Advanced slot needleless electrospinning and air filtration properties of slot electrospun nanofibres

Novel needleless electrospinning technologies for large scale producing polymer nanofibres are developed. Particularly, multi auxiliary fields are applied to improve the electrospinning performance and nanofibre quality. The needleless electrospun nanofibre products have a promising application on air filtration

Gyration Spun Polymeric Fibres for Antibacterial Applications

Hybrid polymeric fibres and fibrous structures have widely been used to construct porous polymer scaffolds with excellent functionally, and are of great interest in biomedical applications. In this thesis, in contrast to electrospinning, a novel approach, gyration spinning with or without pressure is reported to achieve a high production rate for hybrid nanoparticle embedded polymer fibres in the micro to nanometre scale range using either polymer solutions or melts. Polyurethane (PU), nylon, and poly(ethylene oxide) (PEO) were used as the polymers not only because of their excellent biocompatibility, but also depends on good oxidative biostability, processability of PU, good mechanical strength, spinnability and stability for nylon, and non-toxicity of PEO. In the meantime, silver nanoparticles, copper oxide nanoparticles and zinc oxide nanoparticles were used to increase the antibacterial performance to produce hybrid nanofibres using pressurised solution gyration. A pressurised melt gyration process was used for the first time to generate poly(ε-caprolactone) (PCL) fibres and silver coated PCL fibres in the micrometre range (< 50 m) due to the low melting point (60°C) of PCL pellets. The formation of fibres depends on the centrifugal force, pressure blowing and evaporation. Fibre diameter is significantly reduced with a decrease in the weight percentage of the polymer in solution, and an increase in the melting temperature, rotational speed and working pressure. Field emission scanning electron microscopy (FE-SEM) was used to study the characteristics and morphology of the fabricated polymer fibres. Incorporation of Ag nanoparticles into the polymer fibres was confirmed using a combination of advanced microscopical techniques and Raman spectrometry to study the bonding characteristics of the polymer and Ag nanoparticles. Inductively coupled plasma mass spectroscopy (ICP-MS) showed that the substantial concentration of Ag ions in the nylon fibre matrix was producing effective antibacterial properties. Ag nanoparticles and CuO nanoparticles were successfully incorporated into polymer fibres and proved to be of higher antibacterial efficacy than virgin polymer fibres, against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa

Cellulosic Nanocomposites for Advanced Manufacturing: An Exploration of Advanced Materials in Electrospinning and Additive Manufacturing

The effects of formulation and processing of thermoplastics and composites containing Nanocrystalline Cellulose (NCC) were explored and characterized for electrospinning and fused deposition modeling 3D printing advanced manufacturing techniques. Through electrospinning, desirable outcome responses were optimized through design of experiments for electrospun fibers of 3 material systems by controlling up to four formulation and processing factors. Regression models were developed for fiber diameter, beading density, and bead diameter responses for each material system and improved with center point measurements where applicable. The three material systems include: NCC and polycarbonate (PC) in a mixture of tetrahydrofuran and dimethylformamide (THF:DMF), NCC and PC in chloroform, and NCC and polyamide-6,6 (PA 6,6) in formic acid. For NCC and PC in THF:DMF, the inclusion of NCC tended to improve the spinnability of the system. Less beading, smaller fibers, and more pristine fibers were observed with the incorporation of 2-wt.% of NCC with PC. NCC surface modified with (2-dodecen-1-yl) succinic anhydride (cNCC) and PC in chloroform was the least ideal system tested, as it had a very narrow window of parameters to achieve desirable fibers. Concentrations of PC are required to be greater than 15-wt.% to achieve some fibers and this was improved through the addition of cNCC, but the resulting uniformity and repeatability of the chloroform solvent was not ideal for the current benchtop experimental setup. Modified cNCC and PA 6, 6 lead to the most desirable fibers, with 200 to 300 nm fiber diameters that can lead to desired nanoscale effects, like extremely high surface area and slip-flow filtration benefits. The cNCC and PA 6,6 system did not include any beading and produced a regression model for fiber diameter that has an R-squared fit of 0.999, making it excellent for producing desired fiber diameters. Proof of concept application of electrospun fibers in transparent coatings with improved surface properties were presented and validated through microhardness and light transmittance testing. Through fused deposition modeling thermoplastic starch-resin copolymer (TPS) and NCC reinforced TPS was explored. 3D printer filaments were designed and manufactured on a benchtop scale extruder as well as in a scale-up facility used for industrial production. ASTM specimens were 3D printed on the Makerbot Replicator 2X printer with Gcode and slicing parameters optimized for the new formulation. Mechanical properties were measured for impact, tensile, and flexural testing. 3D Printing slightly increased tensile and flexural modulus relative to injection molding techniques, while only slightly decreasing impact, flexural and tensile strength, suggesting that 3D printing may be a suitable replacement process for certain applications. The addition of NCC to TPS increased tensile and flexural modulus at 1, 3, and 5-wt.% loadings while the addition of NCC increased impact, tensile and flexural strength to a maximum at 3-wt.% loading. Scale-Up trials were successful at preparing NCC/TPS filaments for 3D printing, but in general, mechanical properties were at about 65-80% of the desktop filament extrusion