Engineering Rubber Guide: Types, Properties and Selection

Specifying the wrong rubber for an application is one of the most common and expensive mistakes in mechanical design. Getting the material right matters as much as getting the dimensions right.

The eight engineering-grade rubbers most commonly specified in mechanical and fastening applications are NBR, TPE, TPR, silicone, fluorosilicone, Viton (FKM), EPDM and neoprene (CR). Each offers a distinct balance of temperature range, chemical resistance, mechanical strength and cost. For example, silicone offers the widest temperature range (-60 °C to +230 °C), Viton offers the broadest chemical resistance, neoprene is the only grade with inherent flame resistance and TPE and TPR are the only fully recyclable options.

Many other factors distinguish them and may make them more suitable for your application. This guide explores each of the different grades in detail, explaining the unique properties of each, as well as offering guidance on making the right choice for your assembly.

Contents:

• What is Rubber?

• How Many Types of Rubber are There?

• Engineering Rubber: Properties and Applications

• Choosing the Right Type of Rubber for Your Application

• Chemical Compatibility of Engineering Rubbers

• Which Type of Rubber is Right for My Application?

• Key Takeaways

• FAQs

What is Rubber?

Rubber is an elastic material valued for its ability to return to its original shape after deformation. It’s a term used to describe a variety of different polymers that can be found in an enormous number of different products. Everything from gloves to shoes, fasteners to O-rings and more can be made from different types of rubber.

The key properties of rubber are its elasticity, ability to insulate against electricity and its durability to factors like abrasion and wear. Broadly speaking, there are two different categories of rubber: natural rubber and synthetic rubber. 

• Natural Rubber: Derived from natural sources. Traditionally, this used to involve tapping the trunks of rubber trees to extract their sap, which could then be coagulated to form rubber.  In order to be used in hard-wearing applications, natural rubber must typically undergo vulcanisation, a process of cross-linking polymer chains using sulphur or peroxides to dramatically increase strength, elasticity and durability. This also helps to boost its longevity, as without this, natural rubber can rot in a matter of weeks.

• Synthetic Rubber: Synthesised from petrochemicals, much like many forms of plastic. It is produced through chemical polymerisation and is superior in its versatility, thermal stability, durability and elasticity. In many cases, unlike natural rubber, synthetic rubbers don’t require vulcanisation to make them durable enough for hard-wearing applications.

 

How Many Types of Rubber Are There?

Industry classifications recognise over 40 types of rubber, though many of these are not widely used in an engineering context. For utility and brevity, this guide will focus on the varieties of rubber that are the most commonly found in engineering solutions and Accu’s range of products. These are:

• Nitrile Butadiene Rubber (NBR), 

• Thermoplastic Elastomer (TPE), 

• Thermoplastic Rubber (TPR),

• Silicone, 

• Fluorosilicone,

• Viton,

• EPDM, and 

• Neoprene.

A quick engineering note: property values shown are typical ranges for common grades. Actual performance depends on specific formulation, reinforcement and processing. Always consult supplier datasheets for grade-specific data.

 

Engineering Rubber: Properties and Applications

Nitrile Butadiene Rubber (NBR)

• Hardness range: 40–90 Shore A.

• Tensile strength: 10–30 MPa.

• Elongation at break: 100–600%.

• Continuous service temperature: -40 °C to +120 °C.

• Compression set: Low to Medium.

• Chemical resistance: Excellent resistance to mineral oils, fuels, hydrocarbons and greases; moderate resistance to dilute acids; poor resistance to strong oxidising acids, ketones and chlorinated solvents.

• UV/Ozone resistance: Poor.

• Flame resistance: Poor.

Anyone who’s ever worn nitrile gloves or changed a fuel filter in a car has handled NBR. Nitrile Butadiene Rubber, commonly referred to as nitrile rubber, NBR, or by the trade designation Buna-N, is one of the most widely specified synthetic elastomers in engineering. First developed in the 1930s as a solution to fuel-handling applications, nearly a century later it’s still in wide use. NBR's reputation is built on one thing: oil and fuel resistance at a sensible price. It resists mineral oils, fuels, hydrocarbons, greases and dilute acids reliably enough that it has become the default specification for O-rings, seals, gaskets and hydraulic components across the automotive and industrial sectors. 

NBR rubber offers poor resistance to strong oxidising acids, ketones and chlorinated solvents and should not be specified where contact with these substances is likely.

NBR's resistance to oils and its low-temperature flexibility are both governed by its acrylonitrile (ACN) content:

• High ACN (above 45%): maximum oil and fuel resistance, reduced low-temperature flexibility

• Medium ACN (33–45%): the most commonly specified grade, offering a balanced combination of oil resistance and flexibility

• Low ACN (below 33%): enhanced flexibility at low temperatures, reduced oil resistance

NBR has notable limitations for outdoor applications. It offers poor resistance to UV radiation and ozone, both of which cause surface cracking and degradation over time. It’s a mistake that’s seen over and over again: NBR’s behaviour indoors doesn’t match up to how it performs outdoors. If you are looking for a rubber suitable to use outdoors, EPDM or neoprene are more appropriate alternatives.

At Accu, NBR rubber is used in O-Rings.

 

Thermoplastic Elastomer (TPE)

• Hardness range: 10–95 Shore A (highly grade-dependent).

• Tensile strength: 5–35 MPa.

• Elongation at break: 100–800%.

• Continuous service temperature: -50 °C to +125 °C.

• Compression set: Medium (higher than thermoset rubbers).

• Chemical resistance: Good resistance to water, dilute acids and alkalis; moderate resistance to oils; poor resistance to aromatic hydrocarbons and strong solvents. Resistance varies significantly by subtype.

• UV/Ozone resistance: Good to Excellent (SEBS-based grades particularly strong).

• Flame resistance: Poor to Moderate (flame-retardant grades available).

Thermoplastic Elastomer, or TPE, is a form of rubber that combines the formability and recyclability of plastic with the flexibility and function of rubber. You’ll have most likely seen it used for soft-touch grips on tools and implements like toothbrushes, thanks to the fact that it can be overmoulded directly onto rigid substrates and can be easily pigmented. It feels like rubber, but behaves like plastic, which is its main draw for engineering purposes.

Unlike thermoset rubbers, which are permanently cross-linked during vulcanisation and cannot be reprocessed (similar to the difference between thermoset and thermosetting plastics), TPE can be melted and reformed, making it fully recyclable and significantly faster to manufacture, with no curing stage required.

TPE rubber is not a single material but a family of sub-types, including styrenic block copolymers (SBS, SEBS), thermoplastic polyurethanes (TPU) and thermoplastic polyolefins (TPO), each with varying mechanical and chemical properties. Chemical resistance is therefore grade-dependent. Most TPEs offer good resistance to water, dilute acids and alkalis, but performance in contact with the aromatic hydrocarbons in fuels or strong solvents varies significantly and should be verified against specific grade datasheets.  

Some grades of TPE are biocompatible and, where compliance with ISO 10993 is confirmed, are suitable for use in medical applications such as syringe seals, tubing and catheters. 

Accu uses TPE in our range of Moss Pull Tab Plugs.

Thermoplastic Rubber (TPR)

• Hardness range: 50–100 Shore A (typically harder than TPE).

• Tensile strength: 10–30 MPa.

• Elongation at break: 100–500%.

• Continuous service temperature: -20 °C to +120 °C.

• Compression set: Low to Medium.

• Chemical resistance: Good resistance to water, dilute acids and alkalis; moderate resistance to oils and greases; poor resistance to aromatic hydrocarbons and strong solvents.

• UV/Ozone resistance: Good.

• Flame resistance: Poor to Moderate.

You won’t find TPR on your toothbrush, but you’ll find it in the soles of your trainers. Thermoplastic Rubber (TPR) is closely related to TPE and is often considered a harder, more rigid sub-category within the broader thermoplastic elastomer family, though the terms are sometimes used interchangeably in industry. 

Like TPE, it can be melted, reformed and recycled, requiring no vulcanisation stage during manufacture. This gives it the same processing efficiency advantages over thermoset rubbers as TPE.

The key distinction between TPR and TPE lies in mechanical performance. TPR rubber is typically harder and more resistant to abrasion, tearing and flexing, making it better suited to applications where durability under sustained mechanical stress is a priority. Where TPE prioritises softness and low-temperature flexibility, TPR is built to take a beating.

Some trade-offs come with the greater degree of durability. TPR isn’t as resilient in colder temperatures as TPE rubber, which causes TPR to harden and lose flexibility. TPR produces denser smoke on combustion than TPE, which may be a consideration in enclosed environments.

At Accu, TPR is used in our Rubber Washers.

 

Silicone

• Hardness range: 10–80 Shore A.

• Tensile strength: 4–12 MPa.

• Elongation at break: 100–800%.

• Continuous service temperature: -60 °C to +230 °C (up to +260 °C for heat-stabilised grades).

• Compression set: Low to Medium.

• Chemical resistance: Good resistance to water, dilute acids and oxidising agents; poor resistance to concentrated acids, alkalis, aromatic hydrocarbons and fuels.

• UV/Ozone resistance: Excellent.

• Flame resistance: Poor (standard grades); Good to Excellent (flame-retardant grades).

• Dielectric strength: 15–25 kV/mm.

Silicone is the temperature specialist of the engineering rubber world. Nothing else on this list matches its working range, and nothing else stays flexible from a -60 °C cold room to a +230 °C oven without breaking stride. It earned this reputation during the Second World War, when demand for a material that could insulate aircraft electrical systems at high altitude, where temperatures plunge and rubbers become brittle, pushed silicone out of the laboratory and into serial production. Eighty years on, it's still doing essentially the same job, just in a wider set of industries.

Silicone rubber is available in a range of specialist grades, each formulated to enhance specific properties:

• Tear and abrasion-resistant grades: for improved mechanical durability.

• Flame-retardant grades: for applications requiring compliance with fire safety standards.

• Room-temperature vulcanising (RTV) grades: for mould making and in-situ sealing.

• Heat-stabilised grades: for continuous exposure up to +260 °C

• Food-contact grades: compliant with FDA 21 CFR and EU Regulation 10/2011 for direct food and beverage contact.

Silicone also offers a dielectric strength of typically 15-25 kV/mm, making it well-suited to electrical insulation applications, including cable sheaths, connector seals and high-voltage components. On the medical side, silicone has been the dominant implant and tubing material for decades, thanks to its innate biocompatibility and the fact that it’s both sterilisable and stable over long exposures in the body.

Silicone has limitations worth noting. Its tensile strength is lower than most thermoset rubbers, typically 4-12 megapascal (MPa). Standard grades offer poor abrasion resistance unless specifically formulated otherwise. Its naturally high coefficient of friction makes it unsuitable for bearing surfaces, rotary components or any assembly where elements must slide freely against one another, though this can be mitigated in some applications with PTFE coatings or surface treatments. Chemically, silicone performs poorly in sustained contact with concentrated acids, alkalis and aromatic hydrocarbons. If your project requires a material that performs in contact with these substances, Viton or fluorosilicone are more sensible choices.

Accu makes use of Silicone rubber in our Silicone Tapes, Socket Head Cover Caps, Flangeless Masking Plugs, Metric Socket Cap Head Sealing Screws and our Metric Serrated Flanged Hexagon Sealing Nuts.

Fluorosilicone

• Hardness range: 40–80 Shore A.

• Tensile strength: 7–10 MPa.

• Elongation at break: 100–400%.

• Continuous service temperature: -65 °C to +175 °C.

• Compression set: Low to Medium (better than standard silicone).

• Chemical resistance: Excellent resistance to aliphatic and aromatic hydrocarbons, mineral oils, fuels and benzines; poor resistance to ketones, certain hydraulic fluids and strong alkalis.

• UV/Ozone resistance: Excellent.

• Flame resistance: Poor to Moderate.

Fluorosilicone rubber, sometimes known by the abbreviations FVMQ or FSR, is a synthetic elastomer similar to silicone rubber but with a few notable differences. Its name comes from the fact that, unlike regular silicone rubber, fluorosilicone rubber contains trifluoropropyl groups.

This small structural change has an outsized effect on performance. Fluorosilicone has a lower operating temperature range than standard silicone, better tear resistance and a lower compression set, but the key difference comes from its chemical resistance to fuels, mineral oils, aliphatic and aromatic hydrocarbons, all of which standard silicone lacks entirely.

Fluorosilicone does share some of standard silicone's limitations. It performs poorly in contact with ketones, certain hydraulic fluids and strong alkalis. Fluorosilicone should definitely not be specified for applications involving these substances. Cost is also a significant consideration and the first thing to know about specifying fluorosilicone. Components made from it are typically several times the cost of their silicone equivalents, reflecting the complexity of the manufacturing process and the specialist market it serves. It's not a material you reach for casually, but where its specific property profile is needed there are very few substitutes.

Its primary application areas are in the aerospace and automotive industries, where it is used for fuel-contacting seals, O-rings and gaskets in environments with sustained or intermittent exposure to petrochemicals. It is one of a small number of elastomers that can reliably maintain a seal in direct contact with aviation and automotive fuels across a wide temperature range.

Accu supplies fluorosilicone in our ranges of Metric Hexagon Sealing Nuts, Metric Hexagon Sealing Bolts, Metric Socket Countersunk Head Sealing Screws and Metric Serrated Flanged Hexagon Sealing Nuts, among many others.

 

Viton

• Hardness range: 60–90 Shore A.

• Tensile strength: 7–20 MPa.

• Elongation at break: 100–300%.

• Continuous service temperature: -20 °C to +200 °C (specialist grades to +300 °C).

• Compression set: Low (particularly strong retention at elevated temperatures).

• Chemical resistance: Excellent resistance to mineral oils, fuels, aromatic and aliphatic hydrocarbons and many acids; poor resistance to ketones, amines, low-molecular-weight esters and ethers and certain brake and hydraulic fluids.

• UV/Ozone resistance: Excellent.

• Flame resistance: Poor (produces hydrogen fluoride on combustion, a significant hazard in fire-risk environments).

Viton earns its price. It's the rubber engineers specify when failure is expensive, the environment is hostile, and compromise isn't an option. Though with that said, nowhere else on this list is that trade quite so directly reflected in the cost per unit. The material itself goes by several names, which is worth untangling before going further: FKM is the designation under the American ASTM D1418 standard, FPM is the identical material under the European ISO 1629 and DIN nomenclature and Viton is Chemours' trade name (originally DuPont's) for their FKM range. There is no material difference between FKM and FPM, they are the same fluoroelastomer described by two different standards bodies and "Viton" has become industry shorthand for the class in the same way "Neoprene" stands in for polychloroprene. If your supplier quotes FPM and your drawing specifies FKM, you are looking at the same rubber.

FKM's chemical resistance profile is one of the broadest of any engineering rubber. It offers excellent resistance to mineral oils, fuels, aromatic and aliphatic hydrocarbons and many acids. It performs poorly, however, in contact with ketones, amines, low-molecular-weight esters and ethers and certain brake and hydraulic fluids. 

At low temperatures, standard FKM grades begin to harden and lose flexibility below -20 °C, which is a significant limitation in cold-environment applications. Low-temperature FKM grades like Viton GLT and GFLT are available that extend performance to approximately -40 °C, though these are specialist formulations and should be confirmed with the supplier.

An important safety consideration: FKM produces hydrogen fluoride as a decomposition product when burned. This is a highly toxic gas and a serious hazard in any application where fire risk is a design consideration. You’ll see this information mentioned again later in the comparison table, with good reason. It’s a serious hazard that needs to be considered before Viton is specified for any application.

Viton is used extensively in the aerospace and automotive industries for gaskets and seals in fuel lines and high-temperature hydraulic systems, as well as in oil and gas applications and food and pharmaceutical processing, where its resistance to aggressive chemicals and compliance with sanitary requirements make it a reliable long-term specification.

Accu uses Viton in its ranges of Metric Serrated Flanged Hexagon Sealing Nuts, Metric Socket Cap Head Sealing Screws and Metric Slotted Pan Head Sealing Screws, among others.

EPDM

• Hardness range: 40–90 Shore A.

• Tensile strength: 7–20 MPa.

• Elongation at break: 100–600%.

• Continuous service temperature: -50 °C to +150 °C (some grades to +180 °C).

• Compression set: Low to Medium.

• Chemical resistance: Excellent resistance to water, steam, alkalis, dilute acids, ozone and UV; poor resistance to petroleum-based oils, fuels and aromatic hydrocarbons.

• UV/Ozone resistance: Excellent.

• Flame resistance: Poor (flame-retardant grades available).

If you've ever looked at a flat commercial roof and seen a smooth, black rubber membrane stretched across it, you've been looking at EPDM. Ethylene propylene diene monomer is the outdoor rubber. It lives on roofs, in window seals, under car bonnets, around pond liners and in any application where a material needs to face the weather for decades without complaint. EPDM does all of it unglamorously, reliably and for a price that makes most alternatives look extravagant.

EPDM rubber is a synthetic rubber terpolymer synthesised from ethylene, propylene and a diene monomer, typically ethylidene norbornene (ENB). EPDM has exceptional resistance to UV, ozone and weathering. These characteristics make it an ideal choice for outdoor applications due to the fact that it has a high degree of waterproofing and alkali resistance. EPDM can also be found in seals, gaskets and weather stripping in a variety of industries and applications. It’s cheap, it’s reliable and above all, it’s dependable.

On top of that, EPDM has a relatively low embodied energy (the amount of energy required to take it from raw material to finished product) compared to many other synthetic rubbers. This doesn’t make it an ecologically sound choice, though, as recycling it, particularly in membrane form, is costly and challenging.

EPDM isn’t without its drawbacks. It doesn’t bond readily to metal without significant surface preparation and treatment, which can cause issues in assemblies requiring tight bonds. It can also be prone to shrinkage, especially when used in a membrane form, so be sure to check it regularly for signs of this if you use it.  

EPDM also doesn’t boast the same degree of chemical and oil resistance as other forms of rubber. Exposure to fuels, aromatic hydrocarbons and petroleum-based oils can degrade or damage it, making NBR or FKM more appropriate alternatives if you’re working in oil or fuel-processing environments.

Accu utilises EPDM in its range of Sealing Washers, Pozi Raised Countersunk Sealing Wood Screws, P Clips and Hexagon Sealing Self Tapping Screws.

Neoprene

• Hardness range: 30–90 Shore A.

• Tensile strength: 10–25 MPa.

• Elongation at break: 200–500%.

• Continuous service temperature: -40 °C to +120 °C (specialist grades to +150 °C).

• Compression set: Low to Medium.

• Chemical resistance: Moderate resistance to oils, greases, dilute acids and alkalis. Good resistance to ozone, UV and weathering but poor resistance to strong oxidising acids, aromatic hydrocarbons and ketones.

• UV/Ozone resistance: Good to Excellent.

• Flame resistance: Good. Neoprene is inherently flame-resistant due to its chlorine content and will self-extinguish when the ignition source is removed.

Neoprene was the first commercially successful synthetic rubber, launched by DuPont in 1931, partly in response to the strategic vulnerability of natural rubber supply in the years leading up to the Second World War. It was, in effect, the first material to prove that synthetic rubber could be made to perform as well as, or even outperform, natural rubber. Nearly a century on, it's still one of the most widely specified engineering rubbers in the world, though it rarely gets the attention of its more specialist cousins.

Neoprene, the trade name for polychloroprene or CR, isn’t a standout in any area. It doesn't match silicone on temperature range, Viton on chemical resistance or EPDM on weathering. What it does, reliably, is most things competently at once. Moderate resistance to oils, greases, dilute acids and alkalis. Good resistance to ozone, UV and weathering. A broad working temperature range of -40 °C to +120 °C. Elongation at break of 200–500% with full elastic recovery. Usable electrical insulation for low-voltage applications. None of these is a headline property, but the combination is unusual and it's why neoprene turns up in so many places where a single-specialist rubber would be overkill.

The only one of neoprene's properties that can, by itself, be called significant and distinctive is its inherent flame resistance. The chlorine content in its polymer structure causes it to self-extinguish when an ignition source is removed, something most other engineering rubbers can’t do without the addition of flame-retardant additives. This makes CR rubber a commonly specified material in electrical, construction and marine applications where fire safety is a design requirement.

Like all grades of rubber, there are drawbacks to neoprene. Below -40 °C, it can become brittle, it’s difficult to recycle and isn’t environmentally friendly or sustainable to produce. Neoprene has moderate electrical insulation properties, suitable for low-voltage applications, but it is not an appropriate specification for high-voltage insulation. Silicone or EPDM are much better for that. 

Accu makes use of neoprene rubber for Anti-Vibration Grommet Mounts.

Choosing the Right Type of Rubber for Your Application

The table below provides you with a relative overview of the above grades of engineering rubber. Rather than presenting only absolute material properties, each characteristic is scored on a numeric scale from 1 to 10, where 1 represents the lowest relative performance and 10 the highest within this specific group of rubber types.

The scores are intended to highlight how the grades compare to one another, not how engineering grade rubbers compare to other materials, nor to define absolute limits or guaranteed performance.

This scoring system has been used to make trade-offs and design considerations easier to identify at a glance. The values are based on typical, widely recognised behaviour of each grade in engineering use.

 

Note - Viton's flame resistance is scored 2 because, despite being self-extinguishing, it produces hydrogen fluoride on combustion. This presents a significant safety hazard, so the score is given for more than just poor fire performance. On the other hand, neoprene's flame resistance scores 8 because it is inherently self-extinguishing, which is its genuine standout property.

Chemical Compatibility of Engineering Rubbers

Chemical compatibility is, for many engineers, the most important step of the material specification process. It doesn’t matter what the compression set or operation range of a material is if it will quickly decay on exposure to a fuel or oil it’s meant to handle. Selecting the wrong rubber grade for a chemically aggressive environment is one of the most common causes of premature seal and gasket failure. 

Because of this, we’ve separated chemical compatibility out into a separate table to help inform your material selection. The table below provides a quick-reference compatibility guide for the eight engineering rubber grades covered in this article across fourteen commonly encountered chemical substances and environments. 

Ratings are given as C for Compatible, L for Limited or A for Avoid. A Compatible rating indicates generally reliable performance for standard immersion or contact. Limited indicates that performance is grade or concentration-dependent and should be verified against supplier datasheets before specifying. Avoid indicates that the substance is known to cause significant degradation, swelling or loss of mechanical properties. 

Notes:

• Viton / concentrated acids rated Limited rather than Avoid: Viton resists many inorganic acids, including sulphuric and hydrochloric at moderate concentrations. This is one of its genuine differentiators. However, it is attacked by certain oxidising acids at high concentrations, hence Limited rather than Compatible.
• Silicone / ketones rated Limited rather than Avoid: Silicone has moderate resistance to some ketones compared to most other rubbers, which have essentially no resistance. It's not a safe specification but it's not a blanket avoid either, hence Limited.
• NBR / aromatic hydrocarbons rated Limited rather than Compatible: Medium and high ACN grades of NBR have moderate resistance to aromatic hydrocarbons. Not enough to call Compatible, but meaningfully better than EPDM or silicone.
• EPDM / ketones rated Limited: EPDM has moderate resistance to some ketones, which is a genuine but often overlooked property. It's one of the few areas where EPDM outperforms NBR and neoprene.

Which Type of Rubber is Right for My Application?

Selecting the right engineering rubber depends on the dominant demands of your application, whether that’s chemical exposure, temperature range, mechanical durability, outdoor weathering or regulatory compliance. 

• For oil, fuel and hydrocarbon resistance: Viton is the default specification where sustained or intermittent contact with petroleum-based fuels, mineral oils and aromatic hydrocarbons is expected, particularly at elevated temperatures. Where fuel resistance is required alongside low-temperature flexibility, fluorosilicone (FVMQ) is the more appropriate choice. NBR is a cost-effective alternative for applications involving mineral oils and fuels at moderate temperatures, where Viton's high-temperature performance is not required.

• For high-temperature applications: Silicone rubber is the standard specification for continuous service above 150 °C, offering reliable performance from -60 °C to +230 °C, a range no other common engineering rubber matches. Where high-temperature performance must be combined with resistance to fuels or aggressive chemicals, Viton is typically preferred, with specialist grades rated to +300 °C.

• For outdoor and weathering environments: EPDM and neoprene (CR) are the most commonly specified grades where UV radiation, ozone exposure and weathering are primary considerations. EPDM is preferred where water resistance and alkali exposure are also factors, particularly in roofing and construction applications. Neoprene offers a broader mechanical profile and is the better choice where flame resistance or oil contact is also a requirement.

• For sealing applications requiring low compression set: Viton offers the strongest compression set retention at elevated temperatures, making it the preferred specification for static seals in thermally demanding environments. Fluorosilicone is a strong alternative where fuel resistance is also required. NBR and neoprene are appropriate for lower-temperature sealing applications where cost is a consideration.

• For electrical insulation: Silicone rubber is the primary specification for high-voltage insulation applications, with a dielectric strength of typically 15–25 kV/mm. Fluorosilicone offers similar insulation properties with the addition of chemical resistance. Neoprene and EPDM provide moderate insulation suitable for low-voltage applications only.

• For flame-resistant applications: Neoprene (CR) is the only grade in this range with inherent self-extinguishing properties, owing to its chlorine content. All other grades require flame-retardant additives to achieve equivalent performance, with the exception of Viton, which should be avoided in fire-risk environments due to the production of hydrogen fluoride on combustion.

• For medical or food-contact applications: Silicone rubber is the most widely specified grade, with food-contact grades compliant with FDA 21 CFR and EU Regulation 10/2011 and medical grades suitable for implants and surgical equipment. TPE is an alternative for medical applications where compliance with ISO 10993 is confirmed on a grade-by-grade basis.

• For general-purpose applications with no dominant performance requirement: Neoprene (CR) offers the broadest combined property profile of any grade in this range, balancing mechanical strength, weathering resistance, moderate chemical resistance and inherent flame resistance without excelling or failing decisively in any single area. NBR is the more appropriate general-purpose choice where oil or fuel contact is likely.

• For cost-sensitive or recyclable applications: NBR, TPE, TPR and EPDM all offer strong cost-effectiveness relative to the rest of the range. TPE and TPR carry the additional advantage of being fully recyclable and reprocessable. This is a meaningful consideration where sustainability or end-of-life handling are design constraints. Fluorosilicone and Viton are the most expensive grades and should only be specified where their specific performance properties are genuinely required.

Key Takeaways

• Engineering rubber selection almost always comes down to the intersection of three factors: chemical environment, temperature range and cost. Performance extremes in any one dimension sacrifice the other two.

• Oil and fuel resistance and high-temperature performance are the two most demanding requirements to satisfy simultaneously. Viton (FKM) is the only grade in this range that reliably delivers both, but at a cost premium that reflects this.

• Silicone's silicon-oxygen backbone gives it a fundamentally different property profile from all other grades covered here, particularly its temperature range of -60 °C to +230 °C and its dielectric strength.

• TPE and TPR are the only fully recyclable grades covered in this guide. Where end-of-life handling or sustainability are design constraints, they offer a meaningful advantage over thermoset rubbers, which cannot be remelted or reprocessed.

• Neoprene (CR) is the only grade with inherent flame resistance, thanks to its chlorine content. All other grades, with the exception of Viton, which should be avoided in fire-risk environments entirely, require flame-retardant additives to achieve the same performance.

• EPDM and silicone are the best choices where UV and ozone resistance matter, making them the default specifications for long-term outdoor or weathering applications. NBR should not be specified for outdoor use without additional protection.

• Cost and performance are inversely correlated at the extremes of this range. NBR, TPE, TPR and EPDM offer strong cost effectiveness for general applications. Fluorosilicone and Viton are the most expensive grades and should only be specified where their specific performance properties are genuinely needed.

FAQs:

Q: What is the most chemically resistant engineering rubber?

A: Viton offers the broadest chemical resistance profile of any commonly specified engineering rubber. It resists mineral oils, fuels, aromatic and aliphatic hydrocarbons and many acids reliably across a continuous service temperature range of -20 °C to +200 °C. 

Q: What is the best rubber for outdoor use?

A: EPDM and neoprene (CR) are the most widely specified grades for outdoor applications. EPDM's fully saturated polymer backbone makes it highly resistant to UV radiation, ozone and weathering. Its excellent water and alkali resistance make it ideal for roofing, construction and exterior sealing applications. Neoprene offers a broader mechanical profile and is best used where flame resistance or moderate oil contact are also requirements. 

Q: What is the difference between TPE and TPR?

A: TPE (thermoplastic elastomer) and TPR (thermoplastic rubber) are closely related materials. TPR is generally considered a harder, more rigid sub-category within the broader TPE family. Both can be melted, reformed and recycled, requiring no vulcanisation stage during manufacture. 

The key practical distinction is mechanical: TPR typically offers greater abrasion resistance, higher tensile strength and better durability under sustained mechanical stress, while TPE offers superior low-temperature flexibility, with a lower service threshold of approximately -50 °C compared to -20 °C for TPR. 

Q: Which rubber has the highest temperature resistance?

A: Silicone rubber has the widest continuous service temperature range of any commonly specified engineering rubber, operating reliably from -60 °C to +230 °C, with heat-stabilised grades extending to +260 °C. Viton is the preferred specification where high-temperature performance must be combined with resistance to fuels or aggressive chemicals, with specialist grades rated to +300 °C. 

Standard grades of most other engineering rubbers, including NBR, neoprene and TPE, are generally limited to a maximum continuous service temperature of around +120 °C to +125 °C.