Electrohydrodynamic forming of honeycomb-like polymeric structures

• Main Author: Liang, T.
• Published: University College London (University of London) 2015
• Subjects: 621
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654631

In this dissertation, polyethylene oxide (PEO) and ethyl cellulose (EC) have been chosen as model polymers to investigate different aspects of electrohydrodynamic processing and forming. In the first part of the work, electrospraying of PEO was attempted choosing a wide range of single solvents and mixed solvents. The selection of solvents affects the solubility and spinnability of PEO and the morphology of electrospun fibres. In the second part of the research the creation of 3D nanofibrous structures using electrospinning of PEO was investigated. The results demonstrate how the process is influenced by physical and processing parameters. It is reported that electrospun polymer nanofibres self-assemble into three dimensional honeycomb-like structures. The underlying mechanism was studied by varying the polymer solution concentration, collecting substrates and collection distance. The polymer solution concentration was found to have a significant effect on the size of the electrospun nanofibres. The nature of the collection substrate and the magnitude of the collection distance affect the electric field strength, the evaporation of solvent and the discharging of nanofibres. Consequently both the collection substrate and the collection distance had a significant influence on the self-assembly of nanofibres. In the third part of the work, the ways in which relative humidity (RH) plays a key role in the formation of porous structures was investigated using the hydrophilic polymer (PEO) and the hydrophobic polymer (EC). The generation of a 3D honeycomb-like structure was achieved using PEO polymer when RH was increased to between 53% and 93%. The optimum RH was found to be 73%. But efforts to generate 3D honeycomb-like structures using EC were unsuccessful throughout the range of RH investigated (53% - 93%). High speed camera imaging has been an important feature of the work carried out in this thesis.