylene glycol and water (or EGW) as base fluid with suspended copper oxide (CuO) and magnesium oxide (MgO) nanoparticles. The Runge‐Kutta method with the shooting technique is utilized to figure out the deduced nonlinear gotverning equations. The influence of the concerned different admissible parameters on similar distributions (cone and wedge) are graphically illustrated and interpreted accordingly via computed numerical values. It is worth noting that the heat transport rate is greater past the cone rather than the wedge. The presence of CuO and MgO hybrid nanoparticles increases the heat transfer rate of the EGW base fluid.

Cytogenetic Mapping of 35 New Markers in the Alpaca (Vicugna pacos).

Alpaca is a camelid species of broad economic, biological and biomedical interest, and an essential part of the cultural and historical heritage of Peru. Recently, efforts have been made to improve knowledge of the alpaca genome, and its genetics and cytogenetics, to develop molecular tools for selection and breeding. Here, we report cytogenetic mapping of 35 new markers to 19 alpaca autosomes and the X chromosome. Twenty-eight markers represent alpaca SNPs, of which 17 are located inside or near protein-coding genes, two are in ncRNA genes and nine are intergenic. The remaining seven markers correspond to candidate genes for fiber characteristics (BMP4, COL1A2, GLI1, SFRP4), coat color (TYR) and development (CHD7, PAX7). The results take the tally of cytogenetically mapped markers in alpaca to 281, covering all 36 autosomes and the sex chromosomes. The new map assignments overall agree with human–camelid conserved synteny data, except for mapping BMP4 to VPA3, suggesting a hitherto unknown homology with HSA14. The findings validate, refine and correct the current alpaca assembly VicPac3.1 by anchoring unassigned sequence scaffolds, and ordering and orienting assigned scaffolds. The study contributes to the improvement in the alpaca reference genome and advances camelid molecular cytogenetics.

Effect of optical fiber coating on temperature compensation for strain measurement with optical frequency domain reflectometry

The temperature compensation is essential to the strain measurement in distributed optical fiber sensor (DOFS) due to the temperature-strain cross talk. We demonstrated that the temperature sensitivities and characteristics were different among fibers with different coatings. Compared with the uncoated fiber, polyimide coating could increase the temperature-sensitivity coefficient of fibers, while acrylate coating decreases it. The temperature-sensitivity coefficient changed significantly when the fibers were coated with materials due to different thermal expansion coefficient. To study the temperature compensation for stain measurement with DOFS, the experiments were conducted to measure the spectral shifts of scattered light due to temperature and strain changes for acrylate-coated fiber and polyimide-coated fiber bonded to the same steel plate. The temperature-induced strain of steel plate surface was transferred to the optical fibers together with stress-induced strain. Because of different temperature-sensitivity coefficients and fiber coatings, the measured surface strain distributions on the steel plate are different. The expansion coefficient of steel plate measured by polyimide fiber in the experiment was 11.88 × 10 − 6 K − 1, which coincided with theory value. A hypothesis for analyzing the strain transfer of fiber was found in the experiment. When bonded on the substrate for measuring strain, the total elongation of the fiber is consistent with the total elongation of the substrate along the direction of the fiber within the bonded-length range.

Comparison of the Moisture Adsorption Properties of Starch Particles and Flax Fiber Coatings for Energy Wheel Applications.

The adsorption–desorption behavior of flax fibers (FFs) is reported in this paper. FFs are a potential desiccant material for air-to-air energy wheels, which transfer heat and moisture in building heating, ventilation, and air conditioning (HVAC) systems. The raw FFs sample was subjected to physical modification, followed by complementary material characterization to understand the relationship between its structure and its moisture uptake performance. The surface and textural properties of the modified FFs were determined by gas adsorption (N2, H2O) and gravimetric liquid water swelling studies and further supported by spectroscopic (infrared and scanning electron microscopy) results. A FF-coated small-scale energy exchanger was used to determine the moisture transfer (or latent effectiveness; εl) using single-step and cyclic testing. The FF-coated exchanger had εl values of ∼10 and 40% greater compared to similar exchangers coated with starch particles (SPs) and silica gel (SG) reported in a previous study. The enhanced surface and textural properties, along with the complex compositional structure of FFs and its greater propensity to swell in water, account for the improved performance over SPs. Thus, FFs offer an alternative low-cost, environment-friendly, and sustainable biodesiccant for air-to-air energy wheel applications in buildings. The current study contributes to an improved understanding of the structure–function relationship of biodesiccants for such energy wheel applications.

Tremolite-actinolite fiber coatings of sub-nanometer silica-rich particles in lungs from deceased Quebec miners.

Tremolite-actinolite (TA) fibers from the lungs of deceased former Quebec mine workers were found to be coated with sub-nanometer particles. Qualitative chemical analyses were performed on the particles indicating that they were composed of silicon and oxygen. The crystal lattice structure of all amphibole minerals, including the TA series, is arranged as pairs of linear chains of SiO4 tetrahedra that are linked together to form double chains. Our observations of the TA fibers from miner's lungs, made using a high-resolution transmission electron microscope, indicated that the tetrahedral silica chains were progressively split, forming dispersed sub-nanometer particles. The non-tetrahedral sites were removed at the surface of the TA fibers, presumably by the oxidation process involved in attempted phagocytosis, which also resulted in fragmentation of the tetrahedral chains. It was found that the silicon-rich particles (SRPs) were variable in diameter, consistent with fragments formed from the splitting of the tetrahedral chains. The TA fibers from lungs displayed coatings and linear interior zones of SRP parallel to the planes of longitudinal fiber splitting. The literature on very small nanoparticles is consistent with deep penetration of SRP into cell DNA interiors, oxidative stress, and carcinogenesis.

Determination of the mass transfer coefficients in direct immersion solid‐phase microextraction

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.

Tensile response of unidirectional ceramic minicomposites

Mechanical response of ceramic matrix composites is critically dependent on properties of fibers and fiber coatings. In the present study, we examine effects of these and other constituent properties on the tensile response of unidirectionally-reinforced composites through a combination of existing models of fiber fracture, Monte Carlo simulations of concurrent matrix and fiber fragmentation, and complementary experimental measurements. The results show that, contrary to prevailing understanding, the process of fiber fragmentation cannot go to completion in a uniaxial tensile test. At low stresses (before the maximum), fiber breaks are essentially random throughout the bundle; in contrast, at the stress maximum, all additional breaks are localized to regions close to the fracture plane (within a distance dictated by the characteristic transfer length). Therefore, the resulting distributions in fiber pullout length and strength of pulled-out fibers do not match predictions from existing models. Although the composite stress-strain response associated with fragmentation can be accurately predicted by existing fragmentation models, accurate prediction of the point of instability requires consideration of the local response of fibers in the most heavily strained regions (within matrix crack planes). The response in the latter regions leads to instability at stresses and strains that are lower than those obtained from the average stress-strain response. Additionally, the composite strength and failure strain are found to be sensitive to the fiber volume fraction and the matrix strength distribution. One implication is that the full potential of the fibers may not be realizable in composites of practical interest.

Fatigue of improved polyamide mooring ropes for floating wind turbines

This paper describes a study of the fatigue characterization of polyamide mooring ropes for floating wind turbines. Under some conditions polyester ropes, which are favoured for offshore oil and gas platform station-keeping, are too stiff for wind turbine moorings, and polyamide may be a suitable alternative. While early studies on fatigue of braided nylon ropes showed very short lifetimes some recent results have indicated that it is possible to significantly enhance lifetime by modifying rope construction and improving fibre coatings. In this paper yarn-on-yarn abrasion testing is used first to evaluate a new yarn coating. Significant lifetime enhancement was noted, so fatigue testing of ropes was then performed. Results confirm that excellent fatigue lifetimes can be achieved, superior to those for steel chain. Finally, failed yarn and rope samples were examined by microscopy, in order to improve understanding of the fatigue mechanisms leading to failure.

Long-Term Reliability of Fiber-Optic Current Sensors

We present studies on the long-term reliability of interferometric fiber-optic current sensors (FOCS) for use in electric power transmission systems. Accelerated ageing tests are performed on crucial optical sensor components and a three-phase sensor system is subjected to an extended field trial. The sensor components under test include the sensor’s superluminescent light emitting diode light source, the integrated-optic phase modulator and various passive components such as fiber couplers, fiber polarizers, polarization-maintaining fiber connectors, and fiber coatings. The components are exposed to accelerated ageing conditions for extended periods of time, i.e., temperature cycling (between −25 °C and 65 °C for up to 15000 cycles), constant high temperature at dry conditions (up to 115 °C for up to 20000 h), and damp heat (85 % relative humidity at 85 °C for up to 7900 h). Crucial component parameters such as the source wavelength and polarization extinction ratios are repeatedly measured as a function of temperature at defined intervals during the ageing periods and examined for potential drift of component failures. The field trial is carried out for a three-phase FOCS system integrated into 420 kV double-chamber circuit breakers over a period of more than three years. The sensor signals are compared to the signals of conventional current transformers. In addition, the evolution of various operational parameters such as the light source power is continuously recorded. The results prove a high degree of reliability of modern FOCS systems.

OPTIMIZATION OF EXTRACTION CONDITIONS OF VOLATILE COMPOUNDS OF ROASTED BEEF BY SOLID-PHASE MICROEXTRACTION

Aroma is one of the most important sensory attributes for acceptance by beef consumers. The first step in analysing the volatile compounds associated with this attribute is their extraction from the food matrix, solid-phase microextraction has been widely used for volatile compound determination in meat. This study aimed to test six different solid-phase microextraction (SPME) fibre coating materials for their volatile compounds extraction efficiency for roasted beef and to optimize the extraction conditions using response surface methodology. Gas chromatography coupled with a flame ionization detector (GC-FID) and mass spectrometry (GC-MS) were used. The choice of SPME fibre coating was based in the total area obtained by GC-FID analysis for the six fibre coatings. The optimum time and temperature for SPME extraction was 60 °C/65 minutes. The mixed-phase fibre coatings showed the best results for extracting volatile compounds in roasted beef as higher number of compounds were identified. The carboxen/polydimethylsiloxane (CAR/PDMS) fibre extracted the largest number of compounds under the optimum extraction condition. Aldehydes were the predominant class of compounds found in roasted beef, followed by alcohols and hydrocarbons.