Sonosynthesis of cellulose nanoparticles (CNP) from kenaf fiber: Effects of processing parameters

This study optimizes the isolation parameters of cellulose nanoparticles (CNP) from kenaf fiber using central composite design (CCD). The extraction of CNP was based on three stages (i.e. 3 factors). The independent variables (factors) were NaOH dosage, amount of NaClO₂, and sonication time, while the dependent variables (response) were CNP size quality and degradation temperature. Later, size quality responses were fitted with a quadratic polynomial model and degradation point responses with a 2-factor interaction model (2FI). The quadratic model and 2FI models resulted R² values of 0.95 and 0.79, respectively. In addition, the morphological, thermal analysis, and Fourier transform infrared (FTIR) spectroscopy indicated a progressive removal of non-cellulosic constituents. Furthermore, transmission electron microscopy (TEM) confirmed reduction in fiber diameter from ~170 μm to ~100 nm. The optimal parameters for extraction of CNP were found to be 0.2 g of NaOH/4 g of fiber at first stage, 5 ml of NaClO₂/4 g of fiber at the second stage, and 20 min of sonication period during the third stage. Moreover, obtained cellulose nanoparticles were thermally more stable at higher temperature.     

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).     

Palladium immobilized on aminated polyacrylonitrile nanofiber as an efficient heterogeneous catalyst for Heck reaction

Aminated polyacrylonitrile (PAN-NH) nanofiber mats prepared by electrospinning and then aminated by multiamines with different chemical structures have been used for the immobilization of palladium. The PAN-NH fiber morphologies were characterized by scanning electron microscopy (SEM) and the dispersion of palladium particles on the PAN-NH fiber were examined by transmission electron microscopy (TEM). The catalytic activity and recyclability of the prepared heterogeneous palladium catalysts have been evaluated by the Heck reaction of iodobenzene with n-butyl acrylate. It was found that the catalytic activities of PAN-NH-Pd catalysts could be correlated with the chelating energies of the PAN-NH fiber mats with Pd active species.     

Nanocellulose reinforced PVA composite films: Effects of acid treatment and filler loading

Nanocellulose was prepared by acid hydrolysis of microcrystalline cellulose (MCC) at different hydrobromic acid (HBr) concentrations. Polyvinyl alcohol (PVA) composite films were prepared by the reinforcement of nanocellulose into a PVA matrix at different filler loading levels and subsequent film casting. Chemical characterization of nanocelluloses was performed for the analysis of crystallinity (X_c), degree of polymerization (DP), and molecular weight (M_w). The mechanical and thermal properties of the nanocellulose reinforced PVA films were also measured for tensile strength and thermogravimetric analysis (TGA). The acid hydrolysis decreased steadily the DP and M_w of MCC. The crystallinity of MCC with 1.5 M and 2.5 M HBr showed a significant increase due to the degradation of amorphous domains in cellulose. Higher crystalline cellulose showed the higher thermal stability than MCC. From X-ray diffraction (XRD) analysis, nanocellulose samples showed the higher peak intensity than MCC cases. Reduction of MCC particle by acid hydrolysis was clearly observed from scanning electron microscope (SEM) images. The tensile and thermal properties of PVA composite films were significantly improved with the increase of the nanocellulose loading.     

Surface modification and interfacial properties of polysulfonamide fiber treated by air plasma

The surface of polysulfonamide (PSA) fiber was modified by air plasma to improve its wettability and interfacial bonding performance. The surface morphology and chemical composition of the fiber were then evaluated with fieldemission scanning electron microscopy (FESEM) and X-ray photoelectron spectrometry (XPS). Moreover, the wettability and interfacial bonding performance of fiber before and after air plasma treatment were examined by water absorption time and interfacial shear strength (IFSS). FESEM observation confirmed that PSA fiber surface roughened with prolonged treatment duration. XPS analysis showed that the O/C atomic ratio on the PSA fiber surface can be increased from 19.69 % to 38.59 % after 3 min of treatment. Water absorption time dropped from as much as 400 s to about 0 s, indicating that the wettability of the fiber greatly improved. Under the experimental conditions of 40 Pa pressure, 100 W power, and 3 min treatment duration, IFSS increased by 57.01 %, and the interfacial bonding performance of fiber greatly improved.     

Influence of Hydrophobicity of Acetylated Nanocellulose on the Mechanical Performance of Nitrile Butadiene Rubber (NBR) Composites

Novel acetylation process by substitution of acetic anhydride substitution with hydroxyl groups on nanocellulose (NCC) has been explored to increase its dispersion and interaction in nitrile butadiene (NBR) matrix. The crystallinity index was increased after modification when compared to unmodified NCC, but no significant different with increases of treatment time from 1 hour to 3 hours treatments proven by X-ray diffraction (XRD) results. The Fourier transform infra-red (FTIR) showed the existent of acetyl groups on surface of the NCC after treatment by existent of the peak 1736 cm^-1 that attributed to carbonyl groups some peaks were observed at 1430, 1361 and 1248 cm^-1 and confirmed on the acetylation process. The nuclear magnetic resonance (NMR) also show the present of acetyl groups by existent of the signal of proton methyl group at 1.90 ppm and new peaks at 5.42, 4.70 and 4.34 ppm, for all ACN samples. The thermal results by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the acetylated NCCs were 10 % more thermally stable. Transmission electron microscopic (TEM) results showed that no significant changes were observed due to the acetylation process. The results also showed well distributed of individual NCC after acetylation, this improvement was primarily attributed to uniform dispersion of the ACN-NCC and less aggregated occurred. Due to its hydrophobic characteristics, highly crystalline and nano size, ACN-NCC brought a significant improvement up to 25 % on the mechanical properties of nitrile butadiene (NBR) rubber composites.     

Improving the dyeability of poly(lactic acid) fiber using N-Phenylaminopropyl POSS nanoparticle during melt spinning

The dyeability of poly(lactic acid) (PLA) fiber strongly depends on disperse dye structure due to the low dyeing temperature and the short dyeing time. Thus, the dye uptake value of PLA fiber is low for some disperse dyes and is needed to be improved. In the current study, the dyeability of PLA fiber is improved with the addition of N-Phenylaminopropyl polyhedral oligomeric silsesquioxane (AP-POSS) during melt spinning process. The effects of dyeing conditions including dyeing temperature and time, disperse dye type and AP-POSS concentrations are investigated on the dyeability properties of PLA fiber samples. The tensile, thermal and morphological properties of fiber samples are also characterized by tensile testing, differential scanning calorimeter (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As the added amount of AP-POSS increases, the percent crystallinity increases and the tensile strength reduces. According to the dyeing results, AP-POSS is very effective for increasing the dyeability of PLA fiber especially for disperse dyes with low dye uptake values.     

Effect of surface treatment of jute fibers on the interfacial adhesion in poly(lactic acid)/jute fiber biocomposites

Jute fibers have immense potential to be used as natural fillers in polymeric matrices to prepare biocomposites. In the present study jute fibers were surface treated using two methods: i) alkali (NaOH) and ii) alkali followed by silane (NaOH+Silane) separately. Effects of surface treatments on jute fibers surface were characterized using fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analyses. Further, the effects of surface treatments on jute fibers properties such as crystallinity index, thermal stability, and tensile properties were analyzed by X-ray diffraction method (XRD), thermo gravimetric analysis (TGA), and single fiber tensile test respectively. The effects of surface treatment of jute fibers on interphase adhesion between of poly(lactic acid) (PLA) and jute fibers were analyzed by performing single fiber pull-out test and was examined in terms of interfacial shear strength (IFSS) and critical fiber length.     

Wheat Straw Modified with Palmitic Acid as an Efficient Oil Spill Adsorbent

Raw wheat straw was modified to obtain a new oil absorption material, using palmitic acid as the esterifying agent in dimethyl sulfoxide (DMSO) without additional catalysts. The oil absorbency of the esterified wheat straw material towards 0^# diesel reached 24.31 g/g under the following optimum reaction conditions: pretreated wheat straw: palmitic acid weight ratio of 1:10, reaction temperature of 90 °C, and reaction time of 3 h. The chemical composition and structure of wheat straw fiber before and after esterification reaction were compared using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) methods. The results indicate that the esterification reaction was carried out smoothly, and the wheat straw afterwards had lower crystallinity and a rougher surface with more irregular folds. Additionally, the oil sorption capacity, selectivity, and absorption kinetics of the esterified wheat straw were also investigated. The esterified wheat straw showed good potential for converting agricultural residues into efficient cellulosic oil sorbents.     

Effect of Chemical Modifications on Surface Morphological,Structural, Mechanical,and Thermal Properties of Sponge-gourd Natural Fiber

Sponge-gourd (SG) natural fibers obtained from Luffa cylindrica plant were chemically treated separately using alkali (5, 10, and 15 wt%), acetic anhydride (5, 10, and 15 wt%), and benzoyl chloride (5, 10, and 15 wt%). Both untreated and chemically treated SG fibers (SGFs) were subsequently characterized using a field emission scanning electron microscope, a Fourier transform infrared spectrometer, an X-ray diffractometer, a universal testing machine, and a thermogravimetric analyzer. Surface analysis by scanning electron microscopy shows that the alkali treatments promote better outer surface layer than other treatments of the SGF with the exposition of inner fibrillar structure, thereby increasing roughness of the fiber surface. Alkali treatment also improves the crystallinity and exhibits new chemical bond formation in the SGF. The tensile strength and Young’s modulus have been analyzed through a two-parameter Weibull distribution model, where a significant increase in mechanical property of benzoylated fibers has been observed. The thermal stability of the modified fibers is also found to increase by acetic anhydride treatment.     

Synthesis and properties of shape memory polyurethane nanocomposites reinforced with poly(ɛ-caprolactone)-grafted carbon nanotubes

Nanocomposites of polyurethane (PU) and multi-walled carbon nanotubes (MWNTs) were prepared via in-situ polymerization of poly(ɛ-caprolactone)diol (PCL)-grafted-MWNTs, 4,4′-methylene bis(phenyl isocyanate), and 1,4-butanediol. The grafting of PCL onto MWNTs was confirmed by Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The nanocomposites showed more improved mechanical properties compared to conventional nanocomposites with the same MWNT loading. The thermo-responsive shape recovery as measured in a cyclic tensile test was observed to be approximately 80 % for in-situ nanocomposites, though it showed a reduced trend as the wt% of MWNTs increased. X-ray diffraction investigation also showed that the addition of MWNTs into the polyurethane increased the crystallinity. Scanning electron microscopy and TEM measurements showed better dispersion of MWNTs in the nanocomposites synthesized using in-situ method. Consequently, the presence of PCL-g-MWNTs made an important contribution to the enhancement of the mechanical and shape memory properties of polyurethane.     

Structure and performance of<Emphasis Type="Italic">Bombyx mori</Emphasis> silk modified with nano-TiO<Subscript>2</Subscript> and chitosan

Bombyx mori (B. mori) silk was modified with the nano-TiO₂ and chitosan dispersion system by the crosslinking reactions of citric acid (CA) and maleic anhydride (MA). The average size of the nano-TiO₂ particles in the aqueous dispersion system was 36.7 nm. The scanning electron microscopy (SEM) micrographs showed that the nano-TiO₂ particles were spherical and homogeneously dispersed in the dispersion system, and the surface ofB. mori silk fiber treated with the nano-TiO₂ and chitosan dispersion system was rougher than that of the untreated one. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) Spectrometry indicated that the crystallinity of theB. mori silk fiber increased after treatment. It was also found that the nano-TiO₂ and chitosan contributed to significantly enhance the mechanical properties including breaking strength, breaking elongation, initial modulus, rupture work, and elastic recovery property of theB. mori silk fiber. The wrinkle-resistant performance of the treatedB. mori silk fabrics was also greatly improved.     

The effects and roles of PVP on the phase composition, morphology and magnetic properties of cobalt ferrite nanoparticles prepared by thermal treatment method

Cobalt ferrite nanocrystals were prepared from an aqueous solution containing metal nitrates and various of concentrations of poly(vinyl pyrrolidone), followed by calcinations temperature. X-ray diffraction (XRD) analysis was performed to determine the degree of crystallinity of the ferrite nanoparticles. By transmission electron microscopy (TEM), the morphology and average particle size of the cobalt ferrite nanoparticles were evaluated which had good agreement with XRD results. Fourier transform infrared spectroscopy (FT-IR) suggested the presence of metal oxide bands in all samples as well as the effective elimination of organic constituents after calcinations. Vibrating sample magnetometer (VSM), was utilized to evaluate the magnetic properties of the cobalt ferrite nanoparticles.     

Preparation of aminated polyacrylonitrile porous fiber mat and its Application for Cr(VI) ion removal

Porous polyacrylonitrile (PAN) fiber mat was prepared by electrospinning PAN in N,N-dimethylformide solution with poly(methyl methacrylate) (PMMA) as pore-forming agent. Then, the porous PAN fiber mat was chemical modified by the tetraethylenepentamine to acquire aminated porous polyacrylonitrile (APPAN) fiber mat. Common aminated PAN fiber mat was also prepared for comparison. The surface morphologies of the APPAN and PAN fiber mat were characterized by scanning electron microscopy (SEM) and the corresponding specific surface areas were also measured. FT-IR/ATR spectra of the APPAN and PAN fiber mat were recorded for analysis of the surface chemical structures. The Cr(VI) absorption results demonstrated that the porous structure in the fiber could obviously increase the absorption capacity of the fiber mat.     

Thermal Characterization of Alkali Treated Kenaf Fibers and Kenaf-Epoxy Composites

Chemical treatment of natural fibers is a well-defined means of mechanical property improvement in natural fiberreinforced composites. An understanding of mechanical and thermal properties in these media is essential for evaluating heat transfer, thermal degradation, and overall performance of these composites over their product lifetime. However, very little information is available illustrating the effect of such treatment on the thermal properties of kenaf composites. Also, no study to date has reported the thermal conductivity of individual kenaf fibers. This study reports the effects of fiber treatment (in 6 % NaOH) on thermal transport in unidirectionally oriented kenaf-epoxy composites and individual kenaf fibers. The effective thermal conductivities and thermal diffusivities of chemically treated fiber composites show a general increase over untreated fiber composites (0.210 to 0.232 W/m/K at 28 °C, 0.206 to 0.234 W/m/K at 200 °C). This improvement may be attributed to improved interfacial contact between the fibers and epoxy matrix shown in microstructural images after chemical treatment. The thermal conductivity of individual fibers was evaluated at room temperature using two techniques. Results from both techniques showed slight increases after chemical treatment (0.58±0.53 to 1.0±0.13 W/m/K and 1.2±0.54 to 1.6±0.28 W/m/K) but lacked statistical significance. Any improvement in surface crystallinity after chemical treatment does not appear to affect overall fiber thermal conductivity. A better understanding of thermal transport in kenaf fibers and composites enables better estimation of the performance of these composites in different applications. Moreover, the thermal conductivities of individual fibers are useful in understanding the fiber’s contribution to conduction in different fiber reinforcement configurations.     

Study on converting cotton pulp fiber into carbonaceous microspheres

Carbonaceous materials were produced by means of the hydrothermal carbonization of cotton pulp fiber at temperatures in the 245–305 °C range. The morphology, chemical and structural characteristics of the hydrothermally carbonized products were investigated with scanning electron microscopy (SEM), X-ray diffraction, Fourier-transform Infrared Spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS). The hydrothermal product of cotton pulp fiber is made up of carbonaceous microspheres (size: 3–8 µm). The carbonaceous microspheres have different chemical structure with one of cotton pulp fiber and have amorphous structure. The surface of carbonaceous microspheres contains a high concentration of reactive oxygen groups.     

苎麻种质资源纤维结晶度变异及其主要品质性状的关联性研究

从国家苎麻种质长沙苎麻圃中选择有代表性的55个苎麻品种为材料．用X射线衍射法测定苎麻精干麻的结晶度。用面积法计算各个品种的结晶度,分析苎麻纤维结晶度及其与主要纤维品质性状的相关性。研究结果如下：苎麻品种问纤维结晶度有显著性差异。55个苎麻品种纤维结晶度平均值变幅在69％-73％之间,变异系数为0．9769％,纤维结晶度最低是川苎二号。其值为69．03％,最高是印尼麻,其值为72．31％。同一品种的不同季别的苎麻纤维结晶度有一定的差异。二麻结晶度最低,与头麻、三麻之间有显著性差异;同一品种苎麻不同收获期、不同部位纤维结晶度有差异。品种中苎一号、圆叶青和NC01在1／3黑杆时期的纤维结晶度与1／3黑杆前的纤维结晶度有显著性差异,1/3黑杆前收获可显著降低结晶度,但是会降低苎麻的产量：1／2黑杆时期后的结晶度值无显著性差异,结晶度值趋于稳定;苎麻纤维结晶度与断裂强力呈极显著负相关。相关系数为-0．39526＊＊（n=55）;苎麻纤维结晶度与纤维细度呈显著正相关,相关系数为O．31363＊（n=55）。     

Characterization of anatomy, ultrastructure and lignin microdistribution in Forsythia suspensa

Forsythia suspensa, as a traditional Chinese medicinal herb, has been studied extensively. In this work, morphological and anatomical features of F. suspensa stem were examined by light microscopy (LM) and scanning electron microscopy (SEM). The results showed that the slenderness and Runkel ratio is 51 and 0.67, respectively. Anatomical observations indicated that F. suspensa is diffuse-porous wood. Helical thickenings and alternate intervessel pits are present on vessel cell wall. Transmission electron microscopy (TEM) images exhibited that the fiber cell wall is typically differentiated into three layers: middle lamella (ML), primary wall (P) and secondary wall (S₁, S₂ and S₃), and the staining intensities represent differing lignin concentrations. Also, the confocal laser scanning microscopy (CLSM) and scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDXA) were used to investigate the lignin distribution in cell wall qualitatively and semi-quantitatively. Confocal images (488 nm) revealed a high level of lignin autofluorescence in the cell corner middle lamella (CCML), with lower levels of fluorescence in the compound middle lamella (CML) and S₂ region. The results from SEM-EDXA demonstrated that lignin concentration ratio in different regions of fiber wall is 1.3 (CCML):1.1 (CML):1 (S₂).     

Electrospun grape seed polyphenols/gelatin composite fibers contained silver nanoparticles as biomaterials

GSP/gelatin composite nanofiber membranes containing silver nanoparticles were successfully fabricated as a novel biomaterial by electrospinning. The silver nanoparticles (AgNPs) were synthesized with the grape seed polyphenols (GSP) as reducing agent in aqueous solution of gelatin, and then the GSP/gelatin/AgNPs mixed solution was electrospun into nanofibers at 55 °C. The scanning electron microscopy (SEM) confirmed that the composite fibers were uniform and the average fiber diameter ranged between 150 nm and 230 nm with an increase in applied potentials from 14 kV to 22 kV. And the transmission electron microscopy (TEM) showed that silver nanoparticles distributed individually in the fibers with the average particle size of about 11 nm. Furthermore, the ultraviolet visible spectrophotometer (UV-vis spectroscopy) test demonstrated that all of Ag⁺ converted to Ag⁰ when the concentration of gelatin was 24 wt% and the mass ratio of GSP to AgNO₃ was about 5:2. The antibacterial activities of the fiber membranes against E.coli and S.aureus were measured via a shake flank test and demonstrated good performance after the importation of silver nanopaticles. Cytotoxicity testing also revealed that fiber membranes contained silver nanoparticles had no cyto-toxic. All the results indicated that the GSP was effective for the formation and stabilization of silver nanoparticles in composite nanofibers mats which had the potential for applications in antimicrobial tissue engineering and wound dressing.     

The novel use of sodium borohydride as a protective agent for the chemical treatment of vegetable fibers

The vegetable fibers used as reinforcement for polymer matrix composites are usually treated to improve their adhesion with the matrix. The chemical treatment with sodium hydroxide (NaOH) is widely employed, but it may damage the fiber surface structure, reducing its strength. This novel study is related to the use of hydride ions (H^?) as protective agent for vegetable fibers, under alkaline treatment, as a way to promote their use in polymeric composites. Sisal fibers were modified by immersion in a NaOH aqueous solution (2, 5, and 10 % wt/vol) with or without the addition of sodium borohydride (NaBH₄) (1 % wt/vol) under different treatment conditions. The treated fibers were characterized via density and moisture content analyses and also using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effectiveness of NaBH₄ to protect the sisal fiber was more pronounced in moderate NaOH concentrations (5 %) at room temperature or higher for shorter alkaline treatment times.