A
Abrasion Resistance
The ability of rubber to resist surface wearing caused due to mechanical action
Abrasion
The process of wearing down due to friction
Accelerator
A chemical compound that speeds up the vulcanization of rubber
Aging
The change in physical and chemical characteristics of an elastomer that has been exposed to a particular environment over time
Alloy
A composite material produced by blending polymers or copolymers with other polymers under selected conditions to achieve unique physical properties
Abrasion Resistance
The ability of rubber to resist surface wearing caused due to mechanical action
Annealing
A process of holding a material at a temperature near, butbelow, its melting point, to relieve stress caused by material flow into the mold, without distortion of shape.
Antioxidant
Any organic compound that slows the process of oxidation
ASTM
American Society for Testing and Materials. An organization for issuing standard specifications on materials, including metals, compounds and alloys.
Axial Seal
Also called face seal. The expansion/compression takes place on the top and bottom surfaces of the seal’s cross section.
B
Base Line
The mark from which all features are dimensioned.
Barrel
The part of an extruder inwhich the feed screw is located
Batch Number
The unique number assigned to a particular batch of rubber compound or finished parts made in any given production run, to aid traceability.
Blast Finishing
The process of removing flash from molded objects and/or dulling their surfaces, by continuous blasting/rubbing using media such as crushed apricot pits, walnut shells or plastic pellets, thus creating sufficient friction to remove the flash
Bleeding
The release of excess plasticizer or other compound elements onto the surface of a rubber product. This happens when rubbers contain inappropriate levels of plasticizers which are not fully compatible.
Blemish
Anything affecting the appearance of a compound, such as a mark, deformity, or injury.
Blister
An imperfection on the surface of a rubber part caused by accumulation of air or gas beneath the surface.
Bloom
A whitish powdery surface visible on the rubber surface post molding/curing caused by the exudation of certain compound components (such as antiozonants, lubricants, stabilizer pigment, plasticizers, etc.). This discoloration DOES NOT affect material performance in any way.
Bond
A bond is a force that holds the elastomer to some other object. A bond can be mechanical or chemical. Mechanical bonding includes physical fixing without any molecular cross-bridging. Chemical bonding involves molecular bridging or vulcanization with heat and pressure to bond an elastomer with the primed surface.
Bore
A hole machined in a component, which permits the passage of a shaft/tube.
C
Clearance (in a sealing system)
The space between components inmechanical systems which allows for manufacturing, thermal, and dynamic variations in the size and position of the components.
Chemical bonding
A method for bonding rubber to other part/parts by applying special adhesives to the part prior to molding
Coefficient of Thermal Expansion
Determines the amount of linear dimensional change for a particular elastomer, which is temperature dependent
Compound
A mixture of a polymer and associated chemical ingredients such as catalysts, plasticizers, antioxidants, lubricants, etc. necessary to produce a finished rubber material.
Compression Molding
A molding process in which the uncured rubber compound is placed directly into the mold cavityand compressed to its final shape.
Compression Set
The permanent deformation experienced by a rubber material when compressed for a period of time. The term is commonly used in reference to a test conducted under specific conditions wherein the permanent deformation, expressed as a percentage, is measured after a prescribed period of time. This is to test the effectiveness of the seal in terms of retaining its dimensions. Low compression sets are desirable.
Cooling Channels
Channels located within the body of a mold through which a cooling medium is passed to control the mold surface temperature
Cross-linking Agents
A chemical or chemicals that bond the polymer chains of a rubber together during the molding process
Cure
The process (heating) after which raw stock (elastomer compounds) are turned into finished rubber parts.
Clearance (in a sealing system)
The space between components inmechanical systems which allows for manufacturing, thermal, and dynamic variations in the size and position of the components.
Chemical bonding
A method for bonding rubber to other part/parts by applying special adhesives to the part prior to molding
Coefficient of Thermal Expansion
Determines the amount of linear dimensional change for a particular elastomer, which is temperature dependent
Compound
A mixture of a polymer and associated chemical ingredients such as catalysts, plasticizers, antioxidants, lubricants, etc. necessary to produce a finished rubber material.
Compression Molding
A molding process in which the uncured rubber compound is placed directly into the mold cavityand compressed to its final shape.
Compression Set
The permanent deformation experienced by a rubber material when compressed for a period of time. The term is commonly used in reference to a test conducted under specific conditions wherein the permanent deformation, expressed as a percentage, is measured after a prescribed period of time. This is to test the effectiveness of the seal in terms of retaining its dimensions. Low compression sets are desirable.
Cooling Channels
Channels located within the body of a mold through which a cooling medium is passed to control the mold surface temperature
Cross-linking Agents
A chemical or chemicals that bond the polymer chains of a rubber together during the molding process
Cure
The process (heating) after which raw stock (elastomer compounds) are turned into finished rubber parts.
D
Deflashing
Any process used to remove extra rubber (flash) from a molded rubber part
Damping
The ability of an elastomer to absorb forced vibrational energy
Delamination
Separation of two or more surfaces in a composite material.
Diaphragm Seals
Regulator seals used in gas controls, valves, actuators, regulators, pumps and metering equipment.
Die
Molds through which the uncured elastomer is pushed out in the desired shape during the extruding process.
Die Cut Gaskets
Press cut and hand cut gaskets in all types of rubber, most commonly reported using the Shore ‘A’ scale
Durometer
Standard rubber industry test instrument which uses an indenter to measure the hardness of specimen rubber. The hardness of rubber is most commonly reported by a durometer using the Shore ‘A’ scale
Dynamic Seal
A seal used in an environment that subjects it or a mating surface to movement
E
Elasticity
A rubber’s ability to return to its original size and shape after removal of the stress causing deformation such as stretching, compression, or torsion.
Elastic Limit
Maximum stress that a material will stand before permanent deformation occurs
Elastomer
Any of various polymers having the elastic properties of rubber
Elongation
Generally referred to in terms of tensile (pull apart) testing. Elongation is the increase in length of a test specimen, expressed as a percentage of its original (unstretched) length; relative to a given load at the breakpoint
EMI
Electromagnetic interference
Extrusion
When a part is forced from its groove (die) by high continuous or pulsating pressure
F
FDA
Food & Drug administration
Face Seal
Also called axial seal. The expansion/compression takes place on the top and bottom surfaces of the seal’s cross section.
Feed
The area or opening where rubber is injected or transferred into the mold cavity
Filler
Fine material used to reinforce or modify elastomer physical properties, like hardness, curing time, tensile, etc. Typical examples are carbon black, calcium carbonates, clay, silica, etc.
G
Gland
The space in mechanical systems where the seal is installed. It consists of the seal groove and any additional space required for proper seal compression.
Gasket
A static sealing device used to retain fluids under pressure or to seal out foreign matter
H
Hardness
A measurement of resistance to penetration of a rubber sampleby an indenter. Higher values indicate harder materials and vice versa. The hardness of rubber is most commonly reported by durometer using the Shore ‘A’ scale a
I
Insert
A term referring to a metal or plastic component, placed/inserted into a mold cavity prior to the start of the molding cycle, to which rubber is chemically and/or physically bonded during the molding process
Injection Molding
A molding method in which a rubber is heated and forced under pressure into the mold cavity
J
JIT
Just in Time manufacturing, an efficient manufacturing technique developed by the Japanese automotive industry in the 1950’s to reduce inventory as far as possible.
L
LSR
“Liquid silicone rubber”. Used in injection molding of high-quality parts, offering low compression set and great stability and temperature resistance.
Laser Etching
Physically marking a component with a laser, often to uniquely identify each individual component with a unique serial number.
M
Mechanical bond
A method of physically/mechanically attaching the rubber to another object like a metalinsert
Mating Surfaces
Points where different parts of an assembly meet.
Memory
Ability of an elastomer to return to its original size and shape after deformation
Modulus
A measure of resistance of a material to deformation. is measured by the force required to reach a predetermined compression or extension
Mold
Typically made from steel. The rubber part is formed within the machined cavity
Mold Cavity
The hollow space of the mold in which the uncured rubber compound is compressed to give the desired cured finished product
N
Nominal Dimension
The mean dimension of a molded article, from which small dimensional deviations/tolerances (plus and minus) are permitted
Non-fill
An unintentional void or absence of material in the part
O
Oil Resistant
Ability of vulcanized rubber to resist swelling and other detrimental effects of exposure to various oils
O-Ring
A doughnut-shaped object, or torus, that functions as a seal, blocking the passage of liquids or gases, by being compressed between the two mating surfaces comprising the walls of the cavity (gland) into which the ring is installed
Orange Peel
A surface finish on a molded part that is rough and splotchy. Usually caused by moisture in the mold cavity
Oscillating Seal
Most commonly used in faucet valves, in this application the inner or outer member of the gland moves in an arc around the axis of a shaft. Movement is limited to a few turns in one direction and a few turns in the return direction (i.e. faucet on, faucet off)
Outgassing
Primarily occurring in vacuum situations, the volatile (evaporative) components of some rubber compounds may become vaporized in the vacuum and released (outgassed) by the compound into the surrounding environment
Overflow
A designed escape reservoir for rubber compound used to insure mold cavity fill and also allowance for excess compound
Overflow Groove
A groove around the periphery of a mold cavity used to accept any excess material from the cavity during molding. Additional material beyond that which is required to fill the cavity is usually introduced into the cavity to ensure that the part is completely formed and to minimize the presence of entrapped air and voids
Oxidation
The reaction of oxygen with a rubber compound, typically resulting in surface cracking of the rubber material. As oxidation involves the transfer of electrons, reduction in the physical strength of elastomers may also occur from exposure to the oxidizing agent
P
Plasticizer
A chemical agent added to the rubber compounding batch to soften the elastomer for processing, and to improve its physical properties like increase elongation, reduce hardness, improve tack
Parting line
The line visible on the finished molded part, indicating the location where the mold plates were connected
Polymer
A long molecular material chainformed by the chemical combination of many similarly structured, small molecular units
Post-curing
The process of baking or heating parts after they are molded. This process helps to improve the heat and compression set resistance of specific elastomers (e.g. silicones and fluorocarbons)
Q
Quad Ring
Solid elastomeric ring seal with a four lobed cross-section, used similar applications as o-rings, but offering better seal efficiency and lower friction compared to standard o-rings
R
Reinforcing Agent
Fillers like carbon black which are added to the rubber compound batch mix to improve physical properties of the elastomer such as tensile strength
Radial Seal
Seals wherein the compression is applied perpendicular to the seal center-line
Resilience
The capability of elastomers to returnto their original size and shape after deformation
Rubber
A common name for both naturally occurring and synthetically made elastomers
S
Scorching
Premature curing of compounded rubber stock during processing or storage, which if not done might adversely affect material flow and plasticity during subsequent molding and curing processes
Synthetic Rubber
Man-made elastomers such as Silicone, EPDM, FKM, Nitrile, Fluorocarbon, etc.
Seal
Any device used to prevent leakages in the form of passage of a fluid (gas or liquid) or fine particles
Shore A
A hardness scale used to measure the hardness of molded rubber. The Shore A scale is most effectively used to measure rubber with a hardness from 10 to 95 Shore A. For materials harder than 90 to 95 Shore A, the Shore D scale is recommended (see also durometer)
Shrinkage
The linear contraction upon cooling of a molded rubber
Static Seal
A seal that does not move in its environment, except for pulsations caused by cycle pressure
T
Tear Resistance
Resistance to the development of a cut in the seal when tension is applied
Tack
The degree of adhesion of materials of identical nature to each other
Tear Strength
The force required to rupture a material specimen
Tensile Strength
The extension force per cross-sectional area required to fracture a material specimen
Terpolymer
A polymer resulting from the chemical combination of three monomers
Thermal Expansion
expansion in the elastomer caused by temperature increases
Thermoplastic Elastomer (TPE)
A material which exhibits combined characteristics of both plastic (processing properties) and rubber (physical properties).
Thermoset
A material, either rubber or plastic, which when thermally processed undergoes an irreversible chemical reaction to achieve its final state
V
Viscosity
The measure of the resistance of a material to flow under stress
Volume Change
The measure of the swell or shrinkage of a material resulting from immersion in a particular media/chemical agent for a specified time period at a specified temperature
W
Weathering
The detrimental effect on an elastomer after outdoor exposure