The terms &#;crosslinked&#;, &#;vulcanized&#; and &#;cured&#; mean basically the same thing!
In this process, bales of synthetic rubber, plastic resin, and a variety of different compounding ingredients such as carbon black, clay and process oil are mixed together in an internal mixer. Added to these ingredients are curatives which are chemically very active. Once these chemically active curatives are put into a rubber compound, the process variables that go into making the product must be controlled very closely or else this chemical reaction known as vulcanization will take place too soon and the product will be ruined. Once cured or crosslinked, the rubber or plastic cannot be melted or reverted back to its original form. It retains the shape to which it has been cured or crosslinked. A classical example of this is a car tire. If a car tire were made of non-crosslinked plastic, it would soften and melt once it reached the high temperatures tires are exposed to during their normal wear and tear.
The way an egg reacts with heat is an example of how a product reacts when it is crosslinked. An egg has no shape or form before it is cooked (crosslinked). After it is cooked, it will keep whatever shape in which it has been cooked (vulcanized, cured, crosslinked).
The way a candle and a stick of butter melt and flow with heat are examples of how a plastic product reacts that has not been crosslinked. With relatively low heat they will soften and lose shape quickly. At room temperature they harden again. Because they are not crosslinked, this melting and hardening can be done over and over again to the same candle or piece of butter or plastic.
Blends that have a high rubber content almost always have to be crosslinked. Blends that have a high plastic content are usually not crosslinked.
All rubber products are manufactured in one of two constructions or types. The first type is normally called solid or dense rubber. The second type is normally referred to as cellular or sponge rubber.
The table below is an overview of the performance in basic properties of common rubbers.
Natural Rubber Styrene Butadiene Rubber (SBR) Ethylene Propylene Diene Methylene (EPDM) Butyl Rubber (IIR) Neoprene Nitrile Silicone Viton Polyurethane Abrasion Resistance Excellent Good Good Fair Good Good Poor Good Excellent Chemical Resistance Good Good Excellent Good Fair Fair Fair Excellent Fair Compression Set Properties Good Good Good Fair Fair Good Good Good Fair Electrical Properties Excellent Excellent Good Excellent Fair Fair Excellent Fair Good Flame Resistance Poor Poor Poor Poor Good Poor Good Excellent Poor Heat Resistance Poor Fair Excellent Good Good Good Excellent Excellent Fair Low Temperature Properties Excellent Good Good Good Good Good Excellent Fair Good Oil Resistance Poor Poor Poor Poor Good Excellent Fair Excellent Good Ozone Resistance Poor Poor Excellent Excellent Good Fair Excellent Excellent Excellent Permeability to Gases Poor Good Good Excellent Good Good Poor Good Good Physical Strength Properties Excellent Good Good Good Good Good Fair Good Excellent Water Resistance Good Good Excellent Fair Fair Good Fair Excellent FairNatural rubber is the only non-synthetic rubber. It is a natural resource obtained from latex found in the sap of Hevea Brasiliensis trees. Natural rubber has the highest resilience of all rubbers and a low level of heat generation.
A special feature of natural rubber is that at high levels of stress, the rubber becomes very tough. As the natural rubber is stretched the amorphous polymers slip over each other and become aligned and partially crystalline. Strength is added in the direction of the polymer chains. This is called &#;Stress Crystallization&#; making the natural rubber very resistant to tearing.
Natural rubber has many qualities, these include:
Drawbacks of natural rubber:
Chemical Compatibility of natural rubber
Operating temperature range: -50 to +80°C
There are vast array of applications for natural rubber, these include:
High strength and elasticity make this a good material choice for thin, strong products.
Drawbacks of latex:
Typical applications of latex:
Polyisoprene (IR) is a synthetically made rubber which is designed to replicate natural rubber. Polyisoprene has the same chemical structure as natural rubber and offers comparable material properties. However, polyisoprene has a slightly decreased tensile strength, tear strength and elasticity. Natural rubber is normally less pure than polyisoprene and may still contain latex proteins.
Shotblast rubber is often used in construction as it is high wearing and has great abrasion resistance. It is usually made by compounding natural rubber with some cure system and protective agent. As no reinforcing filler is added to the compound, shotblast rubber has low stiffness and density.
Shotblast can offer you:
The common types of applications for shotblast rubber are:
Styrene Butadiene Rubber is the most used rubber and accounts for 45% of all rubber produced. SBR is a family of copolymers made by polymerising styrene and butadiene. SBR is a relatively inexpensive and general-purpose rubber which can often be used as a good substitute for natural rubber. SBR usually has superior abrasion resistance and heat ageing properties compared to NR. However, SBR typically has less resilience and strength.
The double bond in the polymer chain makes SBR very susceptible to attack by ozone and oxygen.
The qualities of SBR are as follows:
Operating temperature range: -25 to +100 °C
Chemical compatibility of SBR:
Common applications for SBR are:
Ethylene Propylene Rubber (EPM) is a copolymer consisting of ethylene and propylene. The ethylene propylene polymer is chemically inert as it contains no double bonds.
Ethylene Propylene Diene Methylene (EPDM) is a terpolymer of ethylene, propylene, and diene monomers.
EPDM has an extra monomer added to its compound which allows the rubber to be vulcanised with sulphur or peroxide. EPM on the other hand can only be peroxide cured.
The ethylene propylene polymer is chemically inert as it contains no double bonds. The lack of double bonds in the chain protects the rubber from weathering, ageing and chemical attack. However, due to the lack of double bonds, EPM cannot be vulcanised with sulphur and must be peroxide cured.
EPDM is like EPM however with a small amount of a third monomer diene added to the rubber compound. The amount of this monomer added to the compound is around 2-5%. The addition of diene introduces double bonds to the side chain of the polymer, making the polymer chemically reactive. EPDM can therefore be sulphur or peroxide cured.
There are over 100 grades of EPM and EPDM available. The grades vary in the ratio of ethylene to propylene as well as the type and amount of the third monomer added, diene. The ratio of ethylene to the compound can affect the properties of the rubber material. For high elasticity applications, a compound with 50-60% ethylene should be chosen. Ethylene levels above 70% show the highest uncured strength.
EPDM is one of the most purchased rubbers and has many qualities, these include:
Drawback of EPDM and EPM:
Operating temperatures: -45 to +125°C, up to 150°C for peroxide cured EPDM.
Chemical compatibility of EPDM and EPM:
EPM/EPDM rubber has many different uses, and these include:
Butyl Rubber (isobutylene-isoprene) is a synthetic rubber which was developed in the &#;s. Butyl rubber demonstrates similar weather and ageing properties as EPM and EPDM as there are only a few double bonds in its main molecular chain which can be attacked.
Butyl rubber has one of the lowest permeabilities to gas of all rubber. This makes it excellent for using inner tubes for tyres and high-pressure/vacuum sealing applications. IIR also has a low resilience and is often used in high-energy absorbing applications.
The key properties of Butyl rubber are:
Drawbacks of Butyl rubber:
Operating temperatures: -50 to +100°C
Chemical compatibility of Butyl rubber:
Butyl rubber can be used for:
Polychloroprene Rubber (CR), commonly referred to as Neoprene, was one of the first oil-resistant rubbers to be developed. Neoprene is a chlorinated elastomer that has a similar structure to butadiene rubber but with one chlorine atom rather than hydrogen in the monomer. The chlorine atoms modify the behaviour of the rubber by making it less bouncy and less reactive. This gives CR relatively good weathering and heat resistance, especially for a polymer which contains double bonds in its chains. The chlorine also gives the material a level of fire protection making it a good material choice for cables. Neoprene offers a degree of stress crystallisation and is reasonably strong even without reinforcing filler.
Neoprene has many qualities such as:
Grades Neoprene rubber is available in:
Drawback of Neoprene rubber:
Operating temperature: -35 to +100°C
Chemical compatibility of Neoprene rubber:
Neoprene can be used for many purposes and these include:
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Black neoprene (10% content) / SBR rubber 70 shore. It is used where a cheaper quality material will suit simple applications such as packing pieces, dust seals, protection pads etc. Where the material is not coming under any duress and slight resistance is required. This product is fully CE, PAH, ROHS, and REACH compliant. Seals, hoses and gaskets are made from neoprene rubber sheeting and are often used with refrigerants and oils, both animal and vegetable. Neoprene rubber sheeting is also used to provide noise isolation in power transformers and as a base for adhesives. Its resistance to burning has led to it being used as weather stripping for fire doors.
Available Finishes: 'SS' has a smooth finish on both sides, 'CC' has a cloth-print finish on both sides and 'CS' has a smooth finish on one side and a cloth-print finish on the other.
Neoprene sheet is resistent to:
Neoprene is a very hardy material. However, the presence of strong oxidizing acids and esters will cause degradation. Ketones and chlorinated, aromatic and nitro hydrocarbons are also not suitable for use with neoprene rubber.
Polymer content: 10%
Density: 1.45sg
Hardness: 70 shore a
Tensile strength: 40 kg/cm2
Elongation at break: - 200%
Min temperature: -30°C
Max temperature: +90°C
Acrylonitrile Butadiene Rubber (NBR) was the first oil-resistant synthetic rubber developed in Germany, in . It was historically referred to as &#;Buna N&#; and is often simply referred to as Nitrile rubber. Nitrile is the standard rubber used in situations where oil resistance is needed.
Nitrile is a copolymer of butadiene and acrylonitrile. The butadiene component provides the elasticity of rubber. The properties of Nitrile mainly depend on the amount of acrylonitrile in the rubber compound. High amounts of acrylonitrile result in a rubber with better oil resistance. Compounds with low acrylonitrile content have a better low temperature flexibility and resilience.
The grade descriptions of Nitrile depend on the percentage of acrylonitrile present in the rubber. Rubbers with higher acrylonitrile content have greater oil and fuel resistance, tensile strength, hardness, abrasion, gas impermeability and heat resistance. High acrylonitrile content can also lead to low-temperature flexibility, resilience, and plasticiser compatibility.
Nitrile can meet customer expectations with properties such as:
Drawbacks of Nitrile rubber:
Operating temperature: -25 to +100 °C
Chemical compatibility of Nitrile rubber:
Black nitrile (10% content) / SBR rubber 70 shore. It is used where a cheaper quality material will suit in simple applications such as packing pieces, dust seals, protection pads etc where the material is not coming under any duress and slight resistance is required. Ideal for use in products when oil resistance is required such as fuel hoses, automotive seals, gaskets, rollers and in printing and textiles, nitrile rubber is an oil-resistant synthetic rubber. This product is fully CE, PAH, ROHS and REACH compliant with excellent mechanical characteristics, black nitrile rubber sheeting is suitable for use with fuels, oils, greases and water.
Nitrile sheet specification:
Available Finishes: 'SS' has a smooth finish on both sides, 'CC' has a cloth-print finish on both sides and 'CS' has a smooth finish on one side and a cloth-print finish on the other.
We stock a majority of these strip materials at all times, so the likely lead time will be between 1 and 2 days. However, should we not hold the specific product required, we'll be able to provide it within 3-5 days. Get in touch to discuss any specific requests.
Compressed fibre (often known by the brand name Klinger) is a high-quality and dependable material commonly used for gaskets. It&#;s made from aramid and synthetic fibres which is bonded with Nitrile.
CNAF has many qualities, and these include:
Specifications
CNAF is suitable for a range of applications, these include:
Silicone offers advantages over other rubber sheeting. It is a very resilient material that maintains its properties at very high and very low temperatures. They are commonly used in pharmaceutical, food and other clean industry applications. Silicone is also a great electrical insulator with excellent ozone and UV resistant capabilities. It offers high tear resistance, tensile strength and good elongation. Remaining constant whatever the temperature, silicone has excellent resistance to heat while remaining flexible at low temperatures. low in flammability, it is resistant to ultra-violet light, weathering, sea water and ozone. It is metal detectable and exhibits low smoke toxicity.
Sheet silicone is FDA-compliant 60 shore.
Silicone polymers differ from rubber as they are made with a silicon and oxygen backbone. Silicone rubbers can exhibit good elasticity over a larger temperature range than other synthetic rubbers.
Silicone rubber is inert and unlike natural rubber, does not cause any reactions within the body. This means that it is appropriate for use within the food processing industry, and it is extensively used in this environment as washers, gaskets, scrapers, curtains, and seals. Silicone is also commonly used in the automotive and medical industries.
Silicone is heavily relied upon in the food and medical industry due to it being FDA compliant not to mention the qualities it has. These include:
Drawbacks of Silicone rubber:
Operating temperature: -80 to +300 °C
Chemical compatibility of Silicone rubber:
Silicone rubber has many different uses, these include:
Fluorocarbon Rubber (FKM) is also commonly known as Viton. Fluorocarbon rubbers are a family of materials based on copolymers and terpolymers. The fluorine atoms in their molecular structure make these rubbers highly resistant to many chemicals as well as making them resistant to high temperatures. These rubbers are some of the most suitable choices for high temperature applications as they offer excellent heat resistance of up to 300°C.
Fluorocarbon rubber is a useful product with qualities such as:
Drawbacks of Fluorocarbon rubber:
Operating Temperature: -10 to +300°C
Chemical compatibility of Fluorocarbon rubber:
This highly reliable rubber source is useful for:
Thermoplastic elastomers (TPE) were developed and introduced in the &#;s. TPEs are copolymers of thermoplastics and rubber. These polymer chains are highly attracted to each other and form crosslinks as they crystallise together. These materials, therefore, behave like elastomers but have the added benefit that they do not require vulcanisation.
Thermoplastic elastomers have many key qualities, these include:
Drawbacks of thermoplastic elastomers:
Operating temperatures: -40 to + 120°C
Thermoplastic Elastomers are used for:
Black nitrile bonded cork. This is an economical and highly compressible material suitable for low and medium bolt pressure, with good flexibility and resilience. The physical characteristics along with fuel and oil resistance make this a general-purpose gasket material.
This reliable and cost-effective material has many qualities, these include:
Drawbacks of nitrile bonded cork:
Operating temperature: -20°C + 120°C
Specification of nitrile bonded cork:
Insertion rubber is reinforced by layers of fabric which are &#;inserted&#; into the rubber. This internal layer of fabric is usually made of nylon or polyester and helps to increase the tensile strength and the tear resistance of the material. The fabric insert also reduces the elasticity of the plastic meaning that the material will better retain its original shape. Insertion rubbers offer similar properties to standard commercial rubber. They offer top level durability and wear resistance as they won't stretch or tear.
Insertion rubber is reliable and long lasting and is often used in extremely abrasive applications such as guards on farming machinery. Insertion rubber is often made using SBR and natural rubber with fabric inserts. For applications where oil and fuel resistance are necessary, it is recommended to use neoprene or nitrile insertion.
Insertion rubber is often cut into gaskets, washers, strips, or pads or manufactured to make sleeves. Insertion rubber sheets are available in a range of thicknesses and with varying amounts of fabric reinforcement. The number of ply refers to the number of fabric layers within the insertion rubber. For example, 5 ply insertion rubber contains 5 layers of reinforcing fabric within the material.
The key properties for insertion rubber are:
Drawbacks of insertion rubber:
Specification for insertion rubber:
Here are the applications for insertion rubber:
If you want to learn more, please visit our website Rubber and Plastic Board.