Extraction,modification, and characterization of natural ligno-cellulosic fiber strands from napier grass

Napier grass is a high-productivity perennial grass that is a very important forage for animals in the tropics. In this research work, fiber strands from Napier grass were extracted and the effect of acetic acid treatment on their chemical composition, morphological and structural changes, and tensile and thermal properties was studied. The acid treatment was carried out using glacial acetic acid solution at three different concentrations (5, 10, and 15%) for 2 h. Chemical analysis indicated lowering of amorphous hemicellulose content on acid treatment. FT-IR spectroscopic studies revealed variation of functional groups on acid treatment. Scanning electron micrographs indicated roughening of the surface of the fiber strands due to the removal of the hemicellulose layer on acid treatment. X-ray diffraction analysis indicated an increase in crystallinity of the fiber strands on acid treatment. The thermal stability and tensile properties of the fiber strands increased on acid treatment. This fiber has competitive advantages when evaluated with other natural fibers and can be developed further as a potential reinforcement in polymer matrix composites.     

Physico-chemical,Tensile, and Thermal Characterization of Napier Grass (Native African) Fiber Strands

This article presents the extraction and effect of alkali treatment on the physical, chemical, tensile, and thermal characteristics of fiber strands obtained from Napier grass, a renewable biomass. In order to improve these properties, the Napier grass fiber strands were treated with sodium hydroxide. The alkali treatment was carried out using NaOH solution at three different concentrations (5, 10, and 15%) for 2 h. Characterization of untreated and alkali-treated Napier grass fiber strands was carried out by studying the chemical composition, surface morphology, functional group variation, crystallinity, and tensile and thermal behavior. It was found that untreated fiber strands have lower cellulose content, crystallinity, tensile properties, and thermal stability than alkali-treated fiber strands. Napier grass fiber strands treated with 10% NaOH showed optimum tensile strength, modulus, and percentage elongation with an improvement of 51.9, 47.3, and 12.1% respectively. Based on the properties determined for alkali-treated Napier grass fiber strands, we expect that these fibers will be suitable for use as a reinforcement in natural fiber composites.     

Impact of alkali treatment on physico-chemical,thermal, structural and tensile properties of Carica papaya bark fibers

This study aims to examine the effect of sodium hydroxide (NaOH) treatment on the physico-chemical properties, structure, thermal, tensile and surface topography of Carica papaya fibers (CPFs). The surface of raw CPFs was modified by soaking with 5% NaOH solution for 15, 30, 45, 60, 75 and 90?min. The results of thermo-gravimetric analysis revealed that the optimum treatment time for alkali treatment was 60?min. It was found that the alkali treatment improved the properties of the CPFs. The results of TGA, FT-IR, XRD and AFM suggest that the treated CPF is a suitable alternative as reinforcement in polymer composites.     

Physicochemical and thermal properties of lignocellulosic fiber from sugar palm fibers: effect of treatment

Sugar palm fiber (SPF) is one of the prospective fibers used to reinforce polymer composites. The aim of this study is to evaluate the physicochemical, thermal, and morphological properties of SPF after alkali and sea water treatments. The chemical constituents group and thermal stability of the SPF were determined using scanning electronic microscopy (SEM) along with energy dispersive X-ray spectroscopy and thermogravimetric analysis (TGA). Fourier transform infrared spectroscopy was carried out to detect the presence of functional groups in untreated and treated SPF. The SEM images after both treatments showed that the external surface of the fiber became clean as a result. However, the sea water treatment affected the fiber properties physically, while the alkali treatment affected it both physically and chemically by dissolving the hemicellulose in the fiber. The TGA results showed that untreated fiber is significantly more stable than treated fiber. In conclusion, the results show that the fiber surface treatment significantly affected the characterization of the fiber.     

The effect of alkaline pretreatment on the thermal decomposition of hemp

The goal of this study was to clarify the effect of alkaline pretreatments on the thermal decomposition and composition of industrial hemp (Cannabis sativa L.) samples. Thermogravimetric/mass spectrometric measurements (TG/MS) have been performed, on untreated, hot water washed, and alkali-treated hemp samples. The main differences between the thermal decomposition of the samples are interpreted in terms of the different alkali ion contents which have been determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. Principal component analysis (PCA) has been used to find statistical correlations between the data. Correlations have been obtained between the parameters of the thermal decomposition and the alkali ion content as well as the altered chemical structure of the samples. The differences in the thermal behavior of the samples are explained by the different K⁺ and Na⁺ contents and the changed structure of the hemicellulose component of the samples due to the pretreatments. The more alkali ions remain in the hemp samples after the alkali treatment, the more ash, char and lower molecular products are formed during thermal decomposition.     

Investigation of Physico-Chemical Properties of Alkali-Treated Prosopis juliflora Fibers

There is ever-increasing interest in using natural fibers in polymer composite systems and textile industry. Prosopis juliflora fibers (PJFs) possess ideal characteristics that make them suitable for various applications. Alkali treatment of PJFs was primarily aimed to change their physico-chemical properties; 5% (w/v) NaOH concentration and 60 min of soaking time were found to be optimal. It is intriguing to note that optimally treated PJFs had higher cellulose (72.27 wt.%), lower hemicellulose (4.02 wt.%) and lignin (12.09 wt.%) contents, higher crystallinity index (73%), tensile strength, and thermal stability.     

Physicochemical and mechanical properties of a novel fiber extracted from the stem of common reed plant

Natural fiber usage rather than the synthetic fibers is attracted by researchers due to their special features such as biodegradable, inexpensive, easy availability, low density, and good thermal properties. This present work deliberates the characterization and testing of untreated and treated fibers extracted from the common reed plant stem. From the characterization, it reveals that the treated fibers had higher crystallinity index value with 75.41% and cellulose content having 64.56%. The thermal stability and mechanical properties of fiber was improved by alkali treatment. The surface roughness of the fibers due to the elimination of the noncellulosic substance on alkali treatment is evidenced by SEM.     

Exploration on the characteristics of cellulose microfibers from Palmyra palm fruits

To obtain cellulose microfibers from Palmyra palm fruit fibers, a new succession of specific chemical treatments including acidified chlorination, alkalization, and acid hydrolysis have been developed. Cellulose microfibers obtained were characterized by different techniques. The chemical analysis indicated an increase in α-cellulose content and decrease in lignin and hemicellulose for the cellulose microfibers over raw fibers. Fourier transform infrared and ¹³C NMR spectra confirmed the removal of non-cellulosic (lignin and hemicellulose) components after chemical treatments. The X-ray diffraction results revealed that the cellulose I was partly transformed into cellulose II by chemical treatments and the crystallinity index of cellulose microfibers was significantly increased as compared to raw fibers owing to removal of non-cellulosic components. Thermogravimetric analysis results demonstrated that the thermal stability was enhanced noticeably for cellulose microfibers than for the raw fibers. The scanning electron micrographs illustrated cleaner and rough surfaces for the cellulose microfibers when compared to those of raw fibers.     

Modification of natural fibers from Thespesia lampas plant by in situ generation of silver nanoparticles in single-step hydrothermal method

Ligno-cellulosic fibers have a great market and propose higher value addition and options to develop various products but they do not have inherent antimicrobial properties. In this study, a simple hydrothermal method was applied to build up antimicrobial properties to natural fibers by in situ-generating silver nanoparticles (AgNPs) in them. Herein, the ligno-cellulosic Thespesia lampas natural fibers were selected to develop antimicrobial activity using silver nitrate (AgNO₃) solution by hydrothermal method. The modified fibers were characterized by SEM, FTIR, XRD, TGA, and antibacterial activity tests. The modified fibers had spherical AgNPs with an average size of 95?nm. The thermal stability of the modified fibers was higher than that of the unmodified fibers. The modified fibers exhibited good antibacterial activity against both the Gram negative and Gram positive bacteria. These modified fibers can be considered as fillers in polymer matrices to make antibacterial composites.     

Thermal behavior of corn fibers and corn fiber gums prepared in fiber processing to ethanol

In this work, a thorough study of all solid products obtained in corn fiber processing to ethanol has been carried out with thermogravimetry/mass spectrometry (TG/MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The thermal behavior of corn fiber, destarched corn fiber, various alkali pretreated fibers and corn fiber gums were compared.It has been established that no significant changes occur in the thermal behavior of the feedstock material as a result of treatment with amylolytic enzymes. On one hand only the concentration of the alkali (NaOH or KOH) seems to be important in determining the chemical composition of the pretreated corn fiber samples. On the other hand, the composition of the corn fiber gums depends on the type and not the concentration of the alkali used in the pretreatment step. The presence of H₂O₂ degrades the structure and alters the composition of the corn fiber to a larger extent. The polymeric hemicellulose which is precipitated after pretreatment with NaOH + H₂O₂ contains less impurities than the corn fiber gum prepared in the absence of hydrogen peroxide.The results indicate that the applied analytical methods are suitable for studying changes in the composition of the variously treated corn fibers. The observed effects of the treatments are in good agreement with data determined with conventional analytical techniques.     

Effects of hydrolysis conditions on the morphology,crystallinity, and thermal stability of cellulose nanocrystals extracted from kenaf bast fibers

Cellulose nanocrystals (CNC) were first isolated from kenaf bast fibers and then characterized. The raw fibers were subjected to alkali treatment and bleaching treatment and subsequent hydrolysis with sulfuric acid. The influence of the reaction time on the morphology, crystallinity, and thermal stability of CNC was investigated. Fourier transform infrared spectroscopy showed that lignin and hemicellulose were almost entirely removed during the alkali and bleaching treatments. The morphology and dimensions of the fibers and acid-released CNC were characterized by field emission scanning electron microscopy and transmission electron microscopy. X-Ray diffraction analysis revealed that the crystallinity first increases upon hydrolysis and then decreases after long durations of hydrolysis. The optimal extraction time was found to be around 40 min during hydrolysis at 45 °C with 65% sulfuric acid. The thermal stability was found to decrease as the hydrolysis time increased. The electrophoretic mobility of the CNC suspensions was measured using the zeta potential, and it ranged from −8.7 to −95.3 mV.     

Mechanical Properties and Chemical Resistance of Short Tamarind Fiber/Unsaturated Polyester Composites: Influence of Fiber Modification and Fiber Content

In the present work, tamarind fibers were extracted from ripened fruits by the water retting process. Using these fibers as reinforcement and unsaturated polyester as matrix, composite samples were prepared by the hand lay-up technique. The effect of chemical surface treatments (alkali and silane) of tamarind fibers on the mechanical properties, chemical resistance, and interfacial bonding was studied. The mechanical properties of the composites with surface modified fibers were found to be higher than those with unmodified fibers. Morphological studies indicated improvement of interfacial bonding by alkali and silane coupling agent treatments of the fibers. The composites were found to be resistant to many chemicals.     

Influence of silver nano‐additive amount on the supramolecular structure,porosity, and properties of polyacrylonitrile precursor fibers

This work examines the influence of the amount of silver nanoparticles added to polyacrylonitrile spinning solutions on their rheological properties as well as the structure and properties of the fibers produced. The influence of the amount of silver nanoparticles on the supramolecular structure of nanocomposite polyacrylonitrile precursor fibers, their porosity, as well as thermal and tensile strength properties was determined. The distribution of the nano‐ additive in fiber cross‐sections and on the surface was estimated. It was found that the addition of silver nanoparticles to polyacrylonitrile precursor fibers in an amount of up to 1.5% does not cause a decrease in the susceptibility of the fiber matter to deformation at the drawing stage. The produced fibers were characterized by an increased total volume of pores of 0.35 cm³/g and tenacity of more than 34 cN/tex. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of Chemical Treatment and Fiber Loading on Mechanical Properties of Borassus (Toddy Palm) Fiber/Epoxy Composites

The aim of the present study was to investigate and compare the mechanical properties of untreated and chemically modified Borassus fiber–reinforced epoxy composites. Composites were prepared by the hand lay-up process by reinforcing Borassus fibers with epoxy matrix. To improve the fiber-matrix adhesion properties, alkali (NaOH) and alkali combined with silane (3-aminopropyltriethoxysilane) treatment of the fiber surface was carried out. Examinations through Fourier transform-infrared spectroscopy and scanning electron microscopy (SEM) were conducted to investigate the structural and physical properties of the Borassus fibers. Tensile properties such as modulus and strength of the composites made with chemically modified and untreated Borassus fibers were studied using a universal testing machine. Based on the experimental results, it was found that the tensile properties of the Borassus-reinforced epoxy composites were significantly improved as compared with the neat epoxy. It was also found that the fiber treated with a combination of alkali and silane exhibited superior mechanical properties to alkali-treated and untreated fiber composites. The nature of the fiber/matrix interface was examined through SEM of cryo-fractured samples. Chemical resistance of composites was also found to be improved with chemically modified fiber composites.     

Untreated and alkali treated fibers from Alfa stem: effect of alkali treatment on structural,morphological and thermal features

Alfa stems are rich in cellulose and they are an inexpensive, easily renewable source of natural fibers with the potential for polymer reinforcement. However, large amounts of non-cellulosic materials, surface impurities and low degradation temperature make natural fibers less attractive for reinforcement of polymeric materials, unless they can be modified in a proper way. In this paper, Alfa stems were treated with NaOH solution with two different concentrations (1 and 5 wt%). Raw and treated stems were crushed to obtain fibers. Stems and fibers were characterized by scanning electron microscopy (SEM) and optical microscopy, respectively. Their crystallinity index was determined by X-ray diffraction, thermal stability by thermogravimetry and structural change by FT-IR and ¹³C NMR spectroscopy. Comparison and analysis of results confirmed some thermal, structural and morphological changes of the fibers after treatment due to removal of some non-crystalline constituents from the plant. SEM showed rougher surfaces after alkalization. FT-IR and ¹³C NMR showed a gradual improvement in cellulose level by alkali treatment with increasing NaOH concentration. The crystallinity index and thermal stability of treated Alfa fibers were also found to be improved.     

Isolation of cellulose fibers from kenaf using electron beam

Cellulose fibers were isolated from a kenaf bast fiber using a electron beam irradiation (EBI) treatment. The methods of isolation were based on a hot water treatment after EBI and two-step bleaching processes. FT-IR spectroscopy demonstrated that the content of lignin and hemicellulose in the bleached cellulose fibers treated with various EBI doses decreased with increasing doses of EBI. Specifically, the lignin in the bleached cellulose fibers treated at 300 kGy, was almost completely removed. Moreover, XRD analyses showed that the bleached cellulose fibers treated at 300 kGy presented the highest crystallinity of all the samples treated with EBI. Finally, the morphology of the bleached fiber was characterized by SEM imagery, and the studies showed that the separated degree of bleached cellulose fibers treated with various EBI doses increased with an increase of EBI dose, and the bleached cellulose fibers obtained by EBI treatment at 300 kGy was separated more uniformly than the bleached cellulose fiber obtained by alkali cooking with non-irradiated kenaf fiber.     

Comparative study on enhanced pectinase and alkali-oxygen degummings of sisal fibers

This paper reports an improved traditional fiber degumming method, where sisal fibers were treated by alkali oxygen and pectinase, respectively, after the solute alkali pretreatment. To explore the influence of various factors on its degumming, efficiency of degumming through single factor and orthogonal experiments was aasessed. The results showed that pectinase/alkali-oxygen method after the first alkali treatment had a good effect on the degumming of sisal fiber, and most of the non-cellulose components such as hemicellulose, lignin and pectin had been removed. After pectinase treatment, the cellulose content and crystallinity were 71.87% and 66.29%, respectively. After alkaline oxygen treatment, the cellulose content was 77.16%, and the crystallinity was 69.09%. In terms of degumming rate, alkali oxygen treatment worked better than pectinase treatment, the degumming rate of pectinase method was about 10%, while that of alkali-oxygen method was more than 20%. In other hand, the pectinase method was much milder and had less damage to fibers. It would provide some references for the future application and development of sisal fiber.

     

Physicochemical properties of new cellulosic Artisdita hystrix leaf fiber

The characterization of new natural fiber is increasing due to its excellent properties. This drives investigators to create high performance composites. The present investigation was designed to study the physicochemical properties of fibers obtained from the leaf of the Artistida hystrix. The Artistida hystrix fibers (AHFs) had crystallinity index (44.85%), cellulose (59.54 wt%), hemicellulose (11.35 wt%), lignin (8.42 wt%), and density (540 kg m^?3). The tensile strength of AHFs was 440 ± 13.4 MPa with an average strain rate of 1.57 ± 0.04%. The calculated microfibril angle of AHFs was 12.64 ± 0.45°, which influenced the mechanical properties.     

Physico-Chemical Properties of Alkali-Treated Acacia leucophloea Fibers

The attractive properties of raw Acacia leucophloea fibers (ALFs) resulted in this present study evaluating the physio-chemical properties of alkali-treated ALFs. The treatment of raw ALFs with 5% (w/v) sodium hydroxide solution with 45 min soaking time was found to be optimum. It was found that optimally treated ALFs had relatively higher tensile strength (357–1809 MPa), Young’s modulus (10.45–87.57 GPa), and percentage of elongation (1.91–5.88%) and high thermal stability. The optimally treated ALFs had high cellulose (76.69 wt.%) and low hemicellulose (3.81 wt.%) and lignin (13.67 wt.%) contents and higher crystallinity index (74.27%), as evidenced by the results of chemical and X-ray diffraction analyses.     

Mechanical properties of polyimide/multi-walled carbon nanotube composite fibers

A series of polyimide (PI)/multi-walled carbon nanotube (MWCNT) composite fibers were prepared by copolymerizing a mixture of monomers and carboxylic-functionalized MWCNTs, followed by dry-jet wet spinning, thermal imidization, and hot-drawing process. The content of the carboxylic groups of MWCNTs significantly increased when treated with mixed acid, whereas their length decreased with treatment time. Both the carboxylic content and length of MWCNTs influenced the mechanical properties of the composite fibers. Fiber added with 0.1 wt% MWCNTs treated for 4 h exhibited the best mechanical properties, i.e., 1.4 GPa tensile strength and 14.30% elongation at break, which were 51% and 32% higher than those of pure PI fibers, respectively. These results indicated that a suitable MWCNT content strengthened and toughened the resultant PI composite fibers, simultaneously. Moreover, raising draw ratio resulted in the increase of tensile strength and tensile modulus of the composite fibers.