Polytetrafluoroethylene morphology

Another field of application of fluorinated biomaterials is connected to lesions or evolving disease pathology of blood vessels. In particular, arteries may become unable to insure an adequate transport of the blood to organs and tissues. Polytetrafluoroethylene (PTFE) and expanded e-PTFE are the preferred materials for vascular prostheses. The interactions of blood cells and blood plasma macromolecules with both natural and artificial vessel walls are discussed in terms of the mechanical properties of the vascular conduit, the morphology, and the physical and chemical characteristics of the blood contacting surface. 

Melillo, L. and Wunderlich, B. Extended chain crystals VIII. Morphology of polytetrafluoroethylene. Kolloid Z. Z. Polymere 250, 417 (1972)... 

Melillio L, Wunderlich B (1972) Morphology of polytetrafluoroethylene extended chain crystals VIII. Kolloid Z Z Polym 250 417... 

Rahl FJ Evanco MA, Fredericks RJ, Reimschuessel AC (1972) Studies of the morphology of emulsion-grade polytetrafluoroethylene. J Polym Sci Part A2 10 1337... 

Seguchi T, Suwa T, Tamura N, Takehisa M (1974) Morphology of polytetrafluoroethylene prepared by radiation-induced emulsion polymerization. J Polym Sci Polym Phys Ed 12 2567... 

In this paper, we report the studies on the adhesion between metals and fluorocarbon polymer films. Fluorocarbon polymer has a dielectric constant of 2.1, lower than that of polyimide, 3.2-3.5, and is attractive to packaging. We have studied the adhesion of Cu to bulk Teflon, a polytetrafluoroethylene (PTFE) polymer, and found enhanced adhesion using a presputtering treatment of the Teflon prior to the deposition of Cu (4). Further analysis shows that the morphological changes of the Teflon due to the sputtering treatment could be a major contributor to the enhanced adhesion observed (5). 

The third design feature is the polymer microstructure. Morphology of polymer can influence wear resistance of polymers. For example, in a semicrystalline polymer, both amorphous and crystalline phases coexist. The amorphous phase has been shown by Tanaka (8) to be weaker than the crystalline phase, thus the former wears faster than the latter. In addition to the difference in phases, the size of the spherulites and the molecular profile can also influence the wear rates. Thus, a control of the morphology through crystallization can improve the wear resistance of a polymer such as polytetrafluoroethylene (11). 

Various micronized polytetrafluoroethylene powders were compounded with silicone rubber (MQ) and the mechanical properties of the composites were evaluated. At a PTFE level of only 5 wt%, the fractured surface of the composites showed layered structure morphology. This stracture effectively improved the tear strength of the MQ but it also lowered the tensile properties of the composites. The addition of fluorosUicone rubber (FMQ) as a compatibilizer, improved considerably the tensile and tear strength of the composites. Extrusion of the MQ/PTFE/FMQ composites on an electric wire indicated that the spherical PTFE powder was suitable for the extrusion process [55]. 

Figure 9.1 depicts a combustion flame and typical morphology of a Mg/PTFE (polytetrafluoroethylene) flame. The luminous cone designated a is dominated by continuum radiation and both fluorocarbon species. The outer aerobic combustion zone b is less optically dense and shows mainly molecular radiation of MgF, MgO, C2, CO and CO2. 

For the analysis of optical properties, films of all nanostructured systems were prepared by spin-coating from 5 wt% solutions in dichloroethane in a similar way as described above. However, for the morphological study, the solutions were drop cast into polytetrafluoroethylene moulds of 4 cm X 4 cm X 1 cm and the solvent was removed by evaporation at room temperature. All samples were then cured at 140 °C during 24 h and post-cured at 165 °C for 2 h. 

Xing, D., He, G., Hou, Z., Ming, P, and Song, S. (2013) Properties and morphology of Nafion/polytetrafluoroethylene composite membrane fabricated by a solution-spray process, Int. J. Hydrogen Energ., 38, 8400-8408. 

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