Fluoroplastics tensile properties

The melt processible fluoroplastics are often desired due to the cost benefits of melt extrusion over paste extrusion. FEP, PEA and specially formulated melt processible perfluoroplastics are used in many of these applications however, in some of these applications, perfluoroplastics may not be the ideal choice. In cases where high cut-through resistance and better tensile properties are required, it is often desirable to employ a partially fluorinated polymer such as ETFE (ethylene-tetrafluoroethylene). ETFE is the copolymer of ethylene and TEE [16] that normally includes an additional termonomer to increase the flexibility required in commercial applications [17]. The increased physical and electronic interactions of the ETFE polymer chain are responsible for the comparatively enhanced physical properties. Additionally, the partially fluorinated polymers may be cross-linked to further improve physical properties. These benefits, however, are obtained at the expense of the unique properties of perfluoroplastics discussed in the Introduction and Overview. 

HTE fluoroplastic exhibits exceptional balance of tensile strength, good electrical properties, good resistance to permeation of vapors and fuels, as well as excellent chemical resistance. Because of its relatively low melting temperature, it is easy to process and can be processed on equipment without the high level of corrosion protection usually required by many other fluoroplastics. HTE is suitable for wire and cable insulation and for extruded Aims used for chemically resistant linings, release layers, and other applications. A summary of properties of the two current grades of HTE is shown in Table 3.13. 

This property is an important consideration in the design of parts from fluoroplastics because they deform substantially over time when subjected to load. Metals similarly deform at elevated temperatures. Creep (also called cold flow) is defined as the total deformation under stress after a period of time, beyond the instantaneous deformation upon the application of load. Significant variables that affect creep are chemical structure of resin, load, time under load, and temperature. Creep is measured under various conditions tensile, compressive, and torsional. 

Fluoroplastics are used in a large number of applications that involve operations at temperature extremes because of the ability of these plastics to withstand very high or low temperatures. A popular method of testing a part is based on monitoring the physical or mechanical properties, such as tensile strength and break elongation, as a result of thermal exposure over time. To check the impact of process-... 

Chemical changes occur when a fluoroplastic part is exposed to the few compounds and elements that can degrade them. Chemical attack over time can result in changes in surface or bulk composition, and a loss of mechanical properties such as tensile or burst strength. The loss of properties is because of a reduction in molecular weight or mass loss of the part. Degradation can introduce impurities into the process stream in the extreme case when massive chemical degradation takes place. 

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