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Glossary: Technical Terms
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- 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
- K-Factor
- A term sometimes used for thermal insulation value or coefficient of thermal conductivity.
- Knit Lines
- See Weld Line.
- Knockout Pin
- A pin that ejects a molded article from the mold.
L
- 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.
M
- 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.
- 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 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.
N
- NIOSH
- Abbreviation for the National Institute for Occupational Safety and Health.
- Nominal Wall
- The nominal wall is what gives the part its basic shape and strength. It forms the framework to
which are added all other details to the part.
- 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.
O
- 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.
P
- Parting Line
- The mark on a molded article caused by flow of material into the crevices between mold halves.
- 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.
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