Polytetrafluoroethylene representation

FIGURE 3.1 Schematic representation of the polytetrafluoroethylene helix. (Adapted from Bunn, C. W. and Howels, E. R., in Nature 174 (1954). With permission from Macmillan Magazines, Ltd.)... 

FIGURE 3.1 Schematic representation of the polytetrafluoroethylene helix. From Koo, G. P. in Fluoropolymers (Wall, L. A., Ed.), Wiley-Interscience, New York, p. 508, 1972. With permission.)... 

Evans and collaborators [59] have shown how an anisotropic microstructure consisting of nodules and fibrils can be produced in polytetrafluoroethylene (PTFE) that gives rise to a very large negative Poisson s ratio. Figure 7.22 is a schematic representation of the deformation of microporous PTFE. 

Figure 7.22 A schematic representation of the structural changes observed in microporous polytetrafluoroethylene undergoing tensile loading in the x direction (a) initial dense micro-structure (b) tension in fibrils causing transverse displacement of anisotropic nodal particles with lateral expansion (c) rotation of nodes producing further lateral expansion (d) fully expanded structure prior to further, plastic deformation due to node break-up. (Reproduced with permission Ifom Evans and Caddock, J. Phys. D Appl. Phys., 22, 1883 (1989)).

Figure 11.3 Three-dimensional representation of polytetrafluoroethylene (PTFE).

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