Extraction of cellulose nanowhiskers from natural fibers and agricultural byproducts

In this work the feasibility of extracting cellulose from cotton, sisal and flax fibers, corn stover and rice husk by means of usual chemical procedures such as acid hydrolysis, chlorination, alkaline extraction, and bleaching was analyzed. Cellulose nanowhiskers from these sources, and from commercial cellulose, were produced by the acid hydrolysis of the obtained celluloses. The final products were characterized by means of Thermogravimetric Analysis (TGA), Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM) and Atomic Force Microscopy (AFM). The chemical procedure used to obtain cellulose nanowhiskers was effective in all cases but differences on the thermal stability, chemical composition, crystallinity and morphology were found due to the dissimilar nature of the different sources. Thus, this work demonstrates that the morphology and physical properties of cellulose nanowhiskers synthesized by the same conditions are strongly dependent on their source.     

Modification of enzyme pretreated cotton fabric using acrylonitrile, acrylonitrile/solvent mixture and its characterization

The presented research deals with modifying the chemical structure of the bioscoured cotton fabric by acrylonitrile, acrylonitrile/acetone, and acrylonitrile/ethanol mixture. The modified cellulose was tested for weight gain, shrinkage, and wicking height and characterized by X-ray diffraction (XRD), thermal analysis (TG/DTA), elemental analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The weight gain and shrinkage % show increased value for modified fabrics. The wicking height increases with addition of solvent. The crystallinity and thermal studies show a significant change. FTIR analysis confirms the modification by the occurrence of -C??N stretching and -CONH₂ stretching. The SEM morphology of modified fabric shows uniform swelling of fibers with better smoothness. The AFM topography reveals that the addition of solvent affects the particle size. Clear surface morphology of modified fabric reveals that this processing method can be used for preparation of medical textiles with more swelling.     

Low-temperature pyrolysis on jute fibers as a thermochemical modification method

Low-temperature pyrolysis up to 200, 250, 300 °C was conducted in order to remove non-cellulosic compounds without damaging the structure of the cellulose in jute fibers. The chemical, morphological, and mechanical aspects of prepared low-temperature pyrolyzed jute fibers were investigated by Fourier transform infrared (FTIR) spectroscopy, the wettability test in water/dichloromethane system, moisture content measurement, X-ray diffraction (XRD) analysis, scanning electron microscope (SEM), and tensile test using universal testing machine (UTM). It was confirmed that hydrophilic compounds including absorbed water, low molecular weight compounds such as waxes, hemicellulose, and lignin were largely removed from the fibers. Increasing amounts of non-cellulosic compounds were removed as the maximum pyrolysis temperature was increased. The degree of hydrophilic nature of jute fibers were reduced by low-temperature pyrolysis and thus water absorptivity of pyrolyzed jute fibers was reduced as maximum pyrolysis temperature increased. Furthermore, XRD analysis and morphological studies by SEM indicated that the crystalline structure of native cellulose was rarely damaged after pyrolysis up to 300 °C. In case of mechanical properties, breaking tenacity and breaking strain of the fibers decreased with increasing maximum pyrolysis temperatures because flaws formed on the surface of pyrolyzed jute fibers acted as weak-links. In agreement with predictions made according to Weibull’s weakest-link theory, it was found that shortened pyrolyzed jute fibers could have higher breaking tenacities compared with raw jute fibers of the same length. In addition, the compatibility with hydrophobic matrix was investigated by the mechanical properties of polypropylene (PP) reinforced with jute fibers. Consequently, it was hypothesized that low-temperature pyrolysis could be used to process raw jute fibers for use as short fiber reinforcements in fiber-polymer systems or be a simple and effective pretreatment method for a wide range of further chemical treatments.     

Enzymatic treatment on cotton fibers: degradation kinetics of pectin and influence of shape change on adsorption

Alkaline pectinase was one of the most effective enzymes to treat cotton as alternative agent to replace the conventional alkaline method. Removal of pectin and cutin was considered the explanation for improvement of wettability as well as water adsorption on cotton fiber. However, degradation kinetics of pectin is unclear, and the influence of fiber shape on property changes after enzymatic treatment was ignored. The main objective of this work was to reveal interactions between pectinase and cotton fiber for mechanism study. A heterogeneous catalysis kinetic equation, which is associated with Langmuir adsorption model and enzyme deactivation, was used to describe the heterogeneous catalysis. The enzymatic process conditions were optimized. Raw cotton fibers, pectinase-treated and alkali-treated fibers were characterized by impurities content determination, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). Mechanism of water adsorption enhancement on treated fibers was discussed. In addition to elimination of the outer impurities, flat fibers with less twist and shape changes of lumen were also obtained to ensure better accessibility and water adsorption after enzymatic treatment.     

Characterization of depolymerized residues from extremely low acid hydrolysis (ELA) of sugarcane bagasse cellulose: Effects of degree of polymerization, crystallinity and crystallite size on thermal decomposition

Sugarcane bagasse cellulose was subjected to the extremely low acid (ELA) hydrolysis in 0.07% H₂SO₄ at 190, 210 and 225 °C for various times. The cellulose residues from this process were characterized by TGA, XRD, GPC, FTIR and SEM. A kinetic study of thermal decomposition of the residues was also carried out, using the ASTM and Kissinger methods. The thermal studies revealed that residues of cellulose hydrolyzed at 190, 210 and 225 °C for 80, 40 and 8 min have initial decomposition temperature and activation energy for the main decomposition step similar to those of Avicel PH-101. XRD studies confirmed this finding by showing that these cellulose residues are similar to Avicel in crystallinity index and crystallite size in relation to the 110 and 200 planes. FTIR spectra revealed no significant changes in the cellulose chemical structure and analysis of SEM micrographs demonstrated that the particle size of the cellulose residues hydrolyzed at 190 and 210 °C were similar to that of Avicel.     

Synthesis and characterization of cellulose carbamate by liquid-solid phase method

An efficient and environmentally friendly method for the synthesis of cellulose carbamate from a mixture of cellulose pulp or the activated cellulose pulp and urea was presented in this paper. Cellulose carbamate with a nitrogen content of 1.21 % and 3.29 % were successfully synthesized via esterification reaction in the high-boiling aprotic and polar N-methyl-2-pyrrolidone solvents (hereinafter NMP). The structures of cellulose carbamate were characterized by Fourier transform infrared spectroscopy (FTIR), Kjeldahl analysis, thermo-gravimetric analysis, scanning electron microscopy (SEM), X-ray diffractometry (XRD), and ¹³C-solid-state NMR. The results showed that some functional groups of the alkali cellulose were substituted by amino in the high-boiling aprotic and polar solvents, then the cellulose carbamate was prepared with the reduced crystallinity and thermal decomposition temperature. In addition, the product was prepared with uniform substitution and distribution of carbamate group in the cellulose chain, which guaranteed its good solubility in aqueous alkali as well as its spinnability to produce fiber.     

Macro-micro structure,antibacterial activity,and physico-mechanical properties of the mulberry bast fibers

In this paper, the mulberry fibers were successfully obtained by a new pretreatment named alkali-assisted microwave plus biological enzymatic technique (AMBET). The morphology, microstructure, physico-mechanical and antibacterial properties of the mulberry bast fibers were investigated by means of scanning electron microscope (SEM), Fourier Transform-Infrared (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), instron tensile tester and antibacterial testing. The results showed that impurities of the bast fibers could be removed by AMBET treatment. AMBET treated mulberry fiber was even, smooth and fine, and typical cellulose I in the mulberry fibers was confirmed by FTIR and XRD analysis. The crystallinity of the AMBET treated fibers was higher than that of the raw mulberry and chemical treated mulberry fibers. Thermal analysis indicated that the mulberry fibers had a good thermal stability. Moreover, the AMBET treated mulberry fibers showed excellent antimicrobial activities against S.aureus. The physical properties of the mulberry fibers indicated the AMBET treated mulberry fibers were ideal candidates for new textile materials.     

Screen printed silver patterns on functionalised aramid fabric

In this work, a simple and low cost method based on screen printing is presented to synthesize a conductive silver pattern on aramid fabric. The aramid fiber was treated with (3-mercaptopropyl)-trimethoxysilane to introduce a tail mercapto group promoting the ordered binding of silver nanoparticles. SEM and AFM images indicated a uniform distribution of silver nanoparticles on fiber surface. FTIR and XRD patterns confirmed the silver layer on the fibers. Furthermore, the electrical property of conductive fiber was characterized by conductive AFM and a digital multimeter, the surface resistance of conductive fabric was as low as 0.20 Ω/cm. And single fiber tensile test indicated that the mild treating process has no significant influence on the mechanical properties of the fiber.     

N-halamine-bonded cotton fabric with antimicrobial and easy-care properties

N-halamine precursor 2,2,6,6-tetramethyl piperidinol (TMP), a hindered amine light stabilizer, was bonded onto cotton fabric by using 1,2,3,4-butanetetracarboxylic acid (BTCA) as a crosslinking agent. A variety of treating conditions including TMP concentration, curing temperature and time, and catalyst were studied. The treated fabrics were characterized using FTIR spectra and scanning electron microscope (SEM). The cotton fabric treated with TMP precursor could be rendered biocidal upon exposure to dilute household bleach. The chlorinated cotton swatches showed great efficacy and inactivated 100 % of Staphylococcus aureus with 7.1 log reduction with 5 min of contact and 83.25 % of E. coli O157:H7 at 10 min of contact. In addition, the wrinkle recovery angle of the treated cotton fabrics increased from 229 ° of untreated cotton fabrics to 253 °. This study provided a practical finishing process to produce cotton fabrics with easy care and antibacterial functionalities at the same time.     

Preparation of adsorbent based on cotton fiber for removal of dyes

Synthetic dyes are used extensively in modern industries, which are toxic and harmful to environment and human. Cotton fiber is a kind of abundant, renewable and eco-friendly cellulose fiber in nature, however, the adsorption capacity of raw cellulose for pollutants was often low. Therefore, an efficient adsorbent for removal of dyes was successfully prepared by grafting beta-cyclodextrin (β-CD) and amino-terminated hyperbranched polymer (NH₂-HBP) onto cotton fibers in this study, which was effective to anionic dyes and cationic dyes. The adsorbent were characterized using FTIR, SEM and XPS analysis. The results of adsorption experiments showed that the adsorbent based on cotton fiber exhibited better adsorption performance for Congo red(CR) and methylene blue(MB). The experimental results revealed that the pH value had a great influence on the adsorption capacity.     

Preparation of Durable Antibacterial Cellulose with AgCl Nanoparticles

In this study, a facile method was developed to coat AgCl nanoparticles (NPs) onto knitted cotton fabrics. The AgCl NPs were characterized by ultraviolet absorption spectrum, X-ray diffraction (XRD) and dynamic laser light scattering (DLS). The AgCl NPs were coated onto cotton fabrics through a pad-dry-cure process with the assistance of 1,2,3,4- butanetetracarboxylic acid (BTCA). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ICP-OES analysis and energy-dispersive X-ray spectroscopy (EDX) confirmed that AgCl NPs were successfully coated onto cotton fabrics. The prepared cotton samples exhibited excellent antimicrobial activity against both Gram-positive S. aureus and Gram-negative K. pneumonia bacteria. Rat skin fibroblast cytotoxicity testing demonstrated the treated cotton fabrics to be non-toxic. The washing durability evaluation showed that the antimicrobial function of cotton fabrics was durable to washing. In addition, the wrinkle resistance of the coated cotton fabrics was improved and there was no obvious change in whiteness.     

菠萝叶纤维制备纳米纤维素晶体的研究

菠萝叶纤维经过氢氧化钠预处理、硫酸水解制备得到纳米纤维素晶体（NCC）,再用扫描电镜（SEM）、傅立叶转换红外光谱仪（FTIR）、热重（TG）分析仪和X-射线衍射分析仪（XRD）对其结构和性能进行表征和分析。结果表明,NCC晶体颗粒尺寸为30~50 nm;红外光谱证明非纤维素部分有效去除;NCC晶型仍属于纤维素I,结晶度从75.9％提高到87.5％;比起原纤维,NCC的降解温度明显降低。     

Synthesis of silver nanoparticles with sericin and functional finishing to cotton fabrics

This research presents a novel strategy to fabricate multi-functional cotton textiles. In this study, silver nanoparticles-sericin (Ag NPS-sericin) hybrid colloid has been prepared using sericin as reducing agent and dispersing agent. Cotton fabrics was oxidized selectively with sodium periodate (NaIO₄) to generate oxidized cotton fabrics, and which has then been finished using Ag NPS-sericin hybrid colloid prepared to obtain multi-functional cotton textiles. The finished cotton fabric not only possessed excellent antibacterial activity, but also it was modified functionally by sericin protein, which endowed antibacterial cotton fabrics relatively smooth surface and good wear ability. Fourier transform infrared spectrogram confirmed that sericin protein was grafted onto cellulose fibers. Ag NPs were characterized by UV-Vis spectroscopy, transmission electron microscope (TEM) and X-ray powder diffraction (XRD). The results of SEM, X-ray photoelectron spectroscopy (XPS) and EDS confirmed that silver nanoparticles and sericin been loaded successfully on the surface of cotton fabrics. The antibacterial experiments showed bacterial reduction rates of S.aureus and E.coli were able to reach above 99 %. After washing 20 times, it showed still good antibacterial activity at over 95 % against S.aureus and E.coli.     

Preparation of electroconductive,magnetic, antibacterial,and ultraviolet-blocking cotton fabric using reduced graphene oxide nanosheets and magnetite nanoparticles

The main goal of present study was the fabrication of cotton fabric with special functions, including electrical conductivity, magnetic, antibacterial, and ultraviolet (UV) blocking. In this regard, the cotton fabric was primarily coated with graphene oxide and then reduction of graphene oxide and synthesis of magnetite nanoparticles accomplished in one step. The alkaline hydrolysis of magnetite precursors and reduction of graphene oxide was simultaneously performed using sodium hydroxide to produce reduced graphene oxide/Fe₃O₄ nanocomposite on the fabric surface. The prepared cotton fabrics were characterized with field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The treated fabrics with reduced graphene oxide/Fe₃O₄ nanocomposite displayed a low electrical resistivity i.e. 80 kΩ/sq. Furthermore, the coated fabrics showed reasonable magnetic properties due to the presence of magnetite nanoparticles on the surface of cotton fabrics. Moreover, this process imparted proper antibacterial properties and UV blocking activity to cotton samples.     

Extraction, preparation and characterization of cellulose fibres and nanocrystals from rice husk

Cellulose fibres and cellulose nanocrystals were extracted from rice husk. Fibres were obtained by submitting the industrial rice crop to alkali (NaOH) and bleaching treatments. Nanocrystals were extracted from these fibres using sulphuric acid (H₂SO₄) hydrolysis treatment. The material obtained after each stage of the treatments was carefully characterized and its chemical composition was determined. Morphological investigation was performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy showed the progressive removal of non-cellulosic constituents. X-ray diffraction (XRD) analysis revealed that the crystallinity increased with successive treatments. The thermal stability of the rice husk fibres and cellulose nanocrystals was also investigated using thermogravimetric analysis (TGA).     

The influence of supermasscolloider on the morphology of sugarcane bagasse and bagasse cellulose

Sugarcane bagasse (SB) was subjected to mechanical and chemical treatments in order to investigate the influence of both treatments on the morphology of cellulose extracted from SB. Samples treated with supermasscolloider (SMC) showed a slight increase in the cellulose content and a highest content after chemical treatment. Furthermore, SEM and XRD results revealed a decline in the fibre average diameter (10-2 μm) and sheet-like fibrils from mechanically treated samples, while the crystallinity index values increased for both mechanical and chemical treatment. FTIR and chemical composition analysis confirmed a partial removal of hemicellulose and lignin by supermasscolloider, whereas the chemical treatments removed a significant amount and this was effectively reflected on the improved thermal stability of cellulose mechanically and chemically treated respectively.     

Dissolution of cellulose in NaOH based solvents at low temperature

Three low-cost types of complex solvents systems were carried out to dissolve cellulose, which were NaOH/urea/acetamide, NaOH/urea/tetraethyl ammonium chloride, and NaOH/acetamide/tetraethyl ammonium chloride. As an effective dissolution, NaOH/acetamide/tetraethyl ammonium chloride behaved as the optimum system, and the solubility was 89 % under the conditions of: NaOH 8 wt%, acetamide 10 wt%, tetraethyl ammonium chloride 6 wt%, distilled water 76 wt%, and freezing temperature ?5°C. With the analysis of Ubbelohde viscometer, infrared spectra (FTIR), wide-angle X-ray diffraction (XRD), and thermogravimetric analysis (TGA) for the original and regenerated cellulose samples, it was indicated that the viscosity-average molecular weight had no significant changes in the dissolution process, the crystalline structure of cellulose was converted to cellulose II from cellulose I in native cellulose, and the regenerated cellulose had a good thermal stability.     

Effect of nano SrTiO3 supporting nano TiO2 on self-cleaning of cotton fabric

This study reports the results of an investigation aiming at finding what affect nano titania (TiO₂) and nano strontium titanate (SrTiO₃) on self-cleaning of cotton fabrics. The photocatalytic activity of nano strontium titanate has been examined on cotton fabric under UV irradiation in various concentrations in mixing of nano titania. The amount of loaded nano titania and nano strontium titanate particles on cotton fabrics were investigated using X-ray fluorescence spectrometry (XRF) and crystallinity of coatings by X-ray diffraction spectroscopy (XRD). The treated cotton fabrics, which were stained with two common synthesized dyes, were exposed to 400 W UV radiation for 30 hours and their self-cleaning property was investigated by a reflectance spectrophotometer. Scanning electron microscope (SEM) images show pervasion of nano materials on the surface of the treated cotton. Adding nano strontium titanate to nano titania showed the most promising photocatalytic activity toward dye degradation.     

The formation and UV-blocking property of flower-like ZnO nanorod on electrospun natural cotton cellulose nanofibers

We report a simple and effective route to fabricate branched hierarchical flower-like nanostructures of ZnO on natural cotton cellulose fiber by combining electrospinning and the low-temperature hydrothermal growth technique. First, natural cotton cellulose nanofibers were prepared by electrospinning cotton cellulose /LiCl/DMAc solution. The electrospun cotton cellulose nanofibers served as flexible substrate, on which the branched, highly uniform, and dense flower-like ZnO were hydrothermally grown. The as-prepared cotton cellulose/ZnO nanocomposite fibers were characterized by SEM, HRTEM, EDS, TG, and UV-vis spectrophotometry. The modified cotton cellulose nanocomposite fibers were not only exhibiting dispersed uniformly, but also rendered excellent protection against UV radiation because of the incorporation of flower-like ZnO nanostructures. Therefore, the as-prepared nanocomposite fibers demonstrate a significant performance in ultraviolet protection and provide a potential application for ultraviolet detection.     

Effect of various shapes of zinc oxide nanoparticles on cotton fabric for UV-blocking and anti-bacterial properties

Various shapes of ZnO — multi-petals, rod and spherical — were prepared and then applied on cotton fabric for UV-blocking and anti-bacterial properties. The ZnO particles were investigated by XRD and SEM. The as-prepared suspension was applied onto cotton fabrics via the pad-dry-cure process at 150 °C. The characteristics of the fabric coating were investigated by SEM, XRD and Atomic Absorption Spectroscopy (AAS). The UV-blocking effectiveness was measured with a UV-Vis spectrophotometer whilst the antibacterial activity was determined using the AATCC 147 method. The results of XRD and SEM on the ZnO powders show that we can produce various shapes of ZnO. The investigation by SEM and AAS clearly revealed that ZnO was effectively deposited on the cotton surface and that the adhesion was retained after washing ten cycles. The sphericals-shaped ZnO and multi-petals shaped ZnO coated fabrics show excellent UV-blocking properties. All treated samples showed good antibacterial activity against Staphylococcus Aureus. The shape of ZnO shows no considerable effect on antibacterial properties.