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ตารางเปรียบเทียบคุณสมบัติของวัสดุ O-RINGS ชนิดต่าง ๆ

Properties	Materials
Properties	NBR	FPM	EPDM sulphur	EPDM peroxide	VMQ	HNBR	FFPM	FVMQ	CR
Compression set	1	1	3	1	2	1	3	2	2
Tear strength	2	2	3	2	4	1	2	3	2
Abrasion resistance	2	2-3	2	2	4	2	3	3	2
Ageing resistance	4	1	2	2	1	2	1	1	2
Ozone resistance	4	1	2	2	1	2	1	1	2
Resistance to oil and grease	2	1	5	5	3	2	1	2	3
Fuel resistance	4**	2**	5	5	4	3	1	2	3
Resistance to hot water [ºC]	80**	80**	130	150	100	100**	***	100	80
Resistance to steam [ºC]	–	–	130	175	120*	–	***	120*	–
Heat resistance standard materials [ºC]	100	200	130	150	200	150	260	175	100
Heat resistance special materials [ºC]	120	–	–	–	250	–	330	–	–
Low temperature resistance standard materials [ºC]	-30	-15	-45	-50	-55	-30	-15	-55	-40
Low temperature resistance special materials [ºC]	-50	-35	–	–	–	-40	-35	–	-50
1 = very good / 2 = good / 3 = average / 4 = low / 5 = weak * = shor term / = better result only with special compound / * = depends on compound

1. NBR (Buna-N)
NBR – acrylonitrile-butadiene rubber / trade name e.g. Perbunan® – (Bayer)
NBR is the most common standard material for O-rings because of its good mechanical properties and resistance to mineral oil-based lubricants and greases. These properties are usually determined by the acrylonitrile content (ACN between 18% and 50%). A low ACN content ensures good flexibility at low temperatures, but offers limited resistance to oils and fuels; as the ACN content increases, the low temperature flexibility reduces and the resistance to oils and fuels improves. The general standard NBR material for O-rings offers an average ACN content to suit a wide range of applications with balanced properties. It has good mechanical-technological values such as high abrasion resistance, as well as low gas permeability and good resistance to mineral oil-based lubricants and greases, hydraulic oils H, H-L, H-LP, non-inflammable pressure liquids HFA, HFB, HFC, aliphatic hydrocarbons, silicone oil and greases, and water to approx. 80ºC.
NBR is generally not resistant to aromatic and chlorinated hydrocarbons, fuels with a high aromatic content, polar solvents, glycol-based brake fluids and non-inflammable hydraulic fluids HFD. It also has a low resistance to ozone, weathering and ageing, but in most applications this has no negative effect.

2. FEP
FEP – encapsulated O-rings / FEP – fluorinated ethylene-propylene
FEP is a thermoplastic material with similar properties to PTFE. Seamless FEP-encapsulated O-rings have an elastic core in FPM or VMQ. They are used at very high thermal and chemical loads. The extremely high chemical resistance of the cover protects the elastic core material against the chosen medium. Another advantage of the cover is its very low coefficient of friction.
This results in a combination of very high chemical and thermal load-bearing ability and the elastic properties of standard commercial elastomers. The core material is chosen to suit the temperature range and medium. Because of its limited flexibility, great care is required during installation. Warming the material in water or oil to between approx. 80ºC and 100ºC increases flexibility and supports the installation. Depending on the core material, the temperature application range is from -55ºC to +200ºC.

3. PTFE
PTFE O-rings / PTFE-encapsulated O-rings / PTFE – polytetrafluoroethylene
PTFE is a fluorinated plastic material. It is noted for its almost universal resistance to chemicals, wide temperature range (-100ºC to + 250ºC), extremely low coefficient of friction, physiological suitability and almost unlimited resistance to ozone, weathering and ageing.
Solid PTFE O-rings are far less elastic than elastomer O-rings, which means they are difficult to install (the installation space usually has to be split), and they tend to “flow”, especially at high temperatures. This is why slotted PTFE O-rings and PTFE-encapsulated elastomer O-rings are used. The position of the gap (pure PTFE O-rings) or of the joint or overlap (PTFE-encapsulated O-rings) is determined here, depending on the particular application.

4. Chemtex-2
CHEMTEX® II PFP HIGH PERFORMANCE PERFLUOROPOLYETHER ELASTOMER (PFP)
CHEMTEX® II PFP is the next generation of perfluoroelastomer technologies from Utex Industries, Inc. CHEMTEX II PFP is a unique elastomer system composed of a perfluoropolyether and a silicone to produce a perfluoroelastomer with exceptional chemical resistance similar to CHEMTEX I PFR but also with exceptional low temperature properties at an economical cost. CHEMTEX II PFP is alloyed for temperature capabilities from -58°F to +392°F, -50°C to +200°C with good dynamic properties.
CHEMTEX II PFP is currently available as a nominal 75 durometer compound 7907, UPS 0393.
CHEMTEX II PFP is available in standard AN series o-rings, style 0566–51 and in custom molded articles and specialty shapes as style 0020.

5. Chemtex-1
CHEMTEX® I HIGH PERFORMANCE PERFLUOROELASTOMER (FFKM)
CHEMTEX® I is the latest in elastomer technologies from Utex Industries, Inc. The first generation of CHEMTEX elastomer is a proprietary alloy of perfluorinated elastomer polymers with a filler system to provide elastomer parts with exceptional chemical resistance, similar to PTFE, temperature capabilities from 20°F to 600°F, -7°C to 315°C with very low compression set.
CHEMTEX I is currently available in general purpose black compounds, a nominal 70, 80 and 90 durometer compound 7807, 7808 and 7809 as well as other specialty compounds suited for 600°F 70 and 90 duro, non-black 70 and 90 durometer and Rapid Gas Decompression (RGD) 70 and 90 duro.
CHEMTEX I is available in standard AN series o-rings and in custom molded articles and specialty shapes.

6. CR (Neoprene)
CR – Chloroprene rubber / trade name e.g. Neoprene® (Du point-Dow Elastomers)
Chloroprenes have excellent resistance to ozone, ageing and weathering and also good mechanical properties. They have average resistance to mineral oils, and are suitable for use with many refrigerants.

7. FFPM (Perlast)
Perlast® – Perfluoroelastomer (FFPM)
1. Almost Chemical Resistance
2. Temperature range -45ºC to +330ºC
3. Extremely suitable for resolving the most difficult sealing problems
4. Areas of application:

Chemicals
Colours and Paint Production
Pharmaceutical & Food
Water Treatment
Crude Oil Extraction
High Vacuum
Power Engineering
Turbine and Pump

8. FFPM (Kalrez)
FFPM – perfluoro rubber / tradename Kalrez® (Du Point-Dow Elastomers)
The chemical and heat resistance of perfluoro elastomers are similar t o those of PTFE. They combine the positive properties of PTFE with the elastic behaviour of FPM. Because this material group is considerably more expensive, perfluoro elastomers are only used if other materials can not meet the specifications and if safety requirements justify the higher expenditure.
Typical applications for perfluoro elastomers include the chemical, oil and semi-conductor industries, high-vacuum technology, and the aerospace industry.

9. HTCR (AFLAS)
Utex HTCR™ is an elastomeric system based on Aflas® fluororubber, a copolymer of tetrafluoroethylene and propylene. HTCR™ is thermally stable for continuous use in temperatures up to 450°F and, depending on the specific application, has serviceability up to 550°F. HTCR™ has excellent resistance to a wide variety of chemicals in many different environments. It also has a good resistance to extrusion at high temperatures and resists gas decompression blistering.

10. VMQ (Silicone)
VMQ – silicone rubber / trade name e.g. Silopren® (Bayer)
Silicone rubbers are noted for its wide thermal range and excellent resistance to ozone, weathering and ageing. Compared with other elastomers, silicone’s mechanical properties are on the low side. Generally, silicone materials are physiologically harmless; they are also used by the food and medical industries.
The standard silicone material can be applied at temperatures from -55ºC to +200ºC and is resistant to water (up to 100ºC), alphatic engine and transmission oils, animal and plant oils and fats.
Silicone is generally not resistant to fuels, aromatic mineral oils, steam (short term up to 120ºC possible), silicone oils and greases, acids and alkalis.

11. EPDM (EPR)
EPDM – ethylene propylene diene rubber /
trade name e.g. Nordel®,(Du point-Dow Elastomers)
EPDM Materials generally have a high resistance to hot water, steam, ageing and chemicals, and are suitable for a wide range of temperature applications. They are devided into sulphurand peroxide-cured types. Peroxide-cured compounds are suitable for higher temperature ranges and have a much lower compression set.
EPDM has a good resistance to hot water and steam, detergents, caustic potash solutions, sodium hydroxide solutions, silicone oil and greases, many polar solvents, many diluted acids and chemicals. Special qualities are recommended for glycol-based brake fluids. EPDM materials are totally unsuitable for use with all mineral oil products (lubricants, fuels). They can be used between -45ºC and +130ºC (peroxide-cured -50ºC to +150ºC)

12. FPM ( Viton)
FPM – fluoro rubber / trade name e.g Viton® (Du Point-Dow Elastomers)
FPM materials are noted for their very high resistance to temperatures and chemicals. Other key benefits are its excellent resistance to ageing and ozone, very low gas permeability (excellent for vacuum application) and the fact that it is self-extinguishing.
The standard FPM material for O-rings has excellent resistance to mineral oils and greases, aliphatic, aromatic and chlorinated hydrocarbons, fuels, non-inflammable hydraulic pressure fluids HFD and many organic solvents and chemicals.
In addition to the standard FPM materials, a number of special compounds with different compositions of polymer chains and varying fluoro-contents (65% to 71%) are developed for special applications.
FPM is generally not resistant to hot water, steam, polar solvents, glycol-based brake fluids and low-molecular organic acids.