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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
Abrasion Resistance -
The ability of a material to withstand mechanical actions such as rubbing, scraping, or erosion,
that tend progressively to remove material from its surface.
Additive -
In the plastics industry: materials added in minor amounts to basic resins or compounds to alter
properties.
Adhesive Assembly -
The process of joining two or more plastic parts by means of an adhesive.
Aging -
The process of, or the results of, exposure of plastics to natural or artificial environmental
conditions for a prolonged period of time.
Alloy -
A term used in the plastics industry to denote blends of polymers or copolymers with other polymers
or elastomers. - i.e. ABS/Polycarbonate.
Ambient Temperature -
The temperature of a medium surrounding an object. The term is often used to denote prevailing
room temperature.
Amorphous -
Devoid of crystallinity or stratification. Most plastics are amorphous at processing temperatures.
Anisotropy -
The tendency of a material to react differently to stresses applied in different directions.
Annealing -
The process of relieving stresses in molded plastic articles by heating to a predetermined temperature,
maintaining this temperature for a predetermined length of time, and slowly cooling the articles
to be painted which might craze due to solvent attack.
ANSI -
Abbreviation for American National Standards Institute.
Antifogging Agents -
Additives which prevent or reduce the condensation of water on a plastic film in the form of small
droplets which resemble fog.
Antioxidant -
Additives which inhibit oxidation at normal or elevated temperatures.
Antistatic Agents -
Chemicals which impart a slight to moderate degree of electrical conductivity to plastic compounds,
thus reducing the accumulation of electrostatic charges on finished articles.
Application -
The act of applying or putting to use. What the molded plastic article will be in its final form.
Arc Resistance -
The ability of a plastic material to resist the action of a high voltage electrical arc, usually
stated in terms of time required to render the material electrically conductive.
Ash Content -
The solid residue remaining after a substance has been incinerated or heated to a temperature
sufficient to drive off all combustible or volatile substances.
Assembly -
The process of joining parts by any of several methods.
ASTM -
Back Pressure -
The resistance of the molten plastic material to forward flow. In molding, back pressure increases
the temperature of the melt, and contributes to better mixing of colors and homogeneity of the
material.
Balanced Runner -
In injection molding, a runner system designed to place all cavities at the same distance from
the sprue.
Barrel -
That part of an extruder inside which the feed screw is located.
Black Specks -
A specific kind of inclusion/contamination often associated with degraded materials.
Blast Finishing -
The process of removing flash from molded objects and/or dulling their surfaces, by impinging
media such as crushed apricot pits, walnut shells or plastic pellets upon them with sufficient
force to fracture the flash.
Blister -
An imperfection on the surface of a plastic article caused by a pocket of air or gas beneath the
surface.
Bloom -
An undesirable cloudy effect or whitish powdery deposit on the surface of a plastic article caused
by the exudation of a compounding ingredient such as a lubricant, stabilizer pigment, plasticizer,
etc.
Blow Molding -
The process of forming hollow articles by expanding a hot plastic element called a parison against
the internal surfaces of a mold.
Blushing -
The tendency of a plastic article to turn white or chalky in areas that are highly stressed.
Boss -
A protuberance provided on an article to add strength, facilitate alignment during assembly or
for attaching the article to another part.
Branching -
The growth of a new polymer chain from an active site on an established chain, in a direction
different from that of the original chain.
Breakdown Voltage -
The voltage required, under specific conditions, to cause failure of an insulation material. See
Dielectric Strength.
Brittleness Temperature -
The temperature at which plastics and elastomers rupture by impact under specified conditions.
Bulk Density -
The density of a modking material in loose form expressed as a ratio of weight to volume.
Bulk Factor -
The ratio of the volume of any given mass of loose plastic material to the volume of the same
mass of the material after molding.
Burned -
Showing evidence of excessive heating during processing or use of a plastic, as evidenced by blistering,
discoloration, distortion or destruction of the surface.
Cavity -
A depression, or a set of matching depressions, in a plastics-forming mold which forms the outer
surfaces of the molded articles.
Charge -
The amount of material used to load a mold at one time or during one cycle.
Charpy Impact Test -
A destructive test of impact resistance, consisting of placing the specimen in a horizontal position
between two supports, then applying a blow of known magnitude. If the specimen does not break,
a new specimen is put in position and the magnitude is increased until the specimen breaks. (ASTM
D-256, Method B)
Chopped Strand -
A type of fiber reinforcement consisting of strands of individual glass fibers which have been
chopped into short pieces.
Clamping Area -
The largest rated molding area an injection press can hold closed under full molding pressure.
Clamping Force -
In injection molding, the pressure which is applied to the mold to keep it closed, in opposition
to the fluid pressure of the compressed molding material within the mold cavity and the runner
system.
Clamping Pressure -
In injection molding, the pressure applied to the mold to keep it closed during the molding cycle.
CTE -
Coefficient of Thermal Expansion: The change in length of a material for a unit change in temperature,
per unit of length.
Coextrusion -
The process of extruding two or more materials through a single die with two or more orifices
arranged so that the extrudates merge and weld together into a laminar structure before chilling.
Colorants -
Dyes or pigments which impart color to plastics.
Color Concentrate -
A plastic compound which contains a high percentage of pigment, to be blended in appropriate amounts
with the base resin so that the correct final color is achieved.
Composite -
An article or substance containing or made up of two or more different substances.
Compound -
A mixture of resin and the ingredients necessary to modify the resin to a form suitable for processing
into finished articles.
Compounding -
The step of mixing base resins with additives such as stabilizers, fillers, pigments into a form
suitable for processing into finished articles.
Compression Molding -
A method of molding in which the molding material, generally preheated, is placed in an open heated
mold cavity, the mold is closed with a top force, pressure is applied to force the material into
contact with all mold areas, and heat and pressure are maintained until the molding material has
cured. This process is most often used with thermoses.
Compressive Strength -
The load sustained by a test specimen in a compressive test divided by the original area of the
specimen.
Conditioning -
Subjecting a material to standard environmental and/or stress history prior to testing.
Copolymer -
This term usually, but not always, denotes a polymer of two chemically distinct monomers.
Core -
A protrusion, or set of matching protrusions, in a plastics forming mold which forms the inner
surfaces of the molded articles.
Corona Resistance -
In an insulated electrical conductor, the resistance of the insulation to breakdown caused by
ionized air in voiks existing in the insulation by the current in the conductor.
Corrosion Resistance -
A broad term applying to the ability of plastics to resist many environments.
Corrosion Resistance -
A broad term applying to the ability of plastics to resist many environments.
Crazing -
An undesirable defect in plastics articles characterized by distinct surface cracks or minute
frost-like, internal cracks, resulting from stresses within the article which exceed the tensile
strength of the plastic.
Creep -
Due to its viscoelastic nature, a plastic subjected to a load for a period of time tends to deform
more than it would from the same load released immediately after application, and the degree of
this deformation is dependent of the load duration.
Critical Strain
Cross-Linking -
The setting up of chemical links between the molecular chains.
Cryogenic -
Pertaining to very low temperatures.
Crystal -
A homogeneous solid having an orderly and repetitive three dimensional arrangement of its atoms.
Crystallinity -
A state of molecular structure in some resins attributed to the existence of solid crystals with
a definite geometric form, Such structures are characterized by uniformity and compactness.
CSA -
Abbreviation for the Canadian Standards Association.
Custom Molder -
A firm specializing in the molding of items or components to the specifications of another firm
which handles the sale of distribution of the item, or incorporates the custom molded components
in one of its own products.
Cycle Time -
In a molding operation, cycle time is the time elapsing between a particular point in one cycle
and the same point in the next cycle.
Damping -
Variations in properties resulting from dynamic loading conditions.
DTUL -
Abbreviation for Deflection Temperature Under Load Degassing In injection molding, the momentary
opening and closing of a mold during the early stages of the cycle to permit the escape of air
or gas from the heated compound.
Degradation -
A deleterious change in the chemical structure, physical properties or appearance of a plastic
caused by exposure to heat, light, oxygen or weathering.
Design Review -
A review of a buluprint, of an application, to be molded in a plastic material. Recommendations
given for design, material, processing, tooling.
Density -
(Absolute) Mass per unit volume of a substance.
Dieletric Strength -
A measure of the voltage required to puncture a material, expressed in volts per mil of thickness
(ASTM D-149)
Dimensional stability -
The ability of a plastic part retain the precise shape in which it was molded.
Draft -
A Slight taper in a mold wall designed to facilitate removal of the molded object from the mold.
Drying -
The removal of moisture from the resin pellets by exposure to certain time and temperature. All
Hydroscopic Material must be dried prior to molding.
Durometer -
An instrument used for measuring the hardness of a material.
Ejector Pin -
A rod, pin or sleeve which pushes a molding off of a core or out of a cavity of a mold.
Elasticity -
The ability of a material to quickly recover its original dimensions after removal of a load that
has caused 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.
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.
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.
Extrudate -
The product or material delivered from an extruder, for example, film, pipe profiles.
Extruder -
A machine for producing more or less continuous lengths of plastics sections such as rods, sheets,
tubes, and profiles.
Extrusion -
The process of foaming continuous shapes by forcing a molten plastic material through a die.
Family Mold -
A multiple cavity mold containing variously shaped cavities, producing different parts.
Fatigue Strength -
The maximum cyclic stress a material can withstand for a given number of cycles before failure
occurs.
FDA -
Abbreviation for Food and Drup Administration, the U.S. agency under the Department of Health,
Education and Welfare which is concerned with the safety of products marketed for consumer use.
Filler -
A relatively inert substance added to a plastic compound to reduce its cost and/or to improve
physical properties, particularly hardness, stiffness and impact strength.
Film -
Films are distinguished from sheets in the plastics industry only according to their thickness.
In general, films have thicknesses less than
Fines -
In the classification of powdered or granular materials such as molding compounds according to
particle size, fines are the portion of the material composed of particles which are smaller than
a specified size.
Finish -
The surface texture of a finished article.
Flame Retardant -
Having the ability to resist combustion (A flame retardant plastic is considered to be one that
will not continue to burn or glow after the source of ignition has been removed.)
Flame Retardants -
Additives that reduce the tendency of plastics to burn.
Flash -
The thin, surplus of material which if forced into crevices between mating mold surfaces during
a molding operation remains attached to the molded article.
Flexural Modulus -
The ratio, within the elastic limit, of the applied stress on a test specimen in flexure to the
corresponding strain in the outermost fibers of the specimen.
Flexural Strength -
The maximum stress in the outer fiber at the moment of crack or break. In the case of plastics,
this value is usually higher than the tensile strength.
Foaming Agent -
Any substance which alone or in combination with other substances is capable or producing a cellular
structure in a plastic mass.
Forming -
A general term encompassing processes in which the shape of plastic pieces such as sheets, rods
or tubes is changed to a desired configuration.
Fracture -
The separation of a body, usually characterized as either brittle or ductile.
Gate -
In injection molding, the channel through which the molten resin flows from the runner into the
cavity.
Gate Blush -
A blemish or disturbance in the gate area of an injection molded article.
Glass Fibers -
A family of reinforcing materials for reinforced plastics based on single filaments of glass.
Impact Resistance -
The resistance of plastic articles to fracture under stresses applied at high speeds.
Impact Strength -
The ability of a material to withstand shock loading.
Injection Molding -
The method of forming objects from granular or powdered plastics, most often of the thermoplastic
type, in which the materials is fed from a hopper to a heated chamber in which it is softened,
after which a ram or screw forces the material into a mold. Pressure is maintained until the mass
has hardened sufficiently for removal from the mold.
Insert -
An article of metal or other material which is incorporated into a plastic molded part either
by pressing the insert into the finished molded part or by placing the insert in the cavity so
that it becomes an integral part of the molding.
ISO -
Abbreviation for the International Standards Organization.
Izod Impact Strength -
A measure of impact strength determined by the difference in energy of a swinging pendulum before
and after it breaks a notched specimen held vertically as a cantilever beam.
K-Factor -
A term sometimes used for thermal insulation value or coefficient of thermal conductivity.
Knit Lines -
See Weld Mark.
Knockout Pin -
A pin that ejects a molded article from the mold. Land Area The area of surfaces of a mold which
contact each other when the mold is closed.
Land (Gate Area) -
Gate dimension parallel to the direction of melt flow.
Low Temperature Flexibility
-
The ability of a plastic to be bent without fracture at reduced temperatures.
Lubricant Bloom -
Irregular, cloudy, greasy exudation on the surface of a plastic.
Machining -
Any of a number of processes, such as drilling, turning, sanding, etc., which may be performed
on a piece of plastic.
Mar Resistance -
The resistance of glossy plastic surfaces to abrasive action.
Material Safety Data Sheets
-
Documentation regarding the toxicity or hazards associated with contact with some substances.
These are prepared by the manufacturer of the plastic.
Mechanical Property -
Properties of plastics which are classified as mechanical include abrasion resistance, creep,
ductility, friction resistance, elasticity hardness, impact resistance, stiffness and strength.
Melt Index -
The amount of a thermoplastic resin, measured in grams, which can be forced through a specified
orifice within ten minutes when subjected to a specified force. (ASTM D-1238)
Melt Strength -
The strength of the plastic while in the molten state. This is a pertinent factor in extrusion,
blow molding and drawing of molten resin from a die.
Memory -
The tendency of a plastic article to revert in dimension to a size previously existing at some
stage in its manufacture.
Metallizing -
A term covering all processes by which plastics are coated with metal.
Mineral Reinforcements -
Inorganic substances used as filler for plastics. Some common examples are: clay, mica, talc.
Minimum Specifications -
The minimum values, usually of mechanical properties, that a compound must meet by Quality Assurance
prior to shipment.
Modified Resins -
Synthetic resins modified by the incorporation of natural resins, elastomers or other additives,
which alter the processing characteristics or physical properties of the basic resins.
Modulus -
Derived from the Latin world meaning "small measure", modulus is the ratio of stress to strain
in the linear region of the s-e curve.
Modulus in Compression -
The ratio of compressive stress to strain within elastic limits of the material.
Modulus in Flexure -
The ratio of the flexure stress to strain, within elastic limits of the material.
Modulus in Shear -
The ratio of shear stress to strain within elastic limits of the material.
Modulus of Elasticity -
The ratio of stress to corresponding strain below the proportional limit of a material in tensile
testing.
Modulus of Resilience -
The energy that can be absorbed per unit volume without creating a permanent distortion.
Moisture Absorption -
The pick-up of moisture from the environment by a material.
Mold (n) -
A hollow form or matrix into which a plastic material is placed and which imparts to the material
its final shape as a finished article.
Mold (v) -
To impart shape to a plastic mass by means of a confining cavity or matrix.
Mold Release -
In injection molding, a lubricant used to coat the surface of the mold to enhance ejection of
the molded article or prevent it from sticking to the tool.
Molding Cycle -
The period of time occupied by the complete sequence of operations on a molding press requisite
for the production of one set of molded articles.
Molding Pressure -
The pressure applied to the ram of an injection machine or press to force the softened plastic
completely to fill the mold cavities.
Molecular Weight -
The sum of the atomic weights of all atoms in a molecule.
Molecule -
The smallest unit quantity of matter which can exist by itself and retain all of the properties
of the original substance.
Monomer -
A relatively simple compound, usually containing carbon and of low molecular weight, which can
react to form a polymer by combination with itself or with other similar molecules or compounds.
NIOSH -
Abbreviation for the National Institute for Occupational Safety and Health.
Notch Sensitivity -
The extent to which the sensitivity of a material to fracture is increased by the presence of
a surface notch or sudden change in section.
Nozzle -
In injection molding, the orifice-containing plug at the end of the injection cylinder which contacts
the mold sprue bushing and conducts the molten material into the mold.
Opaque -
Not able to transmit light.
OSHA -
Abbreviation for Occupational Safety and Health Administration.
Oxygen Index -
A flammability test based on the principle that a certain volumetric concentration of oxygen is
necessary to maintain combustion of a specimen after it has been ignited.
Parting Line -
The mark on a molded article caused by flow of material into the crevices between mold parts.
Pellets -
Tablets or granules of uniform size, consisting of resins or mixtures of resins with compounding
additives which have been prepared for molding operations by extrusion and chopping into short
segments.
Photodegradation -
Degradation of plastics due to the action of light. Pigments General term for all colorants, organic
and inorganic, natural and synthetic, which are insoluble in the medium in which they are used.
Pit -
An imperfection, a small crater in the surface of the plastic.
Plastic -
A material that contains as an essential ingredient one or more organic polymeric substances of
large molecular weight, is solid in its finished state, and, at some stage in its manufacture
or processing into finished articles, can be shaped by flow.
Plastic Deformation -
A change in dimensions of an object under load that is not recovered when the load is removed.
Plasticity -
The ability of a material to withstand continuous and permanent deformation by stresses exceeding
the yield value of the material without rupture.
Plasticize -
To render a material softer, more flexible and/or more moldable by the addition of a plasticizer.
Plasticizer -
A substance or material incorporated in a material (usually a plastic or an elastomer) to increase
its flexibility, workability or extensibility.
Plate-Out -
An objectionable coating gradually formed on metal surfaces of molds during processing of plastics
due to extraction and deposition of some ingredient such as pigment, lubricant, stabilizer or
plasticizer.
Poisson's Ratio -
The constant relating the changes in dimensions which occur when a material is stretched. It is
obtained by dividing the change in width per unit length by the change in length per unit length.
Polyblend -
A colloquial term used for physical mixtures of two or more polymers. Such blends usually yield
products with favorable properties of both components, sometimes opening markets not available
to either of the separate components. The term Alloy is sometimes used for such blends.
Polybutylene Terephthalate
-
(PBTP, PBT) A crystalline polymer formed by the polycondensation of 1, 4-butanediol and dimethylterephthalate.
Polycarbonate Resin -
(PC) A family of special types of polyesters in which groups of dihydric phenols are linked through
carbonate linkages.
Polymer -
(Synthetic) The product of a polymerization reaction. The product of polymerization of one monomer
is called a homopolymer, monopolymer or simply a polymer. when two monomers are polymerized simultaneously
the product is called a copolymer. The term terpolymer is sometimes used for polymerization products
of three monomers.
Polymerization -
A chemical reaction in which the molecules of a simple substance (monomer) are linked together
to form large molecules whose molecular weight is a multiple of that of the monomer.
Polymer Structure -
A general term referring to the relative positions, arrangement in space, and freedom of motion
of atoms in a polymer molecule.
Polyphenylene Oxide -
(PPO) A thermoplastic, linear, non-crystalline polyether obtained by the oxidative polycondensation
on 2, 6-dimethylphenol in the presence of a copper-amine complex catalyst.
Proportional Limit -
The greatest stress which a material is capable of sustaining without deviation from proportionality
of stress and strain. (Hooke's Law).
Prototype Tool -
A preliminary mold built upon which the final mold will be based.
Purging -
In extrusion or injection molding, the cleaning of one color or type of material from the machine
by forcing it out with the new color or material to be used in subsequent production, or with
another compatible purging material.
Reagent Resistance -
The ability of a plastic to withstand exposure to chemicals.
Regrind -
Waste material such as sprues, runners, excess parison material and reject parts from injection
molding, blow molding and extrusion, which has been reclaimed by shredding or granulating. Regrind
is usually mixed with virgin compound at a predetermined percentage for remolding.
Reinforced Plastic -
A plastic composition in which fibrous reinforcements are imbedded, with strength properties greatly
superior to those of the base resin.
Reinforcement -
A strong, inert fibrous material incorporated in a plastic mass to improve its physical properties.
Resin -
(Synthetic) The term is use to designate any polymer that is a basic material for plastics.
Runner -
In an injection mold, the feed channel, usually of circular cross section, that connects the sprue
with the cavity gate. The term is also used for the plastic piece formed in this channel.
Runner System -
This term is sometimes used for the entire resin feeding system, including sprues, runners and
gates, in injection molding.
Screw -
In extrusion, the shaft provided with helical grooves which conveys the material from the hopper
outlet through the barrel and forces it out through the die.
Shear Strength -
The maximum load required to shear the specimen in such a manner that the moving portion has completely
cleared the stationary portion. Sheet Sheets are distinguished from films in the plastics industry
only according to their thickness. In general, sheets have thicknesses greater than .040" .
Short Shot -
In injection molding, failure to fill the mold completely.
Shot -
One complete cycle of a molding machine.
Shot Capacity -
The maximum weight of material that can be delivered to an injection mold by one stroke of the
ram.
Shrinkage Allowance -
The dimensional allowance which must be made in molds to compensate for shrinkage of the plastic
compound on cooling.
SI -
Abbreviation for Le Systeme International d'Unites.
Solvents -
Substances with the ability to dissolve other substances.
SPE -
Abbreviation for the Society of Plastics Engineers.
Specific Gravity -
The ratio of the density of a material as compared to the density of water at standard atmospheric
pressure (1 ATM) and room temperature (73F).
Specific Volume -
The volume of a unit of weight of a material; the reciprocal of density.
SPI -
Abbreviation for the Society of the Plastics Industry.
Splay Marks -
Scan or surface defects on molded part caused by abnormal racing of the melt in the mold.
Sprue -
In an injection mold, the main feed channel that connects the mold filling orifice with the runners
leading to each cavity gate.
Stabilizer -
An agent used in compounding some plastics to assist in maintaining the physical and chemical
properties of the compounded materials at suitable values throughout the processing and service
life of the material and/or the parts made therefrom.
Stiffness -
The capacity of a material to resist elastic displacement under stress.
Strain -
In tensile testing, the ratio of the elongation to the gage length of the test specimen, that
is, the change in length per unit of original length.
Stress -
The force producing or tending to produce deformation in a body measured by the force applied
per unit area.
Stress-Crack -
External or internal cracks in a plastic caused by tensile stresses less than that of its short-time
mechanical strength. Note: The development of such cracks is frequently accelerated by the environment
to which the plastic is exposed.
Stress Relaxation -
The decay of stress at a constant strain.
Stress-Strain Curve -
The curve plotting the applied stress on a test specimen versus the corresponding strain. Stress
can be applied through shear, compression, flexure, or tension.
Structural Foam -
A term originally used for cellular thermoplastic articles with integral solid skins having high
strength-to-weight ratios, but now sometimes also used for high density cellular plastics which
are strong enough for structural applications.
Tensile Strength -
The maximum tensile stress sustained by the specimen during a tension test
Thermoelasticity -
Rubber-like elasticity exhibited by a rigid plastic resulting from an increase in temperature.
Thermoforming -
The process of forming a thermoplastic sheet into a three-dimensional shape by clamping the sheet
in a frame, heating it to tender it soft and flowable. Then applying differential pressure to
make the sheet conform to the shape of a mold or die positioned below the frame.
Thermoplastics -
Materials that become soft when heated and solid when cooled to room temperature. This softening
and setting may be repeated many times.
Thermoplastic Elastomers
-
The family of polymers that resemble elastomers in that they can be repeatedly stretched without
distortion of the unstressed part shape, but are true thermoplastics and thus do not require curing.
Thermosets -
Materials that may not be reheated and softened again. Once the structural framework is set, these
plastics cannot be reformed.
Tool -
In injection molding, the term sometimes used to describe the mold.
Transition Temperature -
The temperature at which a polymer changes from (or to) a viscous or rubbery condition (or from)
a hard and relatively brittle one.
UL -
Abbreviation for Underwriters Laboratories, the non-profit safety testing organization.
Ultimate Elongation -
In a tensile test the elongation at rupture.
Ultimate Strength -
Term used to describe the maximum unit stress a material will withstand when subjected to an applied
load in a compression, tension, flexural, or shear test.
Vacuum Forming -
A method of forming plastic sheets or films into three-dimensional shapes, in which the plastic
sheet is clamped in a frame suspended above a mold, heated until it becomes softened, drawn down
into contact with the mold by means of a vacuum, and cooled while in contact with the mold. Often
used interchangeably with thermoforming.
Vicat Softening Point -
The temperature at which a flat-ended needle will penetrate a thermoplastic specimen under specific
conditions. (ASTM D-15225)
Virgin Material -
Any plastic compound or resin that has not been subjected to use or processing other than that
required for its original manufacture.
Viscoelasticity -
This property, possessed by all plastics to some degree, dictates that while plastics have solid-like
characteristics such as elasticity, strength and form-stability, they also have liquid-like characteristics
such as flow depending on time, temperature, rate and amount of loading.
Viscosity -
A measure of the resistance to flow due to internal friction when one layer of fluid is caused
to move in relationship to another layer.
Void -
In a solid plastic, an unfilled space.
Warpage -
Distortion caused by nonuniform internal stresses.
Water Absorption -
The amount of water absorbed by a plastic article when immersed in water for a stipulated period
of time. All plastics will absorb moisture to some extent.
Water White -
A colloquial term used to describe the appearance of a transparent polymer which has no tint or
color.
Weathering -
A broad term encompassing exposure of plastics to solar or ultraviolet light, temperature, oxygen,
humidity, rain, snow' wind, and air-borne biological and chemical agents.
Yellowness Index -
A measure of the color on the yellow scale.
Yield Point -
In tensile testing, yield point is the first point on the stress-strain curve at which an increase
in strain occurs without an increase in stress.
Yield Strength -
The stress at which a material exhibits a specified limiting deviation from the proportionality
of stress to strain.
Young's Modulus -
The ratio of tensile stress to tensile strain below the proportional limit.
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