Concluding from earlier post, here are alphabets (M-Z). (You may also like to download the PDF at the end of this article and add to your digital library.)
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.
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.
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.)
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.
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.
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).
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.
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.
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.
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.
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