Glossary of Rubber Terminology

Whilst we try to be as straight-forward as possible, using language and phrases that most people will be able to understand, there is no getting away from some important terms within the industry.


An abbreviation for acrylic rubbers.

An abbreviation for acrylonitrile.

An abbreviation for azodicarbonamide, blowing agent.

An abbreviation for azodicarbonamide, blowing agent.

An abbreviation for acetone-diphenylamine condensation product, antidegradant – staining.

An abbreviation for ethylene-acrylic terpolymer.

An abbreviation for polyester type polyurethane rubbers.

Azobis-isobutyronitrile, blowing agent.

The ability of a rubber article to withstand wearing away in service. Standard BS 903: Part A9. Determination of abrasion resistance.

A compound ingredient which speeds up the vulcanisation reaction, enabling it to take place in a shorter time or at a lower temperature or both. The physical properties of the vulcanizate and its resistance to ageing are also improved.

Rubbers based on polymers of organic acrylates.

CH2CHCN (vinyl cyanide); raw material for the manufacture of nitrile rubber, synthetic fibres, and plastics.

See Nitrile Rubber.

A compound ingredient that enables an accelerator to exercise its maximum effect. Inorganic activators are metallic oxides (such as zinc, lead, and magnesium oxides) and organic activators are long chain saturated fatty acids, e.g., stearic, and oleic.

Most rubbers are formed by addition polymerisation. This process simply involves the “addition” of single monomers to each other without creating any by-products.

A substance added to something in small quantities to improve or preserve it.

The deterioration of the physical properties of rubber product when exposed to service conditions. Also, the controlled exposure of rubber samples to a variety of deteriorating influences in the evaluation of antioxidants and antiozonants. See Accelerated Ageing.

In organic chemistry, amines are compounds and functional groups that contain a basic nitrogen atom with a lone pair.

A pungent gas with a characteristic pungent smell. It dissolves in water to give a strongly alkaline solution.

Having no definite shape; non-crystalline.

Aniline is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile starting material for fine chemical synthesis.

A term applied to compound ingredients, mainly antioxidants, which inhibit premature degradation of elastomers.

Flame retardant.

An ingredient added to a rubber compound to protect the product against deterioration by oxygen. Antioxidants belong to the class of compounding ingredients known as protective agents, and their mode of action is considered to be removal of free radicals which are generated by the interactions of oxygen and the polymer at elevated temperatures. Failure to remove these free radicals will results in an ongoing deterioration of the polymer. Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals and chain reactions that may damage the cells of organisms.

An antiozonant, also known as anti-ozonate, is an organic compound that prevents, or retards damage caused by ozone.

A pressure vessel constructed of steel, used for the vulcanisation of rubber products by the ‘open steam’ method. The autoclave may be horizontal (vulcanisation of footwear, cables, hose), or vertical and fitted with a hydraulic ram (e.g., moulding pneumatic tyres).

ADC, blowing agent.

Butylated hydroxytoluene, (2,6-Di-tert.-butyl-p-cresol), antidegradant – non-staining.

An abbreviation for rubber based on butadiene.

Tearing or distortion of a moulded rubber product at the line of separation of the two mould halves (the spew line) due to the sudden release, on opening the mould, of the high pressures developed by the thermal expansion of the heated rubber; other names are “suck back”, “flash back” and “retracted spew”.

A cylindrical container half to two-thirds filled with a grinding charge consisting of unglazed porcelain, glass balls, pebbles, or flint gravel; it is used in the preparation of aqueous dispersions of ingredients for use in the manufacture of products direct from latex.

A material used in fluid bed vulcanisation. It consists of very small spherical particles of glass of a narrow size distribution, approximately 0.1 to 0.2 mm.

The type of internal mixer designed by F.H. Banbury; the name ‘Banbury’ is often erroneously applied to any type of internal mixer.

On an open mill, the proportion of the mill load which runs in the space immediately adjacent to the nip between the rolls. The amount of rubber compound running at the nip or nips of a calendar during the operations of frictioning, sheeting, coating, or profiling.

That part of an extruder in which the screw/ram rotates/translates.

Another name for die swell and extrudate swell. It is a common phenomenon in polymer processing.

An apparatus for preparing moulding blanks. It is a development of the Barwell ram extruder which feeds through interchangeable dies to give the correct profile of blank, which an electronically operated cutter, working across the face of the die, cuts the blanks. Oil is admitted to the ram of the extruder in controlled quantities, set by a metering device, so that the compound is forces from the die in the correct amount to form each blank.

Naturally occurring barium sulphate. BaSO4; it has the high specific gravity of approximately 4.45 and is used as a filler, especially when a high specific gravity rubber compound is desired or is not a disadvantage. Is also used as an acid resistant white filler.

C6 H6, the simplest member of the aromatic series of hydrocarbons; it is a colourless liquid with a boiling point of 80°C and is used in the manufacture of many organic compounds.

A vulcanising agent particularly for silicone rubber and fluoroelastomers; it has been used as a non-sulphur vulcanising agent for natural rubber. It is also a catalyst in emulsion polymerisation.

A slope from the horizontal or vertical in carpentry and stonework; a sloping surface of edge.

A piece of uncured rubber compound of suitable shape and volume to fill the cavity of the mould in which it is to be vulcanised; also termed a “slug”.

The formation of the surface of uncured or cured rubber of a thin coating if a compounding ingredient, often but not necessarily, sulphur, which is present in excess of the amount which the rubber can dissolve.

Used in the manufacture of sponge rubber. (1)    Chemical blowing agents undergo decomposition at the vulcanisation temperature to form a gaseous species such as nitrogen or carbon dioxide, e.g., azo compound, nitroso compounds, sulphonyl hydrazide compounds, ammonium carbonate, ammonium bicarbonate and sodium bicarbonate. (2)    Physical blowing agents are low boiling point organic compounds (e.g., dichloromethane or pentane), which volatise at the processing temperature.

A material used to promote the bonding of rubber to other material, principally metal and textiles.

Relating to botany. A substance obtained from a plant and used typically in medicinal or cosmetic products.

The rubber in unvulcanised filler-rubber mixes which is insoluble in a usual rubber solvent.

Another name for a calendar roll.

The Brinell scale characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece. It is one of several definitions of hardness in materials science.

Broaching is a machining process that uses a toothed tool, called a broach, to remove material. There are two main types of broaching: linear and rotary.

Another name for nitrile rubber.

Another name for styrene butadiene rubber.

An activity or set of activities that can accomplish a specific organizational goal.

A gas, CH2CHCHCH2 (buta-1, 3-diene), used in the manufacture of polybutadiene rubber and as one of the copolymers in the manufacture of styrene-butadiene and nitrile rubbers.

BHT, 2,6-Di-tert.-butyl-p-cresol, antidegradant – non-staining.

Something that is produced during the production or destruction of something else.

An abbreviation for cyclohexylbenzothiazole sulphonamide, the first of the sulphonamide range of delayed action accelerators.

A CE (or 'Conformité Européene', which literally translates as European Conformity) marking is essentially the approval of a product that has been manufactured within the European Economic Area. In order to achieve this certification mark, the products - and manufacturing processes - must have conformed with a number of health, safety and environmental protection standards.

An abbreviation for Chlorobutyl rubber.

An abbreviation for chlorinated polyethylene.

An abbreviation for Computer Numerical Control. Our engineers use CNC to translate drawings from a computer, into directions that our cutting machines are then able to follow – like plotting points on a map – in order to produce intricate and accurate gaskets, pads, washers etc.

An abbreviation for epichlorohydrin homopolymer.

An abbreviation for Certificate of Conformity

An abbreviation for chlorinated polyethylene.

An abbreviation for chloroprene rubber.

An abbreviation for chlorosulphonated polyethylene.

An abbreviation for chlorosulphonated polyethylene.

An abbreviation for N-(Cyclohexylthio)phthalimide, retarder.

CaCO3, a white solid which occurs in nature as chalk, limestone, and marble; the ground product, often termed “white”, is used as an extending filler in rubber compounding.

A machine with two, three or four heavy rolls, used in the rubber manufacturing techniques of coating, doubling, embossing, frictioning, profiling and sheeting.

The various processes carried out on a calender. See Coating, Doubling, Embossing, Frictioning, Profiling and Sheeting.

The name given to a variety of forms of fine particle carbon which have the property of conferring reinforcement on rubber compounds, the degree of reinforcement increasing with decreasing particle size.

In chemistry this is any substance that increases the rate of a reaction without itself being consumed. Enzymes are naturally occurring catalysts responsible for many essential biochemical reactions.

The apparent outward force on a mass when it is rotated.

A device that uses centrifugal force to separate various components of a fluid.

A certificate issued by an authorized party (sometimes the manufacturer, sometimes an independent laboratory) and states that a product meets the required standards or specification.

Chlorinated butyl rubber. Chlorination or bromination of butyl rubber overcomes the difficulty of vulcanisation butyl rubber in mixtures with more highly unsaturated substances due to the preferential absorption of the sulphur by the more highly unsaturated component.

This is the preferred designation for all chloroprene polymers and copolymers. Chloroprene rubber was first introduced commercially in 1931 by DuPont and their trade name, originally DuPrene, later Neoprene, has almost become a generic term for all such rubber. See Chlorobutadiene.

An elastomer made by substituting chlorine and sulphonyl chloride groups into polyethylene. The material is best known by the trade name “Hypalon”, which is the DuPont trademark for their brand of chlorosulphonated polyethylene.

This term is applied to a wide variety of material known chemically as hydrated aluminium silicates, used as inorganic fillers. China clay (kaolin) shows a slight reinforcing effect; ‘treated’ clays show considerably greater reinforcement.

See ‘Sponge Rubber’.

Any process which brings about destabilisation of a latex to such an extent that the particles coalesce. Depending on the form resulting from the agglomeration, the coacervation may be described coagulation, flocculation, or gelation.

In rubber latex, the process whereby the dispersed rubber globules separate out from the watery serum; the globules clot together to form a jelly-like mass, the coagulum. In the preparation of natural rubber, coagulation of the latex is brought about by the addition of either acetic or formic acid, but it may occur spontaneously through the action of microorganisms in the latex.

In chemistry a compound is defined as a substance consisting of two or more elements chemically united in definite proportions by weight. However, many technologists use the term “compound” in the sense of a mixture. In rubber technology, a compound is a composition obtained by adding to an elastomer substance known as compounding ingredients and blending to produce a homogeneous mixture or mix. Other terms for this unvulcanised mix are mixing, stock, blend, or quality. The term may also be used in the sense of the mix formulation, i.e., the kinds and amounts of the elastomers and compounding ingredients used to give the requisite properties in the end product.

The development of rubber compounds which will effectively withstand the conditions under which the products made from them are to be used; the mixes so developed must be capable of being processed in the factory without undue difficulty. The term is also applied to the assembling of elastomer and compounding ingredients ready for the mixing proper.

Any substance added to an elastomer to produce a rubber compound.

The method of manufacture of solid rubber products by simultaneous shaping and vulcanising. An uncured blank of rubber compound is placed in the bottom half of the mould, the top half of the mould placed in position and the mould placed in a heated hydraulic press.

Natural rubber latex as obtained from the tree contains only about 30% by weight of rubber. Concentration of the latex is done by either centrifuging, creaming, electro-decantation, or evaporation.

A reaction that produces water as a by-product.

Conductivity is the measure of the ease at which an electric charge or heat can pass through a material.

Any method of vulcanising rubber products which proceed without interruption from start to finish as compared to the method of vulcanising separate batches of products or sections of a product. Continuous vulcanisation processes include the cold curing of proofed cloth, the vulcanisation of belting and flooring, of cables and certain extruded products by either the Liquid Curing Medium, Fluid Bed, Microwave, or Hot Air techniques.

Belting used mainly in the transmission of materials, although increasing use is being made of conveyor belting in the transportation of passengers.

A ‘high polymer’ resulting from the polymerisation of a mixture of two different monomers; styrene-butadiene rubber, butyl (isoprene –isobutylene) rubber and nitrile (acrylonitrile-butadiene) rubber are typical copolymers.

A valency bond created by the sharing of a pair of electrons; also termed a ‘non-polar’ bond.

A chemical bond that involves the sharing of electron pairs between atoms.

The number of moles of physically effective crosslinks per gram of vulcanizate.

The joining of polymer molecules to each other by valency bonds. In very long chain-like elastomer molecules crosslinking introduces lateral links between either two separate molecules or different parts of the same molecule. See Vulcanisation.

In high polymers crystallisation means the formation of areas of regularity in chain aggregation rather than the formation of discrete crystals, as in simple chemical compounds.

Curing is the process of stabilising materials, after they’ve been processed. For instance, in extrusion, once the material has been fed through our extruder and has been manipulated into the correct profile shape, it is still very malleable; often not suitable for its desired use. After curing however, the material becomes firmer and it is then able to be cut and used as appropriate i.e., for boat fendering, bumpers etc. This term is synonymous with vulcanisation but is generally applied to the factory methods of vulcanising rubber products, e.g., press curing, open steam curing, cold curing.

An abbreviation for dibutyl phthalate, a plasticiser for natural and synthetic rubbers.

An abbreviation for N,N’-Dibutylthiourea, accelerator.

An abbreviation for N,N-Dicyclohexyl-2-benzothiazole sulphonamide, accelerator.

An abbreviation for dioctylphthalate, a plasticiser for natural and synthetic rubbers.

An abbreviation for diorthotolylguandine, an organic accelerator.

An abbreviation for diphenylguandidine, an organic accelerator.

An abbreviation for 4,4’-Dithiodimorpholine, vulcanising agent.

The removal of flash or spew from moulded rubber products. This may be done by hand, by trimming machine or by ‘tumbling’ the products in a barrel held at a temperature low enough to harden the flash and permit it to be rubbed off by the motion of the products in the barrel.

The number of monomer units in the polymer. It is calculated as the ratio of molecular weight of a polymer and molecular weight of the repeat unit.

An accelerator which permits processing of rubber compounds to be carried out with less risk of scorching, but which does not slow down the rate of cure at normal vulcanisation temperatures.

The operation of removing a vulcanised product from the mould in which it has been cured.

The mass per unit volume of any object. The density is essential how compactly structured a material is. For instance, an open-cell foam is a much less dense material, than a solid nitrile sheet.

A non-sulphur vulcanising agent for natural rubber and some types of synthetic rubber. One trade name is Dicup.

(1)    In extrusion of solid rubber sections, the shaped metal plate fitted in the head of the extruder to produce the desired contour; in extrusion of hollow tubing the outer circular part which fits over the pin, pencil, or nozzle to give the hollow section. (2)    A sharp tool used in punching out special shapes of rubber or rubbered fabric or used in preparing test-pieces of vulcanised rubber, e.g., dumbbell strips for tensile testing.

Also known as extrudate swell or Barus effect, is a common phenomenon in polymer processing. Die swell occurs in instances of polymer extrusion, in which a stream of polymeric material is forced through a die, a specialized tool in manufacturing to shape or cut polymeric materials. Die swell is an instance where a polymer stream is compressed by entrance into a die and is followed by a partial recovery or "swell" back to the former shape and volume of the polymer after exiting the die, hence the term die swell.

Another name for diolefin.

A measurement of how dispersible a substance is.

The uniform distribution of particles throughout a medium, e.g., particles of compounding ingredients in rubber.

(1)    The blunt-edge blade which spreads rubber dough on to fabrics in the spreading process. (2)    A blade fitted to a refiner mill to enable the thin sheet of rubber to be removed. (3)    An elastomeric (usually polyurethane) blade used to clean the rollers in laser printers and copiers.

Also termed bivalent gap and ethylenic linkage. The type of bond in which two valency bonds link two atoms in a molecule. It is typical of compounds showing unsaturation, such as ethylene. A double bond does not indicate extra strength of the bond but rather chemical instability and reactivity.

The device needed to perform a durometer hardness test procedure. Durometer devices determine the surface hardness of many different materials, including polymers and elastomers.

An abbreviation for ethylene-acrylic terpolymer.

An abbreviation for ethylene-vinyl acetate.

An abbreviation for epichlorohydrin copolymer with ethylene oxide.

An abbreviation for Ethylene Propylene Diene Monomer. EPDM is a synthetic rubber and used across an array of applications thanks to the desirable attributes and characteristics it holds. Available in a range of different harnesses (See ‘Shore’ for more information on understanding the hardness of rubber), EPDM has excellent resistance to heat, ozone, steam, weather and is an electrical insulator.

An abbreviation for ethylene-propylene rubber.

An abbreviation for ethylene-propylene rubber.

ASTM designation for epichlorohydrin terpolymers.

An abbreviation for ethylene thiourea, an accelerator.

An abbreviation for polyether urethane.

An abbreviation for efficient vulcanisation.

An abbreviation for ethylene-vinyl acetate.

Products that are used to cover rough edges made from plastics and steels.

A term applied to vulcanisation systems in which sulphur, or a sulphur donor is used very efficiently for crosslinking the rubber. EV systems produce vulcanisates with crosslinks that are mainly, monosulphidic, which are thermally and mechanically stable.

A collective term for rubber and rubber-like substances. Tree rubber is a natural elastomer and man-made rubbers are synthetic elastomers.

A stream of electrons (as from a betatron) generated by heat (thermionic emission), bombardment of charged atoms or particles (secondary electron emission), or strong electric fields (field emission).

In tensile testing of rubber, elongation is the increase in the distance between benchmarks on a dumbbell strip or the distance apart of the grips holding a ring test piece, on the application of a loaf to the test sample. It is expressed as a percentage of the original distance between the marks.

An abbreviation for 1-chloro-2,3-epoxypropane, the basis of epoxy resin and chlorohydrin elastomers.

A M-Class synthetic rubber that is made from ethylene, propylene, and a diene comonomer that enables crosslinking via sulphur vulcanization.

ETU, accelerator

This terpolymer is formed from methyl acrylate, ethylene, and a carboxylic monomer. It has properties comparable to those of an acrylic.

A stereospecific polymer produced by the copolymerisation of ethylene and propylene with Ziegler-type catalysts.

An elastomer consisting of a terpolymer of ethylene, propylene, and a diene, e.g., dicyclopentadiene.

A copolymer of ethylene and vinyl acetate which processes like a plastic and preforms like a rubber. The copolymer, of which there are various grades, is similar to rubber in softness and flexibility but can be injection moulded without vulcanisation.

In the broadest sense, any compounding ingredient added to rubber to reduce the cost of the compound. The use of the term is now usually limited to certain cheap petroleum rubber processing oil.

A term descriptive of the product of extrusion especially where no particular shape is specified.

To extrude is the process of forcing a raw material, heated to a high-temperature, and then forced under pressure through a machined die/tool. The end result of the material being extruded, is that it has now formed a new shape/profile, suitable for the application in which is designed.

A machine for carrying out the processing operation of extrusion; also historically termed “tubing machine” and “forcing machine”. The majority of extruders use an electrically driving screw to force the rubber to the head of the machine, but a piston-operated type is also in use. See Barwell Performer/Ram Extruder.

An abbreviation for the Food and Drugs Administration. The U.S. FDA tests and approves a wide range of items for – in our instance – medical applications. This means that, should you require any of our products for use in medical equipment etc. selecting an FDA approved material, would be the most suitable option.

An abbreviation for fast extrusion furnace grade of Carbon Black. See Furnace Black.

An abbreviation for fluorocarbon rubber.

An abbreviation for fluoro methyl silicone

An abbreviation for fluorocarbon rubber.

An abbreviation for fluoro vinylmethyl silicone.

A compounding ingredient added to rubber for the purpose of either reinforcing or cheapening the compound. See Reinforcing Filler and Extending Filler.

An additive used in rubber compounding to reduce the fire hazard.

Another term for spew.

A continuous process for the vulcanisation of extruded sections. The heating medium is a bed of tiny glass sphere fluidised by steam or hot air.

Foam rubber differs from Sponge rubber in ingredients, material manufacturing process, and molecular structure. A blowing agent, typically a gas, is used to create small bubbles in a liquid mixture, creating foam rubber. The properties of the foam rubber are changed, for example flexibility or rigidity, by adding different amounts of polyols, polyisocyanates, water, and additives such as flame retardants, fillers, and colorants. Many different types of blowing agents can be used to produce this cellular structure, and the compounder can control the foaming by adjusting the amount of water used or by using surfactants.

The Food and Drug Administration is responsible for protecting the public health by ensuring the safety, efficacy, and security of human and veterinary drugs, biological products, and medical devices; and by ensuring the safety of our nation's food supply, cosmetics, and products that emit radiation.

A calendaring process in which hot soft unvulcanised rubber compound is applied to a fabric. The cloth passes between the bottom and middle bowls of a three-bowl calendar; it travels at the speed of the bottom bowl and the faster middle bowl shears the rubber into the pores of the fabric.

A type of Carbon Black produced by burning natural gas or oil in a large furnace with a supply of air much lower than required for complete combustion. The main types are super abrasion (SAF), intermediate super abrasion (ISAF), high abrasion (HAF), fast extrusion (FEF), general purpose (GPF), conductive (CF) and semi-reinforcing (SRF).

An abbreviation for copolymer of propylene oxide and allyl glycidyl ether.

A form of high energy ionising radiation which arises from the radioactive decay of atomic nuclei.

Any of a class of organic compounds belonging to the alcohol family; in the molecule of a glycol, two hydroxyl (―OH) groups are attached to different carbon atoms.

‘Raw’ or ‘uncured’.

An abbreviation for Brinell hardness test.

An abbreviation for hydrogenated nitrile rubber.

An abbreviation for Vickers Hardness test.

Hardness, when referred to in the contect of rubber, is literally how firm or how soft the material is. Please see ‘Shore’ for a more detailed explanation on the measuring of rubber hardness.

The rise in temperature which occurs when rubber is deformed. The energy used in deformation is not fully returned when the rubber recovers to its original shape and the ‘lost’ energy shown as a rise in temperature of the rubber. See Flexometer, Hysteresis and Resilience.

The Pará rubber tree, sharinga tree, seringueira, or most commonly, rubber tree or rubber plant, is a flowering plant belonging to the spurge family Euphorbiaceae.

Mixtures of rubber with resins, plasticisers and other additives that are applied at the time of producing the self-adhesive complex in molten form by means of heat at temperatures above 120°C. In this process there is no intervention of water and solvents. Hot melt rubber adhesives are only suitable for low duty applications. Its low melting temperature causes a change in phase which makes it underperform at lower temperatures.

Hydrocarbon polymers, or polyolefins, comprise a main subfamily of vinyl polymers and are obtained via polymerization of nonpolar olefins.

A hydroxy or hydroxyl group is a functional group with the chemical formula -OH and composed of one oxygen atom covalently bonded to one hydrogen atom.

An abbreviation for international rubber hardness degrees.

The international standard that specifies requirements for an effective environmental management system (EMS). It provides a framework that an organization can follow, rather than establishing environmental performance requirements.

The new international standard for occupational health and safety management.

The internationally recognized Quality Management System (QMS) standard that can benefit any size organization.

A method of moulding rubber articles by injection of warm stock into mould cavities.

Of mineral origin, inorganic chemistry is the study of all chemical elements and compounds, except carbon and its compounds; certain simple carbon compounds, e.g., oxides and sulphides, are included in organic chemistry. See Organic Chemistry.

Insertion rubber is an industrial strength rubber sheet, that is then combined with a cloth reinforcement material; improving strength and tear resistance qualities, creating a more hard-wearing sheet.

A machine for the incorporation of compounding ingredients into rubber or similar materials. Two rotors revolve in an enclosed chamber (see Open Mill). It is provided with a hopper for feeding the materials and a sliding or drop-door for discharge of the batch.

Also called electrovalent bond, it is a type of linkage formed from the electrostatic attraction between oppositely charged ions in a chemical compound.

2-Methyl-1,3-butadiene CH2C(CH3)CHCH2. A liquid hydrocarbon of boiling point 34°C. It is regarded as the unit molecule of natural rubber, which is polyisoprene. Synthetic polyisoprene is marketed under a variety of trade names.

An abbreviation for length/diameter ratio; commonly used to describe machine barrels and screws.

An abbreviation for liquid curing medium.

An abbreviation for liquid curing medium.

An aqueous colloid / emulsion of rubber particles; can be up to 65% solids content; generally low viscosity compared to polymer solutions. Only rubber produced by emulsion polymerisation or natural rubber can be found in this form.

Lean manufacturing is a methodology that focuses on minimizing waste within manufacturing systems while simultaneously maximizing productivity.

One of the four most used methods for testing metal hardness.

The continuous vulcanization in liquid baths is called the liquid curing method.

A term used to describe the addition of fillers to a base compound; a heavily loaded mix is one containing a large proportion of fillers. See High Gum Compound.

In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bond and is sometimes called an unshared pair or non-bonding pair.

An abbreviation for mercaptobenzothiazole, an organic accelerator

An abbreviation for dibenzthiazyldisulphide, an organic accelerator of the thiazole class.

An abbreviation for moving die rheometer.

Magnesium oxide, MgO. Heavy calcinated magnesia is used as an inorganic accelerated in ebonite; light calcinated magnesia is the vulcanising agent (along with zinc oxide) for neoprene compounds.

A solid or hollow metal pole used in the assembly or vulcanising of rubber products, e.g., the assembly of hand-built hose.

A mix consisting of elastomer and generally only one other ingredient, the proportion of which is much higher than will be present in the final production mix. Masterbatches are used for cleanliness, convenience, accuracy of weighing small quantities of accelerators.

Masticated Rubber is a rubber compound made of reclaimed/ recycled. natural or synthetic rubber. The term masticated rubber has come to mean a mixture of recycled rubber and fibre.

A machine that shredded rubber scraps and which allowed rubber to be recycled after being formed into blocks or sheets.

A technical document which provides detailed and comprehensive information on a controlled product related to health effects of exposure to the product; hazard evaluation related to the product’s handling, storage, or use; measure to protect workers at risk of exposure; and emergency procedures.

A report that certifies that the chemical analysis and mechanical properties of a material are in conformance with the specified specification.

Another name for formic acid, which is the simplest carboxylic acid, and has the chemical formula H2CO2

Vulcanisation of elastomers by heat produced by high frequency radiation, approximately 12.5 cm wavelength, 2540 MHz.

A machine for masticating rubber, mixing rubber compounds and for warming up rubber compounds prior to calendaring, extrusion, etc. See Open Mill.

Another name for a rubber compound.

Any apparatus for making homogeneous mixtures of materials used in rubber manufacture, e.g., blends of dry powders, rubber cements of solutions and rubber compounds themselves. See Internal Mixer, Open Mill.

Another term for masterbatch.

The process of making rubber products by shaping in a mould; vulcanisation is generally affected at the same time. See Compression Moulding, Injecting Moulding and Transfer Moulding.

An abbreviation for natural rubber.

A nanoparticle is a small particle that ranges between 1 to 100 nanometres in size.

A flammable liquid hydrocarbon mixture. Mixtures labelled naphtha have been produced from natural gas condensates, petroleum distillates, and the distillation of coal tar and peat.

Rubber obtained from botanical sources. The bulk of natural rubber is obtained from the Hevea Brasiliensis tree with small amounts from other vines, shrubs, and plants mainly the Guayule shrub and the Kok-Saghyz plant. See Isoprene. Natural rubber is the most organic of all rubber variants, though it is not used extensively within industrial applications, as it lacks a number of typically required properties that are offerent by alternative materials such as EPDM, nitrile and neoprene.

This name has been widely adopted for the elastomer obtained by polymerising chloroprene. Neopreneis a family of synthetic rubbers that are produced by polymerisation of chloroprene. From a material perspective however, neoprene exhibits good chemical stability and maintains flexibility over a wide temperature range, meaning this is an excellent rubber choice for fan belts, membranes and electrical insulation.

The generic term applied to all elastomers resulting from the copolymerisation of butadiene and acrylonitrile. Nitrile is often used in automotive and aeronautical applications, due to its excellent resistance to oils and fuels. Nitrile is also used in a number of goods, including footwear, adhesives, sealants, sponges, expanded foams, floor mats and a range of other products.

An abbreviation for oscillating die rheometer.

An abbreviation for Occupational Exposure Limit. See Occupational Exposure Limits.

Resistance of an elastomer to swelling and ultimate degradation due to contact with or immersion in an oil. If you require ribber for oil hoses, grease guns, gaskets for oil pipelines, automotive pipes/gaskets etc. then you need to choose a rubber with excellent oil resistance. Natural rubber offers poor oil resistance and will warp, bloat and disintegrate in a short period of time, when in contact with oil. Materials such as neoprene, silicone and nitrile offer much greater oil resistance and are therefore more suitable in oil contact applications.

A mill in which the rolls are exposed, in contrast to those of an internal mixer.

See ‘Sponge Rubber’.

The best cure for a rubber product is always a compromise, but optimum cure may be defined at that time of cure necessary to bring a pre-selected property of the vulcanisate to near maximum (or minimum) value, at the same time ensuring that the other properties are satisfactory.

Prolongation of cure beyond that time which gives the optimum cure. An overcure may be accidental due to variation in curing conditions, or deliberate as in laboratory determination of curing range, or with the object of enhancing a particular property of a vulcanisate, e.g., compression set.

An abbreviation for polycyclic aromatic hydrocarbon

PAHs are proved to have a carcinogenic effect and therefore deemed extremely dangerous. There are a number of EU regulations and legislations in place, to restrict and limit the use of PAH’s in rubber products.

An abbreviation for Polybrominated Biphenyls.

An abbreviation for Polybrominated Diphenyl Ethers.

An abbreviation of parts per hundred of rubber.

An abbreviation for Pressurised Liquid Salt Continuous Vulcanisation

An abbreviation for Polymeric Diphenylmethane Diisocyanate. The generic name of a product used in industrial settings. Polymeric MDI (PMDI), the primary technical/commercial form of MDI, is actually a mixture that contains 25-80% monomeric 4,4'-MDI as well as oligomers containing 3-6 rings and other minor isomers, such as the 2,2'-isomer. The exact composition of PMDI varies with the manufacturer. PMDI is used to make rigid and flexible foam, foundry resin sand binders, and heat insulating material.

An abbreviation for phenyl methyl silicone.

An abbreviation for copolymer of propylene oxide and allyl glycidyl ether.

An abbreviation for Production Part Approval Process.

An abbreviation of parts per hundred of rubber.

An abbreviation for Pressure Sensitive Adhesive.

An abbreviation for polyurethane. Polyurethanes are a family of elastomers that make up an array of artificial rubbers, with a wide array of hardnesses and applications.

An abbreviation for phenyl vinyl methyl silicone.

The Bayer trade name for a nitrile rubber formerly known as Buna N.

Used as processing additives at 5-10 phr and as a rubber extender and softener at > 10 phr.

Also termed softener and processing aid. A compounding ingredient which facilitates processing by making the unvulcanised compound more plastic, aids in the incorporation of powders, reduces the processing temperature and assists mould flow.

Also called brominated biphenyls or polybromobiphenyls, they are a group of manufactured chemicals that consist of polyhalogenated derivatives of a biphenyl core.

Polybrominated diphenyl ethers or PBDEs, are a class of organobromine compounds that are used as flame retardants.

A polyethylene glycol or related compound of the ether-glycol type containing several ether linkages that yields one or more glycols on hydrolysis of these linkages

Polymerised isoprene. Naturally occurring polyisoprene are natural rubber (cis-form) and gutta percha (trans-form). The use of stereospecific catalysts has made possible the manufacture of synthetic cis-polyisoprene and trans-polyisoprene both of which are now available commercially.

A polymer is a large molecule (macromolecule) constructed from many smaller structural units called monomers. When only one species of monomer is used to build a macromolecule, it is known as a homopolymer, two species a copolymer, three species a terpolymer.

A substance which initiates polymerisation and /or controls the formation of the macro molecular structure.

This group of synthetic elastomers is better known under the trade name ‘Thiokol’. Polysulphide rubbers are condensation polymers of sodium polysulphide and dichloro-compounds.

Elastomers resulting from a series of organic reactions, e.g., a polyglycol ester of adipic acid reacted with an aromatic diisocyanate and cured with water, glycol, or further reaction with an aromatic diisocyanate.

Refers to an operation carried out immediately following the cure proper, e.g., post cure inflation of nylon pneumatic tyres. This is often another period of reheating at a high-temperature. This post cure period is implemented after the initial cure has taken place and serves to further stabilise the rubber, ensuring a stronger product for customers. Seals are often post-cured to optimise their stress relaxation properties. See After cure.

A wide variety of additional operations can also be applied to plastic products as they emerge from the die in their extruded form. Some of these operations may be completed by standard or custom devices added inline to the extruder, or as additional steps performed by other staff and equipment at the extrusion facility.

Substances used to preserve foodstuffs, wood, or other materials against decay.

Pressure-sensitive adhesive (PSA, self-adhesive, self-stick adhesive) is a type of non-reactive adhesive which forms a bond when pressure is applied to bond the adhesive with a surface. No solvent, water, or heat is needed to activate the adhesive. It is used in pressure-sensitive tapes, labels, glue dots, note pads, automobile trim, and a wide variety of other products.

A general term applied to the variety of operations required to convert a raw elastomer into finished products. See Calendaring, Compounding, Curing, Extrusion, Mastication, Mixing, Spreading.

Registration, Evaluation, Authorisation and Restriction of Chemicals is a European Union regulation dating from 18 December 2006. REACH addresses the production and use of chemical substances, and their potential impacts on both human health and the environment.

An abbreviation for room temperature vulcanisation.

The time required by the compound in question to reach a given state of cure compared to the time required by a standard compound to reach the same state of cure.

Compounding ingredients which bring about reinforcement of rubbers. The most widely used are Carbon Black, silica and silicates, zinc oxide, treated whitings, high styrene resins and phenolic resins.

Resilience is the ability of a material to absorb energy when it is deformed elastically and release that energy upon unloading. The technical term used to describe “bounce” or “snap”. Increasing resilience means an increasing “bounciness”. Measured on standard test equipment (commonly examples being Dunlop, Tripsometer, Lupke, and Rebound). Standard test pieces are struck by a standard ‘hammer’ and the ‘bounce back’ of the hammer measured. This is expressed as a percentage of the flight path of the hammer.

Vulcanisation of elastomers effected by the incorporation in the compound of certain polymeric resins derived from the condensation of formaldehyde with 4-alkyl phenols. Most frequently used with butyl and EPDM compounds for enhanced heat resistance.

A compounding ingredient which retards the rate of cure of a rubber, thus increasing processing safety.

Rheology is the branch of physics that deals with the deformation and flow of matter, especially the non-Newtonian flow of liquids and the plastic flow of solids.

An abbreviation for Restriction of Hazardous Substances. RoHS, also known as Directive 2002/95/EC, originated in the European Union and restricts the use of specific hazardous materials found in electrical and electronic products. All applicable products in the EU market after July 1, 2006 must pass RoHS compliance.

A standard method for measuring the hardness of metals. The hardness is expressed as a number related to the depth of residual penetration of a steel ball or diamond cone (“brale”) after a minor load of 10 kilograms has been applied to hold the penetrator in position. This residual penetration is automatically registered on a dial when the major load s removed from the penetrator. Various dial readings combined with different major loads, give “scales” designated by letters varying from “A” to “H” the “B” and “C” scales are most commonly in use.

Rotary die cutting is a versatile fabrication process suitable for applications ranging from simple die cut labels and gaskets to complex, multi-layered parts. It can be used on a wide range of materials, including thin metal, plastic, paper, foam, fabric, and laminates, and offers several different die cutting capabilities, such as metal-to-metal, kiss cutting, and perforating. Rotary a machine which produces material for use in veneering by rotating a log longitudinally against a blade.

Trade name for an apparatus used for the continuous vulcanisation of belting, matting, etc.

The name ‘rubber’ derives from the fact, noted in 1770 by Joseph Priestly the English chemist, the caoutchouc would erase or ‘rub-out’ lead pencil marks. Priestly did not actually name it rubber, but at some time between 1770 and 1778 the term became popular.

An abbreviation for styrene-butadiene rubber.

An abbreviation for Standard Malaysian Rubber.

Undesired premature vulcanisation of a rubber compound during the processing operation of mixing, extruding, or calendaring. See Heat History.

Applied to a rubber compound, dough or cement which will vulcanise at room temperature. The time taken to effect vulcanisation may be as short as 30 minutes or as long as several days.

A preliminary or pre-cure given to a product or part of a product, e.g., a moulding may be given a semi-cure in a press and the cure completed in open steam; a thick section of a product may be semi-cured before assembly to the product; a component mat be semi-cured to reduce the flow during the subsequent vulcanisation of the product.

The Shore Scale, is the preferred method for measuring the hardness of rubbers/elastomers and is also commonly used for ‘softer’ plastics such as polyolefins, fluoropolymers and vinyls. The Shore A Scale is used for ‘softer’ rubbers while the Shore D Scale is used for ‘harder’ ones.

Change in dimensions of an unvulcanised rubber (calendared sheet or extruded section) on cooling from the processing temperature. See Coefficient of Thermal Expansion (volume).

Silane is an inorganic compound with chemical formula, SiH4, making it a group 14 hydride. It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid.[5] Silane is of practical interest as a precursor to elemental silicon.

An elastomer of the silicon family. (See Silicones). It is a rubber-like material composed of silicone – itself a polymer – containing silicon together with carbon, hydrogen and oxygen. Silicone rubbers are widely used in industry and there are multiple fomulations. Silicone rubbers often contain fillers to improve properties and/or reduce cost. Silicone rubber is a polyorganosiloxane, the backbone structure consisting of alternating silicone and oxygen atoms with organic groups, usually methyl, vinyl, or phenyl radials, attached to the silicone member.

A quality-control methodology developed in 1986 by Motorola intended to improve business processes by greatly reducing the probability that an error or defect will occur.

In moulding rubber articles, it is necessary to use a blank of slightly greater volume than the mould cavity. This excess is forced out at the mould register during vulcanisation and is known as ‘spew’. It is usually accommodated in the spew groove. The term spew is also applied to the rubber extruded through release holes drilled at the edges of some extruder dies to even up the flow of rubber and produce an accurate section.

A channel cut in the register of a mould to accommodate the spew.

Like foam rubber, sponge rubber has a cellular structure. There are two main types of sponge rubber – open-cell and closed-cell. Open-cell sponge rubber contains open, interconnected bubbles that allow the passage of air, water, and other chemicals (as long as the material is not compressed). Closed-cell sponge rubber contains unconnected, balloon-like cells that hold nitrogen gas, preventing the passage of these substances at low pressures. To produce open-cell sponge rubber, sodium bicarbonate is added to other ingredients in a heated mould. As the uncured sponge rises like a cake, the baking soda creates open, interconnected cells. To make closed-cell sponge rubber, a chemical powder that decomposes under heat and pressure is added. The nitrogen gas that’s released helps to give closed-cell sponge rubber its strong compression set and recovery characteristics.

The degree of vulcanisation of a rubber compound is assessed technically by the indefinite terms of under cure, correct cure, optimum cure and overcure. It may be given precision by (a) measurement of stress-strain relationship of a range of cures, (b) measurement of the modulus at 100% elongation, © measurement of the volume swelling in benzene, or (d) by the use of instruments such as the oscillating disc rheometer and the moving die rheometer.

Styrene-Butadiene Rubber describe families of synthetic rubber derived from Styrene and Butadiene. These materials have good abrasion resistance and good aging stability when protected by additives.

In adhesion, the substrate is the surface or material to which the adhesive is applied.

A cutting agent which splits off active sulphur during the vulcanisation reaction. One example is di-morpholino disulphide (Sulfasan R).

Quantifies the disruption of intermolecular bonds that occurs when a surface is created. In the physics of solids, surfaces must be intrinsically less energetically favourable than the bulk of a material (the molecules on the surface have more energy compared with the molecules in the bulk of the material), otherwise there would be a driving force for surfaces to be created, removing the bulk of the material. The surface energy may therefore be defined as the excess energy at the surface of a material compared to the bulk, or it is the work required to build an area of a particular surface.

the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.

A convenient term for any material possessing the properties of a rubber but produced from other than natural sources. A synthetic version of natural rubber has been available for many years with the same chemical formula. I.e., cis-1,4-polyisoprene, but it has not displaced the natural form. See also Butyl Rubber, Chloroprene Rubber, Ethylene-Propylene Rubber, Nitrile Rubber, Silicone Rubber and Styrene-Butadiene Rubber.

N-tert-Butyl-2-benzothiazole sulphonamide, accelerator.

Tetraethyl thiuram disulphide, accelerator.

An abbreviation for glass transition temperature.

Polymeric 2,2,4-trimethyl-1,2-dihydroquinoline, antidegradant – staining.

The preferred abbreviation for tetramethylthiuram disulphide to prevent confusion with tetramethylthiuram monosulphide.

The preferred abbreviation for tetramethylthiuram monosulphide.

Another term for French chalk.

Rubber tapping is the process by which latex is collected from a rubber tree.

A measurement of the force required to pull something, such as sheet, hose or tube, to the point where it breaks. The tensile strength of a material is the maximum amount of tensile stress that it can take before failure, for example tearing or snapping.

A copolymer consisting of three monomers polymerised together, e.g., ethylene-propylene dicyclopentadiene terpolymer.

TBZTD, accelerator.

TBUT, accelerator.

TETD, accelerator.

TMTD, accelerator.

Engineering tolerances are the permissible limit or limits of variations in measurements deriving from the base measurement.

A method of moulding rubber products which has certain advantages over compression moulding. The transfer mould has an upper cavity or pot into which the uncured blank is placed. The closing of the mould transfers the rubber through a series of holes (feed ports) into the mould cavity proper.

An abbreviation for TAC, peroxide co-agent.

An abbreviation for TAIC, peroxide co-agent.

A term applied to a class of organic accelerators with a very fast and powerful accelerating action; examples are the thuryam disulphides, dithiocarbamates and xanthates. See TMT, ZDC and ZIX.

Any polymer having more than one bond between two adjacent atoms usually carbon atoms and being capable of adding other atoms at that point to reduce it to a single bond.

In organic compounds the linking of some atoms of the molecule by more than one valency bond i.e., double, or triple bonds.

Abbreviation for vinyl methyl silicone.

The Vickers method is based on an optical measurement system. The Microhardness test procedure, ASTM E-384, specifies a range of light loads using a diamond indenter to make an indentation which is measured and converted to a hardness value. It is very useful for testing on a wide type of materials, but test samples must be highly polished to enable measuring the size of the impressions. A square base pyramid shaped diamond is used for testing in the Vickers scale. Typically loads are very light, ranging from 10gm to 1kgf, although "Macro" Vickers loads can range up to 30 kg or more. See Brinell Hardness.

The unsaturated univalent radical CH2CH. Many vinyl compounds undergo polymerisation forming plastics, fibres, and resins. See Vinyl Chloride.

Viscoelastic materials behave both like a liquid and a solid, exhibiting both viscosity and elasticity. See Viscosity and Elasticity.

This term was originally limited to the chemical reaction of rubber with sulphur to bring about the following effects: (a) reduced thermoplasticity, (b) increased tensile strength and resistance to abrasion, and © reduced solubility in organic solvents. Since many other substances can bring about the changes the term has now been widened to include any treatment which will introduce crosslinks in the rubber matrix.

Any substance which will bring about vulcanisation. Elemental sulphur remains a widely used vulcanising agent, but sulphur-containing substances (such as thiuram disulphides) have important uses. Organic peroxides (benzoyl and dicumyl) and nitroso derivatives (e.g., benzoquinone dioxime) are used in vulcanising certain synthetic elastomers.

Finely divided calcium carbonate obtained from natural sources (chalk, limestone, or marble), or as a by-product of another chemical process-precipitated whiting. Strictly speaking, the term ‘whiting’ should be applied only to ‘material prepared by grinding natural chalk’.

A measure of the ability of a material to withstand changes in length when under lengthwise tension or compression. Sometimes referred to as the modulus of elasticity, Young's modulus is equal to the longitudinal stress divided by the strain.

A four-bowl calender in which rolls 1 and 2 are situated in one horizontal plane and the other two, 3 and 4, in a lower horizontal plane. Roll 3 is below roll 2, 1 and 4 being therefore ‘offset’. See Triangular Calendar.

An abbreviation for Zinc dibenzyl dithiocarbamate, accelerator.

An abbreviation for Zinc dibutyl dithiocarbamate, accelerator.

An abbreviation for Zinc diethyl dithiocarbamate, accelerator.

An abbreviation for zinc dimethyl dithiocarbamate, accelerator.

An activator in rubber compounds containing organic accelerators.

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