Fabrication and characterization of dense Chitosan/polyvinyl-alcohol/poly-lactic-acid blend membranes

Dense membranes of Chitosan (CS)/Poly(vinyl alcohol) (PVA)/Poly(lactic acid) (PLA) blend were successfully fabricated using casting technique. The mechanical properties, moisture regain and water vapor permeability of polymer blend membranes were estimated by tensile test, moisture regain rate and dish method test respectively. The microstructures, morphology, chemical composition and thermal properties were also characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) respectively. Results indicated that there were interactions and good compatibility among CS, PLA and PVA. And the blend membranes have good breaking elongation and slightly decreased breaking strength, and show best moisture regain at the case of CS60 (the content of CS in the blends is 60 %). They also have excellent porous structure, which is beneficial to their air permeability and may also contribute to cell regeneration. With the adding of PVA content, the melting peaks of blend membranes reduce and gradually close to that of PVA, demonstrating that the regularity of CS molecular chain may be destroyed and hydrogen bonds of macromolecules in polymers were newly formed. As a result, solution blending of the three polymers could complement their disadvantages and significantly improve the membrane performance of a single polymer, thus promote the mechanical and biological properties of blend membrane.     

Thermo-mechanical and morphological properties of short natural fiber reinforced poly (lactic acid) biocomposite: Effect of fiber treatment

Untreated oil palm empty fruit bunch (REFB), alkali treated EFB (AEFB), ultrasound treated EFB (UEFB) and simultaneous ultrasound-alkali treated EFB (UAEFB) short fibers were incorporated in poly(lactic acid) (PLA) for fabricating bio-composites. The REFB fiber-PLA (REPC) and treated EFB (TEFB) fiber-PLA (TEPC) composites were prepared and characterized. Glass transition temperature, crystal melting temperature, decomposition temperature, melt flow index, density and mechanical properties (tensile strength, tensile modulus and impact strength) of TEPC are found to be higher than those of REPC. The observed crystallization temperature of TEPC is lower than that of REPC. Among all samples, TEPC prepared from UAEFB fiber shows better performances than other samples fabricated by REFB and AEFB fibers. Scanning electron microscopy, Fourier transform infrared spectroscopy and XRD analyses well support all the observed results.     

Processing and characterization of polyacrylonitrile/soy protein isolate/polyurethane wet-spinning solution and fiber

Using dimethyl sulfoxide (DMSO) as a solvent, the polyacrylonitrile/soy protein isolate/polyurethane (PAN/SPI/PU) blend solutions and wet-spun fibers were prepared. The rheological properties of the PAN/SPI/PU solution were investigated. Investigations of the structure and properties of the PAN/SPI/PU fibers involved Fourier transform infrared, enzymatic hydrolysis, scanning electron microscopy, mechanical properties, dye adsorption, contact angle, and moisture regain measurements. The results showed that all PAN/SPI/PU solutions possess pseudoplastic properties, and there are opposite effects of SPI and PU in the PAN/DMSO solution. The apparent viscosity, the amount of non-Newtonian fluid and the extent of structuralization of the PAN/DMSO solution increase with the addition of SPI, whereas these features all decrease with the addition of PU. The biodegrability, the absorption of acidic dye and the moisture regain increase with the proportional increase in weight of SPI in the fiber blend.     

Chitosan–starch composite film: preparation and characterization

Chitosan film has potential applications in agriculture, food, and pharmacy. However, films made only from chitosan lack water resistance and have poor mechanical properties. Forming miscible, biodegradable composite film from chitosan with other hydrophilic biopolymers is an alternative. The objective of this study was to prepare chitosan/starch composite films by combining chitosan (deacetylated degree, 90%) solution and two thermally gelatinized cornstarches (waxy starch and regular starch with 25% amylose). The film’s tensile strength (TS), elongation-at-break (E), and water vapor transmission rate (WVTR) were investigated. The possible interactions between the two major components were evaluated by X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR). Regardless of starch type, both the TS and E of the composite films first increased and then decreased with starch addition. Composite film made with regular starch showed higher TS and E than those with waxy starch. The addition of starch decreased WVTRs of the composite films. The introduction of gelatinized starch suppressed the crystalline peaks of chitosan film. The amino group band of chitosan molecule in the FTIR spectrum shifted from 1578 cm⁻¹ in the chitosan film to 1584 cm⁻¹ in composite films. These results indicated that there was a molecular miscibility between these two components.     

Morphological and crystalline characterization of NaOH and NaOCl treated Agave americana L. fiber

This study investigates the effect of NaOH and NaOCl treatments on chemical composition, morphology and crystalline structure of Agave americana L. fibers. These fibers have been subjected to NaOCl and NaOH alkali treatments at different concentrations.The percentages of lignin and hemicellulose show a decrease with alkaline treatments which, in turn, induces a modification of both morphological and crystalline structures.Unit cell dimensions and crystallite size were more affected with NaOH treatment than NaOCl one. This may result from the mercerisation process which occurs with caustic soda treatment.The observed defibrillization on the treated fiber surface proves the dissolution of the non-cellulosic components present in the fiber cell wall by NaOH and NaOCl treatments. These morphological changes may improve the interaction between matrix and fiber in composites.     

Chitosan Modification and Pharmaceutical/Biomedical Applications

Chitosan has received much attention as a functional biopolymer for diverse applications, especially in pharmaceutics and medicine. Our recent efforts focused on the chemical and biological modification of chitosan in order to increase its solubility in aqueous solutions and absorbability in the in vivo system, thus for a better use of chitosan. This review summarizes chitosan modification and its pharmaceutical/biomedical applications based on our achievements as well as the domestic and overseas developments: (1) enzymatic preparation of low molecular weight chitosans/chitooligosaccharides with their hypocholesterolemic and immuno-modulating effects; (2) the effects of chitin, chitosan and their derivatives on blood hemostasis; and (3) synthesis of a non-toxic ion ligand—D-Glucosaminic acid from Oxidation of D-Glucosamine for cancer and diabetes therapy.     

Surface characterization of sputter silver-coated polyester fiber

The present study concerns modification of surface of polyester fiber by magnetron sputtering using a silver (Ag) target. A detailed characterization of the silver-coated polyester fiber was investigated by scanning electron microscopy (SEM), X-ray diffraction technique (XRD) and X-ray photoelectron spectroscopy (XPS). The results revealed the remarkable changes in the surface morphology and microstructure of silver film on polyester fiber after sputtering for 10 and 30 min respectively. The SEM results showed that the silver particles were uniformly and densely deposited on the surface of polyester fiber. The XRD pattern of silver coated fabric showed that silver film is polycrystalline structure and dominated by the very strong (220) peak. Depth profiling results of silver coated fabric by XPS indicated that mainly metallic silver is existed throughout the whole depth region.     

两亲性壳聚糖/槲皮素纳米胶束的制备及其理化性质研究

槲皮素(QCT)是一种类黄酮化合物,具有较强的抗氧化、抗炎等作用,在热带植物界中广泛存在。但由于槲皮素溶解度低、稳定性差,因此限制了其在食品、医药中的应用。本研究以脱氧胆酸(DA)为疏水基团,N-乙酰-L-半胱氨酸(NAC)作为亲水基团合成了一种新型两亲性壳聚糖(ACS),并制备了两亲性壳聚糖槲皮素纳米胶束(ACS-QNMs)。结果表明,傅里叶红外光谱分析证明DA和NAC已成功接枝到壳聚糖上,荧光分光光度计测定空白胶束的临界胶束浓度值(CMC)为26.92μg/mL,扫描电镜观察纳米载药胶束外观呈球形且分布均匀。纳米粒度电位分析仪测定纳米胶束电位为31 mV。研究表明,槲皮素经两性壳聚糖包埋后,能在人体温度37℃下缓慢释放,同时在室温下稳定储存。     

Processing and characterization of nickel-plated PBO fiber with improved interfacial properties

A new application of conventional electroless nickel plating to improve the interfacial properties of PBO fibers was reported. The relationship between surface morphology and interfacial properties of nickel-plated PBO fiber was explored. The continuous nickel coating consisted of nickel and phosphorus elements determined by Energy dispersive spectrometer (EDS) and transmission electron microscope (TEM), exhibiting high adhesive durability. The influence of bath temperature and plating time on the crystal structure, microstructure and mechanical properties of nickel-plated PBO fibers was systematically investigated. X-ray diffractometer (XRD) results revealed that the crystal structure among nickel-plated PBO fibers did not show differences. Scanning electron microscope (SEM) and Atomic force microscope (AFM) images showed that the process parameters had a great influence on surface morphology and roughness of nickel-plated PBO fibers, which could directly affect the interfacial properties of nickel-plated PBO fibers. Single fiber pull-out testing results indicated that the interfacial shear strength (IFSS) of PBO fibers after electroless nickel plating had a significant improvement, which reached maximum at 85 °C for 20 min. Single fiber tensile strength of nickel-plated PBO fibers was slightly lower than that of untreated one. Thermo gravimetric analysis (TGA) indicated that nickel-plated PBO fiber had excellent thermal stability.     

Surface characterization of low temperature plasma treated wool fiber

Previous investigation results revealed that after the Low Temperature Plasma (LTP) treatment, the hydrophilicity of wool fiber was improved significantly. Such improvement enhances the wool dyeing and finishing processes which might be due to the changes of the wool surface to a more reactive one. In this paper, wool fibers were treated with LTP with different gases, namely, oxygen, nitrogen and gas mixture (25 % hydrogen/75 % nitrogen). Investigations showed that chemical composition of wool fiber surface varied differently with the different plasma gas used. The surface chemical composition of the different LTP-treated wool fibers was evaluated with different characterization methods, namely FTIR-ATR, XPS and saturated adsorption value. The experimental results were thoroughly discussed.     

Preparation and characterization of a novel antibacterial fiber modified by quaternary phosphonium salt on the surface of polyacrylonitrile fiber

A novel antibacterial fiber named MTPB-PANF was synthesized by chemical modification of polyacrylonitrile fiber (PANF). The PANF was firstly reacted with alkali solution to get Na-PANF with -COONa functional groups. Na-PANF was then reacted with different concentration of methyltriphenyl phosphonium bromide (MTPB) into flasks, and the whole system was immersed into a to and fro vibrator. During the synthesis process, this paper investigated on the initial concentration of MTPB, the contact time, the reaction temperature and the pH of the solution that may have effect on the properties of the final fiber. The properties of MTPB-PANF were discussed by fourier transform infrared spectroscopy (FTIR), thermo gravimetric analyzer (TGA), scanning electron microscope (SEM) and the stability of organophosphorus groups on MTPB-PANF examined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The antibacterial activity of MTPB-PANF was examined against pathogenic Escherichia coli and Staphylococci aureus by improved shake flask method in sterile saline and was evaluated by the viable cell counting method. The obtained results showed an excellent antibacterial activity of MTPB-PANF. And the antibacterial mechanism was discussed by the concentration of K⁺ released from cells after bacterial testing.     

我国植物纤维复合材料的发展现状及展望

综述了近年来我国植物纤维复合材料的发展现状及特点,并根据基体材料和增强体材料进行初步分类。简要概括了植物纤维复合材料的应用领域,总结了我国植物纤维复合材料的发展趋势。     

Polycarbazole modified carbon fiber microelectrode: Surface characterization and dopamine sensor

Electropolymerization of carbazole (Cz) by cyclic voltammetry (CV) onto carbon fiber microelectrodes (CFME) (diameter ∼7 μm) in dichloromethane (CH₂Cl₂) solution of 0.1 mol·dm⁻³ tetraethyl ammonium perchlorate (TEAP) results in the formation of polycarbazole (PCz) thin film coatings. CV results showed that these PCz thin films have reversible redox behavior in monomer-free electrolyte solution. The resulting thin polymer films were characterized using Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) and atomic force microscopy (AFM). Results performed at optimum experimental conditions indicate that electrodes show a reversible and stable behavior over sixty eight days of testing for dopamine in 100 μmol·dm⁻³ buffer solution. A detection limit for PCz thin films as low as 0.1 μM (3S/N) was obtained for the polycarbazole (PCz) thin films formed using CV. Hence, this novel sensor can be considered as promising sensor for dopamine detection.     

Preparation and characterization of (POSS/TiO2)n multi-coatings based on PBO fiber surface for improvement of UV resistance

The application of poly (p-phenylene-2, 6-benzobisoxazole) (PBO) fiber as reinforcement in composite material was restricted by its photo-degradation, therefore, some measures should be considered to protect PBO fiber against UV aging. In this study, A series of multilayer coating for (POSS/TiO₂)_n was prepared on PBO fiber surface via LbL assembly technique for enhancement of UV resistance. TiO₂ as UV absorbing material was used to relieve UV-degradation of PBO. Surface elemental composition, surface morphology, mechanical and interfacial properties, and UV resistance of uncoated and coated PBO fibers were investigated. These experimental results show multilayer coating of (POSS/TiO₂)_n was uniform deposition on fiber surface after treatment, tensile strength decreased to certain extent, interfacial shear strength increased in a small range and UV resistance is obvious enhanced. After the same accelerated aging time under UV irradiation, the retention of tensile strength and intrinsic viscosity of coated PBO fibers were much better than that of untreated PBO fibers.     

Design and Preclinical Evaluation of Chitosan/Kaolin Nanocomposites with Enhanced Hemostatic Efficiency

In the current study, hemostatic compositions including a combination of chitosan and kaolin have been developed. Chitosan is a marine polysaccharide derived from chitins, a structural component in the shells of crustaceans. Both chitosan and kaolin have the ability to mediate a quick and efficient hemostatic effect following immediate application to injury sites, and thus they have been widely exploited in manufacturing of hemostatic composites. By combining more than one hemostatic agent (i.e., chitosan and kaolin) that act via more than one mechanism, and by utilizing different nanotechnology-based approaches to enhance the surface areas, the capability of the dressing to control bleeding was improved, in terms of amount of blood loss and time to hemostasis. The nanotechnology-based approaches utilized to enhance the effective surface area of the hemostatic agents included the use of Pluronic nanoparticles, and deposition of chitosan micro- and nano-fibers onto the carrier. The developed composites effectively controlled bleeding and significantly improved hemostasis and survival rates in two animal models, rats and rabbits, compared to conventional dressings and QuikClot^® Combat Gauze. The composites were well-tolerated as demonstrated by their in vivo biocompatibility and absence of clinical and biochemical changes in the laboratory animals after application of the dressings.     

Polyurethane smart fiber with shape memory function: Experimental characterization and constitutive modelling

Segmented polyurethane (PU) polymers are known to have shape memory function, i.e., when they reach certain temperatures, they deform into the memorized shape from any temporary one. In the present study, PU polymers were spun into fibers using the conventional extrusion process to investigate the feasibility of producing smart fibers with shape memory function. The shape memory polymers (SMPs) and their spun fibers were characterized using DSC, DMTA, and tensile test. In particular, the thermo-mechanical deformation behavior, which enables to evaluate the shape memory performance of the SMPs, was characterized using DMTA. Then, the linear viscoelastic theory was utilized for mathematical modelling of the thermo-mechanical behavior of the SMPs. For the shape memory fibers, the large deformation characteristics were also investigated using the thermo-mechanical test, necessitating the development of nonlinear viscoelastic theory to formulate a constitutive equation and to provide an effective tool for designing smart textile structure.     

Surface characterization of aromatic thermotropic liquid crystalline fiber deposited by nanostructured silver

Nanostructured silver thin films were sputtered onto the aromatic thermotropic liquid crystalline fibers of Vectran by magnetron sputtering technology. Plasma treatment was used as pre-treatment in order to improve the deposition of the coating layer. Surface morphology of the coated fibers was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). A full energy dispersive X-ray analysis (EDX) was used to detect the elemental composition of the material. Its conductivity and mechanical properties were measured and analyzed as well. The study revealed that a very thin conductive silver deposition exhibited high electrical conductivity as well as less influence on the mechanical properties of the pre-treated Vectran fiber. The plasma treatment could improved the deposition of the coating layer, but the surface roughness caused by plasma treatment also affected the surface conductivity. It was found that the surface resistivity could reach very low value of 1.66×10⁻³ Ω·cm after sputtering deposition for 30 min.     

Effect of coir fiber content and compatibilizer on the properties of unidirectional coir fiber/polypropylene composites

The main objective of this research was to study the effect of fiber content variation and stearic acid (SA) treatment on the fundamental properties of unidirectional coir fiber (CF) reinforced polypropylene (PP) composites. Several percentages of filler contents were used (10–40 wt %) in order to gain insights into the effect of filler content on the properties of the composites. Coir/PP composites were fabricated by compression molding, and the properties of composites were studied by physico-mechanical and thermal properties. The results from mechanical properties such as tensile strength (TS), tensile modulus (TM) and impact strength (IS) of the CF/PP composites were found to be increased with increasing fiber content, reached an optimum and thereafter decreased with further increase in fiber content. Treatment of the coir with SA as the coupling agent enhanced the mechanical properties, crystallization temperature and crystallinity of virgin PP and water desorption of the resulting composites, resulting from the improved adhesion between the CF and PP matrix. Scanning electron micrographs (SEM) of the tensile fractured samples showed improved adhesion between fiber and matrix upon treatment with SA. Interfacial shear strength (IFSS) of the composites was measured by single fiber fragmentation test (SFFT).     

Development and characterization of light weight plant structured fabrics

Scientists and engineers are increasingly turning to nature for inspiration. Light weight textile fabrics suitable for summer dress material were developed by imitating the branching structure of a plant in order to achieve high water absorption and transportation properties. The absorption property of the fabrics was characterized by using the Moisture Management Tester (MMT) and Transplanar Water Transport Tester (TWTT). The fabrics were analyzed using optical microscopes and Optical Contact Angle (OCA) tester to understand the structure as well as the absorption behavior of these fabrics. The results indicated that plant structured fabrics have a significant faster water absorption and wicking properties over conventional weave structures, makes them highly preferable for summer-wear.