Fluoropolymers mechanical analysis

The following two examples provide first a relatively simple example analysis followed by a second more sophisticated effort that exercises many aspects of advanced fluoropolymer mechanical analysis. 

Fluoropol Tners are used in critical applications where failure may have serious safety, environmental, and/or financial consequences. Modeling is an important tool in determining the root cause of the failure and its correction. The modeling of fluoropolymer components, like other polymer materials, continues to evolve in sophistication. This chapter introduces current and developing methodologies for mechanical analysis. These methodologies promise increasingly accurate predictions and analysis of fluoropolymer materials. 

Failure of parts, irrespective of plastic t5 e, is an inevitable fact of the operation of chemical plants. Fluoropolymers are no exception in spite of their excellent chemical, thermal, and mechanical properties. These plastics form the processing surfaces of equipment where they are exposed to the most aggressive and corrosive chemicals. The repeated exposure of fluoroplastics to these chemicals, in addition to other factors, can affect the integrity and surface quality of the parts. The chapters dealing with properties and part fabrication techniques of fluoropolymers should be consulted extensively. An understanding of the limitations of fluoropolymers and flaws created by fabrication methods is required for successful failure analysis of parts. 

In the addition to homo-PVF2, a large number of copolymers have also been synthesized which allow to optimize the mechanical properties of fluoropolymers. Most common are copolymers with vinyl fluoride, trifluoroethylene, tetrafluoroethylene, hexafiuoropropy-lene, hexafluoroisobutylene, chlorotrifluoroethylene, and pentafiuoro-propene [521,535, 559-562]. Copolymerization with nonfluorinated monomers is possible [563] in principle but has not yet found commercial use. Fluorocarbon monomers that can help to retain or enhance the desirable thermal, chemical, and mechanical properties of the vinylidene structure are more interesting comonomers. Copolymerization with hexafluoropropylene, pentafluoropropylene, and chlorotrifluoroethylene results in elastomeric copolymers [564]. The polymerization conditions are similar to those of homopoly(vinylidene fluoride) [564]. The copolymers have been well characterized by x-ray analysis [535], DSC measurements [565], and NMR spectroscopy [565,566]. 

Although fluoropolymers are virtually inert, and thermally stable (Thermo-Gravimetric Analysis, TGA, indicates that the first 1% weight loss occurs at about 400°C), several ways have been documented for other additives to interact with the PPA. These include chemical reaction, adsorption, abrasion, and competition with the coating mechanism of fluoropolymer based additives. Several tests have been developed to reveal whether the additive is behaving synergistically or antagonistically towards the PPA s ability to coat the capillary die. 

One of the underlying assumptions of this analysis is that there is only a single failure mechanism occurring. This is generally true of the vinyl polymers and also for the fluoropolymers, but may not be true depending on the basic material properties of poly-ethylenes, polypropylenes, and cross-linked poly-ethylenes. Polyolefin materials will exhibit a change in tile failure mode from a ductile failure to a britfle or slit-type failure, depending on the fundamental... 

As the X-ray photoelectron spectroscopy technique is very surface sensitive, the fluoropolymers were carefully transferred - through the air - from the sputtering vessel to the ESCA spectrometer, and analyzed without further chemical or mechanical treatment. All the studied samples were stable in air (see below) and in the spectrometer during the analysis, i.e. no degradation could be detected. 

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