Polytetrafluoroethylene fibrillated

Structural studies were conducted on PE and PTFE (polytetrafluoroethylene) fibrils extracted by coating with C-Pt and stripping with a backing layer. In this case [299, 300] the backing layer was 5% PAA in water. After dissolution of the PAA, fibrils were left for TEM observation. Thin shreds or layers of rubber were tom off blends of natural mbber, polyisoprene, SBR and neoprene using gelatin for the extraction replica [311]. 

Ukihashi H, Asawa T, Gunjima T (1980) Cation exchange membrane of fluorinated polymer containing polytetrafluoroethylene fibrils for electrolysis and preparation thereof. US Patent 4,218,542... 

Fig. 3. Microstructure of expanded polytetrafluoroethylene as shown by scanning eiectron microscopy with different intemoduiar species (a) 30 m (b) 90 m (c) 12 nm. (N Noduies, F Fibrilles)...

Polytetrafluoroethylene suture is composed of expanded polytetrafluoroethylene (ePTFE), resulting in a porous microstructure having longitudinally oriented nodes and fibrils. The suture is sold by W. L. Gore Associates, Inc. under the trade name Gore-Tex Suture. 

The disk is constructed in several formats by the different vendors. One of the popular environmental extraction disks, called the Empore Extraction Disk (3M), consists of 8 to 12 pm particles of sorbent imbedded into an inert matrix of polytetrafluoroethylene (PTFE) fibrils (see Fig. 1.7). The disks consist of 90% sorbent particles and 10% PTFE by weight, with a bed height of approximately 0.5 mm. 

Figure 2.2 Polytetrafluoroethylene graft consisting of nodes and connecting fibrils. Space between the nodes can be controlled.

The unique invention that led to PTFE polymer products expanding and becoming desirably porous made the material suitable for use as implants. The modified structure consists of nodes interconnected by very small fibrils (Fig. 1.11). Briefly, the process is as follows. A fine powder of un-sintered polytetrafluoroethylene is uniformly mixed with a Uquid lubricant and then shaped into a product (sheet, rod or tube) by extrusion. After removal of the... 

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)).

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