KDL Glossary

  • Abrasion Resistance

    The ability of a rubber compound to resist mechanical wear.

  • Ambient Temperature

    The surrounding temperature relative to the given point of application.

  • Backgrind

    Distortion at the parting line, usually in the form of a ragged indentation.

  • Bake-Out

    A process whereby a vacuum system is heated for a given time at some predetermined temperature to degas off the components. (Ex: Gages, Fittings, Valves, Seals, etc.)

  • Blisters

    A raised spot or bubble on the surface or a separation between layers, usually forming a void or air-filled space in the vulcanized article.

  • Bloom

    A dusty or milky looking deposit caused by migration of a liquid or solid to the surface occurring sometime after curing.

  • Buna-N

    (Nitrile) The most commonly used Elastomer for products because of its resistance to petroleum fluids, good physical properties and useful temperature range.

  • Buna-S

    Co-polymers of butadiene and styrene. Also known as SBR and GRS.

  • Butyl

    A co-polymer of iso-butylene and isoprene.

  • Calender

    A machine used to form sheets of rubber between steel rollers.

  • Co-Polymer

    A polymer consisting of two different monomers chemically combined.

  • Compound

    A mixture of polymers and other ingredients to produce a useable rubber material.

  • Compression Set

    The amount by which a rubber specimen fails to return to its original shape after release of compression load. The numerical value is that percentage of the amount compressed that does not return, NOT a percentage of the ENTIRE specimen.

  • Cure Date

    Date when the rubber product was molded. (Ex: 1Q13 means, 1st Quarter of the year 2013)

  • Durometer

    An instrument for measuring the hardness of rubber.

  • Elasticity

    The property of an article which tends to return to its original shape after deformation.

  • Elastomer

    Any synthetic or natural material with resilience or memory sufficient to return to its original shape after major or minor distortion.

  • Elongation

    Generally is “Ultimate Elongation”, or percent increase in original length of a specimen when it breaks.

  • Extrusion

    Distortion or flow under pressure of a portion of seal into clearance between mating metal parts.

  • Filler

    Chemically inert, finely divided material added to the Elastomer to aid in the processing and improvement of physical properties.

  • Flash

    Excess rubber left around a rubber part after molding due to space between mating mold surfaces.

  • Gasket

    A device used to retain fluids under pressure or seal out foreign matter. Normally refers to a static seal.

  • Gate

    The point of rubber entry into a mold cavity.

  • Hardness

    Resistance to a distorting force measured by the relative resistance of the material to an indented point of a standard hardness testing instrument.

  • Hardness, Shore A

    The rubber Durometer hardness as measured on a Shore “A” gauge. Higher numbers indicate harder material. (Ex: 30 Shore is Soft . . . 90 Shore is Hard)

  • HCR

    High Consistency Rubber, rubber that is processed on a rubber mill having much higher viscosity than liquid silicone rubber. (Same as Millable Gum Rubber)

  • LIM

    Liquid Injection Molding, refers to the processing of liquid silicone rubber (LSR).

  • Liquid Silicone Rubber

    Liquid Silicone Rubber, the silicone rubber utilized in the LIM™ process.

  • LSR

    Liquid Silicone Rubber, the silicone rubber utilized in the LIM™ process.

  • Millable Gum Rubber

    Rubber that is processed on a rubber mill having a much higher viscosity than liquid silicone rubber. (Same as High Consistency Rubber)

  • Mismatch

    Unsymmetrical seal caused by dissimilar cavities in mating mold sections.

  • Modulus

    Tensile stress at a specified elongation. (Usually 100% elongation for elastomers)

  • Mold Finish

    The uninterrupted surface produced by intimate contact of rubber with the surface of the mold at vulcanization.

  • Monomers

    A chemical compound that can undergo polymerization.

  • Nitrile

    (Buna-N) The most commonly used Elastomer for products because of its resistance to petroleum fluids, good physical properties and useful temperature range.

  • Occlusion

    The mechanical process by which vapors, gases, liquids or solids are entrapped within the folds of a given substance during working or solidification.

  • Off-Register

    Misalignment of mold halves causing an out-of-round part cross section.

  • Oil Resistant

    Ability of a vulcanized rubber to resist the swelling and deterioration effects of various types of oils.

  • Oil Swell

    The change in volume of a rubber article due to absorption of oil or other fluids.

  • Out-Gassing

    A vacuum phenomenon wherein a substance spontaneously releases volatile constituents in the form of vapors or gases. In rubber compounds, this may include water vapor, plasticizers, air, inhibitors, etc.

  • Permanent Set

    The deformation remaining after a specimen has been stressed in tension for a definite period and released for a definite period.

  • Permeability

    The rate at which a liquid or gas under pressure passes through a solid material by diffusion and solution. In rubber terminology, it is the rate of gas flow expressed in atmospheric cubic centimeters per second through an Elastomeric material one centimeter square and one centimeter thick. (atm cc/cm squared / cm/sec)

  • Pigment

    A colored material, usually a powder or paste, used to color rubber.

  • Polymer

    A material formed by the joining together of many (poly) individual units (mer) of one or more monomers. Synonymous with Elastomer.

  • Post Cure

    The final step in the vulcanization process for the more exotic elastomers. Provides stabilization of parts and drives off decomposition products resulting from the vulcanization process.

  • Resilient

    Capable of returning to original size and shape after deformation.

  • RTV

    Room Temperature Vulcanization, generally silicone rubber, that after mixing, will cure when exposed to air.

  • Rubber, Natural

    Raw or crude rubber obtained from vegetable sources.

  • Rubber, Synthetic

    Manufactured or man-made elastomers.

  • Runner

    The distribution system within a mold connecting the sprue to the gates.

  • SBR

    Styrene butadiene. Very good resilience & tensile strength. Poor ozone & oil resistance.

  • Scorching

    Premature curing or setting up of raw compounding during processing.

  • Screw

    The rotating component of an injection press which delivers the rubber into the mold.

  • Shrinkage

    Decreased volume of seal, usually caused by extraction of soluble constituents by fluids followed by air drying.

  • Silicone Rubber

    Elastomer that retains good properties through extra wide temperature range.

  • Specific Gravity

    The ratio of the weight of a given substance to the weight of an equal volume of water at a specified temperature.

  • Sprue

    The initial entry point of rubber into a mold. In a simple mold, it is the same as a gate.

  • Sprue Marks

    Marks left on the surface of a rubber part, usually elevated, after removal of the sprue or cured compound in the gate through which the compound is injected or transferred.

  • Static Seal

    Part designed to seal between parts having no relative motion. (See Gasket)

  • Tear Resistance

    Resistance to growth of a cut or nick when tension is applied to the cut specimen. Commonly expressed as “pounds per inch thickness”.

  • Tensile Strength

    Force in “pounds per square inch” required to cause the rupture of a specimen of a rubber material.

  • Thermal Expansion

    Expansion caused by increase in temperature. May be linear or volumetric.

  • Viscosity

    The property of fluids by which they resist an instantaneous change of shape. (Ex: Resistance to flow)

  • Vulcanization

    A thermo-setting reaction involving the use of heat and pressure, resulting in greatly increased strength and elasticity of rubber-like materials.