Glossary

Plastics Glossary - E

Ebullioscopy Determination of the concentration of materials in a solution based upon boiling point deviations.

Eddy Viscosity Turbulent viscosity based upon ratio of shear stress to a velocity gradient.

Effective viscosity The processing viscosity of a material in response to all process variables as well as material characteristics.

Ejection bar See Knockout bar.

Ejection ram Small hydraulic piston(s) that operate ejector plates.

Ejection Removal of the molded part from the mold by mechanical means or with compressed air. The process of removing or stripping completed parts from the mold.

Ejector bar The bar (or bars) that is activated by an ejection mechanism that pushes the ejector plate forward.

Ejector Pin A rod, pin or sleeve which pushes a molding off of a core or out of a cavity of a mold.

Ejector plate Metal plate used to operate ejector pins; designed to apply a uniform pressure to the pins during the ejection process.

Ejector retainer plate The back half of the ejector plate that holds the heads of the ejector pins in the plate.

Ejector return pins (surface pins/return pins) Projections that push the mold ejector assembly back as the mold closes.

Ejector Rod A bar that actuates the ejector assembly when the mold opens.

Elastic deformation The portion of deformation of an object under load that can be recovered after load is removed.

Elastic Fluid Fluid in which elastic stresses and hydrostatic pressures are large compared with viscous stresses.

Elastic limit The greatest stress which a material is capable of sustaining without permanent strain remaining on the complete release of the stress. A material is said to have passed its elastic limit when the load is sufficient to initiate deformation.

Elastic Memory A characteristic of certain plastics evidenced by their tendency upon reheating to revert to a shape or dimension previously existing during their manufacture.

Elasticity The ability of a material to quickly recover its original dimensions after removal of a load that has caused deformation.

Elastomer A material which at room temperature can be stretched repeatedly to at least twice its original length and upon immediate release of the stress, will return with force to its approximate original length.

Electroformed molds A reproduction of an item by electrodeposition of a metal over a model or mandrel that is later removed. Made from iron, nickel, and copper, with nickel being the most prevalent.

Electrophoresis Migration of the electrically charged particles toward the oppositely charged electrode.

Electrostatic coating Process in which the coating material is electrically charged as it leaves the spray gun and is attracted to the party which has an opposite charge.

Electroviscous Effect Lyophobic particles that bear an electrical charge and therefore exhibit a viscosity exceeding that of a similar system of uncharged particles.

Elongation at break Elongation recorded at the moment of rupture of the specimen, often expressed as a percentage of the original length.

Elongation The fractional increase in length of a material stressed in tension.

Embossing Technique provides a textured surface to roll goods. It is used in-line with extruders and calendars or off-line in an unwind, emboss, and rewind operation. The focal point of the equipment is the textured roll which imparts the impression into the web material.

Emulsifying Agent Surface-active agent that is primarily used to effect the stability of an emulsion system. Emulsifying agents may be ionic (anionic, cationic, amphoteric) or nonionic in solution.

Emulsifying Process of uniformly dispersing one mutually insoluble material in another.

Emulsion A suspension of globules or fine droplets of one liquid in another. Can also include the suspension of solids such as resins and waxes in liquids.

Emulsion Polymerization Polymerization of a water insoluble monomer that takes place in the presence of water to form a latex. The monomer is usually emulsified and polymerization occurs within the emulsion system.

Emulsion System consisting of two incompletely miscible liquids, one being dispersed as finite globules in the other. A small amount of a third substance may render the dispersion stable. The liquid broken up into globules is the dispersed (discontinuous) phase; the surrounding liquid is the external (continuous) phase. Emulsion can also consist of gas in liquid (foams) or solids in liquids, such as liquid crystals.

Emulsoid Colloidal system in which there is a strong attraction between the disperse substance and the dispersing liquid.

Emulsoid Sol Colloidal suspension in which both dispersion medium and dispersed phase are both liquids.

Endothermic Process Process that absorbs heat.

Endothermic The thermal transition when polymers take in heat.

Engineering Plastics A broad term covering all plastics, with or wirhout fillers or reinforcements, which have mechanical, chemical and thermal properties suitable for use, in construction, machine components and chemical processing equipment.

Engineering thermoplastics A group of thermoplastics generally considered to have superior properties to commodity materials.

Engler Degree Measurement of kinematic viscosity that is obtained by dividing the outflow time of a specified amount of liquid through a standard orifice by the outflow time of water at 20˚C.

English Method Procedure for the preparing of an emulsion whereby a small portion of the water and the surfactants are mixed. The oil and remaining water are then added in successive small portions.

Environmental stress cracking The susceptibility of the thermoplastic resin to crack or craze when in the presence of surface active agents or other environments.

Epoxy molding compound Compounds are mineral filled powders which can be molded on compression or transfer molding presses.

Ethylene vinyl acetate Copolymer member of the polyolefin family, derived from random co-polymerization of vinyl acetate and ethylene. The resins have about the same resistance to chemicals as low-density polyethylene and are commonly used in hot melt adhesives, sealants, and coatings, and processed by injection molding and extrusion. Semi-crystalline material.

Eucolloid Colloid composed of relatively large particles (larger than 0.25µ).

Evolutionary Method of Change Method of changing machine settings in small increments, carefully measuring and recording changes in the process.

Exotherm The temperature vs. time curve of a chemical reaction and the amount of heat given off. Maximum temperature occurs at peak exotherm.

Exothermic Process Process that liberates heat.

Exothermic reaction A reaction in which heat is given off.

Extender A substance added to a plastic composition to reduce the amount of resin required per unit volume. Generally has adhesive action.

External Phase Dispersing medium of a colloidal suspension; the continuous phase of an emulsion.

Extrudate The product or material delivered from an extruder, for example, film, pipe profiles.

Extruder, compounding The basic functions of a compounding extruder are to melt the polymer and evenly disperse and distribute additives or fillers to obtain the specifications of the end product. Large-scale compounding is done on either single or twin screw extruders. Single screws are used for basic operations. Twin screw compounders offer better dispersing capabilities.

Extruder, single screw Basic machine consists of a screw, barrel, drive mechanism, resin feed arrangement, and controls. The constantly turning screw augers the resin through the heated barrel where it is heated to proper temperature and blended into a homogeneous melt. Before the melt can leave the barrel, it must pass through a breaker plate and screen pack. This unit builds up backpressure in the barrel, filters out contaminants, and tends to convert turbulent melt flow into more laminar flow. The melt is then extruded through the die into the desired shape.

Extruder, twin screw Two screws, side by side, are placed within the extruder barrel; they are either counter-rotating or co-rotating. Counter-rotating twin screw extruders are used primarily for processing PVC products such as pipe, siding, sheet, pellets, and film. The co-rotating units are used for compounding materials where thorough mixing and high output rates are important. The twin screw unit resembles a positive displacement screw pump. It conveys the material at low speeds with controlled shear. The positive action assures that all portions of the material experience a uniform residence time.

Extruder A machine for producing more or less continuous lengths of plastics sections such as rods, sheets, tubes, and profiles.

Extrusion blow molding Extruder is operating continuously and the output either feeds an accumulator or flows through the die as an endless parison. Basic equipment consists of an extruder, crosshead die (and accumulator), clamping arrangement and mold.

Extrusion The process of forcing a material in plastic condition through an orifice.

Extrusion, Foam Process for producing plastic sheet of cellular construction. Either a chemical or a gaseous blowing agent is introduced into the polymer melt while the melt is being prepared in the extruder barrel. As the plastic melt exits the die, it expands a predetermined amount, forming a cellular wall.

Extrusion The process of Compacting and melting a plastic material and forcing it through an orifice in a continuous fashion. In the extrusion process, the material is conveyed through the heated machine barrel by a helical screw where it is heated and mixed to a homogeneous state and then forced through a die of the shape required for the finished product.

Exudation Migration of additives from the interior to the surface of a plastic part. See Bloom.

Eye bolts Ringed bolts screwed into tapped holes in the mold.