Glossary of Seal & Rubber Terms
Explore our comprehensive glossary of terms related to seals, rubber materials, and elastomeric components. This guide provides clear definitions and explanations to help you better understand the technical language used in the sealing industry. Whether you're looking for specific material properties or industry-standard terminology, our glossary has you covered.
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Table of Contents
-A-
Abrasion
Abrasion is the gradual wearing away of a surface during use, caused by mechanical actions such as rubbing, scraping, or erosion.
Abrasion Resistance
Abrasion resistance is the ability of a rubber compound, plastic material, metal, or other material to resist mechanical wear.
Absorption
Absorption is the physical process by which one substance attracts and takes in another substance (liquid, gas, or vapor) into its interior.
Accelerated Life Test
An accelerated life test is a set of conditions designed to quickly replicate the deteriorating effects experienced under normal service conditions.
Accelerated Service Test
An accelerated service test is a service or bench test where certain conditions, such as speed, temperature, or continuous operation, are exaggerated to produce results in a shorter time.
Accelerator
An accelerator is a substance that speeds up the vulcanization process of an elastomer, allowing it to occur in a shorter time or at a lower temperature.
Acid Resistant
Acid resistant materials are capable of withstanding the corrosive effects of acids.
Adhere
To adhere means to cling or stick to a surface or another material.
Adhesion
Adhesion is the tendency of rubber to bond or cling to a contact surface.
Adsorption
Adsorption is the physical process by which one substance attracts another (solid, liquid, gas, or vapor) to its surface and causes it to adhere through molecular forces.
Aging
Aging refers to the process of undergoing changes in physical properties over time or with the passage of age.
Aging, Oxygen Bomb
Oxygen bomb aging is a method used to accelerate the change in physical properties of rubber compounds by exposing them to oxygen under elevated temperature and pressure.
Air Bomb
An air bomb is similar to an oxygen bomb but uses air instead and is used for accelerated aging tests.
Air Checks
Air checks are surface markings or depressions caused by trapped air between the material being cured and the mold or press surface.
Air Curing
Air curing is the process of vulcanizing a rubber product in air, as opposed to using a press or steam vulcanizer.
Alpha (α) Particles
Alpha particles are positively charged particles consisting of two protons and two neutrons (essentially helium atom nuclei) and are known for their limited penetration ability.
Ambient Temperature
Ambient temperature refers to the surrounding temperature at a specific point of application. Note: Ambient temperature may differ from atmospheric temperature.
Aniline Point
Aniline point is the lowest temperature at which equal volumes of pure, fresh aniline and an oil will fully dissolve in each other.
Antioxidant
An antioxidant is an organic substance that inhibits or slows down the process of oxidation.
Antiozonant
An antiozonant is a substance that slows or prevents the formation of cracks caused by ozone exposure when an elastomer is under tension, either in static or dynamic conditions, in air containing ozone.
Antirad
An antirad is a material that inhibits damage caused by radiation.
Atmospheric Cracking
Atmospheric cracking refers to cracks that develop on the surface of rubber articles due to exposure to atmospheric conditions.
-B-
Backrind
Backrind is the distortion that occurs along the parting line, often appearing as a ragged indentation.
Back-Up Ring
A back-up ring is an anti-extrusion device made of a hard, durable material placed in the gland between the O-ring and groove sidewalls to prevent the O-ring from extruding.
Bake-Out
Bake-out is a process in which a vacuum system is heated for a specified time at a predetermined temperature to degas all its components, including gauges, fittings, valves, and seals.
Banbury Mixer
A Banbury mixer is a specialized internal mixer used to blend fillers and other ingredients with an elastomer.
Bench Test
A bench test is a modified service test where service conditions are simulated using standard laboratory equipment, which may not be identical to the equipment used in actual product applications.
Beta (β) Particles
Beta particles are negatively charged particles or electrons with limited penetration ability.
Bleeding
Bleeding is the migration of plasticizers, waxes, or similar substances to the surface, forming a film or beads.
Blemish
A blemish is a mark, deformity, or imperfection that detracts from the appearance of a surface or product.
Blisters
Blisters are raised spots on a surface or separations between layers, typically forming a void or air-filled space in a vulcanized article.
Bloom
Bloom is a dusty or milky-looking deposit that may appear on the surface of an O-ring after molding and storage, caused by the migration of a liquid or solid to the surface. It is not to be mistaken for dust from external sources.
Bond
A bond refers to the attachment of an elastomer to another material. Bonds can be categorized into the following types: (a) Mechanical Bond — A physical attachment achieved through methods like "through" holes, interlocking fingers, envelope design, or riveting. (b) Cold Bond — Adhesion of a previously vulcanized elastomer to another material using suitable contact cements. (c) Vulcanized Bond — Adhesion of an elastomer to a primed surface using heat and pressure, vulcanizing the elastomer in the process.
Break
A break is a separation or discontinuity in any part of an article.
Break-Out
Break-out refers to the force required to initiate sliding, measured in the same way as friction. A high break-out value often indicates the development of adhesion.
Brittleness
Brittleness is the tendency of a material to crack when subjected to deformation.
Buna-N
Buna-N is another name for nitrile rubber.
Buna-S
Buna-S is a general term for copolymers of butadiene and styrene, also known as SBR (Styrene-Butadiene Rubber) and GRS (Government Rubber Styrene).
Butt Joint
A butt joint is the joining of two ends of a seal where the junction is perpendicular to the mold parting line.
Butyl
Butyl is a copolymer made from isobutylene with small amounts of isoprene.
-C-
Calender
A calender is a machine that forms sheets of rubber by passing the material between steel rollers.
Coefficient of Thermal Expansion
The coefficient of thermal expansion is the average expansion per degree over a specified temperature range, expressed as a fraction of the material's initial dimension. It can be measured either linearly or volumetrically.
Cold Flexibility
Cold flexibility refers to the ability of a material to remain flexible after being exposed to a predetermined low temperature for a specific duration.
Cold Flow
Cold flow is the continued deformation of a material when subjected to stress over time.
Cold Resistant
Cold resistant materials can endure the effects of cold or low temperatures without losing functionality or serviceability.
Commercially Smooth
Commercially smooth refers to the level of surface smoothness of an article that is considered acceptable for practical use.
Compound
A compound refers to a mixture of polymers and other ingredients combined to create a usable rubber material.
Compression Modulus
Compression modulus is the ratio of compressive stress to the resulting compressive strain, with the strain expressed as a fraction of the material's original height or thickness in the direction of the applied force. It can be measured either statically or dynamically.
Compression Set
Compression set refers to the extent to which a rubber specimen fails to return to its original shape after the removal of a compressive load.
Conductive Rubber
Conductive rubber is a type of rubber that can conduct electricity, typically used in applications where static electricity needs to be discharged.
Copolymer
A copolymer is a polymer made from the chemical combination of two different monomers.
Corrosion (Packing)
Corrosion in packing refers to the degradation of a rigid member, typically metal, at the point where it contacts the packing. The corrosion is caused by the fluid medium trapped in the interface.
Corrosive (Packing)
Corrosive packing refers to the perceived, often incorrect, assumption that the packing itself promotes corrosion of the rigid member due to the trapped fluid.
Cracking
Cracking is a sharp break or fissure in the surface, typically caused by excessive strain.
Creep
Creep is the gradual relaxation of a rubber material under stress, which eventually leads to permanent deformation or "set."
Cross-Section
A cross-section is the view of a seal when cut at right angles to the mold parting line, revealing its internal structure.
Cure
Cure refers to the process of vulcanization, where rubber is chemically treated to improve its elasticity, strength, and durability.
Cure Date
The cure date is the date when an O-ring was molded, typically represented in a format such as 2Q94, meaning the second quarter of 1994.
Curing Temperature
Curing temperature is the specific temperature at which a rubber product undergoes vulcanization.
Cylinder
A cylinder is a chamber where a piston, plunger, ram, rod, or shaft is driven by or acts against the system fluid.
-D-
Degassing
Degassing is the intentional and controlled release of gas from a rubber substance or other material.
Diffusion
Diffusion is the process where two or more substances (solids, liquids, gases, or combinations) mix due to the movement of their individual molecules. Gases diffuse more easily than liquids, and liquids diffuse more easily than solids.
Durometer
(a) A durometer is an instrument used to measure the hardness of rubber by assessing the resistance to the penetration of an indentor point into its surface. (b) It is also a numerical scale used to indicate the hardness of rubber.
Dynamic
Dynamic refers to an application where the seal is exposed to movement or where moving parts come into contact with the seal.
Dynamic Packing
Dynamic packing refers to a packing used in a joint where the components are in relative motion.
Dynamic Seal
A dynamic seal is designed to prevent leakage between parts that are in relative motion.
-E-
Elasticity
Elasticity is the property of a material that allows it to return to its original shape after being deformed.
Elastomer
An elastomer is any synthetic or natural material with resilience or memory that enables it to return to its original shape after being distorted.
Electron Volt
An electron volt is a unit of energy used in atomic calculations, equal to 1.602 × 10⁻¹² ergs.
Elongation
Elongation generally refers to "ultimate elongation," or the percentage increase in the original length of a specimen when it breaks.
ERG
An erg is a unit of energy in the centimeter-gram-second (C.G.S.) system, equivalent to one dyne centimeter or the amount of work done by a force of 1 gram moving 1 centimeter.
Evaporation
Evaporation is the process where a liquid directly converts into its vapor state.
Explosive Decompression
Explosive decompression is the rupture of a material's substructure due to the rapid release of pressure from an elastomer containing dissolved gases, often resulting in blistering or swelling. Some elastomers are resistant to this effect.
Extrusion
Extrusion refers to the distortion or flow of part of a seal under pressure into the clearance between mating metal parts.
-F-
Face Seal
A face seal is a seal formed between two flat surfaces.
Filler
A filler is a chemically inert, finely divided material added to an elastomer to improve processing and physical properties such as abrasion resistance and strength, contributing to varying degrees of hardness.
Flash
Flash refers to the excess rubber left around a molded part due to the space between mating mold surfaces, which is removed by trimming.
Flex Cracking
Flex cracking refers to surface cracking caused by repeated bending or flexing.
Flex Resistance
Flex resistance is the relative ability of a rubber article to endure dynamic bending stresses.
Flock
Flock is a fibrous filler sometimes used in rubber compounding.
Flow Cracks
Flow cracks are surface imperfections caused by improper material flow or failure of the rubber to blend properly during the molding process.
Fluid
A fluid is a substance in either liquid or gas form.
Friction
Friction is the resistance to motion created by the contact between surfaces.
Friction (Breakout)
Breakout friction is the resistance developed when initiating motion.
Friction (Running)
Running friction is the constant resistance experienced during the operation of a dynamic O-ring.
Fuel (Aromatic)
Aromatic fuel contains benzene or aromatic hydrocarbons, which can cause significant swelling in rubber.
Fuel (Nonaromatic)
Nonaromatic fuel is composed of straight-chain hydrocarbons and causes minimal swelling in rubber.
-G-
Gamma (γ) Radiation
Gamma radiation is an electromagnetic disturbance (photons) emitted from an atomic nucleus. This type of radiation travels in wave form, similar to X-rays or light, but has a shorter wavelength (approximately 1 Å or 10⁻⁷ mm) and is highly penetrating.
Gasket
A gasket is a device designed to retain fluids under pressure or to seal out foreign matter. It typically refers to a static seal.
Gland
A gland is the cavity into which an O-ring is installed, encompassing the groove and mating surface of the second part, which together confine the O-ring.
-H-
Hardness
Hardness is the resistance of a material to a distorting force, measured by its relative resistance to an indentor point using various standard hardness testing instruments.
Hardness Shore A
Hardness Shore A refers to the rubber durometer hardness measured on a Shore “A” gauge, where higher numbers indicate harder material. A reading of 35 Shore A is considered soft, while 90 is considered hard.
Hermetic Seal
A hermetic seal is an airtight seal that shows no detectable leakage.
Homogeneous
(a) General - A homogeneous material has a uniform composition throughout. (b) In seals - A homogeneous rubber seal is one that does not contain fabric or metal reinforcement.
Hypalon
Hypalon is the DuPont trade name for chlorosulfonated polyethylene, which is an elastomer.
-I-
Identification
Identification refers to colored dots or stripes on seals used for identification purposes.
Immediate Set
Immediate set is the deformation measured immediately after the removal of the load that caused the deformation.
Immersion
Immersion is the process of placing an article into a fluid so that it is completely covered.
Impact
Impact is the single, instantaneous stroke or contact of a moving body with another body, whether it is moving or at rest, such as a large lump of material dropping onto a conveyor belt.
-L-
Leakage Rate
The leakage rate is the rate at which a fluid (either gas or liquid) passes through a barrier. Total leakage rate includes both the amounts that diffuse or permeate through the material of the barrier and the amounts that escape around it.
Life Test
A life test is a laboratory procedure used to assess the amount and duration of resistance of an article to a specific set of destructive forces or conditions.
Linear Expansion
Linear expansion refers to the increase in any one linear dimension or the average increase of all linear dimensions.
Logy
Logy describes a material that is sluggish, exhibiting low snap or recovery.
Low Temperature Flexibility
Low temperature flexibility is the ability of a rubber product to be flexed, bent, or bowed at low temperatures without cracking.
-M-
mm Hg
mm Hg stands for millimeters of mercury, a measure of absolute pressure in vacuum work, indicating the height of a column of mercury that air or another gas can support. Standard atmospheric pressure supports a mercury column 760 millimeters high (760 mm Hg). Any value below this indicates some degree of vacuum.
Memory
Memory is the tendency of a material to return to its original shape after being deformed.
Mirror Finish
A mirror finish refers to a bright, polished surface.
Mismatch
Mismatch describes an unsymmetrical seal caused by dissimilar cavities in mating mold sections.
Modulus
Modulus is the tensile stress at a specified elongation, typically measured at 100% elongation for elastomers.
Modulus of Elasticity
The modulus of elasticity is one of several measurements of stiffness or resistance to deformation, though it is often incorrectly used to refer specifically to static tension modulus.
Mold Cavity
A mold cavity is the hollow space in the mold that imparts the desired shape to the product being molded.
Mold Finish
Mold finish refers to the uninterrupted surface produced by the intimate contact of rubber with the mold surface during vulcanization.
Mold Lubricant
Mold lubricant is a material typically sprayed onto the mold cavity surface before introducing uncured rubber to facilitate the easy removal of molded rubber parts.
Mold Marks
Mold marks are indentations or ridges embossed into the skin of the molded product due to irregularities in the mold cavity surface.
Mold Register
Mold register refers to the accuracy of alignment or fit of mold sections.
Mooney Scorch
Mooney scorch is the measurement of the rate at which a rubber compound will cure or set, determined using the Mooney Viscometer test instrument.
Mooney Viscosity
Mooney viscosity is the measurement of the plasticity or viscosity of an uncompounded or compounded, unvulcanized elastomeric seal material, obtained using the Mooney Shearing Disk Viscometer.
-N-
Nitrile
Nitrile (Buna-N) is the most commonly used elastomer for O-rings due to its resistance to petroleum fluids, good physical properties, and useful temperature range.
Nominal Dimension
Nominal dimension refers to the nearest fractional equivalent of an actual decimal dimension.
Non-Blooming
Non-blooming indicates the absence of bloom on a surface.
-O-
Occlusion
(a) Occlusion is the mechanical process by which vapors, gases, liquids, or solids are entrapped within the folds of a substance during working or solidification. (b) The term also refers to the materials that are trapped.
Off-Register
Off-register describes the misalignment of mold halves, resulting in an out-of-round O-ring cross section.
Oil Resistant
Oil resistant refers to the ability of vulcanized rubber to resist the swelling and deteriorating effects of various types of oils.
Oil Swell
Oil swell is the change in volume of a rubber article caused by the absorption of oil or another fluid.
O-Ring
An O-ring is a torus; a circular piece of material with a round cross section that creates a seal through squeeze and pressure.
O-Ring Seal
An O-ring seal is the combination of a gland and an O-ring that provides a fluid-tight closure. Moving (dynamic) — An O-ring seal where there is relative motion between some gland parts and the O-ring, such as oscillating, reciprocating, or rotary motion. Non-moving (static) — An O-ring seal where there is no relative motion between any part of the gland and the O-ring (excluding distortion from fluid pressure or swelling from fluid immersion).
Optimum Cure
Optimum cure is the state of vulcanization at which the most desirable combination of properties is achieved.
Outgassing
Outgassing is a vacuum phenomenon where a substance spontaneously releases volatile constituents in the form of vapors or gases. In rubber compounds, these constituents may include water vapor, plasticizers, air, inhibitors, etc.
Over Cure
Over cure refers to a degree of cure that exceeds the optimum level, resulting in the degradation of some desirable properties.
Oxidation
Oxidation is the reaction of oxygen with a compound, typically detected by changes in the appearance or feel of the surface, or by alterations in physical properties, or both.
Oxygen Bomb
An oxygen bomb is a chamber capable of holding oxygen at elevated pressure, which can be heated to an elevated temperature, used for accelerated aging tests.
Ozone Resistance
Ozone resistance is the ability to withstand the deteriorating effects of ozone, which generally causes cracking.
-P-
Packing
Packing is a flexible device used to retain fluids under pressure or to seal out foreign matter, typically referring to a dynamic seal.
Permanent Set
Permanent set is the deformation that remains in a specimen after it has been stressed in tension for a specific period and then released.
Permeability
Permeability is the rate at which a liquid or gas passes through a solid material by diffusion and solution under pressure. In rubber terminology, it is expressed as the rate of gas flow in atmospheric cubic centimeters per second through an elastomeric material that is one square centimeter and one centimeter thick (atm cc/cm²/cm sec).
Pit or Pock Mark
A pit or pock mark is a small circular depression.
Plasticizer
A plasticizer is a substance, usually a viscous liquid, added to an elastomer to reduce stiffness, improve low-temperature properties, and enhance processing.
Plastometer
A plastometer is an instrument used to measure the plasticity of raw or unvulcanized compounded rubber.
Pock Mark
See "Pit or Pock Mark."
Polymer
A polymer is a material formed by the joining together of many (poly) individual units (mer) of one or more monomers; it is synonymous with elastomer.
Porosity
Porosity refers to the quality or state of being porous.
Post Cure
Post cure is the second step in the vulcanization process for more exotic elastomers, providing stabilization of parts and driving off decomposition products resulting from the vulcanization process.
-R-
Radiation
Radiation is the emission of varying energy content from a disturbed atom undergoing internal change. There are two broad classifications: (a) Corpuscular - Comprising streams of particles that are either neutral or charged, such as protons, electrons, and neutrons. (b) Electromagnetic - Comprising wave-like emissions, such as gamma rays and ultraviolet radiation.
Radiation Damage
Radiation damage is a measure of the loss of certain physical properties in organic substances, like elastomers, primarily due to the ionization of the long-chain molecules. This ionization process (i.e., electron loss) can result in redundant cross-linking and possible scission of the molecule, and the effect is cumulative.
Radiation Dosage
Radiation dosage refers to the total amount of radiation energy absorbed by a substance, usually expressed in ergs per gram, with the following units: (a) Roentgen - A quantity of gamma or X-ray radiation equal to approximately 83 ergs of absorbed energy per gram of air. (b) REP (Roentgen equivalent-physical) - A quantity of ionizing radiation causing an energy absorption of approximately 83 to 93 ergs per gram of tissue. (c) REM (Roentgen equivalent-man) - Similar to REP, but used to denote biological effects. (d) RAD - The unit of dosage related to elastomers, independent of the type of radiation or specimen, denoting an energy absorption level of 100 ergs per gram of elastomer. The RAD is approximately equal to 1.2 Roentgens.
Register, Off or Uneven
See Off-register.
Reinforcing Agent
A reinforcing agent is a material dispersed in an elastomer to enhance its compression, shear, or other stress properties.
Relative Humidity
Relative humidity is the ratio of the quantity of water vapor actually present in the atmosphere to the maximum amount possible at a given temperature.
Resilient
Resilient refers to the capability of a material to return to its original size and shape after deformation.
Roentgen
See Radiation Dosage.
Rough Trim
Rough trim is the removal of excess material by pulling or picking, usually referring to the removal of a small portion of flash or sprue that remains attached to the product.
Rubber
Rubber is synonymous with elastomer.
Rubber, Natural
Natural rubber is raw or crude rubber obtained from plant sources.
Rubber, Synthetic
Synthetic rubber refers to manufactured or man-made elastomers.
Runout (Shaft)
Runout (shaft) is synonymous with gyration; when expressed in inches alone or accompanied by the abbreviation “T.I.R.” (total indicator reading), it refers to twice the radial distance between the shaft axis and the axis of rotation.
-S-
Scorching
Scorching is the premature curing or setting of raw compound during processing.
Seal
A seal is any device used to prevent the passage of a fluid, whether gas or liquid.
Service
Service refers to the operating conditions that need to be met.
Shaft
A shaft is a reciprocating or rotating member typically located within a cylinder, not in contact with its walls.
Shelf-Aging
Shelf-aging is the change in a material's properties that occurs over time while in storage.
Shore A Hardness
See Hardness and Durometer.
Shrinkage
Shrinkage can refer to: a) The decreased volume of a seal, usually caused by the extraction of soluble constituents by fluids followed by air drying. b) The difference between the finished part dimensions and the mold cavity used to create the part.
Silicone Rubber
Silicone rubber is an elastomer that retains good properties across an extra wide temperature range.
Size, Actual
Actual size refers to the true dimensions of the O-ring or other seal, including tolerance limits.
Size, Nominal
Nominal size is the approximate size of a part in fractional dimensions and may also indicate the actual size of the groove into which a nominal size seal fits.
Size Number
Size number is an assigned number that indicates the inside and cross-sectional diameters of an O-ring. Sizes established in SAE standard AS 568A have been adopted by the military and industry.
Sorption
Sorption denotes the combination of absorption and adsorption processes occurring in the same substance.
Specific Gravity
Specific gravity is the ratio of the weight of a given substance to the weight of an equal volume of water at a specified temperature.
Sprue Marks
Sprue marks are elevated marks left on the surface of a rubber part after the removal of the sprue or cured compound from the gate through which the compound is injected or transfer molded.
Squeeze
Squeeze refers to the cross-sectional diametrical compression of an O-ring between the surface of the groove bottom and the surface of another mating metal part in the gland assembly.
Static Seal
A static seal is designed to seal between parts that have no relative motion. See Gasket.
Strain
Strain is the deflection that occurs due to a force.
Stress
Stress is the force applied per unit of the original cross-sectional area.
Sublimation
Sublimation is the direct conversion of a substance from a solid state to a vapor state without passing through a liquid state. The vapor can recondense back into the solid state without an intervening liquid phase.
Sun Checking
Sun checking refers to surface cracks, checks, or crazing caused by exposure to direct or indirect sunlight.
Swell
Swell is the increased volume of a specimen caused by immersion in a fluid, typically a liquid.
-T-
Tear Resistance
Tear resistance is the ability to resist the growth of a cut or nick when tension is applied to the cut specimen, commonly expressed as pounds per inch thickness.
Temperature Range
Temperature range refers to the maximum and minimum temperature limits within which a seal compound can function in a given application.
Tensile Strength
Tensile strength is the force in pounds per square inch required to cause the rupture of a specimen of rubber material.
Terpolymer
A terpolymer is a polymer formed by the chemical combination of three different monomers.
Thermal Expansion
Thermal expansion is the expansion that occurs due to an increase in temperature, which can be linear or volumetric.
Threshold
Threshold is the maximum tolerance of an elastomer to radiation dosage, expressed as a total number of ergs per gram (or rads), beyond which the physical properties are significantly degraded. This value is generally arbitrary, depending on the function and environment.
Torque
Torque is the turning force applied to a shaft.
Torr
Torr is the unit of pressure used in vacuum measurement, equal to 1/760 of a standard atmosphere, and is practically equivalent to one millimeter of mercury (mm Hg). Example: 25 mm Hg = 25 torr 1 x 10⁻³ mm Hg = 10⁻³ torr (millitorr) 1 x 10⁻⁶ mm Hg = 10⁻⁶ torr (microtorr)
Torsional Strength
Torsional strength is the ability of rubber to withstand twisting.
TR-10
TR-10 (10% Temperature Retraction) is a measure of the low-temperature capability of an elastomer, indicating the temperature at which a stretched and frozen specimen has retracted by 10% of the stretched amount (ASTM method D1329).
Trapped Air
Trapped air refers to air that is enclosed within a product or a mold during curing, often causing a loose ply or cover, or resulting in surface marks, depressions, or voids.
Trim
Trim is the process of removing mold flash.
Trim Cut
Trim cut is the damage to the mold skin or finish caused by excessive trimming.
-U-
Under-Cure
Under-cure refers to a degree of cure that is less than optimum, which may be evidenced by tackiness, loginess, or inferior physical properties.
Ultimate Elongation
Ultimate elongation refers to the maximum percentage increase in the original length of a specimen when it breaks. See Elongation.
-V-
Vacuum
Vacuum denotes a space occupied by a gas at less than atmospheric pressure. For degrees of vacuum, see vacuum level.
Vacuum Level
Vacuum level refers to the degree of vacuum indicated by its pressure in torr (or mm Hg): (a) Rough vacuum — 760 torr to 1 torr (b) Medium vacuum — 1 torr to 10⁻³ torr (c) High vacuum — 10⁻³ torr to 10⁻⁶ torr (d) Very high (hard) vacuum — 10⁻⁶ torr to 10⁻⁹ torr (e) Ultra high (ultra hard) vacuum — Below 10⁻⁹ torr
Vapor
Vapor is the gaseous state of a fluid that normally exists as a liquid under atmospheric conditions, i.e., a gas whose temperature is below its critical temperature.
Vapor Pressure
Vapor pressure is the maximum pressure exerted by a liquid (or solid) heated to a given temperature in a closed container.
Virtual Leak
A virtual leak is an “apparent” leak in a vacuum system that is traceable to an internal (often accidental) release of occluded and/or sorbed gases. Example: An undetected blister in a fused joint may eventually break down in a vacuum and slowly release its entrapped air, indicating a “leak.”
Viscosity
Viscosity is the property of fluids and plastic solids that resists an instantaneous change of shape, i.e., resistance to flow.
Void
A void is the absence of material or an area devoid of material where it is not intended.
Volatilization
Volatilization is the transition of either a liquid or a solid directly into the vapor state. For a liquid, this transition is called evaporation, while for a solid, it is termed sublimation.
Volume Change
Volume change refers to the alteration in the volume of a seal as a result of immersion in a fluid, expressed as a percentage of the original volume.
Volume Swell
Volume swell is the increase in physical size caused by the swelling action of a liquid.
Vulcanization
Vulcanization is a thermo-setting reaction involving heat and pressure that results in significantly increased strength and elasticity of rubber-like materials.
Vulcanizing Agent
A vulcanizing agent is a material that facilitates the vulcanization of an elastomer.
-W-
Width
Width refers to the cross section or thickness of a seal.
Wiper Ring
A wiper ring is a ring used to remove excess fluid, mud, or other contaminants from a reciprocating member before it reaches the packings.
Abbreviations
ACM
Polyacrylate Rubber
AF
Air Force
AFML
Air Force Material Laboratory
AMS
Aerospace Material Specification
AN
(1) Army-Navy; (2) Air Force-Navy
ANA
Air Force-Navy Aeronautical Bulletin
AND
Air Force-Navy Design
AQL
Acceptable Quality Level
ARP
Aerospace Recommended Practice
AS
Aerospace Standard
ASTM
American Society for Testing and Materials
atm
Atmosphere (atmospheric)
AU
Polyurethane Rubber
BR
Butadiene Rubber
C or °C
Degrees Centigrade
cc
Cubic centimeter
C.G.S.
Centimeter-Gram-Second; system of units for length, mass, and time
CO
Epichlorohydrin Rubber
cpm
Cycles per minute
CR
Chloroprene (Neoprene)
cs
Cross Section
CSM
Hypalon Rubber
Dia
Diameter
ECO
Epichlorohydrin Rubber
EP, EPM
Ethylene-Propylene Rubber
EPDM
Ethylene-Propylene Rubber
EU
Polyurethane Rubber
F or °F
Degrees Fahrenheit
FED
Federal Specification
FKM
(also FPM) Fluorocarbon Rubber
F.P.S.
Foot-Pound-Second; system of units for length, weight and time
FVMQ
Fluorosilicone Rubber
HNBR
Hydrogenated Nitrile Rubber
GRS
“Government Rubber Styrene”; now SBR
ID
Inside Diameter
IIR
Butyl Rubber
in.
Inch
IR
Isoprene Rubber
JAN
Joint Army-Navy
JIC
Joint Industry Conference on Hydraulic Standards for Industrial Equipment
K
Degrees Kelvin (Absolute) — (°C +273)
Max
Maximum
MIL
Military Specification
Min
Minimum
MS
Military Standard
MVQ
Silicone Rubber
NAS
National Aerospace Standard (also National Aircraft Standards [older meaning])
NASA
National Aeronautics and Space Administration
NBR
Nitrile or Buna-N Rubber
No
Number
NR
Natural Rubber
OD
Outside Diameter
psi
Pounds per square inch
PVMQ
Phenyl Silicone Rubber
QPL
Military Qualified Products List
R or °R
Degrees Rankine (Absolute) — (°F +460)
Rad
Radius
RMA
Rubber Manufacturers Association
RMS
Root-Mean-Square; average value of surface roughness measured in microinches
rpm
Revolutions per minute
SAE
Society of Automotive Engineers, Inc.
SBR
Styrene Butadiene Rubber
sfm
Surface Feet per minute
Spec
Specification
T
Polysulfide Rubber
Temp.
Temperature
TFE/P
AFLAS
USAF
United States Air Force
VMQ
Silicone Rubber
W
Width (seal cross section)
WPAFB
Wright-Patterson Air Force Base
XNBR
Carboxylated Nitrile Rubber
References
Parker O-Ring Handbook, www.parker.com/content/dam/Parker-com/Literature/O-Ring-Division-Literature/ORD-5700.pdf. Accessed 22 Oct. 2024.
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