Fluoroplastics methods

THV Fluoroplastic can be processed by virtually any method used generally for thermoplastics, including extrusion, coextrusion, tandem extrusion, blown film extrusion, blow molding, injection molding, vacuum forming, and as skived film and solvent casting (only THV-220). 

Chemical etching requires immersion of the part into a bath for a period of time, then rinsing and drying. This process is more expensive than most other surface treatments, such as flame treatment, thus it is used when other methods are not sufficiently effective. Fluoroplastics are often etched chemically because they do not respond to other treatments, ABS are usually etched for metallic plating, and so on. 

TABLE 3.11 Typical Values of Properties of Dyi Not for Specification Purposes) ASTM Property Method neon THV Fluoroplastics (Nominal Values, Fluoroplastic Grade ... 

Table 2. Comparison of the extraction behavior of tracer einsteinium, fermium, and mendelevium after treatment with various reducing agents. The column-elution method of extraction chromatography was used with the extractant HDEHP adsorbed on a column bed of a fluoroplastic powder (20)...

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-... 

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. 

A variety of parts are made using fluoroplastics. A list of significant parts is presented in Table 10.2. Methods of manufacturing vary for producing parts, although some parts can be fabricated by more than one technique and from more than one fluoropoly-mer. Figures 10.1 through 10.4 show examples of parts made (or lined) with fluoroplastics. 

Selected testing and analytic techniques (Table 10.5) are briefly described in the following sections. An understanding of each method is necessary for the proper application and interpretation of results. Some of these techniques are specific to non-fluori-nated thermoplastics and may require modification when applied to fluoropolymers. Examples of the results of applying some of these techniques to fluoroplastic are presented to illustrate their use. The reader is referred to ASTM methods for additional details regarding the measurement of properties and characterization of the plastics. 

A variety of techniques and apparatus have been developed to study and measure surface properties of pol5uners and other materials. Three of the most useful techniques for such measurements are electron spectroscopy for chemical analysis (ESCA) also known as x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and ion scattering spectroscopy (ISS). Table 10.8 shows a comparison of the sampling depth of traditional methods and the new techniques. These analyses can focus on a much shallower thickness of the surface and virtually yield analyses of the outermost layers of a polymer article. Some of these methods and examples of their application to fluoroplastics are discussed below. 

Fig. 3.33. Specific breaking load at delamination of HDPE coating (1, 1 ), penta-plast coating (2, 2 ) and that of fluoroplast-3 (3, 3 ) versus their formation temperature. The coatings have been deposited by electrostatic method (1-3) and pouring...

A. 2 s PrApArttAA ASTH test method Fluoroplastics ccontdi lonomer Ketones ... 

For these reasons, an investigation was made to determine a simple, yet accurate, method for determining the relative crystallinity of fluoroplastics. An ideal test method was considered as being ... 

Method of synthesis emuision polymerization is used in industry Ebnesajjad, S, Fluoroplastics. Vol. 1. Non-melt Processible Fluoroplastics, William Andrew, 2000. 

Method of synthesis granular resin, water dispersions, and powdered resins are produced by free radical polymerization in aqueous medium TFE polymerizes linearly without branching micropowders are produced by irradiation of PTFE by high energy electron beam or polymerization controlled to produce lower molecular weight Diobny, J G, Fluoroplastics, Rapra, 2006. 

The objective of this chapter is to familiarize the reader with the important types of melt processibie fluoroplastics and the methods to produce them. The emphasis is on the review of commercially significant technologies, which are usually disclosed in patents. The exact polymerization technologies practiced by resin manufacturers are closely guarded. However, the descriptions published in patents and other publications should provide a thorough understanding of the subject. 

This chapter begins with a brief discussion of free radical polymerization, the mechanism by which fluoroplastics are polymerized. Next, preparation of different polymers is described. Each polymerization technique and the corresponding finishing steps are discussed. Characterization methods and the defining properties for each polymer group are also provided. 

In this section, foaming techniques are covered based on the fluoropolymer type, beginning with perfluoroplastics. Next, foaming of partially fluorinated fluoropolymers are reviewed, combining ETFE and ECTFE and separately covering PVDF. Technological reviews are based primarily on patents and publications that focus on potentially commercial methods of foaming fluoroplastics. 

One of the earliest reports of a fluoroplastic foaming technique was issued by Randa in 1963.f ] A physical foaming method was used in which a fluoromethane was the foaming agent along with boron nitride particles (preferred particle size <10 pm) to control the cell size. Examples of fluoromethanes included dichlorodifluoromethane,... 

The heat sealing of FEP has been described in detail in this sectionOther fluoroplastics can be sealed following similar principles to those used for FEP. These films can be heat-sealed by any method that heats the contact surfaces of the film above the melt temperature of the polymer while the surfaces of the film are in intimate eontaet. Fusion heat seal of FEP results in a non-peeling seal without requiring a wide seal area. Distortion and puekering of the film can be reduced by localizing the heat in as small an area as possible. 

Surface preparation of fluoroplastics can be achieved by a number of methods.h i] The plastic surface can be roughened by blasting with water. Other methods include corona bombardment, cross-linking by activated inert gas species, molten metal alloy treatment, sodium hydride treatment, and sodium etching. The treated layer is at most 1 pm thick and does not alter the bulk properties of the fluoroplastic. Surface... 

Fluoroplastics such as PVDF, FEP, PFA, and modified polytetrafluoroethylene can be thermoformedf ] by vacuum forming, pressure forming, and matched-die forming (Fig. 14.56). In all methods, a sheet of the fluoropolymer is heated until it reaches its gel point. It requires more soak (heat up) time than eonvention-ally thermoformed plastics due to its low thermal... 

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