Rubber Types / Materials Key

Metflex Products

Metflex currently produce components in a wide range of rubber types, and we are constantly developing new formulations to widen the scope of applications for our customers, if there are other polymers which are not listed below and with which you currently have a working requirement for please do not hesitate to contact us. The list below is merely a guide to the most commonly used by Metflex within its processes.
Data sheets are available for our fully developed rubber types; please contact our sales team for information.

Key…

ISO designation; Rubber type. (Typical trade names)

Brief description
Optimum temperature of use
Best resistance
Limitations
Typical applications.

NR / IR; Natural rubber / Polyisoprene. (Natsyn®, Cariflex®)
Natural rubber is considered the engineering polymer of choice. Why because it has very high tensile and tear strength.

-50 to +80ºC
Very good resistance to weathering and ozone, severe dynamic abrasion and vibration. High resilience and flex-fatigue resistance and hot tear.
Not widely resistant to most oils and chemicals. Combustible.
Used in tyres, drive couplings for example used in mass transit and boats, bridge bearings, civil engineering.


NBR / XNBR; Acrylonitrile Butadiene rubber. (Buna®, Nipol®, Europrene®)

The oil resistant material used in the gas and oil industry.

-40 to +110ºC
Dependant on level of acrylonitrile content; low gas permeability, good heat age and ozone resistance, resistance to aromatic hydrocarbons and oils. Can be modified with PVC for improved age, weather resistance and fire retardancy. Also can be carboxylated (XNBR) for greatly improved tensile / abrasion resistance and other physical characteristics with higher temperature resistance.

Not recommended for use with polar solvents (e.g. MEK). Weather and ozone resistance only moderate unless specially compounded.
Used in seals and gaskets, diaphragms, drive couplings, audio equipment, hoses in oil and gas industries, also some food contact applications.

HNBR; Hydrogenated nitrile rubber. (Therban®, Zetpol®)
Oil resistance and higher temperature performance.

-40 to +150ºC.
Greatly improved chemical and oil resistance to NBR, with higher temperature limit. Resistant to hot air and water, industrial lubricants, sour oil and gas, some corrosion inhibitors. Very high durability and abrasion resistance. Can be further modified with methacrylate for even higher physical and temperature applications.
The limitations are the same as NBR but the material has an extended temperature range.
Used in hoses, drive belts, seals, gaskets, diaphragms in the oil and gas industries; a good intermediate where fluorocarbon rubbers are too expensive.

CR; Polychloroprene rubber. (Neoprene®)
A good balance of age resistance and moderate chemical resistance.

-35 to +110ºC
Very good resistance to oxidising agents, some oils, ozone & weathering, and refrigerants. Self-extinguishing and good adhesion to metals.
Only moderate petroleum and water resistance unless modified with litharge cure compounds.
Used in belting, coated fabrics, cable jackets and domestic fridge door seals.

SBR; Styrene Butadiene rubber. (Ameripol®, Intol®)
The general workhorse material for the rubber industry.

-40 to +100ºC
Substitute for more expensive NR. Greater hysteresis loss gives better grip in passenger car tyres. Improved ageing over NR/IR.
Moderate weathering and low chemical / oil resistance. Combustible
Used in tyres, audio for example in speaker units for the hi-fi industry, drive coupling and general rubber applications.

EPR / EPDM; Ethlylene Propylene rubber copolymers and terpolymers. (Keltan®, Vistalon®)
The age resistant material.

-50 to +180ºC
Excellent general purpose rubber with very good resistance to weathering and ozone. Normally electrically resistant but can be compounded to be conductive. Excellent resistance to hot water and steam.
Not recommended in certain mineral and synthetic fluids, lubricants and fuels. Combustible and only moderate adhesion to metals.
Used in automotive door seals, cable insulations, hoses and weather proofing / water proofing. Can be compounded for potable water (WRC) goods, foodstuff contact and some biomedical applications.

IIR; Butyl rubber. (Polysar®, Exxon®)
The non-permeable rubber.

-50 to +100ºC
Very low air permeability, insulating. Resistant to ozone and weather, refrigerants and a range of organic and inorganic fluids. Can also be polymerised with chlorine and Bromine to improve chemical resistance and flexibility. High damping.
Limitations include low resilience and combustibility.
Used in seals and gaskets, linings and membranes, diaphragms and some pharmaceutical goods.

IR; Polysoprene (synthetic)
Synthetic natural rubber.

-50 to +80ºC
Advantages; high tensile strength and elongation. More uniform and lighter in colour than NR. Wide hardness range. Very good abrasion resistance to particle abrasion, particularly at lower end of hardness scale in 40-45 IRHD range. Excellent flexing properties. Easily processed. Good adhesion to metal. High resilience.
Disadvantages; moderate heat resistance. Prone to ozone cracking. Combustible. Tensile properties slightly inferior to NR.
Used within chemical and abrasion-resistant linings, hoses, seals and conveyor belting.

AU / EU; Polyurethane rubber. (Urepan®, Vibrathane®)
The abrasion resistant material.

-35 to +70ºC
Outstanding tensile and abrasion resistance properties, with very good resistance to ozone and high energy radiation. Often specified where high durability or abrasion resistance is required with use in hydraulic fluids.
Main limitations are in hot climates where hydrolysis and micro bacterial attack are likely.
Used in hydraulic seals and gaskets, diaphragms and hoses, skateboard wheels and specialised tyres.

ECO; Epichlorohydrin homopolymer, copolymers and terpolymers. (Hydrin®)
Oil resistance and high and low temperatures.

-50 to +130ºC
Resistant to a wide range of oils, water, acids and ozone, weathering and gases. Similar low gas permeability to nitriles but better low temperature flex-fatigue resistance.
Corrosive to metals, so not recommended in rubber to metal bonding. Not recommended in ketones, esters, alcohols and certain hydraulic fluids, oxidising agents and chlorine. Electrically non-insulating.
Used in seals and gaskets, diaphragms, belts and cable sleeves.

MQ and VMQ Silicone Rubber.
Extremely low and high temperature performance.

-50 to +200ºC
Silicone processes excellent long term performance with good resistance to heat ageing, and are useable at temperatures of 200ºc high strength is not exhibited at room temperatures, they do retain their properties at high temperatures to a greater level than other rubbers. Silicones do with prolonged exposure to steam at high pressure, and ageing in closed systems (oxygen essentially excluded) can result in degradation via a hydrolysis reaction, this can be accelerated if acidic peroxide remnants have not been driven off during post curing.

Advantages; high resistance to heat and cold, available in a liquid form. On exposure to flame, an insulating residue of silica is formed which is an insulator, thus cables insulated with silicone can function after short term exposure in a fire. Good physical properties at high temperatures and indeed very small change in dynamic characteristics over a wide range of temperatures.
Disadvantages; low tensile properties (except for high strength grades).
Used for seals, gaskets – for example heating ventilation and air conditioning (HVAC), hoses for food liquid applications.
There are in addition to MQ and VMQ four other variants as follows

1. Fluoro Methyl Silicone FMQ
2. Fluoro Vinyl Methyl Silicone FVMQ
3. Phenyl Methyl Silicone PMQ
4. Phenyl Vinyl Methyl Silicone PVMQ

The advantages of the above are a great increase in fluid resistance when compared with conventional silicone (VMQ) and also strength at high temperatures compared with other fluoroelastomers (FKM,FFKM)
Disadvantages of the four variants are very expensive and they give off vapours during vulcanisation and in the event of fire.
Applications include high temperature parts for aircraft, automotive, tubing, hoses, seals, o-rings and diaphragms.

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