435 technical terms in rubber industry

435 Technical Terms

You Need To Know

in Rubber Industry A Compilation by Rubber & Tyre Machinery World

435 Technical Terms You Need To Know in Rubber Industry http://rubbermachineryworld.com

A Rubber & Tyre Machinery World Compilation – Aug 2016. of 20

A 1. Abrasion : The wearing away of a surface in service by mechanical action, such as rubbing, scraping or erosion. 2. Abrasion Resistance : The ability of a rubber compound to resist mechanical wear. 3. Abrasion Resistance Index : A measure of the abrasion resistance of a rubber relative to that of a standard rubber under the same specified conditions, expressed as a percentage. 4. Absorption : The physical mechanism by which one substance takes up another substance (liquid, gas or vapor) into its interior. 5. Accelerated Life Test : Any set of test conditions designed to reproduce, in a short time, the deteriorating effect obtained under normal service conditions. 6. Accelerated Service Test : A service or bench test in which some service condition, such as speed, temperature or continuity of operation, is exaggerated in order to obtain a result in shorter time. 7. Accelerator : A compounding material used in small amounts, with a vulcanizing agent, to increase the speed of vulcanization.. 8. Acid Resistance : The ability to resist the action of identified acids within specified limits of concentration and temperature. 9. Acrylic : A polymer for which resistance to air and hot oil at temperatures above 30 degrees Fahrenheit are required. 10. Adhere : To cling or stick together. 11. Adhesion : Tendency of rubber to bond or cling to a contact surface. 12. After Cure : Continuation of vulcanization after the desired cure is effected and the heat source removed (also referred to as Post-Cure).

13. Ageing : To undergo changes in physical properties with age or lapse of time. 14. Ageing, Accelerated : Tests run on various rubbers to find out, in as short a period as possible, the destructive influence of light, oxygen, heat and ozone. 15. Ageing, Oxygen Bomb : A means of accelerating the change in the physical properties of rubber compounds by exposing them to action of oxygen at an elevated temperature and pressure. 16. Ageing , Air Bomb : Similar to an oxygen bomb, but used with air. 17. Ageing, Shelf : Ageing during storage. 18. Agglomerate, Compounding material : A cluster of particles of one or more compounding materials loosely held together. Most commonly used to describe carbon black. 19. Air Checks : Surface markings or depressions due to trapping air between the material being cured and the mold surface. 20. Air Curing : Vulcanization of a rubber product in air, as distinguished from in a press or steam vulcanizer. 21. Alpha Particles : Positively charged particles composed of two protons and neutrons (often referred to simply as helium atom molecule); characterized by limited penetration. 22. Ambient Temperature : The surrounding temperature relative to the given point of application. 23. Aniline Point : The lowest temperature at which equal volume of pure, fresh aniline and oil will completely dissolve in one another is the aniline point of the oil. 24. Antidioxidant : An organic substance which inhibits or retards oxidation. 25. Antiozonant : A substance that retards or prevents the appearance of cracks from action of ozone when the elastomer is exposed under tension, either statically or dynamically, to air containing ozone.



26. Antirad : A material which inhibits radiation change. 27. Aromatic oil: A hydrocarbon process oil containing at least 35%, by mass, of aromatic hydrocarbons. 28. Atmospheric Aging Resistance : Loss of physical properties due to the normal action of its surroundings (weather). 29. Atmospheric Cracking : Cracks produced in the surface of rubber articles by exposure to atmospheric conditions. 30. Autoclave : A vessel used for vulcanizing rubber products by means of steam under pressure. 31. Axial Seal : A term usually applied to an O-Ring where the squeeze is applied on the top and bottom surfaces. Another term for face seal.

B 32. Backrind : A molding defect in which the rubber adjacent to the parting line shrinks below the surface of the molded product, with the parting line often being ragged and torn. 33. Back-Up-Ring : (Anti extrusion device) A ring of relatively hard and tough material, placed in the gland between the O-Ring and groove side walls, to prevent extrusion of the O-Ring. 34. Bake Out : A process whereby a vacuum system is heated for a given time at some predetermined temperature to degas all the components, i.e. gauges, fittings, valves, seals. 35. Banbury Mixer : A specific type of internal mixer used to blend fillers and other ingredients with an elastomer. 36. Bank: The reservoir of material at the opening between rolls of a mill or calendar. 37. Batch : The product of one mixing operation. 38. Bench Marks : Two marks of known separation, applied to a specimen to measure the strain of the specimen during extension.

39. Bench Test : A modified service test in which the service conditions are approximated, but the equipment is conventional laboratory equipment and not necessarily identical with that in which the product will be employed. 40. Blank : A portion of a rubber compound of suitable volume to fill the cavity of a mold. 41. Beta Particles : Negatively charged particles or electrons, characterized by limited penetration. 42. Bleeding : Migration to the surface of plasticizers, waxes or similar materials, to form a film or bead. 43. Blemish : A mark, deformity or injury which impairs appearance. 44. Blister : A raised spot in the surface, or a separation between layers, usually forming void or air-filled space in the vulcanized article. 45. Bloom : A dusty or milky looking deposit that sometimes appears on the surface of an molded product after molding and storage, caused by migration of a liquid or solid to the surface. Not to be confused with dust from external sources. 46. Blow : The volume expansion that occurs during the production of cellular or sponge rubber. 47. Blowing Agent : A compounding material used to produce gas by chemical or physical action, or both, in the manufacture of hollow or cellular articles. 48. Bond : The term commonly used to denote the attachment of a given elastomer to some other member. Bonds may be classified by types, as follows:

a. Mechanical - purely physical attachment accomplished by such means as "through" holes, interlocking fingers, envelope design, riveting, etc.;

b. Cold - adhesion of previously vulcanized elastomer to another member through use of suitable contact cements;

c. Vulcanized - adhesion of an elastomer to a previously primed surface using



heat and pressure, thus vulcanizing the elastomer at the same time.

49. Break : A separation or discontinuity in any part of an article. 50. Break-Out : Force to inaugurate sliding. Expressed in same terms as friction. An excessive break-out value is taken as an indication of the development of adhesion. 51. Brittleness : Tendency to crack when deformed. 52. Brittle Point: The highest temperature at which a rubber specimen will fracture under sudden impact. 53. Buna -N : See Nitrile. 54. Buna-S : A general term for the copolymers of butadiene and styrene. Also known as SBR and GRS. 55. Butaprene : See Nitrile. 56. Buffing : The grinding of a vulcanizate, producing a roughened or velvety texture. 57. Bumping, Moulding Process : The application, release, and reapplication of pressure prior to the start of vulcanization to vent entrapped gases, thereby facilitating complete filling of the mould cavities. 58. Butt Joint : Joining two ends of a seal whereby the junction is perpendicular to the mold parting line. 59. Butyl : A copolymer of iso-butylene and isoprene.

C 60. Calender : A machine with two or more parallel, counter-rotating rolls, with controllable roll-to-roll spacing, rotating at selected surface speeds and controlled temperatures. 61. Carbon Black : A material consisting essentially of elemental carbon in the form of near-spherical colloidal particles and particle aggregates. It is produced by partial combustion or thermal decomposition

of hydrocarbons. Primarily used as a reinforcing agent, but also affects many other dynamic properties of a rubber compound. 62. Catalyst : A chemical that, in small quantities, accelerates a chemical reaction without itself necessarily becoming part of the final product. 63. Cell : A single small cavity surrounded partially or completely by walls. 64. Cell, Closed : A cell totally enclosed by its walls, hence not interconnected with other cells.

65. Cell, Open : A cell not totally enclosed by its walls and hence interconnected with other cells.

66. Cellular Rubber : A generic term for materials containing many cells (either open, closed, or both) dispersed throughout the mass of rubber.

67. Cellular Material, Collapse : An undesirable densification of a cellular material resulting from the breakdown of its cellular structure.

68. Cement, Rubber : An adhesive that is either a liquid dispersion or solution of raw or compounded rubber, or both.

69. Chalking : The formation of a powdery residue on the surface of a rubber, commonly resulting from surface degradation.

70. Checking : The short, shallow cracks on the surface of a rubber product, usually resulting from damaging action by environmental elements. 71. Chemical Bonding : A method of bonding rubber to inserts by applying special adhesives to the insert prior to molding. 72. Chemigum : (TM, R.T. Vanderbilt Co.) See Nitrile. 73. Closure Dimension : Dimensions of a molded rubber product that are affected by flash thickness (mold closure) variation.



74. Coagent: A compounding ingredient used in small amounts to increase the crosslinking efficiency of certain non-sulfur vulcanizing systems (especially organic peroxides), or to modify the properties given by such systems. 75. Coating : A uniform layer of chemical primers or adhesives to produce a chemical bond between the rubber and substrate. May also refer to special surface treatments that can be applied to rubber to achieve special properties. 76. Coated Fabric : A flexible product composed of a textile fabric and an adherent polymeric material applied to one or both surfaces. 77. Coefficient of Thermal Expansion : Average expansion per degree over a stated temperature range, expressed as a fraction of initial dimension. May be linear or volumetric. 78. Cold Checks : A defect on calendered sheeting consisting of surface roughness. 79. Cold Flexibility : Flexibility following exposure to a predetermined low temperature for a predetermined time. 80. Cold Flow : Slow deformation, under gravitational force, at or below room temperature. Sometimes referred to as “creep”. 81. Cold Resistance : Able to withstand the effects of cold or low temperatures without loss of serviceability. 82. Commercially Smooth : Degree of smoothness of a surface of an article which is acceptable for use. 83. Compound : A term applied to a mixture of polymers and other ingredients to produce a usable rubber material. 84. Compound, Standard: A control or reference compound prepared according to a prescribed formula and mixing procedure. 85. Compression Molding : Molding process in which the material is placed directly in the mold cavity and compressed to shape by closure of the mold, under heat and pressure.

86. Compression Modulus : The ratio of the compression stress to the resulting compression strain (the latter expressed in the direction of force). Compression Modulus may be either static or dynamic. 87. 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. A low compression set is desirable in molded rubber parts such as seals and gaskets, which must retain their dimensions to maintain an effective seal. 88. Conditioning (Environmental) : The storage of a rubber, under specified conditions (time, temperature, humidity) prior to testing. 89. Conditioning (Mechanical): The prescribed program of deformation of a specimen prior to testing. 90. Conductive Rubber : A rubber capable of conducting electricity. Most generally applied to rubber products used to conduct static electricity. 91. Copolymer : A polymer consisting of two different monomers chemically combined. 92. Corona Resistance : The ability of a rubber acting as insulator to withstand the effects of high voltage discharge. Indications of failure appear as surface cracks. 93. Corrosion (Packing) : Corrosion of rigid member (usually metal) where it contacts packing. The actual corroding agent is fluid medium trapped in the interface. 94. Corrosive (Packing) : A property of packing whereby it is assumed (often incorrectly) to promote corrosion of a rigid member of a trapped fluid. 95. Cracker : A heavy-duty mill having two deeply corrugated or pyramid-cut rolls for breaking down a rubber or a mix, or for cutting rubber or a mix into pieces. 96. Crack : A fissure originating in the surface of a rubber vulcanizate or product as a result of natural weathering.



97. Crack, Flex : A fissure originating in the surface of a rubber vulcanizate, resulting from cyclic deformation (usually bending). 98. Crack, Ozone : Fissures originating in the surface of a rubber vulcanizate, caused by exposure to an ozone-containing environment; these fissures are perpendicular to the direction of strain, and usually occur in rubbers having main chain unsaturation. 99. Cracking : The sharp break or fissure in the surface. Generally due to excessive strain. 100. Crazing : Formation of a random pattern of shallow cracks on a rubber surface usually due to ageing by light. Unlike ozone cracking, crazing does not depend on the presence of a tensile strain in the rubber. 101. Creep : The progressive relaxation of a given rubber material while it is under stress. This relaxation eventually results in permanent deformation, or "set". 102. Crosslink : The chemical bond bridging one polymer chain to another. 103. Crosslinking : Formation of chemical bonds between polymer chains to give a network structure. 104. Cross-Linking Agents : A chemical, or chemicals, that bonds the polymer chains together to form a thermoset rubber product. 105. Cross-Section : A seal as viewed if cut at right angles to the molding line, showing internal structure. 106. Crystallinity : Orientation of the disordered long chain molecules of a polymer into repeating patterns. The degree of crystallinity effects stiffness, hardness, low temperature flexibility, and heat resistance. 107. Cure : The thermo process that causes a chemical change in the raw stock, turning it into the finished rubber part . Also see Vulcanization.

108. Cure Date : The date a rubber product was molded. Normally expressed, for example, as 1Q04, meaning the first quarter of the year 2004. 109. Cure Meter : A testing device that measures the progress of vulcanization. 110. Curing Temperature : The temperature at which the rubber product is vulcanized. 111. Cure Time : The preset time needed to complete the curing process 112. Cylinder : Chamber in which piston, plunger, ram, rod or shaft is driven by, or against, the system fluid.

D 113. Damping : The quality of an elastomer to absorb forced vibrational energy. That property of a material or system that causes it to convert mechanical energy to heat when subjected to deflection; in rubber the property is caused by hysteresis. 114. Deflashing : Any of various processes used to remove the waste edge from a molded rubber part. 115. Degassing : The intentional, but controlled, outgassing of a rubber substance or other material. 116. Density : The mass per unit volume of a material. Also referred to as specific gravity. 117. Desiccant : A compounding material used to irreversibly absorb moisture, particularly for the purpose of minimizing risk of porosity during vulcanization. 118. Die Swell : The difference between the dimensions of the cross section of an extrudate, and the corresponding dimensions of the die orifice from which the extrudate was formed. It is usually expressed as the percent increase in the cross-sectional area. 119. Diene Polymer : A polymer formed from one or more monomer species, at least one of which is a diolefin.



120. Dielectric Properties : The ability of a material to resist puncture due to electric stress. The property is expressed in terms of "volts per MIL thickness". 121. Dielectric Strength: The measure of a vulcanizate’s ability to resist passage of a disruptive discharge produced by an electric stress. 122. Diffusion : The mixing of two or more substances (solids, liquids, gasses, or combinations thereof) due to the intermingling motion of their individual molecules. Gasses diffuse more readily than solids. 123. Dispersion : The application of shearing forces to distribute one or more compounding materials uniformly throughout the mass of a rubber compound. 124. Dumbbell Specimen : A flat specimen of rubber having a narrow straight central portion of essentially uniform cross section with enlarged ends. Used for testing purposes. 125. Durometer : An instrument for measuring the hardness of a rubber; measures the resistance to the penetration of an indentor point into the surface of the rubber. 126. Dusting : The application of a powder to a rubber surface, generally to prevent adhesion to another surface. 127. Dynamic : An application in which the seal is subject to movement, or moving parts contact the seal. 128. Dynamic Packing : A package employed in a joint whose members are in relative motion. 129. Dynamic Properties : Mechanical properties exhibited under repeated cyclic deformation. 130. Dynamic Seal : A seal required to prevent leakage past parts which are in relative motion. Also means a seal which is subjected to reciprocating, rotational, or oscillating motion.

E 131. Ejector Pins :

Pins or blades that, when activated internally to the mold, eject the part from the mold cavity. Sometimes referred to as “knock outs”. 132. Elasticity : The property of an article which tends to return to its original shape after deformation. 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. It is the opposite of plasticity. The term elasticity is often loosely employed to signify the “stretchiness” of rubber 133. Elastomer : Any natural or synthetic material with resilience or memory sufficient to return to its original shape after major or minor distortion. 134. Electron Volt : Unit of energy in atom calculations equal to 1.602 X 1012 ergs. 135. Elongation : Extension produced by a tensile stress. 136. Elongation, Percent : The extension of a uniform section of a specimen expressed as percent of the original length. 137. Elongation, Ultimate : The elongation at the time of rupture. 138. EPDM : Terpolymer of Ethylene-Propylene-Diene (noted for excellent ozone resistance). 139. Erg : Unit of energy (C.G.S.) equal to one dyne centimeter, or approximately equal to the work done by force of One (1) milligram, causing a movement of one (1) centimeter. 140. Evaporation : The direct conversion from liquid to vapor state of a given fluid. 141. Explosive Decompression : The rupture of a rubber article caused by the rapid reversal of pressure, causing dissolved gases in the rubber to escape quickly to the surface of the vulcanizate. 142. Extender : A material (usually organic) used to augment the polymer in a compound. 143. Extensometer : A device for determining elongation of a specimen as it is strained.



144. Extrudate: The material that issues from an extruder. 145. Extruder : A machine designed to force rubber through an orifice, which is shaped to the geometry of the desired end product. 146. Extrusion : The continuous shaping of a material during passage through a die. 147. Extrusion (seal) : Distortion, under pressure, of a portion of a seal into the clearance between mating metal parts.

F 148. Face Seal : A seal between two flat surfaces. In an O-Ring, this means it seals on the top and bottom, not the ID and OD. Also referred to as an axial seal. 149. Fatigue Breakdown : The deterioration of an elastomeric product during repeated deformation. 150. Fatigue Life : The number of deformations required to produce a specified state of fatigue breakdown in a test specimen or product that is deformed under a prescribed set of conditions. 151. Feather Edge : The sharp, thin edge on parts, such as wiper seals and cups. (Also called "Knife Edge"). 152. Filler : A solid compounding material, usually in finely divided form, which may be added in relatively large proportions to a polymer for technical or economic reasons. The most commonly used filler is carbon black. Most fillers also function as reinforcing agents. 153. Filler, Inert : A filler having no reinforcing effect. 154. Fixed Dimension : Dimensions on a rubber product that are not affected by flash thickness or mold closure variation. 155. Flame Resistance : The resistance to burning of material that will not withstand combustion under ordinary conditions. 156. Flash :

Excess rubber left around a rubber part after molding, due to space between mating mold surfaces; removed by trimming. 157. Flex Cracking : A surface cracking induced by repeated bending or flexing. 158. Flex Life : The number of cycles required to produce a specified state of failure in a specimen that is flexed in a prescribed method. 159. Flexometer : A machine that subjects a test specimen to repeated deformation by compression, tension, shear, bending, torsion or any combination thereof. 160. Flex Resistance : The relative ability of a rubber article to withstand dynamic bending stress. 161. Flexural Strength : The ability of a material to flex without permanent distortion or breaking. 162. Flock : Fibrous filler sometimes used in rubber compounding. 163. Flow : Ability of heated plastic, or uncured rubber, to travel in the mold and runner system during the molding process. 164. Flow Cracks : Surface imperfections due to improper flow and failure of stock to knit or blend with itself during the molding operation. 165. Flow Marks : Marks or line on a molded product, caused by imperfect flow of the raw compound during forming. 166. Fluid : A liquid or a gas. 167. Fluorocarbon : A polymer designed to meet the most rigid requirements in oils, solvents, synthetic lubricants and corrosive chemicals, at elevated temperatures. 168. Friction : Resistance to motion due to contact of surfaces. 169. Friction (Break Out) : Friction developed during initial or starting motion.



170. Friction (Running) : Constant friction developed during operation of a dynamic O-Ring. 171. Frosting : T he formation of a matte, whitish appearance on a rubber surface exposed to air, resulting from the action of ozone. Often confused with bloom. 172. Fuel (Aromatic) : Fuel which contains benzene or aromatic hydrocarbons; causes little swell of rubber. 173. Fuel (Non-Aromatic) : Fuel which is composed of straight chain hydrocarbons; causes little swell of rubber. 174. Furnace Carbon Black : A type of carbon black produced by the decomposition reaction of hydrocarbons, when injected into a high velocity stream of combustion gases under controlled conditions.

G 175. Gamma Radiation : Electromagnetic disturbance (photons) emanating from an atomic nucleus. This type of radiation travels in wave form, much like X-Rays or light, but has a shorter wave length (approx. 1 Ado or 107 mm). It is very penetrating. 176. Gasket : A deformable material clamped between essentially stationary faces to prevent the passage of matter through an opening or joint. A static mechanical seal. 177. Gas Permeability : The degree to which a substance resists permeation of gas under pressure. 178. Gates : The openings in an injection or transfer mold that ensure the even flow of material into the cavity. 179. Gate Mark : A raised spot or small depression on the surface of an injection or transfer molded part, where the gates interface the cavity. (Also called "Sprue Mark") 180. Gland : The cavity into which an O-Ring is installed. Includes the groove and mating surface of the second part, which together confine the O-Ring. 181. Glass Transition Temperature :

The approximate mid-point of the temperature range over which a reversible change in a polymer occurs from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one. 182. Grain : The unidirectional orientation of rubber or filler particles in a rubber compound.green strength: the resistance to deformation of rubber stock in the uncured state. 183. Groove : The machined recess into which a seal is fitted.ground vulcanized rubber: vulcanized rubber in particulate form; used as an extender or filler. 184. Guayule Rubber: A form of natural rubber, cis polyisoprene, obtained from the shrub, Parthenium Argentatum. 185. Gum Compound : A rubber compound containing only those ingredients necessary for vulcanization and small amounts of other ingredients for processing, coloring, and for improving the resistance to ageing.

H 186. Hardness : Resistance to a disturbing force. Measured by the relative resistance of a material to an intender point of any one of a number of standard hardness testing instruments. (Also see Durometer). 187. Heat Aging : A test for degradation of physical properties as a result of exposure to high temperature conditions. 188. Heat Build-up : The accumulation of thermal energy generated within a material as a result of hysteresis, evidenced by an increase in temperature. 189. Heat Deflection Temperature : The temperature at which a standard plastic test bar deflects 0.010 in. under a stated load of either 66 psi or 264 psi. 190. Heat History : The accumulated amount of heat a rubber stock has been subjected to during processing operations. Incipient cure or scorch can take place if heat history is excessive.



191. Hermetic Seal : An airtight seal having no evidence of detectable leakage. 192. Homogeneous : A material of uniform composition throughout. 193. Homopolymer : A polymer formed from a single monomer species. 194. Hydrocarbon Solvents - Aromatic : Solvents having basic benzene structure, usually coat tar types such as benzene, toluene orxylene. 195. Hysteresis Loss : The loss of mechanical energy due to hysteresis. 196. Hysteresis : The conversion of mechanical energy to heat in rubber undergoing strain.

I 197. Identification : Colored dots or stripes on seals for identification purposes; seldom used. 198. Immediate Set : The deformation found by measurement immediately after removal of the load causing the deformation. 199. Immersion : Placing an article into fluid, generally so it is completely covered. 200. Impact : The single, instantaneous stroke or contact of a moving body with another, either moving or at rest, such as a large lump of material dropping on a conveyor belt. 201. Impact Resistance: Resistance to fracture under shock force. 202. Impact Strength : A measure of the toughness of the material, as the energy required break a specimen with a single blow. 203. Inhibitor : A material used to suppress a chemical reaction.insert: typically, a metal or plastic component to which rubber is chemically and/or physically bonded during the molding process. 204. IRHD (International Rubber Hardness

Degrees) :

International Rubber Hardness Degrees. An alternate method of measuring rubber hardness. IRHD units are approximately equivalent to Shore A durometer units, although a different apparatus is used. 205. Injection Molding : Molding in which the rubber or plastic stock is heated and, while in the flowable state, is forced or injected into the mold cavity. 206. Insert : Typically, a metal or plastic component to which rubber or plastic is chemically and/or physically bonded during the molding process. 207. Isoprene-acrylonitrite Rubber : A low-plasticity copolymer with around 34 per cent ACN.

K 208. Knit Line : An internal or external defect in a vulcanizate, where raw stock did not unite into a homogeneous mass during vulcanization. 209. Knuckles : Small tough rubber pieces scattered throughout a bale of raw rubber that do not disperse easily or accept carbon black and other compounding materials during mixing.

L 210. Leakage Rate : The rate at which a fluid (either gas or liquid) passes a barrier. Total Leakage Rate includes the amounts that diffuse or permeate the material of the barrier as well as the amount that escapes around it. 211. Life Test : A laboratory procedure used to determine the amount and duration of resistance of an article to specific sets of destructive forces or conditions. 212. Linear Expansion : Expansion in any one linear dimension, or the average of all linear dimensions. 213. Liquid Curing Medium (LCM) : A molten phase, generally a mixture of sodium nitrate, that is used as a heating medium for the continuous vulcanization of a rubber mix, usually following extrusion. 214. Logy : Sluggish, low snap or recovery of a material.



215. Low Temperature Flexibility : The ability of a rubber product to be flexed, bent or bowed at low temperature without cracking.

M 216. mm Hg : Millimeters of Mercury. In vacuum work, a measure of absolute pressure, being the height of a column of Mercury that the air or other gas will support. Standard atmospheric pressure will support a Mercury column 760 millimeters high. Any value less than that represents some degree of vacuum. 217. Mandrel : A bar, serving as a core, around which rubber is extruded, forming a center hole.

218. Masterbatch : A homogeneous mixture of rubber and one or more materials in known proportions for use as a raw material in the preparation of the final compounds. Masterbatches are used to facilitate processing or enhance the properties of the final product, or both. 219. Mastication : The breakdown or softening of raw rubber by the combined action of mechanical work (shear), and atmospheric oxygen, sometimes accelerated by the use of a peptizer, and frequently at elevated temperatures. 220. Mechanical Bond : A method of physically bonding rubber to inserts through the use of holes, depressions or projections in the insert. 221. Memory : The tendency of a material to return to original shape after deformation. 222. Microhardness : An electronic measurement of rubber hardness for specimens below .25 inch in thickness. Microhardness, like Shore A durometer, is also a measure of indentation. 223. Mill : A machine used for rubber mastication, mixing, or sheeting, having two counter-rotating rolls with adjustable longitudinal axis separation that usually rotate at different speeds. 224. Mirror Finish : A bright, polished surface. 225. Mismatch :

A mold defect which produces an asymmetrical part, caused by dissimilar cavities in mating mold plates. 226. Mixer : A machine that incorporates and disperses compounding ingredients into rubber to form a mix or a compound through the action of mechanical work (shear). 227. Mixer, Internal : A machine with a closed chamber in which specially shaped rotors masticate the rubber or incorporate and disperse compounding materials, or both, into the rubber. 228. Modulus : The ratio of stress to strain; that property of a material, which, together with the geometry of a specimen, determines the stiffness of the specimen. In the physical testing of rubber, the force necessary to produce a stated percentage of elongation. 229. Modulus of Elasticity : One of several measurements of stiffness or resistance to deformation, but often incorrectly used to indicate specifically static tension modulus. 230. Mold Cavity : Hollow space, or cavity, in the mold, which is used to impart the desired form to the product being molded. 231. Mold Finish : The uninterrupted surface produced by intimate contact of rubber with mold surface at vulcanization. 232. Molding, Compression : The process of forming a material to a desired shape by flow induced by a force applied after material is placed in the mold cavity. 233. Molding, Injection: The process of forming a finished product by forcing material from an external heated chamber through a sprue (runner, gate) into the cavity of a closed mold. This is accomplished by means of a pressure gradient that is independent of the mold clamping force 234. Mold Lubricant : A material usually sprayed onto the mold cavity surface prior to the introduction of the uncured rubber, to facilitate the easy removal of the molded part. 235. Mold Marks :



Indentations or ridges embossed into the skin of the molded product by irregularities in the mold cavity. 236. Mold Register : Accuracy of alignment/fit of mold sections. 237. Molding Solutions : In the field of custom molded rubber or plastic, the solution to your problems. 238. Mooney Scorch : The measurement of the rate at which a rubber compound will cure or set up by means of the Mooney Viscometer test instrument. 239. Molding Shrinkage : The difference in dimensions between a molded product and the mold cavity in which it was molded, both the mold and product being at normal room temperature when measured. 240. Molding, Transfer : The process of forming a material by forcing it from an auxiliary heated chamber through a sprue hole (runner, gate) into the cavity of a closed mold by means of a pressure gradient that is dependent on the mold clamping force. 241. Monomer : A low molecular weight substance consisting of molecules capable of reacting with like or unlike molecules to form a polymer. 242. Mold Marks : A surface imperfection transferred to a molded product from corresponding marks on a mold. 243. Mooney Viscosity : Measurement of the plasticity or viscosity of an uncompounded, or compounded vulcanized, elastomer seal material by means of the Mooney Shearing Disk Viscometer.

N 244. Naphthenic Oil : A hydrocarbon process oil containing more than 30 %, by mass, of naphthenic hydrocarbons. 245. Necking : The localized reduction in cross section that may occur in a material under tensile stress. 246. Nerve : The elastic resistance of unvulcanized rubber or rubber mixes to permanent deformation. 247. Nip :

The radial clearance between rolls of a mill or calendar on a line of centers. 248. Neoprene (GR-M) : A DuPont Dow Elastomers polymer of chloroprene which is prepared from coal, salt and limestone. 249. Nitrile : (see also Buna-N) The most commonly used elastomer for O-Rings because of its resistance to petroleum fluids, its good physical properties, and its useful temperature range. 250. Nominal Dimension : Nearest fractional equivalent to actual decimal dimension. 251. Non-aromatic : Straight chain organic structures, such as petroleum type solvents. 252. Non-blooming : The absence of "bloom". 253. Non-fill : A defect resulting from the failure of the rubber material to fill out all of a mold cavity. 254. Non-Sulfur Vulcanizing System : A vulcanizing system not requiring free or donated sulfur.

O 255. Occlusion : (A) The mechanical process by which vapors, gases, liquids or solids are entrapped within folds of a given substance during working or solidification; (B) the materials so trapped. 256. Off-register : Misalignment of mold halves causing asymmetrical parts, i.e. top and bottom mold plates don’t line up properly.. 257. Oil Resistant : Ability to vulcanize rubber to resist the swelling and deteriorating effects of various types of oils. 258. Oil Swell : The change in volume of a rubber article due to absorption of oil or other fluid. 259. O-Ring : A product of precise dimensions, molded in one piece, to the configuration of a torus (doughnut) with a circular cross section, suitable for use in a machined groove for static or dynamic sealing.



260. O-Ring Seal : The combination of a gland and O-Ring providing a fluid tight closure. (Some designs permit minimum leakage.) 261. O-Ring Seal / Moving (Dynamic) : O-Ring seal in which there is relative motion between some gland parts and the O-Ring; oscillating, reciprocating or rotary motion. 262. O-Ring Seal / Non-moving (Static) : O-Ring seal in which there is no relative motion between any part of the gland and the O-Ring. (Distortion from fluid pressure or swell from fluid immersion is excluded.) 263. Optimum Cure : State of vulcanization at which the most desirable combination of properties is attained. 264. Outgassing : A vacuum phenomenon wherein 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. 265. Over-Cure : A degree of cure greater than the optimum, causing some desirable properties to be degraded. Usually results in a loss of elongation and an increase in hardness. 266. Overflow Groove : A groove around the mold cavity used to accept excess material from the cavity and to create a better "pack" for the part. 267. Oxidation : The reaction of oxygen on a compound, usually detected by a change in the appearance or feel of the surface, or by a change in the physical properties, or both. 268. Oxygen Bomb : A chamber capable of holding oxygen at an elevated pressure which can be heated to an elevated temperature. Used for an accelerated aging test. 269. Ozone Resistance : Ability to withstand the deteriorating effect of ozone (which generally causes cracking.)

P 270. Packing :

A flexible device used to retain fluid under pressure, or seal out foreign matter. Normally refers to a dynamic seal. 271. Paraffinic Oil : A hydrocarbon process oil, most or all of which is composed of alkanes 272. Parting Line : The line on the surface of a molded part where the mold plates meet. 273. Peptizer : A compounding material used in small proportions to accelerate, by chemical action, the softening of rubber under the influence of mechanical action, or heat, or both. 274. Permanent Set : The deformation remaining after a specimen has been stressed in tension for a definite period, and released for a definite period. 275. Permeability : The rate at which liquid or gas, under pressure, passes through a solid material by diffusion and solution. In rubber terminology : the rate of gas flow, expressed in atmospheric cubic centimeters per second, through an elastomeric material, one centimeter square and one centimeter thick. 276. Permeation : The diffusion of a media (generally a gas) through a rubber or plastic component. 277. PH : Determines the concentration of either an acid or a base. 278. PHR : Abbreviation for parts per hundred of rubber, used for indicating the proportions of ingredients in a rubber compound. 279. Pigment : An insoluble compounding material used to impart color to rubber. 280. Pit (or Pock) Mark : A circular depression, usually small. 281. Plasticity : When subject to sufficient shearing stress, any given body will be deformed. After stress is removed, if there is no recovery, the body is completely plastic. If recovery is complete and instantaneous, the body is completely elastic. A balance between the two is required. 282. Plasticizer :



A substance, usually a heavy liquid, added to an elastomer to decrease stiffness, improve low temperature properties, and improve processing. 283. Plastometer : An instrument for measuring the plasticity of a raw or unvulcanized compounded rubber. 284. Polymer : A material formed by joining together many (poly) individual units (mer) of one or more monomers; synonymous with elastomer. 285. Polymerization : Chemical reaction whereby simple materials, either one or more, are converted to complex material which possesses properties entirely different from the original materials used to start the reaction. 286. Polyurethane : An organic material noted for its high abrasion, ozone, corona and radiation characteristics. 287. Porosity : Quality or state of being porous - the presence of numerous small cavities. 288. Post Cure : The second step in the vulcanization process for some specialized elastomers. Provides stabilization of parts and drives off decomposition products resulting from the vulcanization process. 289. Pot : The chamber, in the transfer or injection mold, where raw material is placed before it is transferred into the cavity. 290. Pot Life : The period of time during which a reacting thermosetting composition remains suitable for its intended use, after mixing with a reaction-initiating agent. 291. Prevulcanization Inhibitor (PVI) : A compounding material that increases the time to incipient vulcanization of a rubber mix. Unlike a retarder, a PVI does not significantly affect the vulcanization rate. 292. Primary Accelerator : The principal highest concentration accelerator used in a vulcanizing system. 293. Processability : The relative ease with which raw or compounded rubber can be handled in rubber machinery. 294. Processing Aid :

A compounding material that improves processability of a polymeric compound by reducing nerve, providing better dispersion of dry material, increasing the extension rate, reducing power consumption during mixing, producing smoother surfaces on calendered and extruded products, improving knitting, etc. 295. Process Oil: A hydrocarbon oil derived from petroleum or other sources, used as an extender or process aid. 296. Pure Gum State : A non pigmented, translucent basic polymer.

R 297. Radiation : An emission, of varying content, from a disturbed atom undergoing internal change. There are two broad classifications : (A) Corpuscular, comprising streams of particles, either neutral or charged, e.g. protons, neutrons, electrons; and (B) Electromagnetic, comprising wave-like emissions as gamma, ultraviolet, etc. 298. Radiation Damage : A measure of the loss in certain physical properties of organic substance, such as elastomers, due principally to ionization of the long chain of molecules; believed to result in redundant cross-linking and possible scission of the molecules. The effect is cumulative. 299. Radiation Dosage : The total amount of radiation energy absorbed by a substance. This value is usually expressed in "ergs per gram", and is denoted by 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 ionization that causes an energy absorption of approximately 83 to 93 ergs per gram of tissue; (c) REM (Roentgen Equivalent - Man) - similar to REP, except used to denote biological effects; and; (d) RAD - the unit of dosage related to elastomers, independent of type of radiation specimen, and denoting energy absorption level of 100 ergs per gram of elastomer : approximately equal to 1.2 Roentgens. 300. Rebound : A measure of the resilience, usually as a percentage of vertical return of a body which has fallen and bounced. 301. Rebound Test : The method of determining the resilient properties of vulcanized rubber by measuring



the rebound of a steel ball or pendulum from a defined height onto a rubber sample. 302. Recipe : A formula, mixing procedure, and any other instructions needed for the preparation of a rubber compound. 303. Reclaimed Rubber : Vulcanized rubber that has been thermally, mechanically, and/or chemically plasticized for use as a rubber diluent, extender, or processing aid. 304. Reciprocating Seal : Seal used in linear motion application. 305. Register : The accurate matching of the plates in a mold. 306. Reinforcement: The act of increasing the mechanical performance capability of a rubber by the incorporation of materials that do not participate significantly in the vulcanization process. 307. Reinforcement Agent : Material dispersed in an elastomer to improve compression, shear or other stress properties. 308. Relative Humidity : The ratio of the quantity of water vapor actually present in the atmosphere, to the greatest amount possible at a given temperature. 309. Release Agent (Mold) : A substance applied to the inside surface of a mold or added to a material to be molded, to facilitate removal of the product from the mold. 310. Resilience : Ability of an elastomer to return to original size and shape after deforming forces are removed; generally expressed in per cent of the ratio of energy removed, to the energy used in compressing. (Resilient : having that capability.) 311. Resin : An organic material of indefinite and relatively high molecular mass that may be used as a softener, processing aid, vulcanizing agent, or reinforcing agent. 312. Retarder : A material used to reduce the tendency of a rubber compound to vulcanize prematurely. 313. Reversion : Deterioration of vulcanizate properties that may occur when vulcanization time is extended beyond the optimum.

314. RMS: Root mean square. A measure of surface roughness, calculated as the square root of the sum of the squares of micro-inch deviation from true flat. 315. Rotary Seal : A seal, such as an O-Ring or a Quad-Ring seal, exposed on either the ID or OD sealing surface to a rotating component, e.g. shaft seals. 316. Rough Trim : Removal of superfluous material by pulling or picking; usually the removal of a small portion of the flash or sprue which remains attached to the product. 317. Rubber : A material that is capable of recovering from large deformations quickly and forcibly, and can be, or already is, modified to a state in which it is essentially insoluble. Also see Elastomer. 318. Rubber, Bound : The portion of the rubber in a mix that is so closely associated with the filler as to be unextractable by the usual rubber solvents. 319. Rubber, Cellular, Closed cell: A cellular material in which practically all the individual cells are non-connecting. 320. Rubber, Expanded: Cellular rubber having closed cells made from a solid rubber compound. 321. Rubber, Gel: The portion of rubber insoluble in a chosen solvent. 322. Rubber Hardness Degree,

International: A measure of hardness, the magnitude of which is derived from the depth of penetration of a specified indenter into a specimen. Commonly referred to as IRHD. 323. Rubber, Natural: cis-1,4-polyisoprene that is obtained from a botanical source, usually Hevea Brasiliensis. 324. Rubber, Oil-extended : A grade of raw rubber containing a relatively high proportion of processing oil. 325. Rubber, Raw : Natural or synthetic elastomer, usually in bales or packages, that is the starting material for the manufacture of rubber articles.



326. Rubber, Sponge: Cellular rubber consisting predominantly of open cells and made from a dry rubber compound. 327. Rubber, Synthetic: Rubber produced by polymerizing one or more monomers with or without post-polymerization chemical modification. 328. Rubber, Vulcanized Compound: A crosslinked elastic material compounded from an elastomer, susceptible to large deformations by a small force and capable of rapid, forceful recovery to approximately its original dimensions and shape upon removal of the deforming force. 329. Runner (Injection or Transfer mold) : The secondary feed channel for transferring material under pressure from the inner end of the sprue to the cavity gate. 330. Runner : The system for leading rubber and plastic materials into the gate of an injection mold. 331. Runout (Shaft) : Expressed in inches and/or TIR (Total Indicator Reading); refers to twice the radial distance between shaft axis and axis of rotation.

S 332. Salt Bath : A heat transfer apparatus, utilizing molten salts as the heating medium, generally used for vulcanization. Commonly used in extrusion systems. 333. SBR : Copolymer of Butadiene and Styrene; an all purpose type synthetic, similar to natural rubber. (Butadiene is a gaseous material of petroleum; Styrene, a reaction product of ethylene and benzene.) 334. Scorch : Premature curing or setting up of a raw compound during processing. 335. Seal : Any device used to prevent the passage of a fluid, gas or liquid. 336. Seal-Off : A minimum .032 inch (.813 mm) step on an insert that minimizes flash on the OD, and prevents flash from forming across the insert. 337. Secondary Accelerator :

An accelerator used in smaller concentrations compared to the primary accelerator, to achieve a faster rate of vulcanization. 338. Service : Operating conditions to be met. 339. Set : The strain remaining after complete release of the force producing the deformation. 340. Shaft : Reciprocating or rotating member, usually within a cylinder; not in contact with the walls. 341. Shelf Aging : The change in a material's properties which occur in storage with time. 342. Sheeting : The process of converting a rubber, rubber mix, rubber dough, or latex into a sheet. 343. Shelf Life : The period of time after production during which a material or product, that is stored under specified conditions, retains its intended performance capabilities. 344. Shock Load: The sudden application of an external force. 345. Shore A : See Durometer. 346. Shore M : A Durometer hardness instrument, using a micro-indentor designed for the purpose of measuring O-Ring hardness. 347. Shrinkage : 1) The ratio between a mold cavity size and the size of a product molded in that cavity, 2) Decreased volume of a seal, usually caused by extraction of soluble constituents by fluids followed by air drying. 348. Silicone Rubber : Elastomer that retains good properties through extra wide temperature ranges. 349. Size, Actual : Actual dimension of the product, including tolerance units. 350. Size, Number : Number assigned to indicate inside and cross section diameters of an O-Ring; established in the SAE standard AS 568, adopted by the military and industry.



351. Skin : A relatively dense layer at the surface of a cellular polymeric material. 352. Sliding Core : A pin on a mold that automatically retracts when the mold opens. 353. Softener : A compounding material used to produce a mix of reduced viscosity, which facilitates incorporation of rubber additives. 354. Sorption : A term used to denote the combination of adsorption and absorption processes in the same substance. 355. Specific Gravity : Ratio of the weight of a given substance, to the weight of an equal volume of water, at any specific temperature. 356. Specimen, Test : A piece of material appropriately shaped and prepared so that it is ready to use for a test. 357. Spew : Surplus material forced from a mold on closure under pressure. Synonym for flash. 358. Spiral Failure : Seal failure in reciprocating applications that result from a twisting 359. Spiral Twist : A type of seal failure in reciprocating application that results from the twisting action that strains or ruptures the rubber. 360. Splice : The uniting of two parts of a vulcanized rubber product to form a continuous length. 361. Sprue : The primary feed channel that runs from the outer face of an injection or transfer mold, to the mold gate in a single cavity mold, or to the runners in a multiple cavity mold. 362. Sprue Hole : The passageway through which a rubber is forced into a mold. 363. Sprue Marks : Marks left on the surface of a rubber part, generally elevated, after removal of the sprue or cured compound in the gate, through which the compound is injected or transfer molded. 364. Squeeze :

Cross section diametrical compression of O-Ring between surface of the groove bottom and surface of the other mating metal part in the gland assembly. 365. Stabilizer : A substance present in or added to raw rubber to maintain properties at or near their initial values during its production, processing, and storage. 366. Static Seal : Part designed to seal between parts having relative motion. (See Gasket) 367. Statistical Process Control (SPC) : The use of statistical techniques on processes and their output, to establish process stability and increase capabilities. 368. Stiffener : A compounding material used to increase the viscosity of an unvulcanized rubber mix. 369. Stiffness : That property of a specimen that determines the force with which it resists deflection. 370. Stiffness, Bending : The force required to produce a bent configuration under specified conditions. 371. Strain : Deflection due to force. 372. Strainer : A machine designed to force a rubber or rubber mix through a sieve to remove extraneous material. 373. Stress : Force per unit of original cross section area. 374. Stress Relaxation : Decreasing stress with constant strain over a given time interval. (Viscoelastic response.) 375. Stock : Unvulcanized, mixed rubber compound of a definite composition. 376. Sublimation : The direct conversion of a substance from solid state to vapor state, passing through a transitory liquid state. The vapor, upon recondensing, reforms into the solid state with no intervening liquid phase. 377. Surface Finish : A numerically averaged value of surface roughness, generally in units of microinches or micrometers.



378. Sulfur Donor Vulcanizing System: A vulcanizing system in which there is no elemental sulfur present, and all of the sulfur available for the crosslinking is provided by the partial decomposition of sulfur-containing materials. 379. Sulfur, Free : The uncombined sulfur in a rubber mix or vulcanizate. 380. Sulfur, Total : All the sulfur present in a material irrespective of its chemical form or origin. 381. Sun Checking : Surface cracks, checks or grazing caused by exposure to direct or indirect sunlight. 382. Swell : Increased volume of a specimen, caused by immersion in a fluid (usually liquid).

T 383. Tack : The property that causes contacting surfaces of unvulcanized rubber to adhere to each other. 384. Tackifier : A compounding material that enhances the ability of vulcanized rubber to adhere to itself or another material. 385. Tear : Mechanical rupture initiated and propagated at a site of high stress concentration caused by a cut, defect, or localized deformation. 386. Tear Strength : The force required to rupture a sample of stated geometry. The maximum force required to tear a specified test specimen, the force acting substantially parallel to the major axis of the specimen. 387. Tear Resistance : Resistance to growth of a cut or nick when tension is applied to the cut specimen. Commonly expressed as pounds per square inch thickness. 388. Temperature Range : Maximum and minimum temperature limits in which a seal compound will function in a given application. 389. Tensile Strength :

Force, in pounds per square inch, required to cause the rupture of a specimen of rubber material. 390. Tensile Stress : A stress applied to stretch a test specimen. 391. Tension Fatigue: A fracture, through crack growth, of a component or test specimen subjected to a repeated tensile deformation. 392. Tension Set: The extension remaining after a rubber specimen has been stretched and allowed to retract. 393. Tension Modulus : Resistance to being stressed; defined as the force, in pounds, necessary to stretch a piece of rubber, one square inch in cross section, a specified amount. Normally expressed as a percentage of original length, and the stress as pounds per square inch at the fixed elongation. 394. Terpolymer : A polymer consisting of three different monomers, chemically combined. 395. Thermal Carbon Black : A soft carbon black formed by the thermal decomposition of natural gas. 396. Thermal Degradation : Irreversible and undesirable change in the properties of a material due to exposure to heat. 397. Thermal Expansion : Expansion caused by increase in temperature; may be linear or volumetric. 398. Thermoplastic : A plastic capable of being repeatedly softened by increase of temperature, and hardened by decrease of temperature. 399. Thermoplastic Elastomer (TPE) : A diverse family of rubber-like materials that, unlike conventional vulcanized rubbers, can be processed and recycled like thermoplastic materials. Often referred to as TPR (thermoplastic rubber). 400. Thermoplastic Vulcanizate (TPV) : A thermoplastic elastomer with a chemically cross-linked rubbery phase, produced by dynamic vulcanization. 401. Thermoset Rubber :



An elastomer or plastic cured under application of heat or chemical means, to make a product substantially infusible or insoluble. 402. Thiokol : An organic polysufide. 403. Threshold : The maximum tolerance of an elastomer to radiation dosage, expressed as a total number of ergs per gram (or rads) beyond which physical properties are significantly degraded. This is generally an arbitrary value, depending on function and environment. 404. Torque : The turning force of a shaft. 405. Torr : The unit of pressure used in vacuum measurement; equal to 1/760 of a standard atmosphere, and for practical purposes, is equivalent to one millimeter of Mercury (mmHg). 406. Torsion Strength : Ability of rubber to withstand twisting. 407. Total Indication Reading (TIR) : System that measures the roundness of a part in relationship to a center line. 408. TR-10 : A measure of the low temperature capability of an elastomer. It is the temperature at which a stretched and frozen specimen has retracted 10% of the stretched amount. TR stands for “temperature retraction”. 409. Transfer Molding : A method of molding in which material is placed in a pot, located between the top plate and plunger, and squeezed from the pot through gates (or sprues) into the mold cavity. 410. Trapped Air : Air which is trapped in a product or a mold during cure. Usually causing a loose ply or cover, or a surface mark, depression or void. 411. Trim : The process involving removal of mold flash. 412. Trim Out : Damage to mold skin or finish by close trimming.

U 413. Under Cure :

Degree of cure less the optimum; may be evidenced by tackiness, loginess or inferior physical properties. 414. Ultimate Elongation : A measure of how far a material will stretch before breaking; expressed as a percentage of its original length. 415. Undercut : A groove on either the outside or the inside of a molded part. 416. UV Absorber : A compounding material that, through its ability to absorb ultraviolet radiation and render it harmless, retards the deterioration caused by sunlight and other UV light sources.

V 417. Vacuum : The term denoting a given space that is occupied by a gas at less then atmospheric pressure. For degrees of vacuum, see Vacuum Level. 418. Vacuum Level : The term used to denote the degree of vacuum evidenced by its pressure in torr (or mmHg) : (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 vacuum = 10-6 torr to 10-9 torr, (e) Ultra High vacuum = below 10-9 torr. 419. Vapor : 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. 420. Vapor Pressure : The maximum pressure exerted by a liquid or a solid, heated to a given temperature in a closed container. 421. Vibration Dampening : The ability of an elastomer to absorb vibrational or shock energy. 422. Viscoelasticity : A combination of viscous and elastic properties in a material, with the relative contribution of each being dependent on time, temperature, stress, and strain rate. 423. Viscosity : The property of fluids and plastic solids by which they resist an instantaneous change of shape, i.e. resistance to flow.



424. Void : The absence of material, or an area devoid of materials where not intended. 425. Volatilization : The transition of either a liquid or a solid directly into vapor state. In the case of a liquid, this transition is called evaporation, whereas in the case of a solid, it is termed sublimation. 426. Volume Change : A change in the volume of a seal as result of immersion in a fluid; expressed as a percentage of the original volume. 427. Volume Swell : An increase in the physical size caused by the swelling action of a liquid. 428. Vulcanization : An irreversible process during which a rubber compound, through a change in its chemical structure (for example, crosslinking), becomes less plastic and more resistant to swelling by organic liquids, while elastic properties are conferred, improved, or extended over a greater range of temperature. 429. Vulcanizing Agent : A material which produces vulcanization of an elastomer.

430. Vulcanizing System : The combination of vulcanizing agent and, as required, accelerators, activators, and retarders used to produce the desired vulcanizate characteristics.

W 431. Water Absorption : The amount of water absorbed by a material under specified test conditions. 432. Weather Resistance : The ability to withstand weathering factors, such as : oxygen, ozone, atmospheric pollutants, erosion, temperature cycling and ultraviolet radiation. 433. Weathering : The detrimental effect upon an elastomer or plastic after outdoor exposure. 434. Width : Seal cross-section or thickness. 435. Wiper Ring : A ring employed to remove excess fluid, mud, etc., from a reciprocating member before it reaches the packings.

435 technical terms in rubber industry

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