Fibre formation techniques

Fibre formation and morphology of the coated nanofibres can be determined using SEM. A small section of the produced web can be placed on a SEM sample holder and should be coated with gold. Electrical conductivity of the coated mats can then be determined by employing the standard four-point probe technique. 

Although the existing fibre-making technique is able to produce a bicomponent fibre of many cross-sectional structures, the production of bicomponent nanofibres has been limited to two basic types of cross-sectional structures, the core-sheath and the side-by-side . These bicomponent nanofibres are eiectrospun via special spinnerets. Two polymer solutions flow within the spinneret as the sheath and core, or side-by-side, to the tip of the nozzle and then are subjected to a co-electrospinning process. The formation of bicomponent nanofibres is determined by the laminar bicomponent jet. 

Polymers owe much of their attractiveness to their ease of processing. In many important techniques, sueh as injection moulding, fibre spinning and film formation, polymers are processed in the melt, so that their flow behaviour is of paramoimt importance. Because of the viscoelastie properties of polymers, their flow behaviour is much more complex than that of Newtonian liquids for which the viscosity is the only essential parameter. In polymer melts, the recoverable shear compliance, which relates to the elastic forces, is used in addition to the viscosity in the deseription of flow [48]. 

Current methods combine at least one of four different principles of allelic discrimination (hybridization, primer extension, ligation, or restriction) with one of four different detection techniques (chemiluminescence/ fluorescence, fluorescence polarization, resonance energy transfer, and mass spectrometry). Assay formats range from (slab)- gel electrophoresis, plates, particles, fibre arrays, and microchip arrays to semi- and homogenous assays that do not require any further sample separation or purification. 

The three major routes are (i) true liquid crystal templating at high surfactant concentrations, which is used for the formation of monoliths, thick layers or, via electrodeposition techniques, formation of thin films (ii) cooperative self assembly at surfactant concentrations where micelles are present in solution, which can be used to make powders (with either well-defined particle shapes or random structures), fibres and thin films grown at interfaces from solution and (iii) EISA at very low surfactant concentrations, where no micelles are initially present in solution, and solutions are in general prepared in nonaqueous solvents. This route is used to prepare thin films by dip or spin coating and powders via aerosol routes. The following sections will look at the current understanding of the mechanisms involved in each route to mesoporous materials. 

As non-degradable polyesters are quite common as textile materials, it comes as no surprise that their degradable counterparts are also readily processable into fibres. Polymer fibres are particularly interesting for biomedical applications, including wound dressings, controlled-release formulations and tissue engineering. Several spinning techniques result in the formation of polymer fibres. 

Raman fibre optics has been used to study the emulsion homopolymerisations of styrene and n-butyl acrylate (35). An IR spectroscopic technique for the examination of radical copolymerisations of acryl and vinyl monomers was developed. A comparative study of the copolymerisation of model monomer pairs was made using monofunctional and polyfunctional compounds. The data established the role of structural-physical transformations, involved in the formation of crosslinked polymers, on the copolymerisation kinetics and on the nonuniformity of distribution of crosslinks in the copolymers formed (151). Raman fibre optics of polymerisation of acrylic terpolymers was also used to monitor as well as an on-line measurement of morphology/composition (66). The high temperature (330 °C) cure reaction of 4-phenoxy-4 -phenyl-ethynylbenzophenone was monitored using a modulated fibre optic FT-Raman spectrometer (80). 

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