Fine structure of PET fibers

Peculiarities of the Fine Structure of PET Fibers and the Relationship to Their Basic Physical Properties... 

Contrary to widespread opinion, the value of Ea is not a constant quantity. As was proved previously [52], the value of E is variable, since it depends on the ordering of macromolecules in the amorphous material of the fiber. At the same time, one can suppose that this ordering will be affected by the specificity of the fine structure of the fiber, and particularly by the type of substructure of the fiber. The relationship determining the modulus Ea appropriate for a definite type of fiber substructure can be derived from Eq. (11) when appropriate values of A are assumed. In the case of the microfibrillar substructure, i.e., for A < I, typical of PET fibers stretched, but not subjected to annealing, this equation has the form [52] ... 

Table 8 Fine Structure Parameters and Axial Elastic Moduli of PET Fibers of Microfibrillar Substructure...

The low electrical conductivity of PET fibers depends essentially on their chemical constituency, but also to the same extent on the fiber s fine structure. In one study [58], an attempt was made to elucidate the influence of some basic fine structure parameters on the electrical resistivity of PET fibers. The influence of crystallinity (jc) the average lateral crystallite size (A), the mean long period (L), and the overall orientation function (fo) have been considered. The results obtained are presented in the form of plots in Figs. 9-12. 

PET fibers in final form are semi-crystalline polymeric objects of an axial orientation of structural elements, characterized by the rotational symmetry of their location in relation to the geometrical axis of the fiber. The semi-crystalline character manifests itself in the occurrence of three qualitatively different polymeric phases crystalline phase, intermediate phase (the so-called mes-ophase), and amorphous phase. When considering the fine structure, attention should be paid to its three fundamental aspects morphological structure, in other words, super- or suprastructure microstructure and preferred orientation. 

Table 11 Thermal Volume Expansivity (a2s) and Related Fine Structure Parameters of Differently Drawn PET Fibers...

Table 12 Fine Structure Parameters of Annealed PET Fibers...

Etching has been used to reveal structures in polymer fibers [179,180], polymer blends [181,182] and in bulk polymers, such as PET [183] and PE [184]. Periodic structures were seen to develop on argon plasma etched, oriented materials, such as nylon and PET, thought to be characteristic of the fold period [185]. Such structures were also shown for ion etched (argon) fibers [186]. Fine scale structures were observed for etched polyamide [187], PET [19,188] and aramid fibers [187] which showed ripple structures transverse to the fiber axis. 

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