Plastics fluoroplastics

Fluoroplastics. Conventional plasticizers are used as processing aids for duoroplastics up to a level of 25% plasticizer. However, certain grades of Kel-E (chlorotriduorethylene) contain up to 25 wt % plasticizer to improve elongation and increase softness the plasticizers used are usually low molecular weight oily chloroethylene polymers (5). 

Storage. Carbon steel and stainless steel should be used for all equipment in ethylene oxide service. Ethylene oxide attacks most organic materials (including plastics, coatings, and elastomers) however, certain fluoroplastics ate resistant and can be used in gaskets and O-rings. See Reference 9 for a hst of materials that are compatible with ethylene oxide. 

MOST PLASTIC MATERIALS ACRYLICS ALKYDS FLUOROPLASTICS CELLULOSICS NO TRACK 78-420 70-360 80-310... 

FLUOROPLASTICS. These plastic materials may be placed into two convenient categories III fluorocarbon plastics, and (2) other fluoroplas-lies. Fluoroplastics are produced by free radical initiated polymerization or copolymerizaiion of the monomers. Fluorocarbon plastics contain no C-H bonds other fluoroplastics contain some C-H and/or C-CI bonds in the basic slructure. 

THV Fluoroplastic can be readily bonded to itself and to many plastics and elastomers and unlike other fluoroplastics does not require surface treatment, such as chemical etching or corona treatment. However, in some cases tie layers are required to achieve a good bonding to other materials.92... 

This behavior results from stress relaxation and other viscoelastic phenomena that are typical of TPs. In addition to using heat TPs such as polyolefins, neoprenes, silicones, and other cross-linkable TPs are example of plastics that can be given memory either by radiation or by chemically curing. Fluoroplastics need no such curing. When this phenomenon of memory is applied to fluoroplastics such as TFE, FEP, ETFE, ECTFE, CTFE, and PVF, interesting and useful high-temperature or wear-resistant applications become possible. 

Source Ebnesajjad, S., Fluoroplastics, Vol. 1, William Andrew/Plastics Design Library, Norwich, NY, 2000 (With permission). 

Ebnesajjad, S. Melt Processible Fluoroplastics The Definitive User s Guide and Data Book, Plastics Design Library. William Andrew Publishing Norwich, NY, 2002. 

Fifoot. R. E.. Fluoroplastics, Modern Plastics Encyclopedia 89. McGraw-Hill Co., New York, October 1988. 

The fluoroplastics are a relatively pricey group which are generally more inert than most other plastics. 

The moduli of fluoropolymers are a function of a number of variables, most important of which is the composition of the polymer and, more specifically, the presence or absence of hydrogen in the polymer. Other variables are those affecting the other mechanical properties of these plastics. They include testing temperature, molecular weight, and crystallinity, which affect the modulus of these plastics independently of the regime/tyqie of measurements. Perfluo-ropolymiers have lower moduli than partially fluori-nated fiuoropiastics. An increase in the fluorine content of the fluoroplastic increases the modulus. 

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-... 

In another example, ] a problem with poor physical properties of molded fluoroplastics was overcome. Transfer molded material was found to have low modulus of elasticity above 150°C and was prone to irreversible cold flow. The solution involved embedding a metal or plastic insert as a core material in the mold. The choice of the core material depended on the end use performance requirements. 

An engineering plastic core was found preferable examples included polyetherether ketone (PEEK), polyphenylene sulfide (PPS), and polyether imide (PEI). Polytetrafluoroethylene bearers were placed in the mold to keep the core material away from the walls of the mold. No special cavity modifications were required. Any hot-melt fluoroplastic could be molded surrounding the insert examples include PVDF, FEP, ETFE, PFA, ECTFE, and PCTFE. 

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. 

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. 

Applications of fluoropolymers are still growing, even decades after the discovery of the first plastic (polytetrafluoroethylene) in this family. The increasing use of fluoropolymers in such dynamic industries as wire and cable insulation, automotive, aerospace, oil and gas recovery, and semiconductor manufacture has led to significant material developments and trends in the last few years. New fluoropolymers have been introduced to the market (amorphous fluoroplastics, modified PTFE, low-temperature fluoroelastomers, and amine-resistant fluo-... 

Liquid electrolytes display significant differences in permeability values. For instance, permeation of hydrogen chloride through polyethylene film when diffusing from concentrated hydrochloric acid is detected in a few minutes, whereas permeation of potassium chloride is not recorded even after three months. Permeation of nitric acid through fluoroplastic film is recorded in a few tens of minutes, while it is necessary to wait more than a year for sulfuric acid to be detected [22]. With increasing concentration of the electrolyte its permeation rises. Pol nners whose electrolyte diffusion factor is D < fO m /s are considered to be practically impermeable. Polyolefins, fluoroplasts and polyesters are easily permeable to hydrochloric, hydrofluoric, nitric, acetic and fluorosilicic acids, and ammonium diffusing form aqua solutes. They are less permeable for sulfuric and phosphoric acids, salts and caustic alkali. Phosphoric acid easily diffuses into PVC as well. In this case [23], diffusion of the acid is conditioned by the presence of a plasticizer in the polymer. 

Polymers used in inhibited plastics (polyolefins, polyamides, fluoroplastics and others) are in their majority harmless and friendly to man [7]. Toxicity of this kind of plastics can arise from additives that are impregnated for special purpose or their decomposition products. The extent of the danger to the human organism of inhibited plastics during their production and application (independently of the purpose) depends on the toxicity of the low-molecular components that isolate into the environment. 

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