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Fluoro Polymers lines Products

Basic Information

Fluoropolymers are used in the chemical processing industry principally for outstanding resistance to almost all chemicals their ability to withstand high temperatures also plays an important part in their functional role. The low mechanical Properties and high permeation rates of fluoropolymers at high temperature limit their use of linings to about 175 Degree Celsius, although they remain chemical inert up to 260 Degree Celsius.

Selection of polymers is an integral part of the overall material selection process. This implies that all the available material such as metals, ceramics and plastics are considered candidates for an application. The End user then considers these materials against established criteria such as required life, mean time between inspection, ease of fabrication, frequency of inspection ,extent of maintenance and capital cost.

More often than not it is the initial capital cost rather than life cycle cost of the equipment that affects the decision made during the material selection step. However the most important piece of data in the medium under consideration over the life of the equipment.

Fluoro polymers

Polytetrafluoroethylene (PTFE)

PTEE PTFE is marketed under the trade name of PTFE by DuPont It is a fully fluorinated thermoplastic having the following formula:

PTFE has an operating temperature range of from K208F toC4308C (K29Degree C toC212 Degree C). This temperature range is based on the physical and mechanical properties of PTFE. When handling aggressive chemicals, it may be necessary to reduce the upper temperature limit. PTFE is unique in its corrosion resistance properties. It is virtually inert in the presence of most materials. There are very few chemicals that will attack PTFE at normal use temperatures. Among materials that will attack PTFE are the most violent oxidizing and reducing agents known. Elemental sodium removes fluorine from the molecule. The other alkali metals (potassium, lithium, etc.) act in a similar manner. Fluorine and related compounds (e.g., chlorine trifluoride) are absorbed into PTFE resin to such a degree that the mixture becomes sensitive to a source of ignition such as impact. These potent oxidizers should be only handled with great care and recognition of the potential hazards. The handling of 80% sodium hydroxide, aluminum chloride, ammonia, and certain amines at high temperatures have the same effect as elemental sodium. Slow oxidation attack can be produced by 70% nitric acid under pressure at 4808F (2508C).PTFE has excellent weathering properties and is not degraded by UVlight.Applications for PTFE extend from exotic space-age usages to molded parts and wire and cable insulation to consumer use as a coating for cookware. One of PTFE's largest uses is for corrosion protection.

Including linings for tanks and piping. Applications in the automotive industry take advantage of the low surface friction and chemical stability using it in seals and rings for transmission and power steering systems and in seals forshafts, compressors and shock absorbers.

Fluorinated Ethylene–Propylene (FEP)

PTEE Fluorinated ethylene-propylene is a fully fluorinated thermoplastic with Some branching, but it mainly consists of linear chains having the following Formula:

FEP has a maximum operating temperature of 375Degree F (190Degree C). After Prolonged exposure at 400Degree F (204C), it exhibits changes in physical strength. To improve some physical and mechanical properties, the polymer is filled with glass fibers.FEP basically exhibits the same corrosion resistance as PTFE with few exceptions but at lower operating temperatures. It is resistant to practically all chemicals except for extremely potent oxidizers such as chlorine trifluoride and related compounds. Some chemicals will attack FEP when present in high concentrations at or near the service temperature limit. FEP is not degraded by UV light, and it has excellent weathering resistance.

FEP finds extensive use as a lining material for process vessels and piping, laboratory ware, and other process equipment.

PFA

PTEE Perfluoralkoxy is a fully fluorinated polymer having the following formula

PFA lacks the physical strength of PTFE at elevated temperatures but has somewhat better physical and mechanical properties than FEP above 300Degree F (149Degree C) and can be used up to 500Degree F (260Degree C). Like PTFE, PFA is subject to permeation by certain gases and will absorb selected chemicals. Perfluoralkoxy also performs well at cryogenic temperatures.

PFA is inert to strong mineral acids, organic bases, inorganic oxidizers, Aromatics, some aliphatic hydrocarbons, alcohols, aldehydes, ketones, ethers, esters, chlorocarbons, fluorocarbons, and mixtures of these. Perfluoralkoxy will be attacked by certain halogenated complexes containing fluorine. This includes chlorine trifluoride, bromine trifluoride, iodine pentafluoride, and fluorine. It is also subject to attack by such metals as sodium or potassium, particularly in their molten states. Refer to PFA has excellent weatherability and is not subject to UV degradation.

Chemical Resistance

PTFE Chemical Resistance Char

Chemical Resistance of PTFE to Common Solvents

Solvent
Exposure Temp., C
Exposure Time
Weight Gain,%
Acetone
20
12 mo
0.3
50
12 mo
0.4
70
2 wk
0
Benzene
78
96 hr
0.5
100
8 hr
0.6
200
8 hr
1.0
Carbon Tetrachloride
25
12 mo
0.6
50
12 mo
1.6
70
2 wk
1.9
100
8 hr
2.5
200
8 hr
3.7
Ethanol (95%)
25
12 mo
0
50
12 mo
0
70
2 wk
0
100
8 hr
0.1
200
8 hr
0.3
Ethyl Acetate
25
12 mo
0.5
50
12 mo
0.7
70
2 wk
0.7
Toluene
25
12 mo
0.3
50
12 mo
0.6
70
2 wk
0.6


Chemical Resistance of PTFE to Common Acids & Bases

Reagent Exposure Temp., C Exposure Time Weight Gain,%
Hydrochloric Acid
10% 25 12 mo. 0
10% 50 12 mo. 0
10% 70 12 mo. 0
20% 100 8 hr 0
20% 200 8 hr 0
Nitric Acid
10% 25 12 mo. 0
10% 70 12 mo. 0.1
Sulfuric Acid
30% 25 12 mo. 0
30% 70 12 mo. 0
30% 100 8 hr 0
30% 200 8 hr 0.1
Sodium Hydroxide
10% 25 12 mo. 0
10% 70 12 mo. 0.1
50% 100 8 hr 0
50% 200 8 hr 0
Ammonium Hydroxide
10% 25 12 mo. 0
10% 70 12 mo. 0.1


Chemical Compatibility of PTFE with Halogenated Chemicals

Chemical Effect on PTFE Sample
Chloroform Wets, insoluble at boiling point
Ethylene Bromide 0.3%weight gain after 24 hr at 100 C
Fluorinated Hydrocarbons Wets, swelling occurs in boiling solvent
Fluoro-naphthalene Insoluble at boiling point, some swelling
Fluronitrobenzene Insoluble at boiling point, some swelling
Pentachlorobenzamide insoluble
Perfluoroxylene Insoluble at boiling point, slight swelling
Tetrabromoethane Insoluble at boiling point
Tetrachloroetylene Wets, some swelling after 2 hr at 120 C
Trichloroacetic Acid Insoluble at boiling point
Trichloroethylene Insoluble at boiling point after 1 hr


PFA Chemical Resistance Char

Effect on PFA of Immersion in Inorganic Chemicals for 168 Hours

Reagent Exposure Temperature, C Tensile Strength Retained,% Elongation Retained % Weight Gain, %
Acids :-
Hydrochloric (conc.) 120 98 100 0
Sulfuric (conc.) 120 95 98 0
Hydrofluoric (60%) 23 99 99 0
Fuming Sulfuric 23 95 96 0
Oxidizing Acids :-
Aqua Regia 120 99 100 0
Chromic (50%) 120 93 97 0
Nitric (conc.) 120 95 98 0
Fuming Nitric 23 99 99 0
Bases :-
Ammonium Hydroxide (conc.) 66 98 100 0
Sodium Hydroxide (conc.) 120 93 99 0.4
Peroxide :-
Hydrogen Peroxide (30%) 23 93 95 0
Halogens :-
Bromine 23 99 100 0.5
Bromine 59 95 95 -
Chlorine 120 92 100 0.5
Metal Salt Solutions :-
Ferric Chloride 100 93 98 0
Zinc Chloride (25%) 100 96 100 0
Miscellaneous :-
Sulfuric Chloride 69 83 100 2.7
Chlorosulfonic Acid 151 91 100 0.7
Phosphoric Acid (conc.) 100 93 100 0


Effect on PFA of Immersion in Inorganic Chemicals for 168 Hours

Reagent Exposure Temperature, C Tensile Strength Retained,% Elongation Retained % Weight Gain, %
Acids/Anhydrides :-
Glacial Acetic Acid 118 95 100 0.4
Acetic Anhydride 139 91 99 0.3
Trichloroacetic Acid 196 90 100 2.2
Hydrocarbons :-
Isooctane 99 94 100 0.7
Naphtha 100 91 100 0.5
Mineral Oil 180 87 95 0
Toluene 110 88 100 0.7
Aromatic :-
O-Cresol 191 92 96 0.2
Nitrobenzene 210 90 100 0.7
Alcohol :-
Benzyl Alcohol 205 93 99 0.3
Ether :-
Tetrehydrofuran 66 88 100 0.7
Amine :-
Aniline 185 94 100 0.3
n-Butylamine 78 86 97 0.4
Ethylenediamine 117 96 100 0.1
Aldehyde :-
Benzaldehyde 179 90 99 0.5
Ketone :-
Cyclohexanone 156 92 100 0.4
Methyl Ethyl Ketone 80 90 100 0.4
Acetophenone 202 90 100 0.6
Esters :-
Dimethylphthalate 220 98 100 0.3
n-Butylcetate 125 93 100 0.5
Tri-n-Butylphosphate 200 91 100 2.0
Chlorinated Solvents :-
Methylene Chliride 40 94 100 0.8
Perchloroethylene 121 86 100 2.0
Carbon 77 87 100 2.3
Tetrachloride
Polar Soivents :-
Dimethylformamide 154 96 100 0.2
Dimethylsulfoxide 189 95 100 0.1
Dioxane 101 92 100 0.6


FEP Chemical Resistance Char

Chemical Resistance of FEP to Common Solvent

Solvent Exposure Temperature, C Exposure Time Weight Gain,%
Acetone 20 12 mo 0.3
50 12 mo 0.4
70 2 wk 0
Benzene 78 96 hr 0.5
100 8 hr 0.6
200 8 hr 1.0
Carbon Tetrachloride 25 12 mo 0.6
50 12 mo 1.6
70 2 wk 1.9
100 8 hr 2.5
200 8 hr 3.7
Ethanol (95%) 25 12 mo 0
50 12 mo 0
70 2 wk 0
100 8 hr 0.1
200 8 hr 0.3
Ethyl Acetate 25 12 mo 0.5
50 12 mo 0.7
70 2 wk 0.7
Toluene 25 12 mo 0.3
50 12 mo 0.6
70 2 wk 0.6


Chemical Resistance of FEP to Common Acids & Bases

Reagent Concentration Exposure Temperature, C Exposure Time Weight Gain,%
Hydrochloric Acid 10% 25 12 mo 0
10% 50 12 mo 0
10% 70 12 mo 0
20% 100 8 hr 0
20% 200 8 hr 0
Nitric Acid 10% 25 12 mo 0
10% 70 12 mo 0.1
Sulfuric Acid 30% 25 12 mo 0
30% 70 12 mo 0
30% 100 8 hr 0
30% 200 8 hr 0.1
Sodium Hydroxide 10% 25 12 mo 0
10% 70 12 mo 0.1
50% 100 8 hr 0
50% 200 8 hr 0
Ammonium Hydroxide 10% 25 12 mo 1
10% 70 12 mo 0.1


Chemical Compatibility of FEP Halogenated Solvents

Chemical Effect on Polymer Sample
Chloroform Wets, Insoluble at boiling Point
Ethylene Bromide 0.3% weight gain after 24 hr at 100 C
Fluorinated Hydrocarbons Wets, swelling occurs in boiling solvent
Fluoro-naphthalene Insoluble at boiling point, some swelling
Fluoronitrobezene Insoluble at boiling point, some swelling
Pentachlorobenzamide Insoluble
Perfluoroxylene Insoluble at boiling point, slight swelling
Tetrabromoethane Insoluble at boiling point
Tetrachlorothylene Wets, some swelling after 2 hr at 120 C
Trichloroacetic Acid Insoluble at boiling point
Trichloroethylene Insoluble at boiling point after 1HR


Chemical Compatibility of FEP with Various Chemicals

Chemical Effect on Polymer Sample
Abietic Acid Insoluble at boiling point
Acetic Acid Wets
Acetophenone Insoluble -0.2% weight gain after 24 hr at 150 C
Acrylic Anhydride No effect at room temperature
Allyl Acetate No effect at room temperature
Allyl Methacrylate No effect at room temperature
Aluminium Chloride Insoluble in solution with NaCL; 1%-5% anhydrous ALCL3 affects mechanical properties
Ammonium Chloride Insoluble at boiling point
Aniline Insoluble-0.3% weight gain after 24 hr at 150 C
Borax No wetting or effect by 5% solution
Boric Acid Insoluble at boiling point
Butyl Acetate Insoluble at boiling point
Butyl Methacrylate No effect at room temperature
Calcium Chloride No effect by saturated solution in methanol
Carbon Disulfide Insoluble at boiling point
Cetane Wets, insoluble at boiling point
Chromic Acid Insoluble at boiling point
Cyclohexanone No effect observed


Chemical Compatibility of FEP with Various Chemicals

Chemical Effect on Polymer Sample
Dibutyl Phthalate Wets, no effect at 250 C
Diethyl Carbonate No effect at the room temperature
Dimethyl Ether No effect observed
Dimethyl Formamide No effect observed
Ethyl Ether Wets,no effect at 250 C
Ethylene Glycol Insoluble at boiling point
Ferric Chloride 1%-5%FeCL3.6H2O reduces mechanical properties
Ferric Phosphate No effect by 5% solution
Formaldehyde Insoluble at boiling point after 2 hr
Forme Acid Insoluble at boiling point
Hexane Wets
Hydrogen Fluoride Wets, no effect 100% HF at the room temperature
Lead No effect
Magnesium Chloride Insoluble at boiling point
Mercury Insoluble at boiling point
Methacrylic Acid No effect at the room temperature
Methanol Wets
Methyl Methacrylate Wets above melting point
Naphthalene No effect
Nitrobenzene No effect
2-Nitro-Butanol No effect
Nitromethane No effect
2-Nitro-2-Methyl Propanol No effect
n-Octadecyl Alcohol Wets
Phenol Insoluble at boiling point
Phthalic Acid Wets
Pinene Wets, Insoluble at boiling point
Piperidene No effect 0.3%-0.5%weight gain after 24 hr at 106 C
Polyacrylonitrile No effect
Potassium Acetate Insoluble at boiling point
Pyridine No effect
Stannous Chloride No effect at Melting point (246C)
Sulfur No effect at 445 C
Triethanolamine Wets, no effect
Vinyl Methacrylate No effect at the room temperature
Water Insoluble at boiling point
Xylene 0.4%weight gain after 48 hr at 137 C
Zinc Chloride No effect at Melting point (260 C)

Permeation Information

Permeation can be defined as passage of gases and liquids through a second material such as solid. It is significant consideration in the selection of the plastic material for the construction of the chemical processing equipment because process fluids may travel across the thickness of the polymer by permeation. Permeated species in sufficient quantities could cause corrosion, contamination.

Permeation is molecular migration through microvoids either in the polymer (if the polymer is more or less porous) or between polymer molecules. In neither case is there an attack on the polymer. This action is strictly a physical phenomenon. However, permeation can be detrimental when a polymer is used to line piping or equipment. In lined equipment, permeation can result in:

  • Failure of the substrate from corrosive attack.
  • Bond failure and blistering, resulting from the accumulation of fluids at the bond when the substrate is less permeable than the liner or from corrosion/reaction products if the substrate is Attacked by the permeant loss of contents through substrate and liner as a result of the eventual failure of the substrate All polymers do not have the same rate of permeation. In fact, some polymers are not affected by permeation. The fluoro-polymers are particularly affected.

Some control can be exercised over permeation that is affected by :-

  • Temperature and pressure
  • The permeant concentration
  • The thickness of the polymer

Increasing the temperature will increase the permeation rate because the solubility of the permeant in the polymer will increase, and as the temperature rises, polymer chain movement is stimulated, permitting more permeant to diffuse among the chains more easily. The permeation rates of many gases increase linearly with the partial pressure gradient, and the same effect is experienced with the concentration of gradients of liquids. If the permeant is highly soluble in the polymer, the permeability increase may be nonlinear. The thickness will generally decrease permeation by the square of the thickness.

The density of the polymer as well as the thickness will have an effect on the permeation rate. The greater the density of the polymer, the fewer voids through which permeation can take place. A comparison of the density of sheets produced from different polymers does not provide an indication of the relative permeation rates. However, a comparison of the sheets' density produced from the same polymer will provide an indication of the relative permeation rates. The denser the sheet, the lower the permeation rate.

The thickness of the liner is a factor affecting permeation. For general corrosion resistance, thicknesses of 0.010–0.020 in. are usually satisfactory, depending on the combination of lining material and the specific corrodent. When mechanical factors such as thinning to cold flow, mechanical abuse, and permeation rates are a consideration, thicker linings may be required. Increasing a lining thickness will normally decrease permeation by the square of the thickness. Although this would appear to be the approach to follow to control permeation, there are some disadvantages. First, as thickness increases, the thermal stresses on the boundary increase that can result in bond failure. Temperature changes and large differences in coefficients of thermal expansion are the most common causes of bond failure. The plastic's thickness and modulus of elasticity are two of the factors that influence these stresses. Second, as the thickness of the lining increases, installation becomes more difficult with a resulting increase in labor costs. The rate of permeation is also affected by the temperature and the temperature gradient in the lining. Lowering these will reduce the rate of permeation. Lined vessels, such as storage tanks, that are used under ambient conditions provide the best service.

Other factors affecting permeation consist of these chemical and physiochemical properties :-

  • Ease of condensation of the permeant. Chemicals that readily condense will permeate at higher rates.
  • The higher the intermolecular chain forces (e.g., van der Waals hydrogen bonding) of the polymer, the lower the permeation rate.
  • The higher the level of crystallinity in the polymer, the lower the permeation rate.
  • The greater the degree of cross-linking within the polymer, the lower the permeation rate.
  • Chemical similarity between the polymer and permeant when the polymer and permeant both have similar functional groups, the permeation rate will increase.
  • The smaller the molecule of the permeant, the greater the permeation rate.

Corrosion of Metals

Metals corrode by an electrochemical reaction where metal loss occurs as oxidation at the anode sites and plating out occurs at the cathode. There are two types of Corrosion known as General Corrosion and Localized Corrosion. General Corrosion refers to a uniform loss of the metal thickness due to the interaction of the metal and the chemical to which it is exposed. This degradation can be measured as corrosion rate in the thickness per year. Localized Corrosion can be of various types such as pitting, Intergranular corrosion and Crevice Corrosion.

Pitting Corrosion is the localized corrosion of a metal surface confined to a point or small area that takes the form of cavities. Pitting is one of the most damaging forms of corrosion.

Intergranular corrosion is sometimes also called “intercrystalline corrosion” or “interdendritic corrosion”. In the presence of tensile stress, cracking may occur along grain boundaries and this type of corrosion is frequently called “intergranular stress corrosion cracking (IGSCC)” or simply “intergranular corrosion cracking”.

“Intergranular” or ‘intercrystalline” means between grains or crystals. As the name suggests, this is a form of corrosive attack that progresses preferentially along interdendritic paths (the grain boundaries). Positive identification of this type of corrosion usually requires microstructure examination under a microscopy although sometimes it is visually recognizable as in the case of weld decay.

Crevice Corrosion refers to the localized attack on a metal surface at, or immediately adjacent to, the gap or crevice between two joining surfaces. The gap or crevice can be formed between two metals or a metal and non-metallic material. Outside the gap or without the gap, both metals are resistant to corrosion.

The damage is normally confined to one metal at localized area within or close to the joining surfaces.

Corrosion of Polymers

Polymers do not corrode by an electrochemical process. The chemical Degradation and Chemical attack are used to describe polymer/chemical interaction. The following descriptions are often used cracking, blistering, chalking, swelling, discoloration. It is difficult to measure the corrosion rate for polymers.

Corrosion of metallic materials takes place via an electrochemical reaction at a specific corrosion rate. Consequently, the life of a metallic material in a particular corrosive environment can be accurately predicted. This is not the case with polymeric materials. Polymeric materials do not experience specific corrosion rates. They are usually completely resistant to a specific corrodent (within specific Temperature ranges) or they deteriorate rapidly. Polymers are attacked either by chemical reaction or solvation. Solvation is the penetration of the polymer by a corrodent that causes swelling, softening, and ultimate failure.

Corrosion of plastics can be classified in the following ways as to attack Mechanism:

  • Disintegration or degradation of a physical nature because of absorption, permeation, solvent action, or other factors
  • Oxidation, where chemical bonds are attacked
  • Hydrolysis, where ester linkages are attacked
  • Radiation
  • Thermal degradation involving depolymerization and possibly repolymerization
  • Dehydration (rather uncommon)
  • Any combination of the above

Results of such attacks will appear in the form of softening, charring, crazing, delamination, embrittlement, discoloration, dissolving, or swelling. The corrosion of polymer matrix composites is also affected by two other factors: the nature of the laminate and in the case of thermoset resins, the cure. Improper or insufficient cure will adversely affect the corrosion resistance, whereas proper cure time and procedures will generally improve corrosion resistance.Polymeric materials in outdoor applications are exposed to weather extremes that can be extremely deleterious to the material. The most harmful weather component, exposure to ultraviolet (UV) radiation, can cause embrittlement fading, surface cracking, and chalking. After exposure to direct sunlight for a period of years, most polymers exhibit reduced impact resistance, lower overall mechanical performance, and a change in appearance. The electromagnetic energy from the sunlight is normally divided into ultraviolet light, visible light, and infrared energy. Infrared energy consists of wavelengths longer than visible red wavelengths and starts above 760 nm. Visible light is defined as radiation between 400 and 760 nm. Ultraviolet light consists of radiation below 400 nm. The UV portion of the spectrum is further subdivided into UV-A, UV-B, and UV-C. Because UV is easily filtered by air masses, cloud cover, pollution, and other factors, the amount and spectrum of natural UV exposure is extremely variable. Because the sun is lower in the sky during the winter months, it is filtered through a greater air mass. This creates two important differences between summer and winter sunlight: changes in the intensity of the light and in the spectrum. During winter months, much of the damaging short wavelength UV light is filtered out. For example, the intensity of UV at 320 nm changes about 8 to 1 from summer to winter.

In addition, the short wavelength solar cutoff shifts from approximately 295 nm in summer to approximately 310 nm in winter. As a result, materials sensitive to UV below 320 nm would degrade only slightly, if at all, during the winter months. Photochemical degradation is caused by photons or light breaking chemical bonds. For each type of chemical bond, there is a critical threshold wavelength of light with enough energy to cause a reaction. Light of any wavelength shorter than the threshold can break a bond, but longer wavelengths cannot break it. Therefore, the short wavelength cutoff of a light source is of critical importance. If a particular polymer is only sensitive to UV light below 290 nm (the solar cutoff point), it will never experience photochemical deterioration outdoors. The ability to withstand weathering varies with the polymer type and within grades of a particular resin. Many resin grades are available with UV-absorbing additives to improve weather-ability. However, the higher molecular weight grades of a resin generally exhibit better weather ability than the lower molecular weight grades with comparable additives. In addition, some colors tend to weather better than others. Many of the physical property and chemical resistance differences of polymers stem directly from the type and arrangement of atoms in the polymer chains. In the periodic table, the basic elements of nature are placed into classes with similar properties, i.e., elements and compound that exhibit similar behavior.

These classes are alkali metals, alkaline earth metals, transition metals, rare earth series, other metals, nonmetals, and noble (inert) gases of particular importance and interest for thermoplasts is the category known as halogens that are found in the nonmetal category. The elements included in this category are fluorine, chlorine, bromine, and iodine. Since these are the most electro-negative elements in the periodic table, they are the most likely to attract an electron from another element and become part of a stable structure. Of all the halogens, fluorine is the most electronegative, permitting it to strongly bond with carbon and hydrogen atoms, but not well with itself. The carbon–fluorine bond, the predominant bond in PVDF and PTFE that gives it such important properties, is among the strongest known organic compounds. The fluorine acts as a protective shield for other bonds of lesser strength within the main chain of the polymer. The carbon–hydrogen bond, that such plastics as PPE and PP are composed, is considerably weaker. This class of polymers is known as polyolefins. The carbon–chlorine bond, a key bond of PVC, is weaker yet. The arrangement of elements in the molecule, the symmetry of the structure, and the polymer chains’ degree of branching are as important as the specific elements contained in the molecule. Polymers containing the carbon–hydrogen bonds such as polypropylene and polyethylene, and the carbon–chlorine bonds such as PVC and ethylene chlorotrifluoroethylene are different in the important property of chemical resistance from a fully fluorinated polymer such as polytetrafluoroethylene. The latter has a much wider range of corrosion resistance. The fluoroplastic materials are divided into two groups: fully fluorinated fluorocarbon polymers such as PTFE, FEP, and PPA called perfluoropolymers, and the partially fluorinated polymers such as ETFE, PVDF, and ECTFE that are called fluoropolymers.

Approaches for selection

Selection of any material will depend on identifying the degradation mechanism, its rate and criteria based on the expected life of the unit. The ability to fabricate the Fluoropolymers in the required shape is another consideration in its selection.

The ability to inspect and maintain the equipment or piping is also an important consideration in the selection process. Many operations are reluctant to shutdown equipment for reasons of downtime, safety and cost associated with the clean up.

Fluoropolymers are principally used for chemical resistance, nonstick, and Product parity applications.

Economics of selecting Fluoropolymers

Carbon steel, stainless steel, high nickel alloys and exotic metals (Ti and Ta) represent an upward progression in terms of corrosion resistance and cost. For Polymeric Materials polylefins, vinyls and some type of fiberglass represent the low end of spectrum. Some other forms of fiberglass and thermoplastics such as polypropylene are in the middle.Fluoropolymers are at the high end of the spectrum and they compete with the high nickel and exotic metals.