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Rubber has been used for thousands of years and was originally sourced naturally from rubber trees. In more recent years, it has often been produced synthetically and today there are a range of different types, each with their own characteristics.
If you have an application that requires the use of rubber components, it’s important to choose the right type for the job. So this guide looks at the most common types of rubber, their typical applications and the benefits and disadvantages of each.
Properties of rubber
Most types of rubber share common characteristics including;
- Elasticity - they return to their original shape after being compressed or stretched.
- Thermal contraction – they respond differently to heat than most other materials, contracting rather than expanding.
- Durability – they are resistant to damage from abrasion, tearing, impacts and water.
Types of rubber
Each type of rubber has different properties that make it more suitable for particular applications. Some of the most common rubber types include:
Natural rubber
Properties – derived from latex and composed of the polymer polyisoprene plus small amounts of proteins, fatty acids, resins and inorganic materials.
Advantages – a large stretch ratio, high strength and resilience, resistance to abrasion, friction, acid, alkali and extreme temperatures, is biodegradable and waterproof.
Disadvantages – is sensitive to ozone cracking.
Applications – typical uses include adhesives, flooring and roofing, gloves, insulation, tyres, gaskets, O-rings, hoses, shock absorber parts and electrical safety matting.
Silicone Rubber
Properties – a semi-organic synthetic rubber consisting of a chain of silicon and oxygen atoms.
Advantages - malleable, biocompatible, resistant to extreme temperatures, fire, ozone, UV radiation and bacterial build-up, good electrical insulation properties. non-porous, non-toxic, water-repellent and recyclable.
Disadvantages – low tear and abrasion resistance and a higher cost.
Applications – typically used in gloves, respiratory masks, implants, medical products, baby care items, cosmetic applicators and food containers.
Nitrile rubber (NBR)
Properties – made by the polymerization of acrylonitrile and butadiene.
Advantages – oil, water and solvent resistance, good compressibility, wear resistance and elongation.
Disadvantages – not suitable for polar solvents such as ozone and chloroform.
Applications – uses include oil seals, O-rings, automotive gaskets, engine hoses and surgical gloves.
Ethylene propylene rubber (EPDM)
Properties – made by the polymerization of ethylene and propylene.
Advantages – excellent durability, stability, gas impermeability, chemical resistance, noise and thermal insulation properties and resistance to damage and deterioration from extreme temperatures and weather conditions.
Disadvantages – is not recommended for food use.
Applications – typically used in roofing sealants, hoses, seals and automobile systems.
Styrene-butadiene rubber (SBR)
Properties - a copolymer of styrene and butadiene
Advantages - superior durability and resistance to abrasion, alcohol, compression, water, wear and ageing.
Disadvantages – has low mechanical strength.
Applications – typically used in hydraulic brake seals, cutting boards, conveyor belts, gaskets and shoe soles.
Butyl rubber (IIR)
Properties - a polymer of isobutene and isoprene.
Advantages – impermeable to most gases, good resistance to heat, sunlight and ozone.
Disadvantages - not recommended for use in leather bags, window frames or steam hoses.
Applications – uses include inner tubes, sport balls, sealants and as an additive in diesel, petrol and chewing gum.
Chloroprene (CR)
Properties - formed by chlorine-butene monomer polymerization.
Advantages - good elasticity, wear, fire and weather resistance and compression deformation.
Disadvantages – has poor storage stability.
Applications - suitable for all types of fire-resistant and chemical-resistant rubber products. Also used in adhesives and corrosion-resistant coatings, high-pressure gaskets, belts and window and door seals.
Rubber failures
“Ozone is responsible for about 21% of service-related failures for rubber elastomers” Zetco
One instance where choosing the correct type of rubber is crucial is applications where valves are employed. Rubber elastomer (O-ring) failure on a manufacturing, mining or industrial scale can be catastrophic and lead to costly downtime, damage to plant and equipment, product recalls and loss of professional reputation.
Those installing or replacing valves containing rubber components should carefully compare properties and confirm suitability with their supplier.
The most common types of elastomer used in valves are:
FKM – a vinylidene fluoride rubber resistant to a range of chemicals and with excellent high temperature properties.
FFKM – a perfluoro elastomer that delivers outstanding performance in aggressive process environments.
EPDM – an ethylene propylene elastomer resistant to ozone, UV and weathering.
NBR – a nitrile elastomer resistant to petroleum-based oils, fuels, water, alcohols, silicone greases and hydraulic fluids.
HNBR – a hydrogenated nitrile butadiene elastomer known for its strength and retention of properties.
With so many different synthetic rubbers now in use, finding the right type for your application can be time-consuming if you’re not an expert.
So the best course of action if you’re installing or replacing components containing rubber is to take advantage of your supplier’s expertise and allow them to make recommendations. This is particularly important if you’re dealing with industrial valves or any components where failure is simply not an option.