Glossary

GLOSSARY

antistick: a coating or surface treatment that prevents the gasket material from adhering to the flanges.

AMS: the abbreviation for American Military Standards

ASTM: the abbreviation for the American Society for Testing and Materials.

beater addition: a manufacturing process used to make gasket material. A water based process where the elastomer is chemically deposited onto the fibers and fillers.

binder: the elastomer or rubber used in gasket material.

butyl (chemical identification:isobutylene isoprene-IIR):is produced by copolymerizing isobutylene with small amounts of isoprene. These rubbers have excellent impermeability to gases, outstanding dielectric properties, good resistance to tearing, good aging properties at elevated temperatures and good chemical stability.

chemical resistance: a gasket material's degradation resistance to the fluid or fluids being sealed.

CI: the abbreviation for cloth-inserted. indicating a sheet of rubber containing one or more plies of fabric covered with rubber.

cloth-both-sides sheet: see CBS. compressed asbestos sheet: a sheet prepared from a rubber compound containing a high percentage of asbestos fiber and vola solvent by the use of a special calender (sheeter) in such a manner that the solvent is volatilized and the compound is caused to build as an oriented sheet on one roll of the sheeter.

compressibility: the property of exhibiting compression under stress In the case of sheet material, the percent of loss of thickness when subjected to a given load applied by a disc of a given diameter for a specified short time and at a specified temperature as defined according to ASTM F-36 test procedures

compression set: the deformation which remains in rubber after has been subjected to and released from a specific compress stress for a definite period of time at a prescribed temperature. Cc Compression set measurements are used to evaluate the creep and stress relaxation properties of rubber.

cork-composition sheet: sheet made from cork granules treated with a binder. creep relaxation: in a flange gasket. loss of stress accompanied constantly decreasing compressed thickness. This type of relaxation is encountered in bolted flange joints

cure time: the time required to produce vulcanization at a given tem perature.

diaphragm sheet: sheet. generally of fabric reinforced rubber, fro which flat diaphragms may be cut. die cut: shaped by punching from a sheet of rubber with a die.

durometer: an instrument for measuring the hardness of vulcanized rubber and plastic.

durometer hardness: an arbitrary numerical value which measures the resistance to indentation of the blunt Indentor point of a durometer. Value may be taken immediately or after a very short specified time.

EPDM (chemical identification:ethylene propylene dienemethylene terpolymer-EPDM) : is a polymer which uses a sulfur cure system. It is recognized for its resistance to weathering and high temperatures. EPDM rubbers are use extensively in outdoor applications. They will withstand the abuse of all types of weather including sunlight, ozone and oxidants, and they exhibit excellent resistance to animal and vegetable oils, water, steam, oxygenated solvents.

elastomer: a macromolecular 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: an increase in length expressed numerically as a fraction or percentage of the initial length.

extrusion: The act or process of shaping sealing compounds by forcing them through a die.

fabric impression: a pattern in a rubber surface formed by contact with fabric during vulcanization.

full-face gasket: a gasket covering the entire flange surface and drilled with bolt holes.

flange: a rib or rim for strength, guiding, or attachment of one object to another. In a gasketed joint, a flange performs all three of these functions

gasket: any of a wide variety of seals or packings used between matched machine parts or around pipe joints to prevent the escape of a gas or fluid.

gasket extrusion: refers to the tendency of a gasket to flow from between flanges, particularly around bolt holes where stresses are concentrated.

hardness: the resistance to indentation. Usually measured with a durometer. (See ASTM D 2240.)

hypalon (chemical identification: chlorosulfonated polyethylene-CSM): chlorosulfonated polyethylene in white chips, used for a wide range of industrial and automotive applications that require high performance.

natural rubber (chemical identification: natural polyisoprene-NR): natural polyisoprene offers an excellent balance of properties, resulting in outstanding performance in many demanding mechanical applications. The major advantages of natural rubber are high resilience, high tensile and tear properties and excellent resistance to cold flow. When exposed to petroleum derivatives, ozone, sunlight and oxygen, natural rubber and its heat aging properties are inferior to many of todayÕs synthetics.

neoprene (chemical identification: chloroprene-CR): is a polymer chloroprene rubber known for its resistance to oil, gasoline, sunlight, ozone and oxidation. ItÕs ability to combine all of these properties make it an excellent general purpose polymer for most applications.

nitrile (chemical identification: butadiene acrylonirile, Buna N, - NBR): is a copolymer of Butadiene and Acrylonitrile. Most nitrile compounds have a relatively high acrylo content, making them exceptionally resistant to petroleum-base oils and hydrocarbon fuels over a temperature range of -40F to +250F.

o-ring: functions as a seal through the mechanical deformation of the elastomeric compound by mating metal surfaces. This creates a condition of zero clearance which blocks the liquid or gas being sealed. The pressure which causes the O-Ring to move is supplied by mechanical pressure or squeeze generated by proper gland design, material selection, and by the system pressure transmitted by the fluid itself.

permeability: the quality or condition of allowing passage of liquids or gases through a layer. Q R SAE: the abbreviation for the Society of Automotive Engineers.

polyurethane: any of various sythetic rubber polymers produced by polymerization of hydroxyl (OH) radical and NCO group from two different coumpounds: used in cuszions, insulation, molded products.

SBR rubber (chemical identification: styrene butadiene, Buna S, GRS): is a synthetic copolymer composed of styrene and butadiene used more often than any of the other synthetics produced today. SBR has similar resistance to solvents and chemicals as natural rubber, and it can successfully bonded to a wide range of materials.

seal: any material or device which prevents or controls the passage of matter across the separable members of a mechanical assembly.

silicone: offers a broad temperature use range of -80F to +400F, and excellent dry heat resistance. Our silicone compounds are inert and guarantee complete compliance to ASTM, military, and FDA specifications required by food, medical, electrical, and filter manufacturers. They are not used in dynamic seals because of relatively poor tensile, tear, and abrasion resistance

temperature resistance: a gasket material's ability to withstand elevated temperatures.

tensile strength: the maximum tensile stress applied while stretching a specimen to rupture. trapped air: air which is enclosed in a product or between a product and a mold surface during cure. (Usually causes a loose ply or cover or a surface mark, depression,or void.)

urethane (chemical identification: polyurethane diisocyanate-CU): is the reaction products of polyethers and polyesters diisocyanates. These rubbers are complex and varied, offering a wide range of pyisical properties.

urethanes come in three basic forms: liquid cast, millable gums, and thermoplastic. Urethanes have outstanding tensile strength and abrasion resistance, and have oil and fuel resistance comparable to nitriles.

viton: DuPont Dow Elastomer's trade name for fluorocarbon elastomers. This fluoroelastomer is well known for its excellent (400¡F/200¡C) heat resistance. Viton offers excellent resistance to aggressive fuels and chemicals and has worldwide ISO 9000 registration. W X Y Z

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