Electrospinning has been recognized as an efficient technique for the fabrication of polymer nanofibers. Various polymers have been successfully electrospun into ultrafine fibers in recent years. These electrospun biopolymer nanofibers have potential applications for wound dressing based upon their unique properties. In this paper, a comprehensive review is presented on the researches and developments related to electrospun biopolymer nanofibers including processing, structure and property, characterization, and applications. Information of those polymers together with their processing condition for electrospinning of ultrafine fibers has been summarized in the paper. The application of electrospun natural biopolymer fibers in wound dressings was specifically discussed. Other issues regarding the technology limitations, research challenges, and future trends are also discussed.
Shear thickening is a non-Newtonian flow behavior, characterized by an increase in viscosity with the applied shear rate. Due to this superior performance of shear thickening fluid (STF), it has received a great deal of attention in the field of armor protection. In this paper, the properties of nanoscale silica STF systems are modified by the addition of nanocellulose (CNF). The rheological properties of the prepared STFs were tested. Kevlar fabrics were immersed in multiphase STF solutions to make STF/fabric composites. The results showed that the addition of nanocellulose (CNF) enhanced the steady-state and dynamic aspects of the shear-thickening fluid. The rheological properties of the shear-thickening fluid were strongest when the content of nanocellulose added was 0.2%, and the single yarn extraction force of the Kevlar composite was much stronger than that of the pure Kevlar without STF. The CNF-modified STF enhances the impact resistance of the composite.
In this paper, the relationship of rheological properties, particle size and particle size distribution of dispersed phase silica at different blending times during the preparation of STF was studied in detail. It is found that with the increase of blending time, the initial viscosity η0 of STF decreases, the critical shear rate γ
c increases, the maximum thickening viscosity ηm decreases, the thickening ratio decreases and the shear thickening effect of the system shows a weakening trend. On the other, the volume average particle size of silica decreases gradually and finally reaches a stable value. The particle size distribution changed from double-interval distribution to single-interval distribution. The variation of shear thickening properties with blending time was explained by combining Cluster and Jamming theory. It is considered that the preparation of STF can be completed when the suspension is transparent and has a uniform viscosity. It is believed that this will play an important role in improving the efficiency of STF preparation and will be of great help to realize industrialized production of STF in the future.
In this paper, polylactic acid (PLA)/cellulose nanocrystalline (CNC) composite fiber membranes were prepared by electrospinning technique. The microstructure of the fiber membranes produced was all transformed from a smooth surface to a nanoporous surface by varying the CNC loading level. The influence of CNC content on the morphology, thermal dynamic properties, and cytotoxic properties of PLA/CNC composite nanofiber membranes was characterized. The results show that water molecules can enhance the hydrogen bonding networks between PLA and CNC. when the cellulose nanocrystal content is less than 10%, the composite membranes have good dynamic mechanical properties and no significant cytotoxic effect.
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