Thermal Stability Of Fibers Research Articles

Effect of oxygen content on the preoxidation structure of polyacrylonitrile fibers

AbstractDuring the preoxidation process of polyacrylonitrile (PAN) fibers, the diffusion behavior of oxygen from skin to core can lead to the formation of radially uneven structure of fibers, which affects the mechanical properties of subsequent PAN carbon fibers. Here we examine the effect of oxygen content on the subsequent structure evolution of fibers with different preoxidation structure, by using13C Solid‐state NMR analysis (13C‐NMR), optical density characterization, differential scanning calorimetry analysis, and thermalgravimetric analysis. The results show that increasing the oxygen content during the subsequent heat treatment can effectively reduce the radial structure difference of fiber, its efficiency is related to the preoxidation degree of fibers. For fibers with lower preoxidation degree, namely less heat treatment work (W), the radial structure difference disappears when the oxygen content reaches 29%. Further study shows that the improvement of radial structure of preoxidized fibers improved fiber thermal stability, its efficiency is also related to theWof fibers; when theWof fibers is 5, the carbonization yield at 800°C increased from 56.79% to 62.61%, which is 10.25% higher; when theWof fibers is 20, under the same oxygen content range, the carbonization yield increased from 68.97% to 69.60%, which is only 0.913% higher.

High-speed electrospinning of phycocyanin and probiotics complex nanofibrous with higher probiotic activity and antioxidation

This study reports for the first time the co-encapsulation of probiotics and phycocyanin by electrospinning. SEM showed that the electrospun fibers exhibited a homogeneous, smooth surface and a circular shape. XRD and ATR-FTIR results showed that Lactiplantibacillus plantarum 1-24-LJ and Pc were co-embedded in the fibers and that the presence of L. plantarum 1-24-LJ promoted the encapsulation of phycocyanin. TG analysis showed that the addition of phycocyanin and L. plantarum 1-24-LJ improved the composite fiber's thermal stability. The fibers co-embedded with phycocyanin and L. plantarum 1-24-LJ had the highest DPPH and ABTS+ activity, indicating that the two may have synergistic antioxidant effects. After 28 days, the viability of the strain could still be above 6 log cfu/g, and the addition of phycocyanin could help to improve the strain's survivability. In this experiment, a co-embedding method for probiotics and antioxidants was proposed, which could effectively increase the survivability of probiotics and improve the antioxidant properties of the fibers.

Characterization of New Natural Fiber from the Stem of Tithonia Diversifolia Plant

ABSTRACT Synthetic fibers are restricted from being used as reinforcements due to increasing awareness of environmental issues and strict laws from government agencies. In recognition of this, the engineering and scientific communities switched their attention to using natural fibers as reinforcement in polymers to make sustainable composites. The fiber was extracted through the water retting process, and characterized from the stem of the Tithonia diversifolia (TD) plant. Physical, chemical, and mechanical properties were investigated and it was found that this fiber has high cellulose content of 65.33 wt.%, and less wax content of 0.67%. X-ray diffraction (XRD) confirmed the crystallinity index as 45%. Surface morphology was carried out through Scanning Electron Microscope (SEM) analysis. Fourier Transform Infrared Spectroscopy (FTIR) results confirmed the chemical functional groups. Thermogravimetric Analysis (TGA), TG and DTG curves were used to evaluate the fiber thermal stability. This result confirms that TD fiber can be used as potential fiber reinforcement in biocomposites.

Zirconia-alumina multiphase ceramic fibers with exceptional thermal stability by melt-spinning from solid ceramic precursor

Zirconia-alumina multiphase ceramic fibers with 80 wt% (Z80A20 fiber) and 10 wt% (Z10A90 fiber) proportions of zirconia were prepared via melt-spinning and calcination from solid ceramic precursors synthesized by controllable hydrolysis of metallorganics. The zirconia-alumina multiphase fibers had a diameter of about 10 µm and were evenly distributed with alumina and zirconia grains. The Z80A20 and Z10A90 ceramic fibers had the highest filament tensile strength of 1.78 GPa and 1.87 GPa, respectively, with a peak value of 2.62 GPa and 2.71 GPa. The Z80A20 ceramic fiber has superior thermal stability compared to the Z10A90 ceramic fiber and a higher rate of filament strength retention due to the stability in grain size. After heat treatment at 1100 °C, 1200 °C, and 1300 °C for 1 h respectively, the filament tensile strength retention rate of Z80A20 ceramic fibers was 87 %, 80 %, and 40 %. While Z10A90 ceramic fiber was fragile after being heated at 1300 °C. The results showed that the high zirconia content facilitated the fiber's thermal stability.

Copper-thiosemicarbazone complexes conjugated-cellulose fibers: Biodegradable materials with antibacterial capacity

Personal protective equipment (PPE) is vital in battling bacteria crisis, but conventional PPE materials lack antimicrobial activities and environmental friendliness. Our work focused on developing biodegradable and antibacterial fibers as promising bioprotective materials. Here, we grafted highly effective antibacterial copper-thiosemicarbazone complexes (CT1–4) on cellulose fibers via covalent linkages. Multiple methods were used to characterize the chemical composition or morphology of CT1–4 conjugated-fibers. Conjugation of CT1–4 maintains the mechanical properties (Breaking strength: 2.35–2.45 cN/dtex, Breaking elongation: 7.19 %–7.42 %) and thermal stability of fibers. CT1 can endow cellulose fibers with the excellent growth inhibition towards Escherichia coli (E. coli) (GIR: 61.5 % ± 1.28 %), Staphylococcus aureus (S. aureus) (GIR: 85.7 % ± 1.93 %), and Bacillus subtilis (B. subtilis) (GIR: 87.6 % ± 1.44 %). We believe that the application of CT1 conjugated-cellulose fibers is not limited to the high-performance PPE, and also can be extended to various types of protective equipment for food and medicine safety.

Development of zinc oxide/hydroxyapatite/poly(D,L-lactic acid) fibrous scaffold for tissue engineering applications

Scaffolds based on polymeric fibers represent an engaging biomedical device due to their particular morphology and similarity with extracellular matrices. The biggest challenge to use fibrous materials in the biomedical field is related to their favorable platform for the adhesion of pathogenic microorganisms. Therefore, their optimum performance not only depends on their bioactive potential but also on their antimicrobial properties. The aim of this work was the design of antimicrobial (zinc oxide, ZnO) and bioactive (hydroxyapatite, Hap) fibrous materials using poly(D, L-lactic acid) (PDLLA) as the polymer fiber substrate. Fiber based composite scaffolds were developed using the Forcespinning® technique. For analysis purposes, the morphological, thermal, antimicrobial and biological properties of the fibrous hybrid system obtained at a concentration of 5 wt% of ZnO and 5 wt% of Hap were studied. The incorporation of the aforementioned nanoparticles (NPs) mixture in PDLLA led to an increase in viscosity and a pseudo-plastic tendency of the precursor solution, which caused an increase in fiber diameters and their dispersion of values. Small cavities and certain roughness were the main surface morphology observed on the fibers before and after NPs incorporation. The fiber thermal stability decreased due to the presence of the NPs. The antimicrobial properties of the hybrid fibrous scaffold presented a growth inhibition (GI) of 70 and 85% for E. coli and S. aureus strains, respectively. Concerning the osteoblast-cell compatibility, PDLLA and hybrid PDLLA scaffold showed low toxicity (cell viabilities above 80%), allowing cell growth inside its three-dimension structure and favorable cell morphology extended along the fibers. This behavior suggests a promising potential of this hybrid PDLLA scaffold for bone application.

Extraction and characterization of natural cellulosic fiber from fragrant screw pine prop roots as potential reinforcement for polymer composites

AbstractBiodegradable natural plant fiber isolated from the prop roots of fragrant screwpine (FSP) plant has been thoroughly studied as a potential replacement for artificial fiber in light weight bio‐based composite applications. Chemical, physical, Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, differential scanning calorimetry, and thermo gravimetric studies were used to determine the appropriateness of FSP fiber for use as a novel reinforcement. FSP fibers were determined to have a density of 1.3852 g/cm3 and a diameter of 27–280 μm respectively. Good specific strength and bonding qualities are provided by a high cellulose content (73.10 wt%) and a low wax content (0.35 wt%). The tensile strength of raw FSP fiber was 915 ± 195 MPa, the young's modulus was 33 ± 12 GPa, and the average strain to failure rate was 4.59 ± 2.17%. Thermal analysis (TG and DTG) confirmed FSP fiber's thermal stability up to 235°C. The findings revealed that FSP fiber (FSPF) is an excellent alternative for constructing polymer‐based bio‐composites and other high‐value products with both technical and environmental requirements.

Metal organic frameworks modification of carbon fiber composite interface

Carbon fiber reinforced polymeric composites (CFRPs) are prone to delamination due to insufficient interfacial properties . Several remedies were carried out to enhance the fiber/matrix interfaces via chemical treatments or utilizing stiffer nanomaterials at the interface. However, some of these treatments are destructive in nature and others are non-scalable. This investigation corroborates a novel methodology for developing hybrid reinforcements that comprise carbon fibers and metal organic frameworks (MOFs). The growth of MOFs is scalable, non-destructive to the fibers, and easily tailorable to control the porous morphologies of the MOFs at the interface. Furthermore, the study demonstrates the feasibility of utilizing the MOFs as a catalyst to grow carbon nanotubes (CNTs) on the carbon fibers. The microstructure of the MOFs was examined via microscopy, Raman analysis, wide-angle X-Ray scattering (WAXS), and Fourier-transform infrared spectroscopy (FTIR). The effects of the MOFs on the fiber thermal stability was probed using thermogravimetric analysis (TGA), while contact angle analysis was employed to probe the effect of the different surface modifications on the fibers hydrophilicity . Several mechanical characterizations including tensile, dynamic mechanical analysis (DMA) and shear lap joint were carried out to discern the effects of the MOFs on the composite structural performance. Several improvements emanated from the MOFs placement on the interface including improving the strength, enhancing the damping parameter by 500%, increasing the glass transition temperature of the composite by 20 °C and alleviating the shear lap joint strength by 40%. • Successful scalable growth of metal organic forms (MOFs) on carbon fibers with unique and controllable morphologies. • Improvements on strength, damping, glass transition and shear lap strength. • Utilization of MOFs as catalyst to grow CNTs directly on carbon fibers at different densities.

Fabrication of polyamide 6/honey/boric acid mats by electrohydrodynamic processes for wound healing applications

In this study, polyamide 6, polyamide 6/honey, and polyamide 6/honey/boric acid nanofibrous mats were fabricated by electrospinning and electrospraying technique to be used in wound healing applications. The morphology and diameter of the fiber mats with and without honey and boric acid were examined by scanning electron microscopy. The morphology of fibers showed that all resulting fibers were in the nanometer range with 253–304 nm average fiber diameter. Fourier Transform Infrared spectrum (FT-IR) and thermal gravimetric analysis (TGA) thermograms showed the successful incorporation of honey and boric acid into the fibers. The results demonstrated that increasing the amount of boric acid slightly increased the fiber diameter. Moreover, boric acid incorporation enhanced the hydrophilicity of nanofibers. The wettability and thermal stability of fibers were quite suitable for wound healing applications. Antibacterial tests demonstrated that the polyamide 6/honey fiber was effective against Escherichia coli, while the polyamide 6/honey fibers loaded with boric acid at 5 and 10 wt% concentration were effective against both Escherichia coli and Staphylococcus aureus. However, the fibers had no antibacterial activity against Acinetobacter baumannii and Pseudomonas aeruginosa. The findings showed that polyamide 6/honey and polyamide 6/honey/boric acid nanofibrous scaffolds had desirable characteristics suitable for potential wound healing applications.

Characterization of polyacrylonitrile thermal stabilization process for carbon fiber production using intelligent algorithms

Composite materials have widened their application range in recent years. The polymeric composite reinforced with carbon fibers can be described as a high-performance structural material which merges two important features: low weight and mechanical stability. Carbon fiber production which uses polyacrylonitrile as precursor is composed of many stages such as polymerization, spinning, thermal stabilization, carbonization, and surface treatment. Thermal stabilization is the critical stage of this production process, during which aromatic rings are generated, and therefore the main factor for the carbon fiber structure definition and thus for this material quality. A thermal stabilization model using intelligent algorithms was developed aiming a possible optimization of the production process and consequent cost reduction. This work was based on real experimental data obtained from a composite material production pilot plant. A qualitative analysis was initially performed using Self-Organizing Maps trained with variables of fiber production reagents and process. Thereafter, a supervised training with feedforward backpropagation neural network was used for a quantitative analysis. Based on this quantitative analysis, the carbon fiber thermal stabilization process was simulated, obtaining 2.98% and 2.48% mean errors relative to experimental results of Volumetric Density and FTIR Conversion index, respectively.

Effect of Acetylation with Perchloric Acid as Catalyst in Sugarcane Bagasse Waste

ABSTRACT Sugarcane bagasse is used as a byproduct of agro-industrial production. However, natural fibers’ hydrophilic characteristics prevent their application in natural fiber/polymer composites due to the hydroxyl groups (–OH) presented in the cellulose molecule. Because of this, several treatments have been proposed. In this research, the acetylation’s influence on sugarcane bagasse fiber’s structure and properties was investigated, and the effect of the amount of perchloric acid as the catalyst to isolate the lignin and decrease its polarity. Sugarcane bagasse fiber was chemically characterized after modification by Fourier Transform Infrared (FTIR) spectroscopy and degree of substitution (DS). Surface morphology, crystallinity, and thermal stability of fibers were evaluated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Thermogravimetry (TGA). A small amount of catalyst content has a significant effect on the DS, causing improved surface morphology and increased thermal stability due to acetylation. However, the crystallinity and lignin content of the fibers decreased after acetylation. According to chemical composition, the crystallinity decreased due to the amorphous phase from hemicellulose deposition. The decrease in the crystalline cellulose enhanced the acetylation reaction and substituted more hydroxyls groups per glucose unit according to DS values. Thus, the catalyst has an essential role in the efficiency of acetylation with sugarcane bagasse fiber.

Cotton fabric finishing based on phosphate/clay mineral by direct-coating technique and its influence on the thermal stability of the fibers

Clay minerals are naturally non-combustible materials with potential applications for protection against thermal degradation in textiles. However, their immobilization on the surface of the fabrics is a complicating factor depending on many variables. The application of clay minerals using the technique of finishing by direct-coating seems a viable alternative, which meets the environmental demand for less polluting, fast, simple, and cheap applications. Thus, in the present work, a study about the influence on the thermal stability of cotton fibers, from the textile fabric containing different formulations based on ammonium polyphosphate (APP) and sodium montmorillonite (Na-Mt) was evaluated. The additives were dispersed into a polymeric paste and applied unilaterally on fabric by direct-coating technique. The treated samples showed an improvement in thermal stability and heat release as a function of the Na-Mt/APP ratio loaded into the fabric. A reduction of the heat release rate (pHRR) around 51.6% and an increase of the carbonaceous residue at 800 °C was observed. The study of the thermal stability of the treated cotton fabric using the techniques of PCFC and TGA, with the aid of an experimental planning allowed the understanding of the interaction and synergy phenomena between the components of the formulation applied via direct-coating.

Morphological, acoustical, mechanical and thermal properties of sustainable green Yucca (Y. gloriosa) fibers: an exploratory investigation.

The objective of this study was to evaluate the acoustical, morphological, mechanical and thermal properties of fibers extracted from the leaves of Yucca (Y. gloriosa) shrub. Several tests were performed on either untreated or alkali-treated (5% NaOH) fibers. The chemical analysis of the fibers was performed to determine their lignin, cellulose, hemicellulose, wax and moisture content. Fourier transform infrared (FTIR) and thermogravimetric analysis were respectively employed to chemically and thermally analyze the fibers. The microscopic examination was also carried out using scanning electron microscope (SEM). INSTRON universal testing machine and an impedance tube system were employed for measuring the tensile properties of the fibers and the sound absorption coefficient values of the samples fabricated from the same fibers, respectively. The results from the experiments revealed that the fibers have low density (1.32g/cm3) and higher cellulose content (66.36wt.%,). The mechanical characterization of these fibers also confirmed they are similar to the other lignocellulose fibers used for the reinforcement of polymer matrix composites. The tensile strength test conducted on Yucca fibres showed that mechanical properties of alkali treated fibers are superior to the untreated fibers. The thermal analysis also demonstrated that the alkali treated fibres can thermally withstand temperatures of up to 364°C which confirms the fact that the thermal stability of fibers was improved by alkali treatment. Fibers extracted from the leaves of Yucca demonstrated fair amounts of mechanical and thermal resistance and strength. The samples fabricated from Yucca fibers demonstrated fair levels of sound absorption coefficients particularly at higher frequency ranges which are typical to the other natural fibers. The possible use of Yucca fibers as either a reinforcing agent for composites or a sound absorbing medium is highly promising.

The effect of boron nitride interphase on the thermal stability of SiC fibers

The SiC fibers were coated with uniform boron nitride interphase by chemical vapor infiltration (CVI). The as-received and BN-coated fibers were heat-treated in flowing nitrogen for 2 h to investigate the effect of BN interphase on the thermal stability of fibers. Tensile strengths of as-received and BN-coated fibers have been measured at room temperature. The effects of heat-treatment on the tensile strengths of fibers were investigated using Weibull distribution. The results showed the deposited BN interphase has turbostratic structure, with nano crystallites of h-BN randomly orientated. Heat-treatment improved the crystallization degree of BN interphase. The as-received fibers had a tensile strength of 2.56 GPa and a Weibull modulus of 5.39. The BN-coated fibers showed lower tensile strength than the as-received fibers, on account of the increased diameter and soft nature of BN. The average strengths of fibers decreased, and BN-coated fibers showed higher strength retention than as-received fibers at the same heat-treatment temperature due to the protection of BN interphase. The BN interphase acts as a compliant layer, which reduces the thermal damage to SiC fibers during heat-treatment.

Quantification of graphene materials in fibers

A method for quantitative determination of graphene materials in fibers by high temperature pyrolysis - element analysis is reported. This method takes advantage of the difference between the thermal stability of fiber and graphene itself to design the corresponding temperature gradient. Firstly, the fiber matrix is removed, and then the carbon element content ratio is measured by element analyzer. This method eliminates the influence of other impurities in the fiber. The experiment is reliable, simple to operate and the relative deviation conforms to the standard range, which is of great significance for quantitative analysis of the content of graphene materials in the fiber.

Comparison of Various Chemical Treatments Efficiency in Relation to the Properties of Flax, Hemp Fibers and Cotton trichomes

ABSTRACT The main aim of this study was to chemically modify the plant fiber surface. Hemp, flax fibers and cotton trichomes were subject of surface treatments using silanization, acetylation, benzoylation, and mercerization processes. The fiber properties were evaluated with the use of fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), wide-angle X-ray analysis (WAXS) and thermogravimetric analysis (TGA). Additionally, humidity and color of the modified fibers were evaluated. Chemical treatment of the plant fibers reduced their hydrophilic nature, increased the moisture resistance, and improved their thermal stability. In all the cases the silanization process proved to be the most effective method of improving fiber thermal stability and moisture resistance, yet mercerization and benzoylation methods offered satisfying results as well.

Thermal Stability of Wood Fibers Produced from Recycled Medium Density Fiberboards

In this study, thermal stability of fibers obtained from recycled MDF was investigated and compared with virgin fibers by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Two different methods, including electrical heating and hydrothermal treatment, were used for recycling the MDF wastes. Electrical heating method was performed at two different times (2 and 4 min) and hydrothermal method was done at three different temperatures (105, 125 and 150 °C). Chemical structure of wood fibers was also studied. TGA and DSC analysis showed higher weight loss of recycled fibers as compared to virgin fibers in a similar degradation region, which means that thermal stability of recycled fibers is lower than virgin fibers. In fact, thermal behavior of recycled fibers was medium between wood and UF resin. DSC analysis showed two exotherms at around 340 and 475 °C. The transition at around 340 °C in fibers thermogram was considered to be due to polysaccharides thermal deterioration and the exotherm at 475 °C was related to lignin carbohydrate complex deterioration. The results of chemical structure analysis showed that lignin and hemicellulose content of recycled fibers was significantly lower than that of virgin fibers, which resulted in decreased thermal stability.

Physico-chemical and thermal properties of untreated and treated Acacia planifrons bark fibers for composite reinforcement

In this work, the effects of alkali treatment on the chemical composition and thermal decomposition of Acacia planifrons fibers were investigated. The fibers originating from the bark of an Acacia planifrons tree were alkali treated with various concentrations (2% and 5% w/v) for 30 min. The treatment was found to diminish the amorphous contents, improve the crystallinity index and thermal stability of the fiber. The crystallinity index of the untreated, 2% alkali-treated and 5% alkali-treated fibers was estimated to be 65.38%, 69.94% and 74.76%, respectively. The thermal stability of the alkali-treated fiber was quite higher than that of the untreated fiber. The results revealed that 5% alkali-treated Acacia planifrons fibers are suitable to be used as reinforcement in polymer composites.

Determination of Fluoxetine in Hospital Wastewater Using Solid-Phase Microextraction Fiber Coated With SWCNT

Fluoxetine is used as an effective antidepressant in psychopharmacology. As a pharmaceutical and personal care product (PPCP) found in superficial waters, fluoxetine influences the wildlife that inhabit these waters. This study was conducted to determine the fluoxetine concentration even in trace quantity in the hospital wastewater, using a solid-phase microextraction (SPME) silica fiber layered with single-walled carbon nanotubes (SWCNTs). An instrumental setup including off-line SPME, which uses a simple carbon nanotube (CNT) to bond capillary column combined with fluorescence spectrometry, was arranged as a sensitive method for the quantification of fluoxetine in real sample. A one at-a-time optimization strategy was applied for optimizing extraction parameters such as extraction time, stirring rate, desorption time, pH, and salt effect on the extraction, preconcentration and determination of fluoxetine in aqueous samples. The advantages of the developed method were: being simple to use with shorter amounts of time for analysis, lower equipment costs, thermal stability of fiber, and high relative recovery in contrast to conventional methods of analysis. Linear ranges were within 0.1-30 µg/L and the detection limit for the fluoxetine was 1×10-4 µg/L.

Characterization of untreated and alkali treated new cellulosic fiber from an Areca palm leaf stalk as potential reinforcement in polymer composites

The research article addresses, a new natural fibers namely Areca Palm Leaf Stalk Fibers (APLSF) were extracted from an Areca palm tree (Dypsis lutescens) and subjected to various concentrations of alkali treatment (NaOH) such as 5%, 10% and 15% by weight. The effects of this treatment on various properties of the fibers such as physical, chemical and mechanical properties were studied. However, the density of the fibers increased and diameter of the fibers reduced. The chemical result showed that the cellulose content was increased while hemicellulose, lignin, wax and ash contents were reduced. The chemical functional groups present in the fibers were confirmed by FTIR. The 5% alkali treated APLSF exhibited a highest tensile strength of 486.41 ± 35.57 MPa, tensile modulus of 9.89 ± 1.46 GPa and elongation at break of 4.91 ± 1.82%. The surface morphology, surface roughness and thermal stability of fibers were examined by SEM, AFM and TGA/DTG.