Glossary of Terms 


Abrasion - Surface loss of a material due to frictional forces. 

Abrasion resistance - The resistance of a material to loss of surface particles due to friction. 

Accelerated aging - A method in which an attempt is made to produce and measure the effects of natural aging in a shorter period. 

Accelerator (of vulcanization) - Any substance, which hastens the vulcanization of rubber causing it to take place in shorter time or at a lower temperature. In earlier days basic oxides such as limes, litharge and magnesia were recognized as having this function. Nowadays the important accelerators are organic substances containing either nitrogen or sulfur or both. According to potency, or speed of action, accelerators are sometimes classified as slow, medium, rapid, semi-ultra and ultra-accelerators. Most accelerators enhance tensile properties, and many improve age resistance.

Accelerator Ultra - An accelerator which causes very rapid vulcanization, even at comparatively low temperatures. Tetramethylthiuram disulfide is a typical ultra-accelerator. The dislkyldithiocarbamates and xanthates are also ultra-accelerators.

Acid Resistant - Withstands the action of acids.

Acrylonitrile - Cyanoethylene, vinyl cyanide, CH2=CHCN a volatile liquid boiling at 178.50 C, prepared by dehydration of ethylene cyanhydrin and by catalytic addition or hydrogen cyanide to acetylene. Used in co-polymerization with butadiene in the manufacture of Buna N or Nitrile rubbers.

Activator - A substance, which by chemical interaction promotes a specific chemical action of a second substance. Most accelerators require activators to bring out their full effect in vulcanization, e.g., zinc oxide or other metallic oxides; some accelerators require a fat acid, especially with zinc oxide.

Adapters - A "V" shaped ring either male or female to fit together with "V" shaped rings to form a set of adjustable hydraulic packing.

Adhesion - The state in which two surfaces are held together by interfacial forces which may consist of molecular forces or interlocking action, or both.

Adhesion Failure - The separation of two materials at the surface interface rather than within one of the materials itself.

Aging - (1) The irreversible change of material properties after environ- mental exposure for an interval of time; (2) Exposing materials to an environment for an interval of time.

Air Checks - See Air trap below

Air trap - Surface markings or depressions due to trapping air voids in body or part due to entrapped gas between the materials being cured and the mold or press surface.

Air Curing - The vulcanization of a rubber product in air as distinguished from vulcanizing in a press or steam vulcanizer.

Aluminum Seal Rings - Sealing rings for pistons made from high grade aluminum alloy.

Ambient Temperature – The temperature of the atmosphere or medium surrounding the gasket in service.

Amines - Derivatives of ammonia in which one or more or (lie hydrogen atoms is replaced by an alkyl or aryl radical. They are called primary, secondary and tertiary amines according to the number of such substitutions. Example: RNH2, R2NH, AND R3N.

Aniline Point - The temperature in degrees Fahrenheit at which a kerosene, diesel fuel or distillate is miscible with an equal volume of aniline. Low aniline point hydrocarbons tend to swell rubbers to a greater degree than those with a high aniline point.

Anti-Extrusion Rings - Also, called back-up rings or anti-extrusion rings. Used to fit behind rubber O-ring seals to prevent extrusion into the gap between the metal pieces

Antioxidant - Usually organic and nitrogenous. A substance, which inhibits or retards oxidation and certain other kinds of aging. Some antioxidants cause staining or discoloration of the rubber compound on exposure to light and are used only in black or dark-colored goods. Others (phenolic), described as non-staining, are used in white or light-colored goods.

Anti-vibration Mounts - Rubber molded pieces used as padding between a motor and the frame to prevent vibration transfer to the machine to which it is mounted.

AQ Seal - A special purpose hydraulic seal.

Aqueous Solutions – Any fluid solution containing water.

Assortment Kits - A convenient package containing several sizes of the same seal, O-ring or retainer ring.

ASTM – Abbreviation for American Standard for Testing Materials – is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems and services.

Autoclave - A pressure vessel into which materials or articles can be placed and exposed to steam under pressure. It is commonly used for vulcanization.

Automatic U-joints - Also called u-cups, ucups or u cups. A "U" shaped sealing ring made from a strong pliable plastic or rubber.



Benchmark Data - The results of an investigation to determine how competitors and/or best-in-class companies achieve their level of performance. 

Bench Test – A modified service test in which the service conditions are approximated, but the equipment is laboratory equipment and not necessarily identical with that in which the product will be employed.

Backringing - Distortion at the mold parting line usually in the form of wrinkles, folds, tears or indention's. In severe cases may cause over-all dimensional changes.

Baffle Rings - A ring used to slow the flow of fluids along a shaft.

Ball Valve Seats - A Teflon ring shaped to fit against the ball in a flow control valve.

Batch - The product of the one mixing operation in an intermittent process. 

Bearings - A machined or molded plastic ring used as a guide ring or wear ring in a hydraulic cylinder.

Bearing Seals - A seal ring made to snap-fit into a ball, roller or spherical bearing to exclude dust, dirt or trash.

Bellows - A corrugated rubber or plastic piece which can stretch with a shaft to keep the shaft clean.

Belts - A v-belt, flat belt or drive belt made from plastic or rubber.

Bias Angle - (1) Acute angle between the direction of the cut and the diameter of the wrap in the production of wrapping for hose; (2) Acute angle between the direction of the cut and the direction of the cords in the production of fabric plies. 

Bill of Material - Total list of all components/materials required to manufacture the product (BOM).  

Blister - A cavity or sac that deforms the surface of a material. 

Bloom - A liquid or solid material that has migrated to the surface of a rubber, thereby changing appearance. Sometimes confused with surface dust. 

Bond - The union of materials by use of adhesives, usually used in related parts vulcanized after attaching. 

Bonded Seals - A flat steel washer with a rubber sealing ring molded into the center to fit over a bolt to provide a seal.

Bonding Agents - Substances or mixtures of substances that are used for attaching rubber to metal, fabrics or other substrates. Generally, the rubber compound is vulcanized by heat in the process. Cyclized rubber or rubber isomers, halogenated rubber, rubber hydrochloride, reaction product of natural rubber and acrylonitrile, polymers containing diisocyanates, are all used.

Brittleness - Tendency to crack when subjected to deformation. 

Bronze Piston Bearings - Guide rings or wear rings made from bronze to fit on a piston in a hydraulic cylinder.

Bumpers - A rubber or plastic part used to prevent metal-to-metal contact.

Buna N - A general term for the copolymers of butadiene and acrylonitrile. Also commonly referred to as Nitrile. 

Buna S - A general term for the copolymers of butadiene and styrene. 

Burst – A rupture caused by internal pressure.

Bushing - A rubber or plastic spacer to provide a wear surface around a shaft.

Butadiene - CH2=CH-CH=CH2. A gaseous hydrocarbon of the diolefin series, boiling at 5~C. Also known as erythrene, divinyl, pyrollylene, Polymerizable to a synthetic rubber, polybutadiene. Butadiene is the chief raw material for making the synthetic rubbers today. Co polymerized with styrene it yields SBR or GR-S; with acrylonitrile the various Buna N or nitrile synthetic rubbers are obtained.

Butt Joint - Joining two ends of material whereby the junction is perpendicular to the ID of an O-ring.

Butyl - A synthetic rubber of the polybutene type exhibiting very low permeability to gases. 


Calendar – A machine equipped with two or more heavy internally heated or cooled rolls, revolving in opposite directions, which is used for continuously sheeting or flying up rubber compound and fractioning or coating fabric with rubber compound.

Canned Wipers - A wiper or scraper ring for a hydraulic cylinder which has a metal outside diameter so that it can be press-fitted into a housing.

Carbon black - Elemental carbon in finely divided form used to reinforce elastomeric compounds. 

Cast Iron Piston Rings - Piston sealing rings made from cast iron used in hydraulic cylinders.

Catalyst - A chemical in small quantities which accelerates a chemical reaction without itself necessarily becoming part of the final product. 

Cellular Rubber - Rubber products which contain cells or small hollow receptacles. The cells may either be open or interconnecting or closed and not interconnecting. 

Characteristics Matrix - An analytical technique for displaying the relationship between process para- meters and manufacturing stations. 

Checking - The short, shallow cracks on the surface of a rubber product, resulting from damaging action by environmental conditions. 

Checking. Sunlight - The development of minute surface fissures as a result of exposing rubber articles to sunlight, generally accelerated by bending or stretching.

Chemical Resistance - The resistance offered by elastomer products to physical or chemical reactions as a result of contact with or immersion in various solvents, acids, alkalis, salts, etc..

Chevron Packings - Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple "V" shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end.

Chevrons - See Chevron Packing above.

Chloroprene - 2-Chloro-l, 3-butadiene, a volatile, colorless liquid which boils at 59c., synthesized from acetylene. It is used in the manufacture of neoprene, which is obtained by polymerizing chloroprene under suitable conditions.

Cloth both sides CBS - Rubber sheet consisting of a ply of fabric or cloth on each surface, (CDS):  Cloth on just one side

Cloth insert C.I- The abbreviation for cloth- inserted, indicating a sheet of rubber containing one or more plies of fabric covered with rubber. 

Clay - Any naturally occurring mineral substance consisting preponderantly of hydrous aluminum silicates, which divided and mixed with water, yields a more or less plastic mass which can be formed and molded, and which will retain its shape on drying. Clays vary greatly in composition but in their purest forms they approach the composition of Kaolinite, A12O3.2Si2.2H20. They are used as compounding ingredients in rubber, some of them having mild reinforcing properties.

Cold Flow - Continued deformation under stress. 

Coefficient of Expansion - The coefficient of linear expansion is the ratio of the change in length per degree to the length at 0 Celsius. The coefficient of surface expansion is two (2) times the linear coefficient. The coefficient of volume expansion (for solids) is three (3) times the linear coefficient. The coefficient of volume expansion for liquids is the ratio of the change in volume per degree to the volume at 0 Celsius.

Compact Seals - Multi-piece seal sets, generally used as piston seals in a hydraulic cylinder. Made to fit in a limit space, compact piston seals contain a primary sealing component, guide rings and back-up rings in one convenient set.

Compound - A term applied to either vulcanized or unvulcanized mixtures of elastomers and other ingredients necessary to make a useful rubber-like material. 

Compressibility - The quality or state of being compressible.  In the case of gasketing, it is the percent loss of thickness when subject to a given load


Compression Deflection Characteristics - The tests for compression-deflection characteristics constitute methods of compression stiffness measurement. One compression test involves the determination of a load required to case a specified deflection, and another is a compression test in which a specified weight or compressive force is placed on the specimen and the resulting deflection is measured and recorded.

Compression Set - The residual decrease in thickness of a test specimen measured 30 minutes after removal from a suitable loading device in which the specimen has been subjected for a definite time to compressive deformation under specified conditions of load application and temperature. Method A measures compression set of vulcanized rubber under constant load. Method B employs constant deflection.

Compression Sheet - A gasketing material primarily containing fibers, rubber and fillers manufactured on a special calendar, known as a “sheeter” in such a manner that the compound is caused to build up under high load as an oriented sheet on one roll of the sheeter

Conductive - To conduct or transmit heat or electricity. 

Contact stain - Discoloration of a product by another material or by a rubber article in the area directly touching it. 

Copolymer - A polymer consisting of two different monomers chemically combined. 

Copper Seal Rings - Rings made from thin copper formed over fibrous filler to seal in high temperature.

Count – The number of warp ends, or the number of filling picks, or both, in a square inch of fabric

Crazing - A surface effect on rubber articles characterized by many minute cracks. 

Creep - The deformation, in either cured or uncured rubber under stress, which occurs with lapse of time after the immediate deformation. 

Creep relaxation – A transient stress-strain condition in which strain increases concurrently with the decay of stress. More simply put, it is the loss of tightness in a gasket measurable by torque loss.

Cross Section - An O-ring as viewed if cut at right angles to the axis showing internal structure. 

Crush Washers - A washer made to be crushed to form a seal.

Cup Packings - Sealing devices made in the shape of a cup with outer lips curved upward usually made from rubber, fabric reinforced rubber or polyurethane.

Cure - The act of vulcanization. See Vulcanization. 

Cushioning Seals - Sealing rings mounted into a cylinder to cushion the stroke or prevent metal to metal contact.

Custom Molded Products - Special shaped parts molded from rubber or plastic made to fit the machine or device it is used in.

Cut - The distance between cuts or parallel faces of articles produced by repetitive slicing or cutting of long pre-shaped rods or tubes such as lathe cut washers. 

Crystallinity - Stretched natural rubber forms a high oriented state and shows X-ray diffraction patterns and other properties common to truly crystalline materials. The amorphous and crystalline regions are not mechanically separable phases, but the same molecule may at the same time have part of its length in a crystalline, and the remainder in an amorphous region.


Denier - A yarn sizing system for continuous filament synthetic fibers.  The denier of filament yarn is the weight in grams of 9000 meters of that yarn

Density - The ratio of mass of a body to its volume or mass per unit volume.  For ordinary practical purposes, density and specific gravity may be regarded as equivalent

Design Failure Mode and Effects Analysis (DFMEA) - An analytical technique used by a design responsible engineer/team as a means to assure, to the extent possible, that potential failure modes and their associated causes/mechanisms have been considered and addressed. 

Design for Manufacturability and Assembly - A simultaneous engineering process designed to optimize the relationship between design function, manufacturability; and ease of assembly. 

Design Information Checklist - A mistake proofing checklist designed to assure that all important items are considered in establishing design requirements. 

Design Reviews - A proactive process to prevent problems and misunderstandings. 

Design Validation - Testing to ensure that product conforms to defined user needs and/or requirements. Design validation follows successful design verification and is normally performed on the final product under defined operating conditions. Multiple validations may be performed if there are different intended uses. 

Design Verification - Testing to ensure that all design outputs meet design input requirements. Design verification may include activities such as: 

Design Review - Performing Alternate Calculations - Understanding Tests and Demonstrations - Review of Design Stage Documents Before Release 

Diaphragm Packing - A packing that spans a gap between a moving and stationary member, permitting limited movement of the former

Diaphragm Sheet - PTFE or sheet rubber (generally fabric reinforced) from which flat diaphragms are cut

Dielectric strength - The measure of a product's ability to resist passage of a disruptive discharge produced by an electric stress; the voltage that an insulating material can withstand before breakdown occurs, 

Discs - Flat, round saucer shaped pieces made from rubber or plastic.

Dished Diaphragm - A molded diaphragm in which the entire center is depressed below the plane of the rim

Disperse - To cause particles or molecules of matter to separate and become uniformly scattered throughout a medium. In a rubber compound, the particles of compounding ingredients are dispersed in the rubber. In latex, rubber globules are dispersed in an aqueous medium.

Distributor Seals - Sealing rings used to seal in oil and seal out dust, dirt or trash on an automobile engine electric spark distributor.

Double Acting Seals - Seal rings which seal in two directions, on the push and the pull stroke of a hydraulic or pneumatic cylinder.

Drift - (1) the continued deformation under strain (2) the change in rubber hardness after a specified period of time

Drum Cure - A method of vulcanizing rubber in which the product is wrapped around a drum and cured in hot air or steam, usually with a separator or wrapping jacket.

Duck - A compact, firm, heavy, plain weave fabric made from cotton or synthetic fibers, or a combination of both. Duck is also known as canvas, army duck, belt duck harvester duck, hose duck and shoe duck. 

Dumb-Bell (Test-Piece) - In the physical testing of rubber, a strip test-piece is used that is shaped like a dumb-bell, i.e., constricted in the middle and flaring out at the ends, as distinguished from circular or ring test-piece. The dumb-bell is the most commonly used form or test-piece. Dimensions are set by ASTM standards.

Duocone Seals - A special cone-shaped sealing ring.

Durability - The probability that an item will continue to function at customer expectation levels, at the useful life without requiring overhaul or rebuild due to wear out. 

Durometer - An instrument for measuring the hardness of vulcanized rubber and plastic. See Shore 

Durometer - The most common Durometer. Type A or A-2 is an instrument for determining the hardness or rubber by measuring its resistance to the penetration (without puncturing) of a blunt indenter point impressed on the rubber surface against the action of a spring; a hand and special scale indicate the resistance to penetration 01. "hardness". The scale reads from zero (0) to 100, zero (0) being very soft and 100 being very hard. The Type D durometer has a sharp indenter point and is used to measure varying degrees of hard rubber up to ebonite.

Dust Seals - Seals used to exclude dust from a machine or device.



Elasticity - A property of any material which makes it tend to recover its original dimensions after removal or the force which deforms it.

Elastic Modulus - The value of the load (in pounds per square inch of original cross-section) required to give an intermediate elongation, is usually called the modulus at that elongation. The expression used is "modulus at 300 percent elongation." Tensile-stress observations of this sort arc exceedingly useful in characterizing a particular compound, since by indicating the position and shape of the stress-curve. They show the relative toughness of the vulcanizate.

Elastomer - An elastic rubberlike material which, in the vulcanized state, at room temperature can be stretched repeatedly to at least twice its original length and which, upon release of the stress, will immediately return to approximately its original length

Elongation - Extension produced by a tensile stress. 

Elongation at break -- the elongation of a test-piece at the moment of rupture, usually expressed as percentage of the original length.

Embrittlement - A rubber compound becoming brittle during low or high temperature exposure or in the process or aging.

EMI (Electromagnetic Interface) - Any conducted radiated or magnetically induced voltage that degrades, obstructs, or repeatedly interrupts the desired performance of electronic equipment. 

Encapsulated O-rings - A rubber O-ring with a thin jacket of PTFE or Teflon surrounding the softer core material, which allows it to be used in chemical applications.

Excluders - Also called wipers or scrapers - used in a hydraulic or pneumatic cylinder to exclude and scrape the rod clean.

Expanded Rubber - Cellular rubber having closed cells made from a solid rubber compound. 

Expansion - The increase in any linear dimension or volume

Extraction Test - A test involving the separation of certain components from a solid by dissolving them in a liquid solvent under suitable conditions

Extrusion - 1) Distortion, under pressure, of portion of seal into clearance between mating metal parts. 2) Material, under pressure, which is forced through the opening of a die in order to obtain a desired cross-sectional shape.



Fabric Count - The number of warp ends per inch, and the number of filling picks per inch

Fabric impression - A pattern in the rubber surface formed by contact with fabric during vulcanization (usually during Drum Curing)

Face Seals - Rubber rings used like a gasket between two flat pieces of metal.

Failure Modes Analysis (FMA) - A formal, structured procedure used to analyze failure mode data from both current and prior processes to prevent occurrence of those failure modes in the future. 

Fastener Seals - See Bonded Seals.

Fatigue - The weakening or deterioration of a material occurring when a repetition or continuous application of stress causes strain

Feasibility - A determination that a process, design, procedure, or plan can be successfully accomplished in the required time frame. 

Fibre Seal Rings - Aa gasket or other die cut, water-jet cut or formed ring used to seal between two surfaces.

Filler - Any compounding material, usually in powder form, added to rubber in a substantial volume to improve quality or lower cost. The most important reinforcing filler is carbon black. The most important inert filler, diluent or extender is whiting.

Finish, Mold - The quality or appearance of the machined surface of a mold. 

Finish, Product - The quality or appearance of the surface of a rubber product. 

Finite Element Analysis - A technique for modeling a complex structure. When the mathematical model is subjected to known loads, the displacement of the structure may be determined. 

Flange Packings - A pipe flange gasket.

Flange Seals - A seal used on the bolt-up flange on a hydraulic system - usually on the hose fitting or pipe flanges.

Flash - Excess rubber on a molded product resulting from cavity overflow at the parting lines where the mold sections are separated. 

Flex cracking - A cracking condition of the surface of rubber articles such as tires and footwear, resulting from constantly repeated bending or flexing in service.

Flex Life - The relative ability of a rubber article to with stand cyclical bending stresses

Flow Marks - Surface imperfections due to improper flow and failure of stock to knit or blend with itself during the molding operation. 

Friction - Resistance to motion due to the contact of surfaces.

Friction Coating - A rubber covering applied to the weave of a fabric simultaneously with impregnation

Full-face Gasket - A gasket covering the flange surface and including bolt holes



Gap Seals - A seal ring used to seal between the gaps of metal or plastic.

Gasket - A flat, non-moving, compressible rubber-like device squeezed between two flat surfaces forming a static seal. Gaskets can be made from homogeneous rubber, fabric reinforced rubber, fibrous materials with rubber binders, flexible graphite, PTFE and many other materials. Some gaskets are made from a combination of metal and fibrous materials and some are all metal. An o-ring, while not flat is also referred to as a gasket at times.

Gate - (rubber injection or transfer mold) - The orifice used to control the flow of rubber, and through which a shaped cavity in a mold is filled with rubber. 

Gland Bearing Rings - Also called guide rings or wear rings used as a bearing surface for the rod of a hydraulic ram or cylinder.

Gland Seals - Seals or packings used the main sealing device in a ram or cylinder.

Glandsele - The brand name of a type of rod seal.

Glass Temperature (Tg) - The temperature at which a rubber becomes glass-like. a more recent name for Second Order Transition point.

Glass transition point - Temperature at which a material loses its glass-like properties and becomes a semi-liquid. 

Globe Valve Discs - Teflon rings used to seal in a globe valve.

Glyd Ring - Also known as wear rings or guide rings - made from plastic, Teflon or soft metal to act as a bearing surface for a cylinder rod.

Grain - The unidirectional orientation of rubber or filler particles occurring during pro- cessing (extrusion, milling, calendaring) resulting in anisotropy of a rubber vulcanizate. 

Graphited throughout - Braided from yarns which have received a prior application of graphite, or, in the case of braid-over-braid construction, an application to each successive braid

Grease Seals - Also called oil seals, rotary seals or shaft seals. Made of rubber to seal grease in a housing with a rotating shaft.

Green strength - (1) The resistance to deformation of a rubber stock in the uncured state. (2) Uncured adhesion between plied or spliced surfaces. 

Grommets - A rubber ring used to fit into a hole in sheet metal aloow wires, shafts or rod to exit the housing without touching the metal.

Guiding Elements - Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods.

Guide Rings - See also wear rings, guide rings or bearing rings. Usually made from a form of Teflon or PTFE.



H-ring - Also called H-Wiper. An "H" shaped rod wiper ring made from NBR or polyurethane for a hydraulic or pneumatic cylinder.

Hardness - The relative resistance of rubber to the penetration (without puncturing) of a blunt point impressed on its surface.

Hat Packings - Usually made from leather, it is used as a rod seal or ram seal in a hydraulic cylinder.

Head - The height of a column or body of fluid above a given point expressed in linear units.  Head is often used to indicate gage pressure.  Pressure is equal to the height times the fluid’s density

Heat history - The accumulated amount of heat a rubber stock has been subjected to during processing operations, usually after incorporation of the vulcanizing agents. Incipient cure or scorch can take place if heat history has been excessive. 

HiClean - A brand name for rod wipers.

High Pressure Seals - Seals to be used in high pressure hydraulic applications made from Teflon, urethane or fabric reinforced material.

Homogeneous - Products that are o uniform composition throughout

Hydraulic Cylinder Kits - A selection of seals used to completely repair a cylinder or ram.

Hydraulic Packings - Packing rings used in a hydraulic ram or cylinder,

Hydrolysis - Chemical decom- position of a substance involving the addition of water. 

Hysteresis (a) - The heat generated by rapid deformation of a vulcanized rubber part. It is the difference between the energy of the deforming stress and the energy of the recovery cycle. 

Hysteresis (b) - Hysteresis or energy loss is the difference between the work input and the work output as measured under the curves or extension and retraction (stress and elongation curves). The difference becomes heat build-up.



ID - Symbol for inside diameter

Insert - A part, usually metal, which is placed in a mold and appears as an integral part of the molded product. 

Internal Mixer - An enclosed mixing machine for rubber or other suitable material, inside or which are two (2) heavy mixing rotors which revolve in opposite directions with a small clearance between themselves and tine enclosing walls. The mixing chamber is jacketed or otherwise arranged for water-cooling, and is provided with a feeding hopper which can be closed by means of a pneumatically operated, vertical ram. Leading examples are the Banbury, the Boiling and the Shaw mixers.

Interstices - Openings, such as between fibers in a cord, or threads in a woven or braided fabric

IRHD (International Rubber Hardness) - For complete definition see ASTM D 1415-68 Standard Method of Test for International Hardness of Vulcanized Natural and Synthetic Rubbers. 

Isolators - A term used to describe a bearing seal - which replaces an oil seal providing more reliable sealing.



Joint - An interstice (crevice) between rigid members of a fluid container



Kaizen - Taken from the Japanese words kai and zen where kai means change and zen means good. The popular meaning is continual improvement of all areas of a company not just quality. 

Kantseal - A brand name of a special seal.

Knit mark - Where raw stock did not unite into a homogeneous mass during the vulcanization. This is also called poor knitting. See Flow marks 

K-Type Fluid Seals - A "K" shaped sealing ring used in a hydraulic or pneumatic cylinder.



Labyrinth Seals - A non-contacting, rotary seal with a series of internal grooves to divert the flow and lubricating fluids in the direct of its source used on a shaft.

Lantern Rings - A spacer ring with grooves and port holes used in the stuffing box of a pump or other rotating equipment utilizing braided packings, to allow an outside source of lubrication.

Lathe Cut Seals - A seal or gasket ring cut square on a lathe machine. 

Leakage Rate - The quantity of media passing through and/or over the faces of gaskets in a given length of time. i.e. cubic feet per minute, cubic centimeters per minute, milliliters per hour or parts per million

Lip Packing & Rings - Could be the description of a u-cup or of an oil seals. A seal with a lip design to provide sealing.

Lip Seals - Seal rings having lips to provide a flexible, dynamic sealing against a shaft.

Loaded Lip Seals - A hydraulic u-cup which has an O-ring or quad ring fitted into the u-shaped groove to assure good low pressure sealing on a reciprocating shaft.

Loaded U-Cups - Same as loaded lip seals.

Low Film - A thin film of oil on the shaft of a hydraulic cylinder.

Low temperature flexibility - The ability of a rubber product to be flexed, bent, or bowed at specified low temperature without loss of serviceability.



Magnesia - (a) Heavy calcined: Magnesium oxide by calcination of magnesite (natural magnesium carbonate), and then ground for use as a compounding ingredient for molded goods and hard rubber. (b) Light calcined: Magnesium oxide by calcination of purified magnesium carbonate and/or magnesium hydroxide. It has a fine particle size and a bulk factor of 10 to 30 pds. per cubic ft. Used chiefly in neoprene stocks. (c)Extra light calcined: Prepared similarly by calcination of magnesium carbonate, but with a bulk factor of 4 to 6 pds. per cubic ft. Used chiefly in neoprene stocks.

Maintainability - The probability that a failed system can be made operable in a specified interval or downtime. 

Mandrel - A bar, serving as a core, around which rubber is extruded, forming a center hole. 

Master Batch - A preliminary mixture of rubber and one or more compound ingredients for such purposes as more thorough dispersion or better processing, and which will later become part of the final compound in a subsequent mixing operation. 

Masticate - To work rubber on a mixing mill or in an internal mixer till it becomes soft and plastic. To break down. MASTICATOR - A machine for plasticizing rubber by mechanical work.

Matte Finish - A dull surface, as opposed to a smooth plate finish

Metal O-rings - An O-ring usually made from hollow stainless-steel tubing, with a small vent hole.

Micro-voids - The spaces in a gasket, on a micro level, that allow media permeation

Mill - A machine with two horizontal rolls revolving in opposite directions used for the mastication or mixing of rubber. 

Mirror finish - A bright, polished surface

Mixing - The process of incorporating the ingredients or a rubber compound into the rubber, usually done on a mixing mill or in an internal mixer. The mixing process consists in (1) breaking down the rubber, (2) gradual incorporation or compounding ingredients, (3) final working of the rubber after all ingredients are in, and (4) removing the mixed compound from the mill in sheets.

Modulus - The ratio of stress to strain. In the physical testing of rubber, the load necessary to produce stated percentage of elongation, compression or shear. 

Modulus - In the physical testing of rubber, the ratio of stress to strain, i.e., the load in pounds per square inch or kilos. per square cm. of initial cross-sectional area necessary to produce a stated percentage-elongation. It is a measure of toughness, is influenced by pigmentation, state of cure, quality or rubber and other factors.

Mold Register - Means used to align the parts of a mold. 

Mooney scorch - A measure of the incipient curing characteristics of a rubber compound using the Mooney viscometer. 

Mooney Viscometer - A laboratory testing machine for measuring the plasticity of raw rubber or unvulcanized rubber compounds. A knurled steel rotor disc winch is centrally embedded iii the heated rubber specimen firmly held in a cavity under pressure is caused to rotate at a low speed (2 rpm). The resistance offered by the plastic rubber mass to the rotation of the rotor disc is the measure of the plasticity of the rubber. The machine is also used to determine the scorch characteristics of rubber mixes.

Mooney viscosity - A measure of the viscosity of a rubber or rubber com- pound determined in a Mooney shearing disc viscometer. 

Mounts - A rubber molded part used as a motor mount or to mount device against a frame without allowing vibration to pass through the mounting.

“M" factor - The factor that provides the additional preload capability in the flange fasteners to maintain sealing pressure on a gasket after the internal pressure is applied to the joint



Nebar - A special type of gasket material used in electrical transformers.

Neoprene - Synthetic rubber made by polymerizing 2-chlor-1, 3-butadiene. Neoprene compounds are rioted for their resistance to oil, sunlight and ozone. There are various types, most of which are vulcanizable without the use or sulfur.


Nerve - The elastic resistance of unvulcanized rubber or rubber compounds to permanent deformation during processing. 

Nilos Rings - A special seal ring.

Nitrile Rubber - A generic term comprising the various copolymers of butadiene and acrylonitrile. the copolymers vary essentially in butadiene-acrylonitrile ratios, Mooney values and staining properties. They are resistant to solvents, oils, and greases and to bent and abrasion. Some trade names are Chemigum, Krynac, Nipol, Hycar, and Paracril. The Germans first produced the nitrile rubbers and called them Buna N and Perbunan.

Non-Blooming - The absence of a bloom. 

Novathan - A name for a type of polyurethane sealing material.





OD - Symbol for outside diameter

Oil Resistance - Ability to withstand swelling by a specified oily liquid for specified time and temperature, expressed as percentage swelling or volume increase of specimen. Oil Resistance - as applied to vulcanized elastomer compositions: resistance to change in size and shape and resistance to loss in physical (mechanical) properties due to contacts with or immersion in an oil.

Oil Resistant - Ability of a vulcanized rubber to resist the swelling and deteriorating effects of various type of oils. 

Oil Seals - Also called grease seals, rotary seals or shaft seals. Made of rubber to seal grease in a housing with a rotating shaft.

Oil Swell - The change in volume of a gasketing product resulting from contact with oil

Open Cell - A cell not totally enclosed by its walls and hence interconnecting with other cells. 

Open Steam Cure - A vulcanization process that takes place under direct steam pressure in an autoclave. It is used where direct pressure molding is not possible. In -the case of vulcanization of sheeting, or coated fabrics, rolls of product are wound onto steel drums (with suitable interleaf) which are placed in the autoclave for cure. Some tubing arid shaped products are placed on pans for extra curing.

Optimum Cure - State of vulcanization at which maximum desired property is attained. 

Opti-Seal - A special seal ring to provide optimum sealing.

O-rings - O-ring seals are circular rings of various cross-sectional configurations installed in a gland to close off a passageway and prevent escape or loss of a fluid or gas. An O-ring is specified by three of its features: its dimensions, material, and hardness. Material and hardness specify the elastomeric compound and Shore A (durometer) hardness of the compound that is used to manufacture the O-ring. An O-ring's dimensions are described by stating its inside diameter (I.D.) and its cross-section. Designing for O-rings depends on three major and interrelated variables: the operating conditions or environment the seal will experience, the gland geometry into which the seal will be installed and the three variables account for the fact that there are so many different types of seals and applications.

Overcure - A state of excessive vulcanization resulting from overstepping the optimum cure, i.e., vulcanizing longer than necessary to attain full development of physical strength. Manifested by softness or brittleness, and impaired age resisting quality of the vulcanizate.

Oxidation - Active oxygen organic materials. This is called oxidation. Rate of degradation will increase with rising temperatures.

Ozone - An allotropic from oxygen, (03), produced by (he actions of electrical discharges in air. It is a gas with a characteristic odor, and Is a powerful oxidizing agent. Rubber compounds in a stretched condition are susceptible to the deteriorating action of ozone in the atmosphere, which results in a cracked condition.

Ozone cracking - The surface cracks, checks, or crazing caused by exposure to an atmosphere containing ozone.



Packaging - A unit that provides protection and containment of items plus ease of handling by manual or mechanical means. 

Packing - An adjustable sealing device on a ram, valve stem or pump shaft --- old technology and leakage is required for lubrication. If packing leaks, it is simply tightened slightly to 'control' the leakage. For pumps and valves, packings can be rope-like, braided into continuous lengths and then cut to size to fit a shaft. For hydraulic applications, v-shaped fabric reinforced rubber rings are used. Early hydraulic packings were made from leather. For a rubber O-ring, that particular item can be found called a seal, a gasket and a packing ring - even in U.S. government technical specifications dating back 50 years.

Pads - A rubber part used as an anti-vibration device.

Pan Based Carbon - A carbon fiber derived from the carbonization process of a ply acrylonitrile fiber in an inert gas

Paper Finish - That finish resulting from vulcanizing in contact with paper

Parachute Packings - Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple "V" shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end.

Parbacks - A back-up ring with a concave shape on one side, used as an anti-extrusion ring for an O-ring.

Permanent set - The amount by which an elastic material fails to return to its original form after deformation. 

Permeability - To permit passage of gas through the molecular structure of a given material. 

Pick - An individual filling yarn of a fabric or jacket

Piston Bearing Rings - Also called guide rings, wear rings, piston guide rings.

Piston Guide Rings - Also called guide rings, wear rings, piston rings usually made from nylon or POM.

Piston Rings - Any ring used on the piston of a hydraulic or pneumatic cylinder.

Piston Seals & Packings - Any seal or packing ring used on the piston of a hydraulic or pneumatic cylinder.

Piston T-Seals - A "T" shaped rubber seal, with back-up rings of a harder material on each side, used as a piston seal.

Pitch Based Carbon - A carbon fiber derived from the carbon residue found at the bottom of a cat cracker in a refinery

Plasticity - (1) A measure of the resistance to shear of an unvulcanized elastomer; (2) A tendency of a material to remain deformed after reduction of the deforming stress to or below its yield stress. 

Plasticizer - A substance that softens or plasticizes another substance through its solvent action.

Plunger Pump Seals - Packing seal rings used to seal the plunger of a reciprocating pump.

Plunger Seals - Sealing rings used on a plunger.

Plugs - A cone shaped rubber part used to be forced into a tube end or hole to make a complete seal.

Pneumatic Seals - Any seal or packing ring, usually flexible rubber, used to seal against compressed air instead of hydraulic fluid or other liquid.

Pock marks - Uneven blister-like elevations, depressions, or pimpled appearance. 

Poisson's Ratio - The ratio of lateral concentration per unit of diameter to longitudinal extension per unit of length in a bar of material longitudinally stressed. For a body which does not change its volume on deformation, it is 0.5. For metals, the ratio is usually considerably less than 0.5. In the case of vulcanized rubber, pure gum, having practically no volume change on extension, shows a ratio of approximately 0.5 for small deformations; compounded rubber may increase in volume on extension, consequently the ratio drops below 0.5. For rubber the ratio is constant only for small extensions.

Polymer (a) - A material formed by the joining together of many (poly) individual units (mar) of a monomer. 

Polymer (b) - A polymer is a very long chain of units of monomers prepared by means of an addition and/or a condensation polymerization. The units may be the same or different. There are copolymers, dipolymers, tri- or terpolymers, quadripolymers, high polymers, etc...

Porosity - The presence of numerous small holes or voids. 

Post cure - Heat or radiation treatment, or both, to which a cured or partially cured thermosetting plastic or rubber composition is subjected to enhanced the level of one or more properties. 

Preliminary Bill of Material - An initial Bill of Material completed prior to design and print release. 

Preliminary Process Flow Chart - An early depiction of the anticipated manufacturing process for a product. 

Press-in Wipers - A wiper or scraper ring for a hydraulic cylinder which has a metal outside diameter so that it can be press-fitted into a housing.

Pressure - (No, Low, Poor) - May refer to inadequate pressure in mold/press, oven heater or autoclave during Cure. Symptoms may be porosity, unfills, blister, low adhesions, etc...

Pressure-Absolute - The pressure above zero absolute i.e. the sum of atmospheric and gage pressure

Pressure-Atmospheric - Pressure exerted by the atmosphere at any specific location.  (Sea level pressure is 14.7lbs/sq. in. absolute)

Pressure Gage - Pressure differential above or below atmospheric pressure (Expressed as lbs/sq. in. or P.S.I.G)

Process Failure Mode and Effects Analysis (PFMEA) - An analytical technique used by a manufacturing responsible engineer/ team as a means to assure that, to the extent possible, potential failure modes and their associated causes/mechanisms have been considered and addressed. 

Processing Aids - Waxes, low molecular weight polyethylene, metal soaps, petroleum oils, and other agents which dissolve or lubricate rubbers, soften them and act as processing aids.

Product Assurance Plan - A part of the Product Quality Plan. It is a prevention-oriented management tool that addresses product design, process design, and when applicable software design. 

Production Trial Run - Product made using all production tools, processes, equipment, environment, facility; and cycle time. 

Protectors - A rubber or plastic cap or cup shaped ring used to protect threads or fragile items during shipping or assembly.

Proto-Types - A part that is made during the design process to determine the feasibility or suitability of a project.

PSI - The abbreviation of pounds per square inch

PTFE - The abbreviation for Polytetrafluoroethylene.  DuPont’s trademarked name for this is Teflon

Pusher Rings - A ring that fits against another sealing device to push it in order to activate it or energize it in the absence of pressure or in low pressure applications.

P x T Value - A numerical value resulting from the multiplication of the internal pressure and the temperature of the fluid involved.  In English system, usually psi x F = PTValue




QPL - Abbreviation for Qualified Products List (associated with US Government specifications)

Quality Planning Sign-Off - A review and commitment by the Product Quality Planning Team that all planned controls and processes are being followed.



Radial Shaft Seals - Also called grease seals, rotary seals or shaft seals. Made of rubber to seal grease in a housing with a rotating shaft.

Rebound - Rebound is a measure of the resilience, usually as the percent- age of vertical return of a body which has fallen and bounced. 

Rebound test - Method of deter- mining the resilient properties of vulcanized rubber, by measuring rebound of a steel ball or pendulum falling from a definite height onto a rubber sample. 

Recovery - The degree to which a product returns to its normal dimensions or shape after being distorted

Recovery (gasketing) - The increase in thickness of a gasket after a load is removed

Register - The accurate matching of the plates of a mold. 

Reinforcing Agent - In rubber compounding, a finely-divided substance or filler which, when properly dispersed in rubber, produces improved physical properties in the vulcanized product, i.e., greater energy of resilience, greater resistance to abrasion, higher modules of elasticity and tensile strength Certain grades of furnace blacks are the most important reinforcing agents for black stocks. For light-colored stocks, calcium silicate, precipitated calcium carbonates, silica and clay are the most commonly used.

Reliability - The probability that an item will continue to function at customer expectation levels at a measurement point, under specified environmental and duty cycle conditions. 

Reproducibility - The variation in the average of measurements made by different operators using the same gage when measuring identical characteristics of the same parts. 

Resilience - The property of a material that enables it to return to its original size and shape after removal of the stress which causes the deformation. 

Retarder - Any substance whose presence ill relatively small proportion retard a chemical reaction. Specifically, a substance which when added in small proportion to a rubber compound, retards the rate of vulcanization. An anti-scorching agent; examples, phthalic anhydride, salicylic acid.

Reversion - (1) A deterioration of physical properties that may occur upon excessive vulcanization of some elastomers, evidenced by a decrease in hardness and tensile strength, and an increase in elongation; (2) A similar change in proper- ties after air aging at elevated temperatures. Natural rubber, butyl, polysulfides and epichlorohydrin polymers exhibit this effect (extreme reversion may result in tackiness). Most other polymers will harden and suffer loss of elongation on hot air aging. 

Reversion - The softening of some vulcanized rubbers when they are heated too long. Usually accompanied by an increase in extensibility, a decrease in tensile strength and a lowering of the stress required to produce a given elongation. Extreme reversion may result in tackiness; the rubbers "revert" to an unvulcanized then to a non-polymeric condition.

RFI - Radio Frequency Interface  - a radiation of radio frequency energy that cases an electronic device to produce noise that might interfere with the function of an adjacent device. The disruption of the normal functionality of a satellite due to radio interference. 

Rheology - The science of deformation and flow of matter. Deals with the laws of plasticity, elasticity and viscosity and their connections with paints, plastics, rubber, oils, glass, cement, etc...

Rheometer (Monsanto) - An oscillating disk cure meter used for determining vulcanization characteristics of a rubber compound. 

Rimseal - A sealing device used on the rim of round plate or rim of a wheel.

Rings - Round sealing devices.

RMS - Root Mean Square - The measure of surface roughness, obtained as the square root of the sum of the squares of micro-inch deviation from true flat. 

Rod Seals - Any seal used on the rod of a hydraulic or pneumatic cylinder made from rubber or plastic.

Rollers - A round, flat ring used as a wheel or guide.

Rotary Seals - Seals used on rotating shafts - see lips seals, grease seals, oil seals.

Rotation (Flange) - The warping, bowing or bending of a flange that can occur from too much bolt load

Rotocure - Rotary press. 

Roto Glyd - A flat plastic, PTFE or Teflon ring used on a rotating shaft.

Rubber - A material that exhibits elastic properties that allow recovery from large deformations quickly and forcibly. A tough, waterproof substance obtained through polymeric synthesis or in natural form from the sap of various species of plants or trees. 

Rubber Latex - Colloidal aqueous emulsion of an elastomer.


Scorch - Premature vulcanization of a rubber compound, generally due to excessive heat history. Also see Mooney Scorch; 

Scorching - A term frequently used to denote premature vulcanization of a rubber compound, occurring on a mill or calendar, or in an extruder. Same as burning or "setting up".

Scraper Rings - A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder.

Scrapers - Also, called a wiper ring - A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder.

Seal - An elastomeric ring-shaped component used in a constantly moving, dynamic application - either reciprocating or rotating shaft - providing a near positive no leak mode in a hydraulic cylinder, ram, mixer or gear box - as examples. (Note: no sealing device is absolutely 100% positive). Seal rings can be u-shaped, v-shaped, o-shaped, metal inserted, radial lipped, multiple lipped or a simple flat ring.


Sealability - The measure of fluid leakage both thru and across both faces of a gasket.  Measured either by using ASTM F-37 or DIN 3535 equipment and procedures

Seal Cages - A special device used to assist a seal ring.

Seal Kits - Any group of seals, O-rings, wiper rings and back-up rings used to repair a specific hydraulic cylinder.

Seal-Master Machine Instant Seal Making Machine - A special CNC controlled machine for making seals instantly

Seats - A stationary ring which is pressed into a housing and acts as the matching face of a mechanical seal.

Shaft Repair Kits - A package of seals which includes all seals needed to repair the rod end of a hydraulic or pneumatic cylinder.

Shaft Seal & Packings - Any seal ring used on the rod of a hydraulic ram.

Shallex - A brand name for vee packings, chevron or parachute packings.

Sheeter - The special calendar used to make compressed sheet

Sheet Materials - Rubber or fibrous material used to make gaskets.

Shims - Flat, thin metal gasket-like parts used as spacers to position machinery or align equipment.

Shore A Hardness - An indentation method of rating the hardness of rubber using a Shore Durometer with the A scale from 0 to 100. 

Shrinkage - Contraction of molded rubber upon cooling. 


Skim Coat - A layer of rubber laid on a fabric but not forced into weave.  Normally laid on fractioned fabric

Skin - A relatively dense layer at the surface of a cellular material. 


Skive - The process of slicing or veneering off a sheet of PTFE from a billet

Simulation - The practice of mimicking some or all of the behavior of one system with a different, dissimilar system. 

Simultaneous Engineering - A way of simultaneously designing products, and the processes for manufacturing those products, through the use of cross functional teams to assure manufacturability and to reduce cycle time. 

Single Acting Seals - Rings which are designed to seal only in one axial direction.

Slab - A thick sheet

Slip O-rings - A type of ring which fits over an O-ring to relieve friction.

Smoke sheets - Plantation natural rubber sheets that, after passing through a mill that puts the conventional ribbing design on them, are washed and hung on racks in a smoke house where they undergo a combined smoking and drying process. 

Snap-in Wipers - A rod wiper which is made from one homogeneous material, either rubber or polyurethane, which is designed to snap-fit into a matching machined groove.

Solosele - The brand name of a particular single acting u-cup seals.

Spacers - A ring or gasket with flat sides to provide specific dimensional spacing between two components.

Special Characteristics - Product and process characteristics designated by the customer including govern- mental regulatory and safety; and/or selected by the supplier through knowledge of the product and process. 

Specific gravity - The ratio of the mass of a unit volume of a material to that of the same volume of water at a specified temperature. 

Speedi Sleeves - The name of a thin, round tube which slips over a rotating shaft to provide a new, clean sealing surface for a rubber lip oil or grease seal.

Splice - A joint or junction made by lapping or butting edges, straight or on a bias, and held together through vulcanization or mechanical means. 

Spring Energized Seals - Any sealing ring that utilizes a metal garter spring or finger spring to assist in energizing the seal when there is not sufficient pressure.

Spring Loaded Seals - See spring energized seals above.

Sprue - (1) The primary feed channel that runs from the outer face of an injection or transfer mold to mold gate in a single cavity mold or to runners in a multiple cavity mold; (2) The piece of material formed or partially cured in the primary feed channel. 

Sprue mark - A mark, usually elevated, left on the surface of an injection or transfer molded part, after removal of the sprue. 

Squeeze - Cross section diametrical compression of O-ring between bottom surface of the groove and surface of other mating metal part in the gland assembly. 

State of cure - The cure condition of a vulcanizate relative to that at which optimum physical properties are obtained. 

Stem Packing - A type of homogeneous or multi-braided packing used on the stem of a valve to stop leakage.

Stepseal - A seal ring with a step cut groove to match up against a housing machine to fit.

Strain - The unit change, due to force (stress), in the size or shape of a body referred to its original size or shape – it is a non-dimensional quantity, but is frequently expressed in inches per inch, centimeters per centimeter, etc.

Stress - Force per unit of original cross sectional area required to stretch a specimen to a stated elongation. 

Stress relaxation - The decrease in stress after a given time of constant strain. 

Stress-Strain - The relationship of load and deformation in a body under stress.  In rubber this is most commonly the relationship of tension (stress) and elongation (strain)

Substrate - A material upon the surface of which an adhesive promoter is applied for any purpose such as bonding or coating. 

Subsystem - A major part of a system which itself has the characteristics of a system, usually consisting of several components. 

Swelling - The increase in volume or linear dimensions of a specimen immersed in a liquid or exposed to a vapor. 

Switch Seals - Seals used in electrical switching devices to keep moisture out.

System - A combination of several components or pieces of equipment integrated to perform a specific function.



Tack - The ability to adhere to itself; a sticky or adhesive quality. 

Team Feasibility Commitment - A commitment by the Product Quality Planning Team that the design can be manufactured, assembled, tested, packaged, and shipped in sufficient quantity at an acceptable cost, and on schedule. 

Tear Resistance - Resistance to tearing, measured as the force required to tear completely across a specially-designed nicked rubber test piece or right-angled test piece by elongating it at a specified rate. Express in lbs. per inch of thickness of specimen.

Tear Strength - The maximum load required to tear apart a specified specimen, the load acting substantially parallel to the major axis of the test specimen. 

Telescopic Packing - Packing sets used on telescopic cylinders, each stage having a different diameter.

Temperature Range - Lowest temperature at which rubber remains flexible and highest temperature at which it will function. 

Tensile Strength - Force in pounds per square inch required to cause the rupture of a specimen of a rubber material. 

Tensile Strength - The capacity of a materiel to resist a force tending to stretch it. Ordinarily the term is used to denote the force required to stretch a material to rupture, and is known as "breaking load", "breaking stress "ultimate tensile strength". lit rubber testing, it is the load in lbs. per square inch or kilos per square centimeter of original cross-sectional area, supported at the moment of rupture by a piece of rubber being elongated at a constant rate.

Tensile Stress at Given Elongation - The tensile stress required to stretch a uniform section of a specimen to a given elongation. 

Tension Set - The extension remaining after a specimen has been stretched and allowed to retract. 

Thermal Cycling - The repetitious heating and cooling of a tank, vessel or piping system.  The duration of the cycle can vary tremendously

Thermal Deterioration - The elongation at the moment of rupture.

Thermoplastic Rubber - Rubber that does not require chemical vulcanization and will repeatedly soften when heated and stiffen when cooled; and which will exhibit only slight loss of its original characteristics. 

Thermosetting Rubber - Chemically vulcanized rubber that cannot be remelted or remolded without destroying its original characteristics. 

Thorseals - A brand name for a polyurethane hydraulic u-cup seal.

Timing Plan - A plan that lists tasks, assignments, events, and timing required to provide a product that meets customer needs and expectations. 

Tips - A rubber cup-shaped part used on the end of a rod or shaft to provide shock resistance or cushioning.

Tolerance - The upper and lower limits between which a dimension must be held

Torque - A force that either attempts, or actually does, product rotary movement.  With reference to bolts, it is the work to produce an axial clamping force on a gasket

Trim - The Process Involving removal of mold flash. 

T-Seals - A "T" shaped rubber sealing ring with harder back-up rings on each side for rod or piston sealing.

Tube Springs - A rubber or plastic cushioning device used to assist spring or cover the outer portion of a coil spring.



U-Cup - a type of seal used in a hydraulic or pneumatic cylinder. Its cross section is U-shaped to allow oil to energize the seal body to properly block oils and seal correctly.

Undercure - Degree of cure less titan optimum. May be evidenced by tackiness, loginess (lack of snap or resilience), or inferior physical properties.

Ultimate Elongation - The maxi- mum elongation prior to rupture. 

Undercure - State of vulcanization less than optimum. It may be evidenced by tackiness or inferior physical properties. 

U-Packings - A "U" shape cup sealing ring designed to seal in one direction along a shaft or rod in a hydraulic or pneumatic cylinder.



V-Packing - Also known as Vee Packing, Vee Sets, Chevron Packing, Parachute Packing. A multiple ring set of packings whose center rings or sealing rings are V-shaped to form sealing lips. The V-rings stack on top of each other and have a male and female adaptor on each end to make the set flat. This packing type is adjustable.

Valve Discs - A PTFE or Teflon disc used on a valve as a seat to provide positive sealing when shut off.

Value Engineering (Value Analysis) - A planned, clean sheet approach to problem solving, focusing on specific product design and process characteristics. Where value analysis is employed to improve value after production has begun, value engineering is employed to maximize value prior to expenditures of facilities and tooling money. 

Valve Packing - Braided packing used in the stuffing box of a valve stem to make a positive seal.

Valve Seats - A PTFE or Teflon disc or ring used on a valve as a seat to provide positive sealing when shut off.

Valve Stem Packing - Braided packing used in the stuffing box of a valve stem to make a positive seal.

Vee Packing - Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple "V" shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end.

VHAP - The abbreviation for Volatile Hazardous Air Pollutant

Vibration Mounts - A rubber piece used to eliminate vibration between to components.

Viscosity - The resistance of a material to flow under stress. 

Voice of the Customer - Customer feedback both positive and negative including likes, dislikes, problems and suggestions. 

Voice of the Process - Statistical data that is feedback to the people in the process to make decisions about the process stability and/or capability as a tool for continual improvement. 

Voids - The absence of material or an area devoid of materials where not intended. 

V-Packings - Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple "V" shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end.

V-Rings - Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple "V" shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end.

Vulcanizate - Rubber in its cured or vulcanized state.

Vulcanizating Agent - Any material which can produce in rubber the change in physical properties known as vulcanization, such as sulfur, polysulfides, organic polynitro derivatives, peroxides arid quinone dioximes.

Vulcanization - An irreversible process during which a rubber compound through a change in its chemical structure (for example, cross-linking) becomes less plastic and more resistant to swelling by organic liquids and elastic properties are conferred, improved, or extended over a greater range of temperature.



Warp - The lengthwise yarns in a woven fabric

Washers - Round, flat rings used as spacers, gaskets or slip devices under the head of a bolt.

Water Absorption - The increase in weight and volume after immersion in water. 

Water resistance - The ability to withstand swelling by water for a specified time and temperature. 

Wear Rings - Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods.

Wear Sleeves - Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods.

Wear Strips - Strips of abrasion resistant plastic, PTFE or Teflon material - Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods.

Weathering - The surface deterioration of a rubber article during outdoor exposure, such as cracking, crazing or chalking

Weft - An English term for filling

Wetting - Completeness of contact between particles dispersed in a medium, such as carbon black rubber. 

Wheels - Round rollers to provide easy movement of a machine or component.

Wicking - Leakage through a gasket (not around it)

Wiper Rings - Also, called a wiper ring - A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder.

Wire reinforced - A product containing wire(s) to give added strength, increased dimensional stability or crush resistance

Work Pressure - The maximum operating pressure encountered during normal service



X-Rings - Also called quad rings or quatro rings, rubber rings of a special shape used to replace O-rings and eliminate the rolling found when using O-rings.



“Y” Factor - The minimum design seating stress in either psi or megapascals over the contacted area of the gasket.  The stress required to provide a sealed joint with a 2 psig (virtually 0 psig) internal pressure in the joint

Yield Strength - The stress at which a product exhibits a specified limiting permanent set

Young's modulus - The ratio of normal stress to corresponding stress or compressive stresses below the proportional limit of the material.



Zinc Oxide, Activator - Accelerators of vulcanization do not always exert their full influence unless the rubber mixture contains substances known as activators. Zinc oxide is an activator and gives its best activity in the presence of an organic acid like stearic acid with which it forms a rubber-soluble soap.

Zurcon - A type of material used to make guide rings, wear rings, bearings or seals.