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Liquid Silicone Rubber Glossary and Links |
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Liquid Silicone Rubber Molding Terms and Links:
Liquid Silicone Rubber Suppliers: Wacker Silicone:
http://www.wackersilicones.com
Mold Makers with Cold Runner Technology: Kipe Molds: http://www.kipemolds.com
Glossary of Liquid Silicone Rubber Molding Terms: # | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W |X|Y|Z
2-Componet Molding, Silicone Abrasion Surface wear caused by relative motion between two or more contacting objects Abrasion Resistance The ability of a rubber compound to resist surface wearing by mechanical action Absorption The physical mechanism by which one substance takes up another substance into its interior ABS Acrylonitrile-butadiene-styrene Accelerated Life Test Any set of test conditions designed to reproduce, in a short time, the deteriorating effect obtained under normal service conditions Accelerator A substance that speeds up curing or vulcanization of natural/synthetic rubbers Acid Resistance Withstands the action of acid Acrylic A polymer for which resistance to air and hot oil at temperatures above 30 degrees Fahrenheit is required Adhere To cling or stick together Adhesion Tendency of rubber to bond or cling to a contact surface After Cure Continuation of curing after heat source removed Aging The change in physical and chemical properties of an elastomer that has been exposed to a particular environment over time Aging, Accelerated Air Trap A process whereby a vacuum system is heated for a given time at some predetermined temperature to de-gas all the components, such as gauges, fittings, valves, seals Base Line The mark from which all features are dimensioned or measured from Batch The product of one mixing operation or shipment of Liquid Silicone Rubber Batch Number The assigned number that identifies a batch of Silicone Rubber Blemish A mark, deformity or injury which impairs appearance Blisters A raised spot on the seal's surface created by an internal void, or air-filled pocket Bloom A milky surface discoloration caused by the migration of certain compound components (i.e. antiozonants) to the rubber's surface after molding or storage. The milky film serves as a protective coating shielding the part from oxidation Bond The term commonly used to denote the attachment of a given elastomer to some other member, classified as follows: 1) Mechanical: purely physical attachment accomplished by through holes, interlocking fingers, envelope design in silicone rubber 2) Cold: adhesion of previously vulcanized elastomer to another member through use of suitable bonding agent 3) Chemical: adhesion of an elastomer to a previously primed or glass particle surface using heat and pressure, thus curing the silicone rubber Bore A hole machined in a component which permits the passage of a shaft Bore Seal A sealing system, usually in a radial orientation, in which the primary sealing surface is between the OD of a silicone rubber seal ring and the ID of a bore Boss Protuberance on a plastic part designed to add strength, facilitate alignment, provide fastenings, etc Brittleness Tendency to crack upon physical deformation Back to top... Carbon Black A black material used as a filler in rubber. It gives the rubber its black color and the hardness characteristics Cavity The features of a mold which are directly responsible for forming the final shape of a molded part Chemical bonding A method for bonding rubber to secondary parts by applying special adhesives or having a glass element on part prior to liquid silicone molding Clamping Plate A plate fitted to a mold and used to fasten the mold to a plate Clamping Pressure The pressure applied to the mold to keep it closed during a cycle of an silicone injection molding machine Clearance The space between components in a mechanical system which is present to allow for manufacturing, thermal, and dynamic variations in the size and position of the components. Coating A uniform layer of chemical primers or adhesives applied to a surface to produce a chemical bond between the liquid silicone rubber and substrate. May also refer to 2-component silicone molding or special surface treatments that can be applied to silicone rubber to achieve desired properties Coefficient of Thermal Expansion Average expansion per degree over a stated temperature range, expressed as a fraction of initial dimension, linear or volumetric Cold Flexibility Flexibility following silicone rubber exposure to a specified low temperature for a specified period of time Cold Flow A term describing the tendency of certain materials to continue to deform or "creep" under constant sealing pressure Cold Runner Runner less liquid silicone injection molding system of delivering liquid silicone to heated cavity Cold Slug The first bit of material to enter a silicone injection mold; so called because in passing through a sprue orifice it is cured Compound A mixture of a polymer and associated chemical ingredients necessary to produce a finished high consistency rubber material. The term is commonly used when referring to a specific rubber not liquid silicone rubber which is delivered in closed system Compression Molding A traditional molding process in which the uncured high consistency rubber compound is placed directly into the mold cavity, and compressed to its final shape by the closure of the mold. Considered unacceptable for many applications because parts must be deflash causing debris. Compression Set 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 is expressed as a percentage and measured after a prescribed period of time. Low compression set is desirable in molded rubber parts such as seals and gaskets, which must retain their dimensions to maintain an effective seal Compressive Strength The maximum compressive stress carried by a test specimen during a compression test Concentricity A condition in which two or more features (cylinder, cones, spheres, hexagons, etc..) in any combination, have a common axis Conductive Silicone Rubber A silicone rubber capable of conducting electricity. Most generally applied to silicone rubber products used to conduct static electricity or as an RF shield Conversion Fahrenheit to Celsius F = (° C x 9/5) +32 or C = (° F - 32) x 5/9 Cooling Channels Channels located within the body of a plastic injection mold through which a cooling fluid is circulated to control the mold surface temperature Core The mail portion of a liquid silicone rubber injection or plastic mold. Core Bar A steel bar used to hold machined core in place in the liquid silicone injection mold Core & Cavity Set A sub set of a liquid silicone rubber injection or plastic mold that fits within a mold base. This technique generally lowers silicone or plastic tooling investment CPE Chlorinated Polyethylene CPVC Chlorinated Polyvinyl Chloride Cracking Sharp breaks or fissures in silicone rubber surfaces resulting from excessive strain or exposure to adverse environmental factors Creep The progressive relaxation of an elastomeric material under constant sealing pressure (compressive load) Cross-linking Agents A chemical or chemicals that bond the silicone rubber polymer chains of a silicone rubber together during the liquid silicone molding process Cross Section-Axial When the part is flat (relative), the cross section that is at 90 to the linear plane Cross Section-Radial When the part is flat (relative), the cross section in the linear plane Cure The heat induced process that causes a chemical change in the liquid silicone rubber material, turning it into the finished silicone rubber part Cure Time The preset time needed to complete the liquid silicone rubber curing process Curing temperature The temperature of liquid silicone rubber thermoset vulcanization Cross-Sectional Compression The deformation placed on a silicone rubber part to affect a seal. It is expressed as a percentage of the seal's original cross-section Back to top... Damping The ability of a silicone elastomer to absorb forced vibrational energy Daylight Opening The clearance between two platens of a silicone injection molding machine in the open position Deburr Removal of material from a drilled or punched hole, waste from saw cuts of material or sharp or rough edges Deep Injection A common molding defect identified by the deep depression in the rubber part at the point of injection Deflashing Any of various processes used to remove extraneous silicone rubber from a silicone injection molded rubber part. Generally the sign of poor mold design or maintenance. Density Weight per unit volume of a substance expressed in grams per cubic centimeter Diametrical Clearance The gap between the two mating metal surfaces forming a gland's internal cavity. Through slight oversizing and accompanying compression of the O-Ring seals this gap to prevent system leakage Diaphragm Gate Used in symmetrical cavity filling to reduce weld-line formation and improve filling rates Die Cut The process of stamping out the ID or OD by placing the part on a mechanical fixture to perform this function Direct Gate The sprue feeds directly into the mold cavity Dispersion Finely divided particles of a material in suspension in another substance Draft The degree of taper of a side wall or the angle of clearance designed to facilitate removal of parts from a mold Drooling The extrusion or leakage of molten liquid silicone rubber from a nozzle or nozzle sprue bushing area while or prior to shooting Durometer Standard rubber industry hardness test for liquid silicone rubber molded or extruded parts. The hardness scale most commonly used for silicone rubber durometer is the Shore A scale Dwell A pause in the application of pressure to a mold, made just before the mold is completely closed, allowing any gases formed or present to escape from the molding material Dynamic Seal A seal used in an environment that subjects it or a mating surface to movement Back to top... EC Ethyl cellulose Edge Gate A method of injecting liquid silicone rubber into the mold cavity Ejector Housing U shaped frame which is an integral part of the tool containing the ejector retainer plate and ejector plate Ejector Pin (knockout Pin) A pin or plate that is driven into a mold cavity from the rear as the mold opens to force out the finished part Ejector Plate The part of the mold which backs up the retainer plate and keeps the knockout pins from falling out Ejector Rod A bar that actuates the ejector assembly when the mold opens Elastic Limit Maximum stress that a material will stand before permanent deformation occurs Elasticity The property of an article, generally liquid silicone rubber, which tends to return to its original shape after deformation Elastomer Any natural or synthetic material with resilience or memory sufficient to return to its original shape after major or minor distortion, i.e. liquid silicone rubber Elongation Generally referred to in terms of tensile (pull apart) testing, elongation is the increase in length of a test specimen, expressed as a percentage of its original-unstretched length, relative to a given load at the breakpoint EMI Electromagnetic interference Encapsulating Enclosing an article in a closed envelope of liquid silicone rubber or plastic, by immersing or over molding the object in a silicone rubber or plastic EP Ethylene propylene EPDM Ethylene propylene diene monomer rubber ESCR Environmental stress crack resistance ETFE Ethylene-tetrafluoroethylene EVA Ethylene-vinyl acetate Extending Flash Flash that is formed at the parting line of a liquid silicone mold, can be minimized by good silicone mold practices Extrusion When part or all of a component is forced from its groove by high continuous or pulsating pressure Back to top... Face Seal A sealing system in which the sealing occurs in the axial direction of the seal. If the seal ring were to be placed flat upon a desktop, the seal compression would occur between the top and bottom of the seal Family Mold A multi-cavity mold where each of the cavities forms one of the component parts of the assembled finished part Fan Gate This gate is used to help reduce stress concentrations in the gate area by spreading the opening over a wider area. Less warpage of parts can usually be expected by the use of this gate type. Frequently used in large silicone rubber parts FDA Food & Drug administration Feather Edge The sharp, thin edge on parts such as wiper seals. Also called a knife edge Filler A finely divided material used to reinforce or modify elastomer physical properties, impart certain processing properties, or reduce cost. Typical examples are carbon black, clays, calcium carbonates and silicas Fillet A rounded filling of the internal angle between two surfaces of a part Fin The web of material remaining in holes or openings in a molded part which must be removed for final assembly Flame Resistance The resistance to burning of material that will not withstand combustion under ordinary conditions Flash Excess rubber left around a liquid silicone rubber part after molding, due to space between mating mold surfaces; removed by trimming. Sign of poor silicone rubber mold maintenance or design. Flexural Strength The ability of a material to flex without permanent distortion or breaking Flow The ability of heated plastic or uncured rubber to travel in the mold and runner systems during the molding process Flow Line A disturbance in the homogeneous structure of a liquid silicone molded part generally caused when material knitted or blended with itself during the silicone molding operation Flow Marks Wavy surface appearance of an object silicone molded caused by improper flow of the liquid silicone rubber or plastic into the mold. A mark made by the freezing-in of a visible flow pattern Fluid A liquid or gas Fluorocarbon Viton [® DuPont Dow Elastomers], Fluorel [TM, 3M Co.] Polymer designed to meet the most rigid requirements in oils, solvents, synthetic lubricants and corrosive chemicals, at elevated temperatures Friction Resistance to motion due to contact of surfaces. Friction, Break Out Friction developed during initial or starting motion. FRP Fiber reinforced plastics Fused Disposition Modeling Process (FDM) Thermoplastic modeling material is fed into the temperature-controlled FDM extrusion head and heated to a liquid state. The head extrudes and deposits the material in ultra-thin layers onto a fixture-less base Fixture Block of metal or wood used to maintain the proper shape or to perform secondary operation. Back to top... Gamma Radiation Electromagnetic disturbance (photons) emanating from an atomic nucleus. This type of radiation travels in wave form, similar to X-Rays or light, but has a shorter wave length (approx. 1 Ado or 107 mm) Gasket A static (stationary) sealing device used to retain fluids under pressure or to seal out foreign matter Gate A silicone injection molding or plastic orifice through which the silicone rubber or plastic enters the cavity Gate Edge A gate that is cut along one edge of the silicone rubber or plastic mold cavity Gate Fan Large cross sectional area for feeding plastic into the silicone rubber or plastic cavity. Flow channel tapered from the silicone rubber or plastic runner to the gate Gate Flash A gate that encompasses entire periphery of the silicone rubber or plastic part. Usually of low sectional thickness in relation to silicone rubber or plastic part Gate Mark A raised spot or small depression on the surface of a silicone rubber or plastic injection molded part where the gates interface the cavity Gate Sprue The type of gate in which the liquid silicone rubber or plastic is injected directly from the molding press into the cavity Gate Underside The orifice found between the "A" and "B" plate which carries the resin into the cavity in an overlap of the part in such a manner so as to obtain a clean break on the part. Usually found in thermoset molding Gates the openings in an injection or transfer mold whereby material enters the mold cavity Geometric Dimensioning & Tolerancing A means of specifying engineering design and drawing requirements with respect to actual function and relationship of part features, it is a technique which properly applied ensures the most economical and effective production of these features Gland The space in a mechanical system into which a seal is installed. the gland consists of the seal groove and any additional space required to achieve the proper compression of the seal. Care should be taken to distinguish between the terms gland and groove, which are separate but related concepts Back to top... Hardness A measurement of the resistance to penetration of a silicone rubber sample by an indenter on a Durometer tester. High values indicate harder materials while low values indicate softer materials. HDPE High-density polyethylene HDT Heat-deflection test Heat deflection temperature The temperature at which a standard plastic test bar deflects 0.010 in. under a load of either 66 or 264 psi Heat Sealing A method of joining plastic parts or films by simultaneous application of heat and pressure to areas in contact. Hermetic Seal An airtight seal HIP High-impact polystyrene HME High-vinyl modified epoxy HMW High molecular weight Hob A master model in hardened steel. Also the wearing in of an A&B plate of a silicone injection mold Honing A machining process that sharpens, enlarges, and smooths material through the use of a fine-grit stone Hot Runner Manifold Runner less plastic injection molding of a thermoplastic, the melt stays molten until is reaches gate at cavity. Hot Stamping Engraving operation for marking plastics in which roll leaf is stamped with heated metal dies onto the face of an article by means of felt rolls, ink is applied to type or by means of heat and pressure, type is impressed into the material, leaving the marking compound in the indentation Back to top... Impact Resistance Relative susceptibility of plastics or silicone rubber to fracture by shock as indicated by the energy expended by a standard pendulum type impact machine in breaking a standard specimen in one blow Injection Molding A molding method in which a liquid silicone rubber or plastic material is heated and forced under pressure into the mold cavity Injection Pressure The pressure on the face of the silicone injecting ram when injecting material into the mold Injection Tearout A molding defect identified by a hole in the silicone liquid rubber part at varying widths and depths located at the point where the silicone rubber is injected into the cavity area Insert A term referring to a metal or plastic component, placed ("inserted") into a mold cavity prior to the start of the molding cycle, to which rubber or plastic is chemically and/or physically bonded during the molding process Insert Molding A means of producing a part with two or more materials, the metal, plastic or liquid silicone rubber part is inserted into the mold and plastic or silicone rubber is injected onto to the part attaching by means of mechanical or chemical bond Internally Lubricated Rubber A silicone rubber formulation containing lubricating materials incompatible with the silicone rubber structure causing it to leach out as a lubricant ID (Inner Diameter) The innermost (smallest diameter) surface of a circular object, such as a bore or a round seal Insert Typically, a metal or plastic component to which rubber or plastic is chemically and/or physically bonded during the molding process. Isoprene-acrylonitrite Rubber A low-plasticity copolymer with around 34 per cent ACN. Back to top... Jetting A turbulent flow of plastic or silicone rubber accelerating the speed of the melt can be caused by undersized gate or bad mold design Jig A tool for holding parts of an assembly during the manufacturing process Back to top... Knit Line Place or line where two or more flow fronts come together after going around a flow restriction or post Knock Out (Ejector) Pins Normally pins or blades that, when activated internally to the plastic or liquid injection mold, eject the part from the mold Knock Out (Ejector) Plate A plate in a plastic or liquid silicone rubber injection mold connects and drives the ejector pins in the plastic or silicone mold Back to top... Laminar Flow The flow of a resin in a plastic or liquid silicone rubber mold is accompanied by solidification of the layer in contact with the mold surface that acts as an insulator through which material flows to fill the remainder of the cavity Land A shut off surface of a cavity on a plastic or liquid silicone rubber mold by which excess air escapes LCP Liquid crystal polymer LDPE Low-density polyethylene LIM Liquid injection molding is injection molding silicone rubber, Casco Bay Moldings specialty LLDPE Linear low-density polyethylene LMW Low molecular weight LSR Liquid silicone rubber is generally a platinum cured, two-component, low viscosity, heat-curable silicone rubber system delivered in a closed drums or buckets. Casco Bay Moldings specialty L/D Ratio The length over diameter ratio defining a silicone rubber injection or plastic screw Back to top... Machine Shot Capacity This is the maximum weight of PS (not silicone rubber) which can be displaced or injected by a single stroke MBS Methyacrylate-buadiene-styrene MDPE Medium-density polyethylene Mechanical Bond A method of physically bonding liquid silicone rubber to inserts through the use of holes, depressions or projections in the insert Melt Index A measure in grams of plastic material that can be forced through an orifice of 0.0825 inches when subjected to a force of 2160 grams in 10 minutes at 190°C Memory Ability of an silicone rubber or elastomeric material to return to its original size and shape after deformation Mismatch Unequal cross-sectional match between the two mold halve, seen in the silicone injection molded part MMA Methyl methacrylate monomer Modulus Tensile stress at specific elongation, normally 100% elongation for silicone elastomers Modulus of Elasticity One of several measurements of stiffness or resistance to deformation, but often incorrectly used to indicate specifically static tension modulus Moisture Marks or Welds Marks on the finished part that are caused from moisture in the resin and look like weld lines except they may be in the wrong areas for weld lines Mold Typically made from steel for liquid silicone tooling, article is produced by injecting silicone into machined cavity Mold Base Mold frame that holds mold cavities Mold Cavity Hollow space of the mold within which the liquid silicone rubber is injected and cured to the desired finished product form Mold Finish The surface finish of the silicone injection mold which imparts the desired surface quality to the finished molded silicone product Mold Marks Slight irregularities in the surface of molded articles caused by mold machining marks, or damage to the mold itself Mold Shrinkage The difference in dimension, expressed in inches per inch, between a silicone part and the steel cavity in which it was injection silicone molded, when both are measured while at room temperature Mold Three Plate Integral moving plates in a conventional silicone injection mold, containing the cavities and allowing the injection point or gate to feed directly into the part MSDS Material safety data sheet Mud Set A purchased universal injection mold base which reduces injection mold fabrication cost MW Molecular weight Back to top... Neoprene (GR-M) A DuPont Dow Elastomers polymer of chloroprene which is prepared from coal, salt and limestone, not injection molded Nitrile Or 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 Nominal Dimension The mean dimension of a liquid silicone injection molded article, from which small dimensional (plus and minus) deviations are allowed as manufacturing tolerances Non-fill An unintentional void or absence of material in the liquid silicone rubber part Nozzle The hollow cored metal nose of a liquid silicone injection screw and barrel that seats off against an LSR mold Back to top... O-Ring A doughnut-shaped object that functions as a seal, blocking the passage of liquids or gases, by being compressed between the two mating surfaces comprising the walls of the cavity into which the ring is installed Off-register Misalignment of mold halves causing out-of-round O-Ring or part cross section Oil Resistant Ability of liquid silicone or natural rubber to resist swelling and other detrimental effects of exposure to various oils Orange Peel A surface finish on a liquid silicone molded part that is rough and splotchy Oscillating Seal Most commonly used in faucet valves, in this application the inner or outer member of the gland moves in an arc around the axis of a shaft. Movement is limited to a few turns in one direction and a few turns in the return direction (i.e. faucet on, faucet off) Outgassing A phenomenon wherein a substance (i.e. silicone or natural rubber) spontaneously releases volatile constituents in the form of vapors or gases normally during curing process with liquid silicone rubber. Overflow A designed escape reservoir for liquid silicone rubber, used to insure mold cavity fill and also allowance for excess compound, generally frowned upon because part requires post molding trimming OD, Outer Diameter The outermost, largest, surface of a circular object, such as a shaft or a round seal. the term OD is frequently used to indicate both the circumferential surface itself as well as the measured diameter of that surface Ozone Resistance Ability to withstand the deteriorating effect of ozone, which generally causes cracking Back to top... PA Polyamide (nylon) Pack Out The filling of the liquid silicone mold cavity or cavities as full as possible without causing undue stress on the silicone mold or causing flash to appear on the finished parts PAI Polyamide-imide PAN Polyacrylonitrile Parting line The witness line on the surface of a silicone molded part corresponding to the location where the LSR mold plates were in contact PB Polybutylene PBT Polybutylene terephthalate PBTP Polybutylene terephthalate PC Polycarbonate PCTFE Polychlorotrifluoroethylene PE Polyethylene PEC Polyphenylene ether copolymer PEEK Polyetherether ketone PEH Polyphenylene ether homopolymer PEI Polyetherimide PEO Polyethylene oxide Permanent Set The deformation remaining in a liquid silicone rubber specimen following both stress and relaxation over a period of time Permeability The rate at which liquid or gas, under pressure, passes through a solid material by diffusion and solution. In silicone 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 PES Polyethersulfone PET Polyethylene terephthalate PETG Glycol-modified PET PETP Polyethylene terephthalate PF Phenyl-formaldehyde PFA Perfluoroalkoxy (resin) PH Determines the concentration of either an acid or a base PI Polyimide PIB Polyisobutylene Plasticize To soften a silicone rubber by making it plastic, less viscous or moldable, either by means of a plasticizer or the application of heat Plasticizer A chemical agent added to the rubber compound batch mix to soften the elastomer for processing, as well as to improve physical properties of the compound product (i.e., increase elongation, reduce harness, improve tack) Plate Retainer The plate on which demountable pieces, such as mold cavities, ejector pins, guide pins, and bushings are mounted during molding Plate Stripper A plate that strips a liquid silicone molded piece from core pins or force plugs. The stripper-plate is set into operation by the opening of the mold Platens The mounting plates of a press to which the entire mold assembly is bolted Platen Movable The large back platen of an silicone injection molding machine to which the back half of the mold is secured during operation. The platen is moved horizontally or vertically by either a hydraulic ram or a toggle mechanism Platen Stationary The large front plate of an silicone injection molding machine to which the front plate of the mold is secured during operation PMMA Polymethyl methacrylate PMS Paramethylstyrene PMT Polymethylpentene Polymer A material formed by joining together many (poly) individual units (mer) of one or more monomers; synonymous with elastomer Post Cure The process of baking or autoclaving silicone parts after molding. This process is used to improve the heat and compression set resistance of specific elastomers like silicones and fluorocarbons PP Polypropylene PPO Polyphenylene oxide PPS Polyphenylene sulfide Pressure Injection The pressure on the face of the injection ram at which molding silicone rubber is injected into a mold, liquid silicone rubber generally uses much lower injection pressures when compared with plastic injection PS Polystyrene PTFE Polytetrafluoroethylene PU Polyurethane Purging Cleaning one color or type of liquid silicone rubber from the cylinder of an injection molding machine by forcing it out with the new color of LSR PVC Polyvinyl chloride PVDF Polyvinylidene Fluoride PVF Polyvinyl Fluoride Back to top... QS 9000 Quality System model, used in conjunction with the ISO 9000 standard, for the automotive industry Quench Bath The cooling medium used to quench molten thermoplastic materials to the solid state Quick Cast An SLA build style that produces a thin shell with a honeycombed interior. This method is used mostly for investment castings when the SLA model will be used as a sacrificial mold Back to top... Radial Seal Compression is applied perpendicular to the seal center-line Rapid Prototyping Fabrication of a physical, three-dimensional part of arbitrary shape directly from a numerical description, typically a CAD model, by a quick, highly automated and totally flexible process. Reciprocating Seal Seals used in moving piston and rod situations Regrind A process that finely grinds plastic part runners and rejected parts Relative Humidity The ratio of the quantity of water vapor actually present in the atmosphere, to the greatest amount possible at a given temperature Reinforcing Agent Fillers, such as Carbon Black, added to the elastomeric batch mix to improve such physical properties as tensile strength Resilience The capability of returning to original size and shape after deformation RF Radio-Frequency Rockwell Hardness A standard method for measuring the hardness of metals. The hardness is expressed as a number related to the depth of residual penetration of a steel ball or diamond cone after a minor load of 10 kilograms has been applied to hold the penetrate in position, designated by letters varying from "A" to "H" the "B" and "C" scales are most commonly in use. Rotary Seal Seals for rotating shafts, with the turning shaft protruding through the I.D. (hole) of the O-ring RTV Molding A procedure where a part is molded in a silicone mold to reproduce up to twenty urethane parts Rubber A common name for both naturally occurring and synthetically made elastomers like liquid silicone rubber Runnerm The channel that connects the sprue with the gate for transferring the molten liquid silicone rubber to the cavities Rubber-Natural A natural product of the juices of certain tropical plants (latex), improved through heat treating with sulfur (vulcanization) Rubber Synthetic Man-made elastomers such as Nitrile, Fluorocarbon, Silicone and liquid Silicone rubber Back to top... SAN Styrene-acrylonitrile SBR Styrene-butadiene (rubber) Seal Off A feature on two liquid silicone mold halves or cavity inserts seal off the cavity with the exception of the silicone injection gate and air venting ports Seal Any device used to prevent the passage of a fluid, liquid or fine particles Selective Laser Sintering (SLS) A laser traces the shape of the part to be modeled in a thin layer of powder. The laser sinters (softens and bonds) the powder particles together. This process is repeated over layers of powder Shore A A hardness scale used to measure the hardness of molded silicone rubber. The Shore A scale is most effectively used to measure liquid silicone rubber with a hardness from 10 to 95 Shore A Short shot A condition where there is insufficient liquid silicone rubber is introduced into a LSR mold cavity to completely fill the cavity, resulting in a partially formed part Shot The complete amount of silicone rubber required to fill all silicone mold cavities completely Shot Capacity The maximum weight of liquid silicone rubber which an injection machine can inject with one forward motion of the screw Shrinkage The ratio between a mold cavity size and the size of a product molded in that cavity Single Cavity Mold A silicone injection mold having only one cavity and producing only one finished part per cycle Sink Marks A shallow depression or dimple on the surface of a finished plastic part due to shrinkage or low fill of the cavity, much less prevalent in liquid silicone rubber parts Sliding Core A pin on a mold that automatically retracts when the mold opens SMA Styrene maleic anhydride SPC (statistical Process Control) Methods of controlling our processes to prevent defects from being made Specific Gravity The ratio of the mass of a unit volume of a material to that of the same volume of water at a specified temperature Spiral Twist A type of seal failure resulting from a twisting action that strains or ruptures the rubber Splay Marks Marks or droplet-type imperfections found on the surface of the finished parts that may be caused by the spraying of the melt through the gates and into the cool cavity Sprue The primary feed channel that runs from the outer face of a silicone injection mold to the mold runner and gates Sprue Bushing A hardened steel insert in the silicone injection mold that accepts the silicone molding machine nozzle and provides an opening for transferring the silicone or molten plastic Static Seal A seal that, except for pulsations caused by cycle pressure, does not move in its environment Static Mixer A helix like device that mixes two liquids by redirecting the flow path into each other repeatedly, common with RTV Silicone and some liquid silicone rubber applications Statistical Process Control (SPC) The use of statistical techniques on processes and their output to establish process stability and increase capabilities Stereolithography Apparatus (SLA) Selective curing of a photopolymer resin by an ultraviolet laser, built on a descending platform, in a vat Strain the deformation caused by an applied stress Stress Force per original cross section that is applied to a specimen Stress Relaxation Decreasing stress with constant strain over a given time interval or viscoelastic response Stripper Plate A plate that strips a molded plastic or liquid silicone rubber part from core pins Sublimation The direct conversion of a substance from solid state to vapor or gas state Submarine Gate Tunnel gate, a type of edge gate where the opening from the runner into the mold is located below the mold parting line Suck Back A method of decompressing a molds runner system by retracting the screw on a plastic or silicone injection molding machine Surface Finish A term usually used in reference to the roughness parameter of a surface's texture, general expressed in units of microinches (µin) or micrometers (µm) Surface Grinder A commonly used machine tool which is used to grind mold plates and components to a specified dimension and to provide a high accuracy and smooth surface finish Swell The linear or volumetric change of a material resulting from immersion in a particular liquid for a specified period of time. Swell is a general indicator of the compatibility of a material for use in a particular environment Back to top... Tab Gate A small removable tab about the same thickness as the molded item but usually perpendicular to it for easy removal Tack The degree of adhesion of materials of identical nature to each other Tear Resistance Resistance to the growth of a cut in the seal when tension is applied Tear Strength The force required to rupture a sample of stated geometry Tear Bead A designed in feature generally in a silicone or natural rubber compression mold which allows easy and precise tear off of overflow bead Temperature Range The working range marked by the limits of minimum and maximum operating temperatures for effective seal or silicone rubber part performance Tensile Strength the extension force per cross-sectional area required to fracture a material specimen TFE Polytetrafluoroethylene Thermal Expansion Linear or volumetric expansion caused by temperature increases Thermoplastic A material which when thermally processes undergoes a reversible phase change to become plastic and capable of being molded to a desired shape, upon cooling, the material reverts to its original properties Thermoplastic Elastomer (TPE) A material which combines the processing characteristics of a plastic but displays rubber-like properties upon completion of processing Thermoset A material, either an elastomer (silicone rubber) or plastic, which when thermally processed undergoes an irreversible chemical reaction to achieve its final material state Threaded Core A part of a plastic or liquid silicone rubber injection mold that shapes an internal thread and must be unscrewed from the finished piece TIR A measurement of roundness with relationship to a center-line and expressed in total diametric deviation Torque A turning or twisting force, generally associated with the rotation of a shaft Total Indicator Reading (TIR) A term used to indicate how the measurement of the roundness of a part, as rotated about its center-line, should be interpreted Toughness Property of resisting fracture or distortion. Usually measured by impact test, high impact values indicating high toughness TPE Thermoplastic Elastomer combines the rubber-like performance of elastomers with the processing advantages of plastic. Scrap material can be recycled without significant loss in physical properties but physical properties are more limited TPR Thermoplastic rubber TPU Thermoplastic polyurethane TPX Polymethylpentene Transfer Molding A method of molding a natural rubber of silicone elastomer which material is placed in a pot, located between the top plate and plunger, and squeezed from the pot through gates into the mold cavity Trapped Air Air which is trapped in a product or a liquid silicone rubber mold during cure usually causing a discoloration or defect Trim The process involving removal of mold flash something that should be avoided with proper liquid silicone rubber tool design Tunnel Gate An edge gate where the opening from the runner into the mold is located below the mold parting line also know as submarine gate Two Shot Molding A means of producing two-color parts in thermoplastic or liquid silicone rubber materials by successive molding operations Back to top... UL Underwriters' Laboratories |
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