Blending poly(lactic acid) (PLA) with polyhydroxybutyrate-valerate (PHBV) presents a practical approach to producing fully biobased blends with tailored material properties and improved foam morphologies. This study investigated the effects of the PLA/PHBV blend composition on the morphology, as well as the thermal and mechanical properties, of both solid and microcellular PLA/PHBV injection molded components. Nitrogen (N2) in the supercritical state was used as the physical blowing agent for the microcellular injection molding experiments. Thermal analysis results showed no difference in the thermal properties of solid and microcellular injection molded specimens. It was also found that the T g of the PLA phase in the PLA/PHBV blends decreased with increasing PHBV content for both solid and microcellular specimens. In addition, PHBV content exceeding 45% significantly increased the crystallinity of PHBV in the PLA/PHBV blends and improved the storage modulus of both solid and microcellular components. PLA/PHBV blends were immiscible when the content of PHBV exceeded 30%; PLA/PHBV blends were only miscible with a low weight ratio of PHBV. The increase of PHBV content significantly decreased the cell size and increased the cell density in the microcellular specimens and resulted in some interesting bimodal microcellular structures within the PLA/PHBV (70:30) blend. Additionally, adding PHBV decreased the tensile strength slightly for both solid and microcellular specimens. Furthermore, adding PHBV did not cause any significant changes in the modulus of the solid or microcellular specimens.

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A new type of deacetylated cellulose acetate (DA)@polydopamine (PDA) composite nanofiber membrane was fabricated by electrospinning and surface modification. The membrane was applied as a highly efficient adsorbent for removing methylene blue (MB) from an aqueous solution. The morphology, surface chemistry, surface wettability, and effects of operating conditions on MB adsorption ability, as well as the equilibrium, kinetics, thermodynamics, and mechanism of adsorption, were systematically studied. The results demonstrated that a uniform PDA coating layer was successfully developed on the surface of DA nanofibers. The adsorption capacity of the DA@PDA nanofiber membrane reached up to 88.2 mg/g at a temperature of 25 °C and a pH of 6.5 after adsorption for 30 h, which is about 8.6 times higher than that of DA nanofibers. The experimental results showed that the adsorption behavior of DA@PDA composite nanofibers followed the Weber's intraparticle diffusion model, pseudo-second-order model, and Langmuir isothermal model. A thermodynamic analysis indicated that endothermic, spontaneous, and physisorption processes occurred. Based on the experimental results, the adsorption mechanism of DA@PDA composite nanofibers was also demonstrated.

The drug-loaded polyvinyl alcohol (PVA)/chitosan (CS) composite nanofibers intended to be used as matrix for transdermal drug delivery were fabricated by electrospinning, and then crosslinked through glulataraldehyde (GA). The morphology, chemical structure, thermal behavior, mechanical properties, hydrophilicity and drug release properties of drug-loaded PVA/CS composite nanofibers before and after crosslinking were characterized. The results showed that the morphology of PVA/CS composite nanofibers was not been destroyed in both crosslinking and in vitro drug release process. The Young's modulus, tensile strength, thermal properties and hydrophobicity of crosslinked PVA/CS composite nanofibers significantly increased in comparison with those of PVA/CS (without crosslinking) due to the formation of crosslinking network structure. In vitro release studies showed that crosslinked PVA/ CS composite nanofibers had lower drug release rate and smaller amount of drug burst release than that of PVA/CS. According to release exponent "n", the release of ampicillin sodium from crosslinked PVA/CS composite nanofibers fit to the Fickian diffusion mechanism. Those results demonstrate the potential utilization of crosslinked PVA/CS composite nanofibers as a transdermal drug delivery system. K E Y W O R D Schitosan (CS), crosslinking, drug delivery, electrospinning, polyvinyl alcohol (PVA) How to cite this article: Cui Z, Zheng Z, Lin L, et al. Electrospinning and crosslinking of polyvinyl alcohol/ chitosan composite nanofiber for transdermal drug delivery.

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The first commercial bottom blown oxygen copper smelting furnace has been installed and operated at Dongying Fangyuan Nonferrous Metals since 2008. Significant advantages have been demonstrated in this technology mainly due to its bottom blown oxygen-enriched gas. In this study, a scaled-down 1:12 model was set up to simulate the flow behavior for understanding the mixing phenomena in the furnace. A single lance was used in the present study for gas blowing to establish a reliable research technique and quantitative characterisation of the mixing behavior. Operating parameters such as horizontal distance from the blowing lance, detector depth, bath height, and gas flow rate were adjusted to investigate the mixing time under different conditions. It was found that when the horizontal distance between the lance and detector is within an effective stirring range, the mixing time decreases slightly with increasing the horizontal distance. Outside this range, the mixing time was found to increase with increasing the horizontal distance and it is more significant on the surface. The mixing time always decreases with increasing gas flow rate and bath height. An empirical relationship of mixing time as functions of gas flow rate and bath height has been established first time for the horizontal bottom blowing furnace.

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