Electrospun poly(D,L-lactic acid) nanofibers and composite nanofibers filled with carbon nanocapsules: processing, fiber characterization and electrical conductivity

• Main Authors: Huan-ShengChien, 簡煥聲
• Other Authors: Chi Wang
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/96016924333196134459

博士 === 國立成功大學 === 化學工程學系碩博士班 === 100 === Abstract Using dimethylformamide as the solvent, electrospinning of PDLLA (D-lactide content: 10%) solutions with various concentrations was performed by means of a heating jacket for controlling the solution temperature ranging from 25 to 104oC. In addition, an IR emitter was used to control the surrounding temperature at ~110oC. The effects of solution properties and processing variables on the morphologies of the cone/jet/fiber were investigated, and the internal structure of the electrospun fibers was characterized using polarized FTIR, WAXD and DSC. A detailed study, starting with the properties of electrospinning solutions to the internal structure of the electrospun fibers, is presented. For a given solution with a sufficiently high concentration, the solution viscosity can be adjusted to a different level by tuning the operating temperature. The solution viscosity was significantly reduced at elevated temperatures, thereby giving rise to a reduction in electrospun fiber diameter. The fiber diameter was dramatically decreased to 330 ± 20 nm for the solution electrospun at elevated temperatures. For a solution with an insufficient entanglement density, it can be enhanced with the addition of fillers. In the last part of the dissertation, we propose another method for preparing ultrafine electrospun fibers. The addition of insoluble filler using carbon nanocapsules (CNCs) is proposed to enhance the development of the entangled network structure in a prepared semi-dilute solution. As CNC fillers were added into the 10, 13, and 15 wt% PDLLA solutions, the number of beaded fibers was decreased after electrospinning. Above 1 wt% of CNC was added into the prepared solution, the formation of beaded fibers was eliminated, while solution viscosity and conductivity were dramatically enhanced. Therefore, electrospun fibers with relatively smooth fiber shape were obtained, and fiber diameter could be further reduced to 90 ±10 nm. Moreover, this work was also motivated by the lack of reported studies on the percolation conduction behavior of deformable fibrous mats containing nanosize conducting particles, such as CNCs. We demonstrate the effect of filler on the microstructure of as-spun composite fibers. The conduction behavior of a PDLLA/CNC composite fiber mat were also investigated.