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Appendix :Uses and substitutions of Specialist Equipment
This document is the appendix of the general comment to the Restriction report on Per- and polyfluoroalkyl substances (PFAS) from Industrial Gas Detectors and Monitors Manufacturers Association) submitted on 22. September 2023
Table of content
The characteristics and functions of PFAS .............................................................................2 Summary .............................................................................................................................. 2 Chemical resistance ............................................................................................................2 Ozone resistance .................................................................................................................3 Repellency from water and oil / non-adhesion ....................................................................4 Heat resistance ....................................................................................................................5 Electric insulation .................................................................................................................5 Low friction, self lubrication..................................................................................................6 Gas barrier properties/Gas permeation properties..............................................................7 low refractive index ............................................................................................................10 Weatherability ....................................................................................................................10 Durability ............................................................................................................................11 Resistance to creep / Compression set.............................................................................11
Uses of PFAS in Specialist Equipment .................................................................................13 Summary ............................................................................................................................ 13 1Sealing materials ......................................................................................................14 2Coating/Lining ........................................................................................................... 14 3filteringmembrenes ...................................................................................................16 4cutting parts ..............................................................................................................18
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The characteristics and functions of PFAS
Summary PFASs have many functions. The characteristics and functions of PFAS which are mainly used in Specialist equipment are described in this section.
PFAS has excellent properties such as, chemical resistance, electric insulation, heat resistance, repellency from water and oil, non-adhesion, weatherability, and others. PFASs are used where multiple of these properties are required simultaneously. We recognize that the ability to provide these various properties in a single material is the most important property of PFAS, and at present we do not have information on any other substance with this function other than PFAS.
Chemical resistance Fluoropolymers compared to other general-purpose resins
Table 1 Classes of Substances at 20 C, Chemical Compatibility Chart - LDPE, HDPE, PP, Teflon Resistance (calpaclab.com) 1
* Not for tubing chemical resistance (except PVC) ** Except for oxidizing acids (See oxidizing agents, strong) *** TPE gaskets Excellent: 30 days of constant exposure causes no damage. Plastic may tolerate for 30 years. Good: Little or no damage after 30 days of constant exposure for the regent Fair: Some effect after 7 days of constant exposure to the reagent. The effect may be crazing, cracking, loss of strength or discoloration. Not recommended: Immediate damage may occur. Depending on the plastic, the effect may be severe crazing, cracking, loss of strength or dis coloration, deformation, dissolution or permeation loss.
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Table 2 Property Comparison of Fluoroelastomers (FKM) with Other Rubbers1
: Excellent : Good : Fair : Marginal : Poor
"Cleanliness" is defined as the fact that fluoropolymers are not easily eluted by acids, alkalis, or solvents (chemical resistance), do not contain other materials such as plasticizers in the molding process, and do not contain products that would thermally decompose during the material molding process.
Ozone resistance Ozone is known to degrade plastic materials in two ways: A: Substances with double bonds (C=C) in their structures (such as natural rubber, chloroprene rubber, butadiene rubber, etc.) undergo decomposition in which ozone reacts with the double bonds to produce ketones, when they come into contact with ozone. B: When ozone exists in water, peroxy radicals are generated. Non-fluorine materials (eg polyethylene, polypropylene, etc.) deteriorate even if they do not have double bonds. Fluoropolymers does not have decomposition pathways such as A and B even if it comes into contact with ozone, so it can be used for a long time without deterioration.
1 https://www.daikinchemicals.com/library/pb_common/pdf/catalog/RC-1L.pdf document in Japanese. Last accessed on 14 July, 2023
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translated from the
Thermoplastic resin
Ozon Resistance
Soft vinyl chloride
PVC
Rigid vinyl chloride
PVC
Vinylidene chloride resin
PVdC
ABS
ABS
Polyethylene
PE
Nylon Acrylic resin Fluoropolymer resin Phenolic resin Melamine resin Furan resin Epoxy resin
N
PMMA
PTFE
PF
PVC
FF
EP
Unsaturated polyester resin
UP
Table 3 Comparison of ozone resistance properties of plastics
Repellency from water and oil / non-adhesion Since the fluoropolymers have a small polarizability, the intermolecular force is small. Because of its characteristics, fluoropolymers have repellency and non-adhere properties on the surface. In general, the repellency from various liquids is evaluated by the contact angle, and the larger the contact angle, the higher the repellency.
Contact angle
Figure 1 Contact angles with water 4/19
Adhesion energy refers to the amount of work required to pull a liquid contacting a solid away from the solid. The larger the contact angle, the smaller the adhesion energy. It means that a liquid in contact with a small adhesion energy solid easy to separate from the solid.2
Material name
Contact angle with water (o)
PTFE
114
FEP
115
Silicone resin
90~110
Paraffin
105~106
PE
88
PCTFE
83
PA
77
Phenolic resin
60
Copper(electropolishing)
9.6
Aluminium(electropolishing)
4.6
Table 4 Surface properties of various plastics and metals
Adhesion energy (dyn/cm) 43.1 42.0 47.8~72.7 52.7~53.8 75.2 97.7 109.0 144.2 145.0
This characteristic is sometimes called "mold releasability". It can also be expressed as antifouling because it does not easy to adhere.
Heat resistance
Fluoropolymers have high heat resistance as follows. They have higher heat resistance
compared to other general-use resins
Fluoropolymers
Heat resistance :
PTFE
PFA
FEP
ETFE
maximum operating temperature (C) 260
260
205
150
Table 5 The heat resistance of Fluoropolymer 3
PCTFA 120
PVdF 120
Other general-use
resins
PP
PVC
100
60
Electric insulation When the dielectric constant is low, the insulation in electrical components can be made thinner, leading to downsizing and weight reduction of the equipment. In applications where
2 Japan Fluoropolymers Industry Association(2020), , 14th edition. Page 34 Translated from Japanese. 3 DAIKIN INDUSTRIES, LTD. (2009) Page 4
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downsizing and weight reduction are necessary, it is an essential feature
Fluoropolymer
PTFE
FEP
PFA
Dielectric
constant
2.1
ETFE
2.32.8
Non-fluoropolymer
PVC
PEEK
TPI (Thermoplastic
Polyolefin
Dielectric constant
46
3.24.5
Polyimide)
2.83.2
2.34
Table 6 The dielectric constants of various resins
Fluorine rubber
FKM
FEPM
34
2.53.5
Non-fluorine rubber
Silicone rubber
EPDM
3.210
2.53.5
Low friction, self lubrication Friction coefficient of fluorine resin is lower than that of other resins. It is because polarizability (Mobility of electrons in an electric field) of C-F bonding is low (0.68) and the intermolecular force is weak. (Reference: polarizability of C-Cl bonding is 2.59) 4
Types of plastic
Plastic / Plastic
Plastic / Steel
Steel / Plastic
PTFE
0.04
0.04
0.10
PE
0.10
0.15
0.20
PS
0.50 *)
0.30
0.35
PMMA
0.80 *)
0.50 *)
0.45 *)
*) indicates occurrence of stick-slip motion. Measurement condition: Bowden-Laden type measurement equipment, load: 9.8-39.2N, sliding speed: 0.01cm/s Plastic/Steel indicates sample material/pin material PE: polyethylene PS: polystyrene PMMA: polymethylmethacrylate
Table 7 Comparison of friction coefficient among PTFE and other materials5
As an example of low friction, Table8 shows friction coefficient of PTFE.
Type
ASTM test Measurement
method
condition
Unit
PFA
PTEF
FEP
Coefficient of static friction
Against polished steel
-
0.05
0.02
0.05
Table 8 Comparison of static friction coefficient among PFA, PTFE and FEP6
4 Japan Fluoropolymers Industry Association(2020), , 14th edition. Page 9 Translated from Japanese. 5 Japan Fluoropolymers Industry Association(2020), , 14th edition. Page 24 Translated from Japanese. 6 DAIKIN INDUSTRIES, LTD. (2009) Page 53
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One of the characteristics related to friction is "self lubrication". The molecules of PTFE separate from molding of PTFE due to friction. The molecules in crystals of PTFE separate easily because intermolecular forces are weak. PTFE moves and attaches to the friction mating surface and generates friction between them. It lowers friction coefficient. 7 Gas barrier properties/Gas permeation properties Fluoropolymer film are less steam permeability.
Figure 2 The degree of steam permeability 8 steam permeability (g/m2/d)
7 Japan Fluoropolymers Industry Association(2020), , 14th edition. Page 24 Translated from Japanese. 8 DAIKIN INDUSTRIES, LTD. (2009) Daikin Fluoropolymers HandbookPage 109
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Fluorine elastomers are less atmospheric (nitrogen, oxygen) permeability.
Table 9 Comparison of gas permeability of elastomer9
Temperature
Material
degree
He
H2
O2
N2
CO2
CH
Celsius
Vinyl methyl silicone rubber
VMQ
25
400
400 200 1600
N/A
N/A
50
570
500 280 1550
Ethylene
25
16.5 5.90 79.2
propylene rubber
N/A
N/A
N/A
EPDM
50
46.6 13.7 183
Perfluoroelastomer FFKM
25
10.3 8.25
2.5
8.1 28.7
3.3
Styrene butadiene
25
rubber
SBR
50
17.5 30.5
13
4.8
94
N/A
42
74
34.5 14.5 195
Vinylidene fluoride
fluororubber
25
binary FKM
2.95
4.6
1.0
0.8
3.9
0.6
Vinylidene fluoride
fluororubber
25
Ternary FKM
Chloroprene
25
Rubber
CR
50
nitril-butadiene
25
rubber
Mid-high NBR
50
2.64 4.13
1.7
0.7
1.6
0.4
10.3
3.0 0.89 19.5
2.5
N/A
28.5 10.1 3.55 56.5
9.8
9.32 12.1 2.94 0.81 23.5 N/A
23.4 33.7 10.5 3.58 67.9
nitril-butadiene rubber
High NBR
25
5.2
5.42 0.73 0.18 5.67
N/A
50
14.2 17.0
3.5 1.08 22.4
butyl rubber
25
6.4
5.5
0.99 0.25 3.94
0.6
IIR
50
17.3 17.2 4.03 1.27 14.3
3.2
10,/,sec,atm
C2H2 C3H8
10000
N/A
or
more
91.2 N/A
246
N/A N/A
N/A N/A
N/A N/A
N/A N/A
N/A N/A
18.9 26.9 68.3 78.3 8.25 11.2 19.8 33.1 1.28
N/A 5.82
9 DAIKIN INDUSTRIES, LTD. (2009) Daikin Fluoropolymers HandbookPage 78
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Property of Gas Permeability
Property
N2
O2
Gas permeability
H2
coefficient
CO2
Gas Permeability
CH4
C2H4
Water-vapor permeability
Table 10
Water Absorption
Gas Permeability of FEP film10
Standard Test method
ASTM D1434
JIS Z0208 ASTM D570
Unit
/satm g/24h 24h
FEP film
12010-10 37010-10 1,08010-10 97010-10 6610-10 4410-10
1.6 <0.01
Fluoropolymers permeate small molecular gases, such as oxygen and nitrogen, conversely, large molecular gases do not permeate. Fluoropolymer properties are used in permeate membranes for measurement and analysis.
Gas
N2 O2 CO2 CH4 CH3 CH C2H4
FEP 1.210-8 3.710-8 9.710-8 0.6610-8 0.6610-8 0.1110-8 0.4810-8
Gas Permeability PTFE
1.110-8 3.210-8 8.910-8
Low Density Polyethylene 0.7410-8 2.210-8 9.610-8 2.210-8 5.210-8 7.210-8
Temperature: 25 degree Celsius(77F) Units: cm3 (ST P) cm/cm2atm
Table 11 Comparison of gas permeability of various materials11
10 DAIKIN INDUSTRIES, LTD. (2009) Daikin Fluoropolymers HandbookPage 78 11 DAIKIN INDUSTRIES, LTD. (2009) Daikin Fluoropolymers HandbookPage 80
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Low refractive index Amorphous fluoropolymer resin has high transmittance. This is utilized for optical components and optical fibres.
Figure 3 Comparison of transmittance 1
Wavelength (nm)
Weatherability
Fluoropolymer resin has high weatherability and can be used outdoors. It does not react to
sunlight such as ultraviolet rays. It is not susceptible to oxidizing effects of atmospheric
oxygen and other substances (see "chemical resistance"). It can be used in a wide
temperature range from low to high (see "heat resistance"). It has high water repellency
and does not absorb water, so it is not affected by humidity changes. It can be said that
fluoropolymer resin has high weather resistance because it has the above points.
Table 12 Fluoropolymer resin weatherability comparison 12
Fluoropolymer resin
General resin
PTFE PFA FEP ETFE PCTFE PVdF PP PVC
Weatherability
Excellent, Good Not very good Needs attention Not good
Regarding the graph below, it can be seen from the accelerated weatherability test with the Sunshine Weather Meter that the gloss retention rate decreases by no more than 10% even after 4000 hours of exposure. 13
12 DAIKIN INDUSTRIES, LTD. (2009) Page 4
13 https://www.kyoeishoji.co.jp/business/chemical/fusso_toryo.html translated from the document in Japanese. Last accessed on 21 July, 2023
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Gloss retention rate of paint film (%)
Fluoropolymer resin paint
Urethane paint
Acrylic silicone paint
Figure 4 AcceElexrpaotesudrewetimatehebryawbieliatythteersmt eotfepr(ahi)nt
Tensile strength (MPa)
Figure 5 Outdoor exposure test Comparison of tensile strength between ETFE and other materials 14
Durability It means that it can be used for a long time. Due to its high chemical resistance and high weatherability, PFAS can achieve high durability.
Resistance to creep / Compression set When a constant load is applied to a polymeric material, creep occurs, in which deformation progresses over time. Similarly, compression set occurs where the deformation does not recover when the force is removed. Both properties are known to be correlated. When rubber materials are used in elastic applications such as packings or diaphragms, it is required to
14 https://www.taiyokogyo.co.jp/feature/etfe_film.html translated from the document in Japanese. Last accessed on 21 July, 2023
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minimize the effects of both properties. Experimental examples of "30% creep time (Hour)" for major rubber materials are shown below. Creep is known to be worse at higher temperatures, Experiments have shown that FKM and silicon exhibit good properties.
NR SBR CR NBR IIR FKM Silicon
Table 13
50 degree Celsius 190 1250 4200 3900
70 degree Celsius 103 203 550 380
100 degree Celsius 3.8 14 45 41 2.7 1650
120 degree Celsius
7.4 12.2
305 1550
150 degree Celsius
180 190
Quoted from the journal of "the Society of Rubber Science and Technology, Japan", 1960(Vol33), P882-892,
"Stress relaxation and creep properties of various vulcanized rubbers".
Examples of compression set test results are shown below. In general, it is difficult to quantitatively compare materials because the measured values differ depending on the compounding and hardness of the rubber. Here, the compression set of the materials was compared by comparing the minimum value of each material in the database. FKM and silicon showed relatively good properties, showing the same tendency as creep.
NR SBR CR NBR IIR EPDM FKM Silicon
Compression set JISK6301 100 degree Celsius70h Min 20 Min 23 Min 9 Min 23 Min 11 Min 6
Table 14
The minimum value of each material was quoted from the data described in "Material Database / Organic Materials" (1989), The Nikkan Kogyo Shimbun".
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Uses of PFAS in Specialist Equipment
Summary PFAS are a very important group of substances for Specialist Equipment, which depends on these uses to maintain safety, as they are highly effective in chemical resistance, Repellency from water and oil, and electric insulation. PFAS polymer resins are two to ten times more expensive than other commodity plastics. There is no use other than where the equipment does not work without the use of PFAS. General electronics components are not covered in this document. However, since our equipment also uses common electronic circuit parts, we also use parts common to information equipment and general consumer EEE. For usage and non-substitutable information for such parts, please refer to Japan 4EE Opinion RCOM21, No.4543 and additional Opinion Information and Non-Substitutable Information to be submitted in September 2023. Semiconductors are also used in our products. Many PFASs are used in semiconductors and semiconductor manufacturing equipment. Comments on most of the items in this section have been submitted by industry associations that specialize in the respective items. We hope that dossier submitters consider the manufacturer's opinions.
PFAS applications 1Sealingmaterials(Fluoropolymer O-rings) /No alternative technologies 2coating(Fluororesin coating) /No alternative technologies 3filteringmembrenes(PTFE,FEP,ETFE,PFA,PCTFE) /No alternative technologies 4cutting parts(PTFE,PFA) /No alternative technologies
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1 Sealingmaterials(Fluoropolymer O-rings) parts description Packings, gaskets, and O-rings
Packings and gaskets exist to connect and seal by placing/placing them between parts. As an example, they are used in piping and pipe connections. Gases and liquids that pass through pipes leak out through the smallest gaps, and packing gaskets exist to prevent this. Packing in the narrow sense is used for power system parts, and those used for non-moving parts are called gaskets. Various innovations have been made in molding and realizing functions, such as spiral gaskets made of alternating layers of thin metal strips and PTFE sheets, and wrapped gaskets made of 0.4~0.8 mm hot PTFE, covering gaskets of metal or other materials. Those with a circular/round cross section are called O-rings. In addition to PTFE, fluoropolymer rubbers such as FKM and FFKM are also used for this application.
Fig. Packings, gaskets, O-rings 2coating(Fluororesin coating) A surface treatment in which the surface or inner surface of a base material is covered with a fluoropolymer is called a coating or lining. A relatively thick covering is often referred to as a lining, while a thin covering is often referred to as a coating. There are various methods such as molding, bonding a sheet to the base material, bonding powder, or covering with a liquid. Fluoropolymers used include PTFE, PFA, PCTFE, FEP, and ETFE. Coatings and linings are applied to parts in contact with fluids. The parts include the inner surface of the piping and parts in contact with the fluid.
parts description Flame arrestor(sintered metal) surface
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Sintered metal flame arrestor is used to prevent the internal gas sensor element from becoming an ignition source. Surrounding gas reaches the sensor element through fine gaps in the sintered metal, but when water is adsorbed on the sintered metal, the flow path of the gas narrows. Therefore, in order to prevent water adsorption and corrosion on sintered metal, a fluorine coating is applied for the purpose of adding repellency from water and chemical resistance. Inside the metal nipple
Fluorine coating is applied to the inside of the metal nipple which is part of the gas flow path for the purpose of adding non-adhesion in order to prevent the gas concentration from decreasing due to the adsorption of highly adsorptive gases.
Repellency from water The flame arrester (sintered metal) is given water repellency by applying a fluorine coating to prevent clogging due to water adsorption and corrosion.
Non-adhesion Fluorine coating is applied to parts of metal pipes that cannot be used due to insufficient
strength of fluororesin pipes, such as when it is necessary to cut threads to fix them. Chemical resistance
Fluorine coating is applied to the parts used in the gas flow path to provide chemical resistance. Fluorine coating can be used in acids, alkalis, organic solvents, ozone, and oils.
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3filteringmembrenes(PTFE,FEP,ETFE,PFA,PCTFE) Membrane filters are to remove and separate specific substances or objects from fluids. A wide variety of materials are used. If fluorine compounds are necessary, PTFE, FEP, ETPE and PFA are frequently used.
electrode film electrode film of Electrochemical gas sensor PTFE porous membrane Electrochemical gas sensor
1Electrochemical gas sensor is constituted by a working electrode formed on a PTFE porous membrane, a reference electrode, a counter electrode, electrolyte and a housing which is holding other components.
2Every electrode is connected to a potentiostat circuit and the working electrode is implied fixed potential to that of the reference electrode.
3The PTFE porous membrane is in contact with atmosphere which may contain intended gas to be detected.
4The gas to be detected goes through by diffusion in the membrane and reaches the interface of the working electrode and the electrolyte.
5The gas is electrochemically oxidized or reduced. 6The oxidized or reduced reaction involves transfer of electrons between chemical species
and the working electrode, hence current flows in the circuit. 7The current is measured to determine the concentration of the gas to be detected
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The following properties are required for the membrane used in this application. There is currently no other material that possesses these properties at a level that can be used in products.
Gas permeability The membrane must have gas permeability at atmospheric pressure. Water resistance The embrane must have sufficient water resistance not to leak electrolyte. Corrosion resistance The membrane must have corrosion resistance. Examples of corrosive gases are NOx, SOx, halogen and halogen halide. Chemical resistance Heat resistance The membrane must have sufficient heat resistance over 150 to coat electrocatalyst. Non-adsorptive The membrane must have sufficient non-adsoptive. If the gas to be detected is adsoabed on the membrane, the gas can't go through the membrane,or it takes time to go through the membrane.
Galvanic oxygen sensor
1. Oxygen gas in the sample reaches through the membrane into the sensor. 2. The oxygen gas taken in is reductively decomposed at the cathode. A current flows according to the oxygen amount taken in. 3. The current is read as a voltage through a resistor such as a thermistor.
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The following properties are required for the membrane used for this application. Gas permeability The measurement target gas is taken into electrodes. Without sufficient oxygen permeability, measurement is not possible even in terms of no pressures. Among fluorine compounds, FEP has better oxygen permeability than other polymeric membranes. Chemical resistance The membrane is also used in an environment where various gases (acid, alkali, organic solvents, etc.) contact at all times. Chemical resist products, which do not deteriorate even under these environment and do not elute components of filteringmembrenes in contact with any sample, are required. Water resistance
The membrane must have sufficient water resistance that water does not permeate electrodes. Weather resistance The membrane does not change in an exposure test for 10 years as a material.
4cutting parts(PTFE,PFA) (Example of finished products: diaphragm galvanic oxygen sensors, oxygen detectors)
parts description It is a part manufactured by cutting a block of resin. Because it is a small-lot production product, it is produced by cutting that does not require mold costs. Another reason for cutting is that there are places where sealing properties are required. Here, I will touch on the machined parts used in the casing of the galvanic oxygen sensor. There are various materials, but we will describe the case where PTFE and PFA, which have higher chemical resistance, are used.
Fig. Example of Fluoroplastic Cutting Parts 18/19
Structure and measurement principle of galvanic cell type oxygen sensor
Cutting parts
1. Oxygen gas in the sample reaches through the membrane into the sensor. 2. The oxygen gas taken in is reductively decomposed at the cathode. A current flows according to the oxygen amount taken in. 3. The current is read as a voltage through a resistor such as a thermistor.
Fluoropolymer casing are required when parts require chemical resistance. There is a need to measure oxygen concentration even in places where acids, alkalis, and organic solvents are always present. In this application, it is necessary to have chemical resistance such that it does not deteriorate even when it comes into contact with various gases (acids, alkalis, organic solvents), does not elute components even when it comes in contact with any sample. Also, as a material, it is necessary to have weather resistance properties such as not changing in a 10-year exposure test and not softening or deforming in the surrounding environment of -40 to 70 C. If you try to perform the same function with other materials, for example, phenolic resins and polyamide resins can be mentioned as resins that are resistant to acetone as a general organic solvent, but phenolic resins are resistant to strong alkalis. Polyamide-based resins cannot be used as a substitute because they do not have durability against strong acids.
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