A glossary of industrial rubber terms from J-Flex – manufacturers of rubber mouldings, silicone sheetings, and much more

As industrial rubber specialist J-Flex has developed an extensive glossary of terms related to the industrial rubber industry. From silicone sheetings through to rubber mouldings to moulded silicone rubber seals we have definitions that can help you gain an understanding of the various technical terms.

Choose a term from the drop down list to find out a full explanation below – if the term you’re looking for is not on our list, please let us know by phone or email, so we can add it for everyone’s benefit.

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Abrasion Resistance

Abrasion properties of rubber are difficult to define. Many different abrasion machines have been designed but they do not always give similar results. The most common abraders are AKRON, Dunlop and DuPont. Results are recorded as volume loss per standard test piece, or as the difference in volume loss when compared with a standard material of known abrasion value. Indices of relative abrasion are also used.

ISO REFERENCE: 4649

Accelerated Ageing

Heat ageing is widely used as a method of evaluating long term ageing properties. Hardness and dumbbell type tensile test pieces are placed in an air circulating oven for a specific period of time at a given temperature (e.g. 7 days at 70°C). The properties of the rubber are then tested and compared with the properties before ageing. The percentage retained for each property is recorded (change in hardness is recorded in degrees).

ASTM REFERENCE: D573

BS REFERENCE: BS 903 Part A19

ISO REFERENCE: 188

Chemical Resistance

 This is usually expressed as the change in properties (such as hardness, strength and elongation at break) caused by the presence of chemicals under defined conditions (including concentration, time and temperature).

Coefficient of Friction

Ratio of the force needed to move an elastomer over a given surface to the total forces pressing on the elastomer and surface.

Compression Set

A cylindrical button of rubber of known thickness is compressed to a fixed height (typically 70% or 75% of its original height) at a defined temperature for a specific period of time. The button is then released, allowed to recover (typically for 30 mins) and the thickness is measured. Compression Set is the height that is not recovered expressed as a percentage of the amount by which it was compressed.

ASTM REFERENCE: D395

ISO REFERENCE: 815

Diaphragm Rubber Sheetings

Premium grade elastomer reinforced fabric sheetings intended primarily for diaphragm applications.

Diaphragm Seals

Precisely produced diaphragms and sensitive flap valves for use in gas controls, valves, actuators, regulators, pumps and metering equipment.

Die Cut Gaskets

Press cut and hand cut gaskets in all types of rubber and non-metallic materials.

Dielectric Strength / Electrical Properties

The resistance of an elastomer to the conducting of an electrical current.
Anti-static and conductive properties of rubbers are defined by measuring their electrical resistance. Typical measurements are obtained through the thickness of a sample by using 25mm sq. electrodes under a pressure of 45N and applying a voltage of 500V DC @ approx. 6mA. (Energy dissipated into the test piece is limited to 3W max.) The surfaces should be cleaned before measuring. Patterned surfaces should be wetted with a conductive solution or paint. Results should be recorded in Ω, defining the conditions of testing.
 

ASTM REFERENCE: D991 & D257

ISO REFERENCE: 2878

Elongation at Break

Elongation is defined as the length at breaking point expressed as a percentage of its original length (i.e. length at rest) e.g. if a rubber reaches twice its length before breaking its elongation is 100%.

ASTM REFERENCE: D412

ISO REFERENCE: 37

Fabricated Sleeves

Fabricated sleeves from a variety of rubber and composite materials primarily used to connect, discharge or compensate movement.

Flame Resistance

Flame resistance testing requires a standard burner and fuel which gives a flame of known characteristics. Rubber samples are then placed at a certain position in the flame and removed after an ignition period. The time taken for the rubber to self-extinguish is recorded with notes regarding afterflow and any hot particles emitted by the sample at any stage.

Fluid Resistance / Volume Swell

Fluid resistance is commonly measured by the effect of the fluid on the volume of the rubber exposed as a volume change (e.g. +100% indicates that the volume of the rubber has doubled as a result of exposure to the fluid, -10% indicates that the volume of rubber has decreased as a result of exposure to the fluid). Volume change is measured by determining the weight of a sample in air and water before and after exposure to the fluid under defined conditions. The sample is normally totally immersed in the fluid.

Fluid resistance may also be defined in the same way as chemical resistance (above) i.e. by change in properties of the rubber.
W1 Wt in air (initial) W2 Wt in water (initial) W3 Wt in air (swollen) W4 Wt in water (swollen)

ASTM REFERENCE: D471

BS REFERENCE: BS 903 Part A16

ISO REFERENCE: 1817

Foam Impact Protection Profiles

Impact protection foam profiles provide highly visible protection on sharp corners, edges, machinery, racking and vehicles – preventing accidents in the workplace.

Inflatable Seals

Specially fabricated elastomer seals designed to inflate with air to form a tight barrier between two surfaces.

Hardness

Measured in degrees and based on the penetration into the rubber of a defined indentor under a set load. Three scales are commonly used: IRHD (International Rubber Hardness Degrees), Shore A and Shore D for hard materials over 90° Shore A. IRHD is preferred for most specifications but Shore A is also in widespread use.

ASTM REFERENCE: D2240 & D1415

ISO REFERENCE:  48

Hysteresis

The build up of heat in an elastomer sample caused by rapid deformation.

Modulus

Modulus is measured as the force per unit area required to extend a rubber to a stated percentage of its original length e.g. to 100%, 200% or 300%. It is often written as M100 = 3.0 MPa (i.e. modulus at 100% = 3.0 Mpa).

ASTM REFERENCE: D412

ISO REFERENCE: 37

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Moulded Silicone Rubber Seals

Precisely moulded seals for pharmaceutical, food, beverage and other clean industries – available in small and high volume.

Neoprene, Nitrile & EPDM Sheetings

Normally thin gauge precisely calendered elastomer sheet made from Neoprene, Nitrile & EPDM.

Ozone Resistance

Ozone causes cracking in rubber. Test pieces are usually placed under a small degree of tension e.g. by bending round a mandrel or stretching by 5%. The sample is exposed under static conditions to a controlled atmosphere containing ozone (typically 50 pphm). The cracks are graded by standard photographs, by measurement or by description, e.g. ‘visible under 10 x magnification’ ‘visible to the unaided eye’ etc. Results may be recorded as the time taken to reach a particular grade of cracking, or by the grade of cracking apparent after a fixed period of time.

ASTM REFERENCE: D1149

ISO REFERENCE: 1431-1

Pressure Rollers

Seafood de-shelling rollers made from special soft grade of polyurethane for Offshell Europe machinery official refurbishers for Offshell Europe machinery.

Rebound Resilience

The measure of the rebound (bounce) of a metal ball dropped at a given height onto an elastomer sample.
Resilience is measured on standard test equipment ( of which there are several types – e.g. Dunlop, Tripsometer, Lupke, Rebound). Standard test pieces are struck by the ‘hammer’ and the ‘bounce back’ of the hammer measured. This is expressed as a percentage of the flight path of the hammer.

ASTM REFERENCE: D2632

ISO REFERENCE: 4662

Rubber Bellows

Moulded or fabricated protective covers for hydraulic rams and sensitive equipment. Stock range also available.

Rubber Extrusions

Rubber profiles, sections and seals produced by extrusion technique.

Rubber Mouldings

Rubber components produced by compression, transfer or injection methods.

Specific Gravity / Density

Density is defined as the mass per unit volume and is measured by weighing the rubber sample in air and water.

ISO REFERENCE: 2781

Silicone Sheetings

High performance sheet rubber made from silicone elastomer.

Tear Strength

Tear Strength is measured as the force required to tear a standard piece. The standard test pieces are designed to produce weak points where a tear is initiated.

ASTM REFERENCE: D624

ISO REFERENCE: 34

Tensile Strength

This is measured in various units and is expressed as a force per unit area. A standard dumbbell type test piece of known cross sectional area is used which is stretched until it breaks. The force required to do so is then recorded and expressed as force per unit area.

ASTM REFERENCE: D412

ISO REFERENCE: 37

Thermal Conductivity

The ability of an elastomer to conduct heat.

Viton™ Adhesive

A flexible multi purpose adhesive made from Viton™ fluoroelastomer with good adhesion at high temperatures.

Viton™ Sealant

Special caulk sealant made from Viton™ fluoroelastomer – ideal as a gap sealer in corrosive and hazardous environments.

Viton™ Sheetings

High performance rubber sheet made from Viton™ fluoroelastomer.

Vulcanised Joined Rings

Sealing rings normally made from extruded sections and cords c/w fully vulcanised joints.

Weather Resistance

Weather resistance is a fairly subjective test and it is necessary to state clearly the conditions under which the exposure took place i.e. dates, geographic location, angle and direction of exposure relative to the sun etc.

The properties of test pieces are measured before and after exposure and expressed as percentage changes (with exception of hardness changes which are usually recorded in degrees). The change in any property may be measured but the most common are hardness, tensile strength, elongation at break and modulus at 100% and 300%.

ASTM REFERENCE: D1171

ISO REFERENCE: 4665

This guide is intended to assist understand the most frequently used terms from the rubber industry. The information contained should be used in conjunction with the national & international standards and legislation relating to properties and safe application of rubber. Ultimately it is the direct responsibility of the customer to make the final decision as to the suitability of a rubber material for a particular application.

Why buy from J-Flex?

If you are looking for a friendly and helpful industrial rubber products supplier, with great product knowledge and excellent customer service, then you’re in the the right place. We supply a vast range of quality items including rubber sheet and an array of fabrications made from premium grade elastomers including silicone and Viton™ - many of which are available for next day delivery. With over 35 years operating experience, J‑Flex is the preferred supplier of industrial rubber products - providing specialist rubber sheetings and engineered rubber components you can trust. Whether you are looking for silicone sheets, rubber mouldings, gaskets, extrusions, bellows, fabrications, rubber sealants or adhesives -including Viton™ sheets and sealants, J‑Flex can help. You'll find our Accreditations & Awards information here.