Fibre morphology

The blending of polymers is a technique which is being increasingly applied for improving the mechanical properties of synthetic textile fibres (1,2), for superior properties may be achieved which are not obtainable from any of the individual blend components. By careful control of blend composition and phase morphology, fibre properties can be adjusted to meet... 

In order to obtain continuous polymer fibres, highly volatile solvents must be used in order to ensure complete evaporation of the solvent before the jet reaches the collector. The temperature and humidity in the electrospinning chamber also impact the rate of solvent evaporation. These, combined with the distance between the tip and the collector, determine whether the obtained polymer fibres are wet or dry, as well as influence their morphology. Fibres obtained at higher temperatures have heen found to have smaller diameters due to reductions in the solution viscosity, while increases in humidity result in the formation of pores in the fihres. Decreases in fibre diameter are also observed when higher voltages and solutions with higher conductivities are used. ... 

Fibres, film and moulded objects may be made from the polymer but properties are very dependent on morphology which is greatly affected by processing conditions and by subsequent annealing. 

Morphological features for POPs can range from low-temperature elastomers (when aliphatic alkoxy substituents of different length are attached to the polyphosphazene skeleton), to crystalline, film- and fibre-forming materials... 

Morphologically, the lens is arranged so that dedifferentiated or disorientated lens fibres are not eliminated but are pushed to the core (Spector, 1984,). Damage to the cell-fibre membranes or to the proteins they contain is irreversible. The lens is therefore dependent on the peripheral cells of the epithelial layer for protection against insult. 

No shrink-resist polymer developed so far meets all the above requirements [301]. There is clearly some similarity with easy-care finishing of cotton. Although effective crosslinking agents are readily available for application to cotton, the morphological complexity of the wool fibre is such that an equally effective polymer has yet to be identified for wool treatment [304]. 

The emphasis is on commercial materials and formulations. The reason is that commercial materials are rarely pure materials. A pure homopolymer is a rare species in the real-world materials. To arrive at the desired material s properties, either a copolymer is used, sometimes a blend or a dispersion, or additives or filler materials including rubber particles, carbon black or fibres of various type and make may be added, and are thus commonplace in commercial products. This implies a more complex constitution and morphology than expected for pure polymers. However, obviously, the methods described herein can be applied to pure, unmodified, polymers as well. 

The importance of the uniformity of structure and morphology for the strength of the fibre is illustrated in Fig. 73. It shows that the observed filament strength of the PpPTA microfilaments is considerably higher than the strength... 

Also, other factors may influence the fracture morphology as is demonstrated by the following examples. Glass fibres having an isotropic structure... 

Hence, by controlling parameters such as temperature or the concentration of the different reactants, the morphology of the inorganic nanostructures formed from organic templates can be finely and widely tuned. Finally, long, double-walled glass nanotubes (fibres) ten times narrower than those currently available with a monodisperse diameter... 

Grubb, D. T., andjelinski, L. W. (1997). Fibre morphology of spider silk The effects of tensile deformation. Macromolecules 30, 2860-2867. 

Ruigrok, R. W., Barge, A., Albiges-Rizo, C., and Dayan, S. (1990). Structure of adenovirus fibre. II. Morphology of single fibres./. Mol. Biol. 215, 589-596. 

Numerous disperse dyes are marketed in a metastable crystalline form that gives significantly higher uptake than the corresponding more stable modification. The molar free enthalpy difference can be used as a criterion of the relative thermodynamic stabilities of two different modifications [53]. Certain dyes can be isolated in several different morphological forms. For example, an azopyrazole yellow disperse dye (3.52) was prepared in five different crystal forms and applied to cellulose acetate fibres. Each form exhibited a different saturation limit, the less stable modifications giving the higher values [54]. 

The paper-making properties of all of these fibres are quite different from each other and also from wood. This is mostly due to the differing morphology and to some extent the differing chemistry of the fibre cells. The photomicrograph (Figure 1.2), shows a comparison between various non-woody fibre types. 

Figure 2.2 Light photomicrographs of fibre preparations illustrating the morphological differences between softwood and hardwood commercial pulps (a) bleached sulfate pine (softwood), (b) bleached sulfate eucalyptus (hardwood). Scale bar = 200 /an.

Source Adapted from (i) Cell Wall Mechanics of Trecheids , M.R.E. London, Yale University, 1967, p. 169-170 (ii) A Microscopic Study of Coniferous Wood in Relation to its Strength Properties , H. Garland. Ann. Missouri Botan. Gard., 1939, 26, 1-95 (iii) Morphological Foundations of Fibre Properties , L.J. Rebenfeld, J. Polymer Sci., 1965, C9, p. 91-112). 

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