Solid fibre types

The liquid structure of the fibres can be solidified by linear hydrogen bond chains which may run parallel or perpendicular to the fibre axis. The strongest and most prominent type of chain-like bonding interaction is provided by the amide group, which has been extensively studied in helical peptides and proteins. Here, a few characteristics of interest are summarized before turning to solid fibres. The assumption is that other hydrogen bond chains between COOH" OOC and OPOsH - O3PO—, for example, are of a similar character. 

The three processes have many features in common. The conversion of the spun polymer melt or solution to a solid fibre involves cooking, solvent evaporation or coagulation depending on the spinning type used. Cooling of a fine filament is generally very rapid solvent evaporation involves simultaneous outward mass transfer and inward heat transfer while coagulation involves both of the two-way mass transfers. 

For use as insulation, a polyester low melt bonded fiber is blended with other type of fibers. However with a eertain mix of hollow fibers, insulation, as well as resilience can be improved. A polyester fiber blended with a bico low melt or chemical bond is used to produce high loft wadding. The fiber used is normally a solid fibre. 

Pulsed deuteron NMR is described, which has recently been developed to become a powerftd tool for studying molectdar order and dynamics in solid polymers. In drawn fibres the complete orientational distribution function for the polymer chains can be determined from the analysis of deuteron NMR line shapes. By analyzing the line shapes of 2H absorption spectra and spectra obtained via solid echo and spin alignment, respectively, both type and timescale of rotational motions can be determined over an extraordinary wide range of characteristic frequencies, approximately 10 MHz to 1 Hz. In addition, motional heterogeneities can be detected and the resulting distribution of correlation times can directly be determined. 

The final main category of non-Newtonian behaviour is viscoelasticity. As the name implies, viscoelastic fluids exhibit a combination of ordinary liquid-like (viscous) and solid-like (elastic) behaviour. The most important viscoelastic fluids are molten polymers but other materials containing macromolecules or long flexible particles, such as fibre suspensions, are viscoelastic. An everyday example of purely viscous and viscoelastic behaviour can be seen with different types of soup. When a thin , watery soup is stirred in a bowl and the stirring then stopped, the soup continues to flow round the bowl and gradually comes to rest. This is an example of purely viscous behaviour. In contrast, with certain thick soups, on cessation of stirring the soup rapidly slows down and then recoils slightly. 

Fibre optic-based flow-through optical biosensors The dramatic advances in fibre optic development in die last decade have promoted construction of sensors where radiation, whether emitted, transmitted or reflected, is conducted fi-om the sample to the detection system. The wide variety of available optical waveguide types (solid rods, hollow cylinders, micro-planar geometries) has been used with varying success in sensor development. 

The weight of gas adsorbed is sometimes measured, and for this purpose various kinds of microbalance have been used. McBain s sorption balance consists of a delicate helical quartz spring,5 suspending the adsorbing solid the upper end of the spring is fixed, and the lower end observed with a cathetometer. Bradley6 has used a balance with a beam, supported in the centre by a fine horizontal quartz fibre and references to other types of balance are given by McBain.7... 

More work is required in order to clarify the molecular structure of these fascinating molecular assemblies which seem to be on the borderline between fluid and solid micellar rods. Their formation develops through a certain type of precipitation, also typical for solid micellar fibres. However, the binding forces between the head group molecules (tetraalkylammonium and phenol) are weak, meaning that the fibres are not as stiff and uniform as the crystalline fibres described later. Aqueous suspensions of the described fibres dissolve massive amounts of small hydrocarbon molecules, e.g. 20 mol % of hexane, but the dissolving of hydrophobic porphyrins in them has not yet been achieved. 

These fibres are solid-like and should not be confused with the fluid myelin figures and their helical precursors obtained upon the swelling of lecithin crystals (see Figure 5.1). The fluid structures flow and change their shape and width constantly, whereas the solid types simply widen after addition of more material. Once a crystalline fibre is formed it adds material to the highly curved edges, much less to the more planar bilayer surfaces (Figure 5.7). 

Lopato, L.M. et al.. Theory, production technology, and properties of powders and fibres Features of solid solution formation with a fluorite type structure in the system Zr02- Hf02"Y203 with different synthesis methods, Powder Metallur. Metal Ceram. 45 (2006) 1-7. 

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