The effect of water immersion on the thermal degradation of cotton fibers

The decomposition behavior of cotton fibers is examined using thermogravimetric analysis. The effect of the test parameters on the thermal degradation of raw cotton fibers is determined. Focus is given to the influence of water immersion on the thermal behavior of cotton fibers. For less mature fibers a clear difference is noted between the degradation profiles of the water-immersed and untreated samples. On the contrary, only a small change is noted on the degradation profile for more mature fibers after water immersion. The maturity and variations in water-soluble content of the fiber are found to be important factors influencing the thermal behavior of raw cotton fibers. Inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to underpin the effect of water immersion on cotton fibers. This improved understanding for the role of maturity and water soluble constituents in thermal degradation of cotton fibers may lead to develop routes that improve thermal stability and smoldering characteristics of cotton fibers as relevant for future applications.     

Bi-phobic cellulose fibers derivatives via surface trifluoropropanoylation

The surface modification of cellulose fibers with 3,3,3-trifluoropropanoyl chloride (TFP) was studied in a toluene suspension. The characterization of the modified fibers was performed by elemental analysis, Fourier transform infrared (FTIR), 13C-solid-state NMR, X-ray diffraction, thermogravimetry, and surface analysis (XPS, ToF-SIMS, and contact angles measurements). The degree of substitution (DS) of the ensuing trifluoropropanoylated fibers ranged from less than 0.006 to 0.30, and in all instances the fibers' surface acquired a high hydrophobicity and lipophobicity resulting from a drastic reduction in its energy. The hydrolytic stability of these cellulose derivatives was also evaluated and shown to be permanent in time in the presence of neutral water, still appreciable in basic aqueous solution at pH 9, but, as expected quite poor at pH 12.     

Single stage purification of flax,hemp, and milkweed stem and their physical and morphological properties

Agriculture biomass is an alternative possible solution for the extraction of cellulose, compared to the classical soft and hard wood. However, the valorization of cellulose is challenging for the researchers as it involves multiple steps. In the present study, the raw fibers of flax, hemp, and milkweed stem fibers were purified in single step using hydrogen peroxide in water. By this method authors successfully extracted the purified cellulose fibers without damaging the fiber length. The purified fibers were characterized to understand the thermal, functional, crystalline, and morphological properties by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The FTIR results showed the effective removal of lignin and significant improvement in thermal stability was observed by TGA. Evidently, the SEM results showed significant improvement in the morphology compared to that of the raw fibers. XRD results showed that the treatment does not affect the crystallinity of the fibers.     

Development of protective polymer coatings for silver halide fibers and their application as threshold level sensors for chlorinated hydrocarbons in sea water

The stability of silver halide fibers in artificial sea water (ASW) with and without a protective polymer coating and the influence of high salt concentrations on the sensor response was investigated. In contrast to bare silver halide fibers, the polymer coated fibers remain stable in contact with chloride solutions. This enables the application of a recently presented mid-IR fiber evanescent wave spectroscopy (FEWS) sensor system for the quantitative detection of chlorinated hydrocarbons (CHC) also in sea water.     

Effect of gamma radiation on the physico mechanical properties of recycled HDPE/modified sugarcane bagasse composite

In this work, the sugarcane bagasse (SCB) fibers were used as reinforcing filler for recycled high density polyethylene (rHDPE) to form eco-friendly composite. The SCB surface was chemically modified to improve the compatibility with rHDPE matrix. The SCB fibers were alkali modified using 10% sodium hydroxide (SCBm) and acetylated using acetic anhydride (SCBac). The chemically modified SCB fibers were characterized using Fourier transform infrared (FTIR) and scanning electronic microscopy (SEM). The composites were prepared by mixing of rHDPE with 15 phr (parts per hundred parts rHDPE) of different SCB samples. Neat rHDPE and its composites with SCB were irradiated by gamma radiation dose of 50–250 kGy. The Effect of gamma radiation on the water up-take, mechanical properties and the thermal stability of (rHDPE) and its composites was studied. The effect of gamma radiation on the compatibility between rHDPE and SCB was also investigated. The results showed that the combination between the chemical modification of fibers and the irradiation of polymer composites were more effective in compatibility improvement than chemical modification alone. The irradiated (at 100 kGy) composite containing of SCBac gave the best mechanical properties, lowest water up-take and the highest thermal stability.     

Preparation and Properties of Cellulose/Waste Leather Buff Biocomposites

The aim of the present work was to utilize waste leather buff (WLB) as filler in cellulose and make biocomposites for packaging applications such as wrappers. Cellulose was dissolved in the environmentally friendly ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). To this solution, WLB was added in amounts of 5 to 25 wt.% of cellulose. The cellulose and cellulose/WLB composite films were prepared by regenerating the corresponding cast solutions in a water coagulation bath followed by washing and drying. These films were tested for their tensile properties, thermal stability, and morphology. The tensile modulus and strength of the composite films were lower than those of the matrix. The lowering of the tensile modulus and strength with increasing WLB loading was attributed to the random orientation of the leather fibers of WLB in the composites. However, the % elongation at break of the composite films was found to be higher than that of the matrix and increased with increasing WLB content. The possible interaction between the matrix and WLB filler was probed using FT-IR analysis. The thermal stability of the composite films was higher than that of the matrix. The increase in thermal stability of the composite films was attributed to cross-linked collagen protein leather fibers in WLB. The fractographs of the composite films indicated good interfacial bonding between cellulose and leather fibers of WLB. These composite films may be considered for packaging and wrapping applications.     

A novel strategy to increase performance of solid‐phase microextraction fibers: Electrodeposition of sol‐gel films on highly porous substrate

In the present work, the effect of substrate porosity for preparation of solid‐phase microextraction (SPME) fibers was investigated. The fibers were prepared by electrodeposition of sol‐gel coatings using negative potentials on porous Cu wire and compared with previous reported technique for preparation of SPME fibers using positive potentials on smooth gold wire. Porous substrate was prepared by electrodeposition of a thin layer of Cu on a Cu wire. The extraction capability of prepared fibers was evaluated through extraction of some aromatic hydrocarbons from the headspace of aqueous samples. The effect of substrate porosity and some operating parameters on extraction efficiency was optimized. The results showed that extraction efficiency of SPME fibers highly depends on porosity of the substrate. The LOD ranged from 0.005 to 0.010 ng/mL and repeatability at the 1 ng/mL was below 12%. Electrodeposited films were characterized for their surface morphology and thermal stability using SEM and thermogravimetric analysis, respectively. SEM analysis revealed formation of porous substrate and subsequently porous coating on the wire surface and thermogravimetric analysis showed high thermal stability of the prepared fiber.     

Novel antibacterial fibers of quaternized chitosan and poly(vinyl pyrrolidone) prepared by electrospinning

The preparation of continuous defect-free fibers from quaternized chitosan derivative (QCh) has been achieved by electrospinning of mixed aqueous solutions of QCh with poly(vinyl pyrrolidone) (PVP). The average fiber diameter significantly decreases from 2800 to 1500 nm on increasing the polyelectrolyte content. In order to impart to QCh/PVP electrospun fibers stability to water and water vapor, the fibers have been crosslinked by incorporation of photo-crosslinking additives into QCh/PVP spinning solutions and subsequent UV irradiation of the electrospun fibers. Photo-crosslinked QCh-containing electrospun mats show high antibacterial activity against the Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli.     

A visible coalescence of droplets on hydrophobic and hydrophilic fibers in water-in-oil emulsion

The droplets’ coalescence is instantaneous and rather complex in emulsion. The theoretical analysis of this process was presented by a former research, while visible experiments to verify these are still scarce. This work aims to show and analyze the visible water droplets’ coalescence on hydrophobic bamboo charcoal fibers and hydrophilic glass fibers in water-in-oil emulsion. An experimental setup with microscope and high-speed camera was designed and established to record the water droplets’ coalescence. The water droplets’ collision coalescence on bamboo charcoal fibers was observed, and the diameters of water droplets detaching from the fibers with different angles were measured. The angle between the fiber and the flow velocity can affect the diameters of water droplets detaching from the bamboo charcoal fibers, and cross-fibers can the enormously increase water diameters compared with single fiber. Meanwhile, the water droplets’ collision coalescence on glass fibers was observed and the result shows that the collision coalescence also occurred on the hydrophilic glass fibers when the droplet diameter was small. In addition, other factors, including flow velocity and droplets’ diameter for the coalescence on the hydrophilic glass fibers were investigated.     

Thermal behavior of polypropylene fiber-reinforced concrete at elevated temperatures

The influence of polypropylene (PP) fibers on thermal behavior of concrete at elevated temperatures was studied by simultaneous thermal analysis. Two kinds of polypropylene fibers differing in form and size were applied as fillers. Special emphasis was given on the thermal behavior of PP fiber-reinforced concrete subjected to heat treatment, i.e., at 200 and 300 °C. Thermal events of concrete samples with and without fibers were characterized. In comparison to concrete sample without fibers, the results showed that the presence of polypropylene fibers affected the thermal stability of concrete samples. It was found that the influence of the kind and the amount (1.8 vs. 3.0 kg m^?3) of PP fiber on the thermal stability of concrete samples was not significantly pronounced.     

连续SiC(Al)纤维的耐超高温性能及其机理

以有机金属聚合物聚铝碳硅烷为原料, 利用先驱体转化法制备出连续SiC(Al)纤维. 采用一系列分析测试对纤维的组成、结构以及耐超高温性能进行了表征, 通过与Nicalon纤维的比较, 对连续SiC(Al)纤维的耐超高温机理进行了研究. 结果表明, 连续SiC(Al)纤维具有优异的耐超高温性能,在1800 ℃氩气中处理1 h后, 纤维的强度保留率为80%左右; 元素分析和27Al MAS核磁共振等分析表明, 连续SiC(Al)纤维为近化学计量比的SiC纤维, 纤维中微量的铝元素以Al—O和Al—C键两种形式存在; 在超高温条件下, 两种不同存在形式的铝均能够抑制纤维中晶粒的长大. 纤维具有近化学计量比的组成和铝元素在高温条件下对于晶粒长大的抑制, 是连续SiC(Al)纤维具有优异耐超高温性能的原因.     

Monitoring the polymerization process of polypyrrole films by thermogravimetric and X-ray analysis

Bio-composite fibers were developed from wood pulp and polypropylene (PP) by an extrusion process. The thermo-physical and mechanical properties of wood pulp-PP composite fibers, neat PP and wood pulp were studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The thermal stability of bio-composite fibers was found to be significantly higher than pure wood pulp. An understanding into the melting behaviour of the composite system was obtained which would assist in selecting a suitable temperature profile for the extruder during processing. The visco-elastic properties of bio-composite fibers were also revealed from the study. The generated bio-composite fibers were also characterized using Fourier transform infrared spectroscopy (FTIR) to understand the nature of chemical interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Changes in absorption peaks were observed in FTIR spectra of bio-composite fibers as compared to the pure wood pulp which indicated possible chemical linkages between the fiber and polymer matrix.     

Thermal and degradation behavior of fique fiber reinforced thermoplastic matrix composites

The influence of untreated and treated fique fibers on the crystallization process and thermal degradation of different thermoplastic matrix composites has been evaluated. The fique fibers have been treated with different chemicals according with the type of thermoplastic matrix employed. Additionally, a copolymer of poly(propylene) with maleic anhydride (MAPP) has been used as compatibilizer. The treatments introduce an increment on the thermal stability of fique fibers respect to untreated fibers. Crystallization is affected by the presence of fique fibers showing important differences for each type of composites. Fiber presence has an important influence on the matrix morphological characteristics, as observed by dynamical mechanical analysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cellulose nanofibers from curaua fibers

Curaua nanofibers extracted under different conditions were investigated. The raw fibers were mercerized with NaOH solutions; they were then submitted to acid hydrolysis using three different types of acids (H₂SO₄, a mixture of H₂SO₄/HCl and HCl). The fibers were analyzed by cellulose, lignin and hemicellulose contents; viscometry, X-ray diffraction (XRD) and thermal stability by thermogravimetric analysis (TG). The nanofibers were morphologically characterized by transmission electron microscopy (TEM) and their surface charges in suspensions were estimated by Zeta-potential. Their degree of polymerization (DP) was characterized by viscometry, crystallinity by XRD and thermal stability by TG. Increasing the NaOH solution concentration in the mercerization, there was a decrease of hemicellulose and lignin contents and consequently an increase of cellulose content. XRD patterns presented changes in the crystal structure from cellulose I to cellulose II when the fibers were mercerized with 17.5% NaOH solution. All curaua nanofibers presented a rod-like shape, an average diameter (D) of 6–10 nm and length (L) of 80–170 nm, with an aspect ratio (L/D) of around 13–17. The mercerization of fibers with NaOH solutions influenced the crystallinity index and thermal stability of the resulting nanofibers. The fibers mercerized with NaOH solution 17.5% resulted in more crystalline nanofibers, but thermally less stable and inferior DP. The aggregation state increases with the amount of HCl introduced into the extraction, due to the decrease of surface charges (as verified by Zeta Potential analysis). However, this release presented nanofibers with better thermal stability than those whose acid hydrolysis was carried out using only H₂SO₄.     

Characterization of hybrid epoxy composites reinforced by murta and jute fibers

The primary focus of the present work was to fabricate and characterize hybrid epoxy composites using jute and murta bast fibers. Murta and jute fibers with lengths of 35 mm each were mixed randomly with a polymer matrix by varying their relative amounts but keeping the total weight of the fiber mixture fixed at 30%. The hybrid composites were characterized based on values obtained from the experiments carried out to assess properties such as density, thermal stability, water absorption/retention, tensile/flexural/compressive/impact strengths, and hardness. The composite containing equal amounts of the two fibers exhibits synergism and superior properties.     

Novel blends from agave fibers and poly(methyl methacrylate)

Cellulose-rich fibers were isolated from Agave lechuguilla (AL) and Agave fourcroydes (AF) growing in the Mexican northeast. These fibers are a valuable feedstock for the preparation of blends with synthetic polymers like poly(methyl methacrylate), PMMA. Blends of different types of agave fibers (dewaxed, mercerized, and grafted) and PMMA were prepared and investigated by means of tension measurements and dynamic mechanical analysis. The fiber-containing blends are more stable than the plain PMMA. Surprisingly, the mechanical stability of the blends is practically independent of the pretreatment of the fibers. Methyl methacrylate (MMA) was grafted onto the biopolymer fibers initiated by the cerammonium nitrate redox initiator. Grafting yields of 26.5% were realized with fibers from AL while up to 75.8% MMA was grafted onto fibers from AF. The materials were characterized by means of FTIR spectroscopy and DSC.     

Studies of the properties of CHG-Loaded alginate fibers for medical application

Biomaterial-centered infection (BCI) is an important cause affecting wound healing, and preventing infection can accelerate wound healing and improve patients' cooperation. Our objective was to establish a dressings model by sustainably releasing chlorhexidine gluconate (CHG) to develop an effective method to inhibit wound infection. In this study, CHG-loaded alginate fibers was fabricated by wet blending spinning technology. The drug entrapment was confirmed by scanning electron microscopy, fourier transform infrared spectra, differential scanning calorimetry, X-ray diffraction and optical microscope. The content of chlorhexidine gluconate in fibers was determined by high performance liquid chromatography. Analysis indicated that chlorhexidine gluconate was successfully encapsulated into the alginate fibers and fibrous surface folds and area increases due to the grafting. The thermal stability of co-spun fibers was improved with the increasing content of chlorhexidine gluconate. Co-spun fibers exhibited better antibacterial activity and stability in comparison with pure alginate fibers, indicating that alginate fibers grafted with chlorhexidine gluconate has wider application prospect in the field of biomedical dressings.     

Qualitative characterization of the diffusion of cationic-modified PVA into the cellulose fiber pores

In this work, the diffusion of cationic poly (vinyl alcohol) (CPVA) with well-defined structures into the pores of bleached kraft fibers was investigated at equilibrium level of adsorption by means of adsorption, solute exclusion technique (SET), and nuclear magnetic resonance (NMR) relaxation method. The results showed that the interaction between CPVA and dextran polymers was weak, which allowed us to use the SET method to investigate the variation in the pore size of fibers upon diffusing CPVAs. Both adsorption and SET methods confirmed the diffusion of CPVA polymers into the fiber pores. However, the NMR technique was unable to reflect the pore size changes. The main reason for such results was probably the error that occurred in removing water between fibers via applying the water retention value (WRV) test prior to the NMR analysis. In fact, not all of the water on the fiber surface, especially on the surface of CPVA-modified fibers, could be removed by the WRV, introducing some error in the NMR analysis.     

Effect of Fiber Treatment on Dimensional Stability and Chemical Resistance Properties of Hybrid Composites

In this work, oil palm empty fruit bunch (EFB) and jute fibers were treated by 2-hydroxy ethyl acrylate (2-HEA) to enhance interaction with the epoxy matrix in hybrid composites. Hybrid composites were fabricated by the hand lay-up technique by reinforcing chemical-treated oil palm EFB and jute fibers in an epoxy matrix. Physical (density, void content, water absorption, and thickness swelling) and chemical resistance properties of treated hybrid composites were characterized. Chemically treated oil palm EFB/jute fiber reinforced hybrid composites display better dimensional stability (water absorption and thickness swelling) and chemical resistance as compared to untreated hybrid composites.     

Physicochemical and tensile properties of alkaline-treated new natural cellulosic Gossypium arboreum fiber

This article describes the characterization of novel natural lignocellulosic bark fibers extracted from the stem of the Gossypium arboreum (cotton) plant. The G. arboreum stem fibers were treated with 5% (w/v) aqueous NaOH solution for different soaking times, and the Fourier transform infrared spectroscopy analysis was conducted to examine the chemical compounds of the raw and treated fibers. The cellulose content improved from 70.06 to 83.91% after the treatment. The X-ray diffraction results indicate that the crystalline index and size were enhanced. Thermogravimetric analysis was performed to study the thermal properties and found that the thermal stability was higher for the treated fibers. The tensile strength and modulus were increased for the alkaline-treated fibers compared to the untreated fibers.