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definitions of engineering terms |
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Abrasion Resistance
the ability to withstand the effects of repeated wearing, rubbing, scrapping,
etc.
Amorphous
Latin meaning without form. Non-crystalline structure.
Anneal
to prevent the formation of or remove stresses in plastics by cooling from a
suitable temperature.
Arc
1) a luminous glow formed by the flow of electric current through ionized air, gas,
or vapor between separated electrodes or contacts.
2) a portion of the circumference of a circle.
Arc Resistance
1) the resistance to the flow of current offered by the voltaic arc (i.e., if
the carbons of an arc lamp are 1/32 inch apart, the arc resistance will be
1-1/2 ohms).
2) the resistance of a material to the effects of an arc passing across its
surface stated as a measure of the total elapsed time taken to form a
conducting path (of material carbonizing by the arc flame) across the surface
under prescribed conditions of applications of a high voltage, low current arc
(as across an insulator).
AWG
abbreviation for American Wire Gauge, a standard system for designating wire
diameter.
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Base
the material woven (such as paper, woven cotton, glass fabric or glass fiber
mat, felted asbestos, aramid fibers, graphite, and nylon fabrics) in the form
of sheets or rolls which can be impregnated with resin to form laminated
plastics.
Binder
the organic or inorganic material which encapsulates and holds together the
base in reinforced or otherwise heterogeneous composites.
Bond Strength
the measure of the force required to separate objects or materials bonded
together.
Breakdown
the disruptive discharge through insulation due to failure under electrostatic
stress.
British Thermal Unit (B.T.U.)
the quantity of heat required to raise the temperature of one pound of water
1°F from 58.5°F to 59.5°F (its point of maximum density).
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Canvas
a cotton fabric weighing more than four ounces per square yard. (used as the
base material for NEMA grades C, CE and some L grade laminates.
Celsius
also referred to as Centigrade, is equal to the difference between the
temperature in Fahrenheit less 32 and the quantity divisible by 1.8.
formula: °C = (°F-32) ÷ 1.8
Cement
A dispersion of "solution" of unvulcanized rubber or a plastic in a
volatile solution. This meaning is peculiar to plastics and rubber industries
and may not be an adhesive composition.
Coefficient of Thermal Expansion
The unit change in dimension of a material for a unit change in temperature.
Coefficient of Friction
Static: the ratio of the limiting friction developed to the corresponding
normal pressure, if 2 surfaces move relative to each other.
Composite
1) a structure or an entity made up of distinct components. 2) a complex
material, such fiberglass, in which two or more distinct, structurally
complementary substances, especially glasses and polymers, combine to produce
structural or functional properties not present in any individual component. 3)
reinforced laminates (i.e. canvas phenolic, glass epoxy, etc.)
Compressive Strength
crushing a load at failure divided by the original sectional area of the
specimen.
Conductivity
the reciprocal of volume resistivity. It is the conductance of a unit cube of
any material.
Copolymer
A polymer formed through the inter-polymerization of two (or more) chemically
different monomers with each other.
Copper Clad Laminate
laminates (i.e. FR4) having copper foil bonded to one or both surfaces and
intended primarily for use in printed circuits.
Corrosion
chemical action which causes destruction of the surface of a a material by
oxidation or chemical combination. Also caused by reduction of the electrical
efficiency between a metal and a contiguous substance or to the disintegrating
effects of strong electrical currents or ground return currents in electrical
systems. The latter is known as electrolytic corrosion.
Crazing
minute lines appearing in or near the surface of materials such as plastics,
usually resulting as a response to environment. Crazing cannot be felt by
running a fingernail across it (if the fingernail catches , it is a crack).
Creep
the dimensional change with time of a material under load. At room temperature
it is also called cold flow.
Crystallinity
a molecular structure resulting from the formation of solid crystals with a definite
geometric pattern.
Cross-Linking
the setting-up of chemical valence links between the molecular chains of
polymer molecules, leading to the formation of a 3-dimensional network of
polymer chains which is infusible and insoluble. This usually reduces the
thermoplasticity of the material.
Cure
to change the physical, chemical, or electrical properties of a material by
chemical reaction, by the action of heat and catalysts alone or in combination,
with or without pressure. Specifically to convert a low molecular weight
polymer or resin to and insoluble, infusible state.
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Delamination
the separation of a laminate along the plane of it's layers. Also the separation
of bonded insulation within the adhesive layer or at the adhesive interface.
Density
weight per unit volume of a given substance.
Dielectric
1) any insulating medium which intervenes between two conduits and permits
electrostatic attraction or repulsion to take place across it. 2) a material
having the property that energy required to establish an electric field is
recoverable in whole or in part, as electric energy. (see insulation for
clarification)
Dielectric Constant (Permittivity or Specific Inductive Capacity)
the specific inductive capacity or a dielectric. That property of a dielectric
which determines the electrostatic energy stored per unit volume for unit
potential gradient.
Dielectric Strength
the voltage which an insulating material can withstand before breakdown occurs,
usually expressed as a voltage gradient (such as volts per mil).
Dimensional Stability
ability to retain precise shape and size.
Dissipation
unusable or lost energy, as the production of heat in a circuit.
Dissipation Factor (loss tangent, tans, approx. power factor)
the tangent of the loss angle of the insulating material.
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Elongation
the fractional increase in length of a material stressed in tension.
Epoxy Resins
straight-chain thermosetting resins containing at least one 3 membered ring
consisting of 2 carbon atoms and 1 oxygenation.
Extrusion
the method of processing plastic by forcingheat softened plastic through an
opening of the desired shape of the cross-section of the finished product.
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Fabric-Base Laminate laminated insulating material formed by bonding woven cloth (of fiber glass, cotton, or synthetic fibers) with resin under heat and pressure.
Fahrenheit
equals 1.8 multiplied to the sum of the temperature in Celsius and 32.
formula: - °F = 1.8 x (°C + 32)
Fiber
a thread or threadlike structure such as cellulose, wool, silk, or glass yarn.
(See also fibre and filament.)
Fibre
1) a specific form of chemically jelled fibrous materials manufactured in
sheets, rods, and tubes. 2)commonly used interchangeably with fiber.
Filament
1)fiber characterized by extreme length. 2)the resistance wire through which filament
current is sent in a therm ionic tube to produce the heat required for electron
emission.
Filament Winding
resin impregnated roving or single strands of glass or other reinforcement
wound in a predetermined pattern onto a suitable form or mandrel and then
cured.
Fishpaper
a type of vulcanized fibre paper treated chemically for insulating purposes
where high mechanical and electrical strength and flexibility are required.
Flash Point
the lowest temperature at which a flammable liquid will produce a combustible
vapor that will burn in the presence of a flame, under certain prescribed
conditions of test.
Flexural Strength
the strength of a material in bending, expressed as the tensile stress of the
outermost fibers of a bent test specimen at the instant of failure.
Formulation
a combination of ingredients before processing or made into a finished product.
Also used as a synonym for a material, compound.
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Glass Cloth
fabric used as insulating material base formed by weaving yarns comprising
glass filaments and possessing high strength, heat resistance, and dielectric
properties.
Glass Fiber
glass in fibrous form.
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Heat Distortion Point
the temperature in degrees C at which a standard test bar (ASTM D648) deflects
0.010 inches under a stated load of either 66 or 264 psi, when the temperature is
raised at a specific rate of increase.
Heat Loss
power dissipated as heat.
High-Pressure Laminates
Laminates molded and cured at pressures not lower than 600 psi (pressures of
1000 to 2500 psi are not uncommon).
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Impact Resistance
relative susceptibility of material to fracture by physical shock.
Impact Strength
ability to withstand physical shock loading or work required to fracture under
shock loading a specified test specimen in a specified manner.
Impregnate
to fill the voids and interstices of a material with a compound (this does not
imply complete fill or complete coating of the surfaces by a hole free film.)
Inert
deficient in active properties; not affecting other substances when in contact
with them such as inert gases.
Infrared
the band of light in the electromagnetic spectrum that lies between the visible
light range and the radar range.
Insulation
material having a high resistance to the flow of electric current, to prevent
leakage of current from a conductor.
Insulation Resistance
the ratio of the applied voltage to the total current between two electrodes in
contact with a specific conductor under prescribed conditions of test.
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Kelvin
the absolute temperature scale (metric).
formula: - K = °C + 273
Kraft Paper
relatively heavy, high strength sulfate paper used for electrical insulating
material.
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Laminate
(verb) to build up to desired shape or thickness.
(noun) a material composed of successive layers of material, usually bonded
together under heat and pressure.
Light Transmission
the amount of light that a plastic will allow to pass.
Loss Factor
the product of the power factor and the dielectric constant.
Low Pressure Laminates
laminates molded and cured in the range of pressures from 400 psi down.
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Mat
a randomly distributed felt of fibers, usually glass, used in reinforced
plastics.
Mica
a transparent, flaky mineral which splits into thin sheets and has excellent
insulating and heat resisting properties.
Moisture Resistance
the ability of a material to resist absorbing ambient moisture.
Monomer
the simple, unpolymerized form of a compound which is the building block of a
polymer.
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Permeability
1) the passage or diffusion (or rate of passage) of a gas, vapor, liquid, or
solid through a barrier without physically or chemically affecting it. 2) the
ability of a material to carry magnetism as compared to air which has a
permeability of 1.
Permittivity
preferred term for dielectric constant. It is that property of a dielectric
material that determines how much electrostatic energy can be stored per unit
of volume when unit voltage is applied.
Phenolic Resin
as synthetic resin produced by the condensation of phenol with an aldehyde
(usually formaldehyde).
Plastic
high polymeric substances, including both natural and synthetic products, but
excluding the rubbers, that are capable in their manufacture of flowing under
heat and pressure.
Plasticizer
chemical agent added to plastics to make them softer and more flexible.
Polymer
a compound formed by the chemical union of two or more monomer of the same
kind.
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Reinforcement
material used to reinforce, strengthen or give dimensional stability to another
material.
Resin
a substance that is polymeric in structure and predominantly amorphous.
Resistance
property of a conductor that opposed the current flow produced by a given difference
of potential. The ohm is the practical unit of resistance.
Rockwell Hardness
a test for hardness (resistance to indentation) in which a hardened steel ball
or diamond point is pressed into the material under test.
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Shear Strength
ability of a material to withstand shear stress or stress at which a material
fails in shear.
Specific Gravity
the density of any material divided by that of water at a standard temperature.
Surface Resistivity
the resistance of a material between two opposites sides of a unit square of
its surface.
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Tear Strength
force required to initiate or continue a tear in a material under specified
conditions.
Tensile Strength
the longitudinal stress required to break a prescribed specimen divided by the
original cross-sectional area at the point of rupture (usually expressed in
lbs. per square inch).
Thermal Conductivity
the ability of a material to conduct heat; physical constant for quantity of
heat that passes through volume of a substance in unit of time for unit
difference in temperature.
Thermoplastic
plastics capable of being repeatedly softened by increases in temperature and
hardened by decreases in temperature. These changes are physical rather than
chemical.
Thermoset
a classification of plastic resin that cures by chemical reaction when heated
and, once cured, cannot be resoftened by heating.
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Volume Resistivity
resistance between opposite faces of 1 cm cube of material, usually in ohm-cms.
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