Thermal Stability Of Fibers Research Articles

Valorization of Tunisian alfa fibres and sumac tannins for the elaboration of biodegradable insulating panels

Alfa leaves are important renewable raw materials in Tunisia where they are used basically in handcrafts and paper industry. Sumac is also an abundant species in Tunisia known for its high tannin content and is basically used in traditional medicine. To valorize these natural resources, we studied, for the first time, the possibility of making insulating panels based on alfa fibres and sumac tannins based adhesive. Firstly, alfa leaves were treated with an alkali solution as it is one of the standard procedures commonly used in the paper industry to extract cellulosic fibres. Mercerization effects were studied by characterizing fibres thermal properties and fibres surface morphology. Secondly, the sumac tannin based resin was formulated and characterized. Finally, the insulating panel was elaborated and characterized by determining its thermal conductivity. The thermal gravimetric analysis results show improvement in the thermal stability of fibres after alkali treatment. Environmental Scanning Electron Microscopy showed changes on treated alfa surface which could promote the fibre-matrix adhesion. The reactivity of sumac tannins to formaldehyde test (Stiasny number) showed the possible use of sumac tannins in wood adhesive formulation. Thermomechanical analysis and strength analysis of sumac tannin/hexamin based resin highlighted acceptable bonding properties. The thermal conductivity measurement showed an average value equal to 0.110 W/m K.

Improving the Side-mode Suppression Ratio and Reducing the Frequency Drift in an Opto-Electronic Oscillator With a Feedback Control Loop and Additional Phase Modulation

We present two stabilization methods for an opto-electronic oscillator. By using a frequency discriminator with a feedback control loop the long-term stabilization was improved, and a frequency drift of 0.05 ppm/K was achieved without any fiber thermal stabilization. In addition, the phase-noise degradation as a result of the discriminator control loop was investigated. To the best of our knowledge, this has not been done before for this type of method. Our study revealed that a properly designed control loop does not increase the phase noise. The second stabilization method was used to increase the side-mode suppression ratio. This was achieved with an additional control loop in the form of an oscillator-loop phase modulation. In this way, a 5-dB increase in the side-mode suppression ratio was recorded. The phase-noise degradation was less than 1 dB in the close-in region. The two methods were designed to operate simultaneously. This design provides both simplicity and cost effectiveness for the stabilized opto-electronic oscillator.

Comparison of mechanical and interfacial properties of kenaf fiber before and after rice-washed water treatment

Rice-washed water was used to treat kenaf fiber using a spray coating method. Untreated kenaf fiber was compared with rice-washed water treated kenaf fiber in order to evaluate the treatments effects on mechanical and interfacial properties. The tensile strength and interfacial shear strength of kenaf fiber were improved by the rice-washed water treatment. Differences in the surface morphology of treated and untreated kenaf fiber was observed using FE-SEM photograph. TGA testing indicated that rice-washed water treated kenaf fiber improved the fiber's thermal stability. Static contact angle measurements of wettability demonstrated that the surface treated kenaf fiber was hydrophilic than that of untreated kenaf fiber. This relatively simple and environmentally friendly rice-washed water treatment of Kenaf fibers resulted in improve mechanical and interfacial properties.

Dynamic Prediction Models and Optimization of Polyacrylonitrile (PAN) Stabilization Processes for Production of Carbon Fiber

Thermal stabilization process of polyacrylonitrile (PAN) is the slowest and the most energy-consuming step in carbon fiber production. As such, in industrial production of carbon fiber, this step is considered as a major bottleneck in the whole process. Stabilization process parameters are usually many in number and highly constrained, leading to high uncertainty. The goal of this paper is to study and analyze the carbon fiber thermal stabilization process through presenting several effective dynamic models for the prediction of the process. The key point with using dynamic models is that using an evolutionary search technique, the heat of reaction can be optimized. The employed components of the study are Levenberg–Marquardt algorithm (LMA)-neural network (LMA-NN), Gauss–Newton (GN)-curve fitting, Taylor polynomial method, and a genetic algorithm. The results show that the procedure can effectively optimize a given PAN fiber heat of reaction based on determining the proper values of heating ramp and temperature.

Nanoscale-supported heteropoly acid as a new fiber coating for solid-phase microextraction coupled with gas chromatography–mass spectrometry

In the present study, 12-tungstophosphoric (PW) acid as heteropoly acid, supported on silica-coated γ-Fe2O3 nanoparticles (NPs), was used as a new fiber coating for solid-phase microextraction (SPME). The γ-Fe2O3@SiO2-PW nanocomposite with high surface area was synthesized and characterized by SEM and FT-IR. The prepared nanocomposite was immobilized on a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some phenolic compounds (PCs) from water sample in combination with gas chromatography-mass spectrometry (GC-MS). A one-at-a-time optimization strategy was applied for optimizing the important extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate, pH, and desorption temperature and time. In optimum conditions, the repeatability for one fiber (n=3), expressed as relative standard deviation (R.S.D. %), was between 4.8% and 9.6% for the test compounds. The detection limits for the studied compounds were between 0.004 and 0.05pgmL−1. The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis.

The effect of surface modifications on sisal fiber properties and sisal/poly (lactic acid) interface adhesion

The main aims of this work were to study the effect of surface modifications on sisal fiber properties as well as on fiber/poly (lactic acid) (PLA) interface adhesion. For this purpose, alkali, silane and combination of both treatments were applied to sisal fiber. The effects of treatments on fiber thermal stability, fiber wettability, morphology, tensile properties and on fiber/PLA interfacial shear strength (IFSS) were studied. After treatments IFSS values improved at least 120%, however, tensile strength of sisal fibers decreased. Alkali treatment removed some non-cellulosic components (hemicelluloses, lignin) as confirmed by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The removal of non-cellulosic materials led to fibrillated and rough morphology as observed by optical microscopy (OM). FTIR spectrum of silane treated fibers showed a band related to silane amino group and contact angle measurements confirmed that fibers became more hydrophobic. All treatments used improved fiber/PLA adhesion.

Microextraction of phenolic compounds using a fiber coated with a polyaniline-montmorillonite nanocomposite

A highly porous fiber coated polyaniline/montmorillonite clay was prepared for solid-phase microextraction. The nanocomposite was synthesized by in-situ polymerization. The resulting material was characterized by scanning electron microscopy, UV-Vis and FT-IR spectroscopy. The prepared nanomaterial was immobilized on a stainless steel wire for fabrication of the solid-phase microextraction fiber. The fiber was evaluated for the extraction of some phenolic compounds from aqueous sample solutions in combination with gas chromatography–mass spectrometry. A one at-the-time strategy was applied for optimizing extraction temperature, extraction time, ionic strength, pH, stirring rate, desorption time and desorption temperature. Under optimum conditions, the repeatability for one fiber (n = 3), expressed as relative standard deviation (R.S.D. %), was between 4.6 and 9.1 %. The quantitation limit for the studied compounds was between 5 and 14 pg mL−1. The developed method offers the advantage of being simple to use, with shorter analysis times, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis.

Mechanical and thermal characterization of iron(II) 2,2′‐bipyridine complex supported polyacrylonitrile fiber as a novel photocatalyst

In this study, the mechanical and thermal properties of amidoximated polyacrylonitrile fibers immobilized with iron(II) 2,2′‐bipyridine complex (Fe(bpy)32+) have been investigated to support their commercial application for wastewater treatment. The mechanical properties were evaluated with respect to breaking strength and elongation at break in both dry and wet conditions. Dynamic mechanical analysis, differential scanning calorimetry, and thermogravimetric analysis techniques were used to determine the thermal behavior. The results indicate the effect of Fe(bpy)32+ immobilization on the breaking strength of the dry fiber samples were negligible, and the corresponding elongation at break decreased gradually with Fe(bpy)32+ content increasing. In addition, water treatment greatly affected the mechanical properties of the fibrous materials. Thermal studies reveal that Fe(bpy)32+ immobilization led to better fiber thermal stabilization in terms of higher storage modulus at high temperature regions, larger glass transition temperature, and smaller weight loss. The 2,2′‐bipyridine ligands were found to be responsible for the better mechanical and thermal performance of the fibrous materials by enhancing the intermolecular crosslink. POLYM. ENG. SCI., 55:1052–1058, 2015. © 2014 Society of Plastics Engineers

Three dimensionally honeycomb layered double hydroxides framework as a novel fiber coating for headspace solid-phase microextraction of phenolic compounds

A new solid phase microextraction (SPME) fiber based on high-temperature three dimensionally honeycomb layered double hydroxide (TDH-LDH) material is presented. The fiber coating can be prepared easily, it is mechanically stable and exhibits relatively high thermal stability. This study shows that three dimensionally honeycomb layered double hydroxide generated porous morphology. The TDH-LDH material was tested for the extraction of some phenolic and polycyclic aromatic hydrocarbon compounds from aqueous sample solutions in combination with gas chromatography–mass spectrometry (GC–MS). The TDH-LDH fiber contains polar groups and its efficiency for non-polar polycyclic aromatic hydrocarbon compounds was lower than phenolic compounds. On the other hand, a high tendency towards the adsorption of polar phenolic compounds was observed for the proposed fiber. The effects of the extraction and desorption parameters including extraction temperature, extraction time, ionic strength, stirring rate, pH and desorption temperature and time have been studied. In optimum conditions, the repeatability for one fiber (n=5), expressed as relative standard deviation (R.S.D. %), was between 2.8% and 7.1% for the phenolic compounds. The detection limits for the studied phenolic compounds were between 0.02 and 5.8ngmL−1. The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis

Synthesis And Characterization Of Thermally Resistant Aromatic Polyamide-metal Complexes

Amino group terminated oligomeric aromatic polyamides were prepared using phosphorylation technique and subsequently converted into Schiff’s base coordination polymers by reaction with Co (II), Ni (II) and Cu (II) complexes of salicyladehyde [M(SAL)2] and 2-hydroxy-1-naphthaldehyde [M(NAPHTHAL)2]. These polyamide metal complexes were characterized by elemental analysis, IR spectroscopy and thermo gravimetric analysis; and an oxygen and nitrogen coordinated structure was inferred. Magnetic moment values of the different products indicated the variation in geometry. Introduction of metal ions into the polyamide chains enhanced the thermal stability of the coordination polymers as compared to the respective polymeric ligands. As an extension of this simple and easy technique, the thermal stability of fibers, films, sheets and blocks of amino group containing polyamides can be increasing by introduction of metal ions through Schiff base formation. These polyamide Schiff base complexes are expected to show promising antimicrobial activities.

Thermal Degradation of Flax Fibres as Potential Reinforcement in Thermoplastic Composites

This work reports on a study of thermal degradation of flax fibres to gain an improved understanding of the use and limitations of flax fibres as reinforcement for thermoplastic composites manufactured by the vacuum forming process. The effect of heating on chemical decomposition and thermal stability was performed, using fourier transform infrared spectrometry (FTIR) and thermogravimetry (TG) techniques. In addition, the characterisation of micro structures of failure surface following tensile testing of the composites was conducted. The results show that the hemicelluloses decomposition of flax fibres during thermal degradation is a factor to have the detrimental effect on the thermal stability of fibres, particularly with low heating rate. The present investigation, A decrease of hemicellulose and pectin content of the fibres, a decrease of consolidation temperature and an increase of heating rate during the manufacturing of flax fibre thermoplastic composites should improve their mechanical performance.

Keggin-type heteropoly compounds supported on montmorillonite clays offering strong option for efficient solid-phase microextraction coating

Keggin-type heteropoly compounds supported on montmorillonite clays were prepared and used as a highly porous fiber coating material for solid-phase microextraction (SPME). The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography–mass spectrometry (GC–MS). A one at-the-time optimization strategy was applied for optimizing the important extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate, and desorption temperature and time. In optimum conditions, the repeatability for one fiber (n=3), expressed as relative standard deviation (R.S.D.%), was between 5.1% and 8.4% for the test compounds. The detection limits for the studied compounds were between 0.02 and 0.05pgmL−1. The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost of equipment, thermal stability of fiber, and high relative recovery in comparison to conventional methods of analysis.

Crystallization of zirconia doped basalt fibers

Crystallization of basalt fibers containing 0–7wt% ZrO2 was studied. Fibers were drawn from basalt glasses and annealed in air at different temperatures. Phase composition of obtained samples was determined by XRD. Kinetics of crystallization processes was investigated by DSC. Kinetic models and parameters were estimated for crystallization of spinel-like phase, pyroxene and plagioclase using model-free analysis. It was found that doping of fibers with 1–3wt% ZrO2 increased Arrhenius parameters of aluminosilicate crystallization. When the zirconia content was 5–7wt% the crystallization mechanism significantly changed. This phenomenon resulted in increasing of fiber thermal stability.

Periodic mesoporous organosilica with ionic liquid framework as a novel fiber coating for headspace solid-phase microextraction of polycyclic aromatic hydrocarbons

Periodic mesoporous organosilica based on alkylimidazolium ionic liquid (PMO-IL) was prepared and used as a highly porous fiber coating material for solid-phase microextraction (SPME). The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography–mass spectrometry (GC–MS). A one at-the-time optimization strategy was applied for optimizing the important extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate, and desorption temperature and time. In optimum conditions, the repeatability for one fiber (n=3), expressed as relative standard deviation (R.S.D.%), was between 4.3% and 9.7% for the test compounds. The detection limits for the studied compounds were between 4 and 9pgmL−1. The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis.

Effect of carbon nanostructures on the carbonization of polyacrylonitrile

Composite materials based on polyacrylonitrile with carbon nanofillers (technical-grade carbon, thermally expanded graphite, carbon nanotubes) were synthesized. A carbonization of film and fiber composite samples in the temperature range 20–1000°C provided a noticeable increase in the thermal stability of fibers and a rise in the electrical conductivity of the composite material. Dependences of the degree of carbonization on the concentration of nanostructures, type of material, and nature of modifier were determined. Differential-thermal and X-ray diffraction analyses revealed the formation of oriented nucleus structures of turbostratic carbon in the temperature range 450–550°C.

Preparation and Characterization of High Latent Heat Thermal Regulating Fiber Made of PVA and Paraffin

A convenient method for preparing the thermal regulating fibers with high latent heat has been developed. PVA thermal regulating fibers were prepared via a wet spinning process, with paraffin being the phase change material. The structures and properties of these fibers were investigated by SEM, TGA, DSC and tensile strength tester. With the paraffin content in the fibers increasing from 30wt% to 70wt%, the latent heat of the fibers increases from 42.8J/g to 87.8J/g and the paraffin phase structures change from separation into partial interconnection. PVA matrix can not wrap paraffin effectively when the paraffin content increases up to 50wt%, so the paraffin loss in the spinning process increases. The thermal stability of fibers with low paraffin content is better than that of fibers with high paraffin content. After 100 heat-and-cool cycles, the latent heat of fibers lose a little. The tensile strength of these thermal regulating fibers is good enough for application in wrapping, filling, and nonwovens.

Elasticity, microstructure and thermal stability of foliage and fruit fibres from four tropical crops

A comparative analysis of the elasticity, microstructure and thermal stability of fibres (thickness ranging from 43.4 to 189.4 µm) isolated from pineapple leaves (PALF), coconut coir (COIR), banana leaf-stem (BAN) and oil palm empty fruit bunch (OPEFB) reported in this study. Statistical analysis of the mechanical properties derived from tensile test to rupture reveals significant differences (P<0.05) in the fibre strength (σ), stiffness (E) and extensibility (parameterized by the strain to rupture, ɛ). It is observed that COIR fibres yield the smallest strength, σ (=99.8±22.5 MPa), and stiffness, E (= 0.5±0.1 GPa), while PALF fibres yield the largest σ (=639.5±301.6 MPa) and E (=7.1±3.1 GPa); PALF fibres exhibit the smallest ɛ (=0.11±0.03) but OPEFB fibres yield the largest ɛ (=2.0±1.3). From scanning electron micrographs, it is observed that cellulose fibril rupture predominates in OPEFB, COIR and BAN fibres; a large proportion of the cellulose fibrils fail by pullout in PALF fibres. Thermogravimetric analysis reveals that all fibres are thermally stable up to 250 °C; the fibre residue ranges from 30 to 80 wt% after heating to 500 °C. In particular, BAN experiences the highest weight loss and PALF experiences the lowest weight loss. The findings lend to a simple approach for determining the performance of the composites by assessing the type of natural fibres for reinforcing polymeric matrices.

The Research on the Disperse Form of PEO Fiber by Electrostatic Spinning Method

We prepared PEO nano fiber with different concentration of PEO acid solution by electrostatic spinning in different technology conditions. Then we studied the property of solution by rotary viscometer instrument and electrical conductivity spectrometer, the disperse form of the fiber by SEM scattered forms, the thermal property of the composite was studied by thermogravimetry and derivative thermogravimetry (TG-DTA). The conclusion is the disperse form of fiber is controlled by the concentration of solution, the voltage of spinning, the distance of solidification. The important factor is about the solution. To increase the solution viscosity and the solidification distance, reduce the spinning voltage would decrease the diameter of the fiber. Thermal stability of fiber was significantly better than powder.

Effect of ultraviolet irradiation on the thermal stability of bleached eucalyptus kraft pulp

The changes occurring on cellulosic fibers caused by ultraviolet irradiation at 360 nm for 24 h and 48 h were investigated. A never-dried industrial Eucalyptus urograndis elemental chlorine free–bleached kraft pulp sample (O/OD[EP]DP sequence) was used throughout the work. After irradiation, the cellulosic fibers were analyzed for polymerization degree changes, extractive and pentosan content, ultraviolet and visible spectrometric changes of water leachate from the fibers and thermal analysis (TGA/DTA). The ultraviolet treatment had no effect on the degree of cellulose polymerization. The water extracted from ultraviolet-treated fibers revealed cellulose oxidation, with increasing absorbance signals for carbonyl and carboxyl groups. Those oxidations influenced fiber thermal stability.

Thermal and Mechanical Properties of Sansevieria Green Fiber Reinforcement

The green fibers were extracted from sansevieria leaves and treated with 5% aqueous NaOH solution. The primary and derivate thermograms of the untreated and alkali-treated fibers were measured using a TGA/DTA instrument. The thermal stability of fibers was found to increase on alkali treatment. Thermal conductivity, diffusivity, and specific heat capacity of fibers were investigated as a function of temperature. It was found that the thermal conductivity and thermal diffusivity of fiber decreased with increase of temperature. From a tensile test it was found that mechanical properties of the fiber improved after alkali treatment.