Accelerator |
A chemical additive which speeds up the rate of
a chemical reaction and thereby reduces the gel time and cure time. Another term is promoter. |
Adhesion |
The property of forming a steady or firm attachment. |
Adhesive Failure |
The failure at the bond line between a substrate and an adhesive; the adhesive
separating entirely from the substrate. |
Aging |
The change in properties of a material with time under specific conditions. |
Ambient Temperature |
The temperature of the surrounding environment. |
Arc Resistance |
The time required for an arc to establish a conductive path in a material. |
"B" Stage |
The intermediate stage during the curing process when the material has gelled but is not
fully cured. |
Bond Strength |
A measure of force or pressure required to separate a layer of material from its base. |
Breakdown Voltage |
The voltage at which the insulation between two conductors will break down. See
Dielectric Strength. |
Burning Rate |
A term describing the tendency of materials to burn at different temperatures. |
Cast |
To form plastic objects by pouring a fluid system into an open mold. |
Catalyst |
A material which initiates and/or accelerates a chemical reaction but normally does not
enter into the reaction. |
Centipoises |
A unit of viscosity (with water as the standard) for indicating the fluidity or flow
property of a liquid at room temperature. |
Chemical Resistance |
A measure of the sensitivity of a material to attack or corrosion by a chemical material. |
Classes Of Insulation |
Arbitrary temperature ratings based on composition and/or experience with a particular
material. |
Coating |
A finishing, protecting, or enclosing layer that seals a component from its immediate
environment. See Dipping. |
CTE |
Coefficient Of Linear Thermal Expansion The fractional change in length of a material for a unit change in temperature. Measured
in inch/inch/°F or cm/cm/°C. |
Cohesion |
The internal affinity of a material to itself. |
Cohesive Failure |
Failure within the adhesive under a stress, resulting in a broken bond with all adherent
surfaces still covered with adhesive. |
Compressive Strength |
A measure of the resistance of a material to a crushing load. Measured in
pounds/square inch or megapascals. |
Conductivity (Electrical) |
The reciprocal of volume
resistivity. Conductance of a unit cube of any material. |
Copolymer |
A compound resulting from the chemical reaction of two chemically different monomers
with each other. |
Cross-Linking |
Reacting together large molecules to change the physical properties of material.
Cross-linking involves formation of a three dimensional molecular network with thermosetting resins. |
Cure Cycle |
The time and temperature necessary for a material to reach most of
its optimum properties. |
Cure Time |
The time for reacting thermosetting plastic or rubber composition to reach certain
properties. For materials which react under the conditions of mixing, the start of
reaction is the time of initial exposure to the conditions necessary for reaction to occur. |
Curing Agent (Hardener) |
A cross-linking agent that reacts with a resin to form a copolymer. |
Curing Temperature |
The temperature at which a material cross-links or cures. |
Density |
The weight per unit volume of a material. Measured in pounds/gallon, or kilograms/liter.
Specific gravity is the density in kilograms/liter. |
Dielectric Constant |
The ratio of the capacitance of a material to the capacitance of air. |
Dielectric Strength |
The maximum electrical voltage which an insulating material can withstand without
breakdown (conducting electricity). Expressed in volts/mil. |
Dipping |
The process of coating or impregnating of insulating materials by immersion into the
uncured material. |
Dissipation Factor |
The measure of the loss of power which takes place in virtually all dielectric materials,
usually in the form of heat. It's expressed as the ratio of the resistive (loss) component
of the current to the capacitive component of current and is equal to the tangent of the
loss angle. |
Elongation |
The increase in length of a material when stress in tension. Measured as a percentage
increase over the unstressed material. |
Embedment |
The enclosure of an electronic, electrical, or electromechanical device in a resin matrix.
Most commonly, the embedding matrix is composed of a thermosetting polymer than can be converted from a liquid to a solid by heat, chemical reaction and/or a
combination of these. The device is buried or encased in the liquid, which then forms a
protective shell when the liquid hardens. |
Encapsulating |
Enclosing an article in a closed envelope of a material. |
Epoxy Resins |
A specific type of chemical structure based on ethylene oxide. |
Exotherm |
The amount of heat given off by a chemical reaction. |
Failure |
See Adhesive Failure, Cohesive Failure |
Filler |
An inert material added to a plastic to improve properties and/or decrease cost, most
commonly limestone. |
Flame Retardant |
The property of a material that extinguishes a flame once the source of heat has been
removed. |
Flexural Strength |
The strength of a material in bending. |
Gassing |
The propensity of a material to form a gas during cure. |
Gel Time |
The time it will take a thermosetting material to become solid at a given temperature and
mass. |
Glass Transition Temperature(Tg) |
The temperature at which cured resins undergo a change from a glassy state to a softer
more rubbery state. |
|
Hardener |
A material or mixture of substances added to a plastic composition which cross links
another material, typically a polymer. See Curing Agent. |
Hardness |
Resistance of a material to deformation by indentation.
See Shore
Hardness. |
Heat Deflection Temperature |
HTD - The temperature at which a standard test bar will deflect 0.010" under a static load of
264 psi. A method to approximate Tg. |
Hertz |
A term replacing cycles-per-second as an indication of frequency.
Abbreviated Hz. |
Impact Strength |
The ability to withstand shock loading; or, work required to fracture under shock
loading a specified test specimen in a specified manner. See IZOD Impact
Strength. |
Impregnate |
To fill the voids of a material with a compound. |
Insulation
|
Material having a high resistance to the flow of electric current. |
Izod Impact Strength |
The amount of force necessary to fracture a notched piece of plastic with a hammer
type impact. Measured in foot pounds/inch of notch. |
Lap Shear Strength |
A measure of adhesive strength when placed between two metal coupons and pulled in
a tensile mode. |
MMD |
meter-mix-dispense equipment. A dispensing machine that
meters the proper amount of resin to hardener, mixes the two together and
dispenses the mixture in to the unit to be potted. |
Mixing Ratio |
The optimum amount of resin and hardener that gives the desired properties. |
Modulus Of Elasticity |
The measure of stress to strain in a material that is elastically deformed. |
Moisture Absorption |
The amount of water a material will absorb under certain conditions. |
Moisture Resistance |
The ability of a material to resist degradation from moisture in the air or when immersed
in water. |
Organic |
Composed of matter or chemicals of hydrocarbon origin. |
Paste |
A high viscosity material that resists flowing on a vertical surface. |
Pigment |
A coloring agent. |
Plastic |
Highly polymeric materials that deform under stress and temperature. See
Thermoset
and Thermoplastic. |
Polymerize |
To unite chemically two or more monomers of polymers of the same kind to form a
molecule with higher molecular weight. |
Post Cure |
Additional time/heat cycles to which a cured thermosetting plastic is subjected in order
to enhance the properties. |
Pot Life |
The amount of time a mixed material may be easily used at a specific temperature. It Is
usually measured as the time it takes for a material to double in viscosity. |
Potting |
The process where an insulating material is poured into a container and the container
remains as an integral part of the unit. |
Pressure Gellation |
A process for molding in which the shrinkage is minimized by forcing the material under
pressure into the mold and gelling it in stages. |
Promoter |
See Accelerator |
Release Agent |
A chemical agent used to prevent a material from adhering to a surface such as a mold. |
Resin |
An organic substance of natural or synthetic origin characterized by being polymeric in
structure. |
Resistivity |
The ability of a material to resist passage of electric
current through itself or on its surface. |
Set Time |
See Gel Time |
Shelf Life |
The amount of time a material may remain useable in its original containers. |
Shore Hardness |
A method of determining the hardness of a material using a pointed gauge. Shore A
and 00 and 000 is
used to measure soft materials and Shore D is used to measure harder materials.
See Hardness cross reference for comparison between type of
Shore hardness. |
Silicone |
Polymeric materials composed of molecules of silicon and oxygen. |
Solvent |
A liquid substance which dissolves other substances. |
Specific Gravity |
Metric measurement of Density, abbreviated Sp.G. See Density. |
Substrate |
Any material on whose surface an adhesive is spread for bonding or coating. |
Surface Resistivity |
The resistance of a material to the flow of electric current over its surface. Measured in
ohms/centimeter. |
Tensile Shear Strength |
See Lap Shear
Strength. |
Tensile Strength |
The ultimate pulling force required to break a material. Measured in pounds/sq. Inch or
megapascals. |
Tg |
See Glass transition
temperature |
Thermal Conductivity |
A measure of a material's ability to conduct heat. Measured in BTU-inch/hours-square
foot/°F or calorie-centimeters/second-square centimeters/°C. |
Thermal Expansion |
See Coefficient of Linear Thermal
Expansion. |
Thermoplastic |
A plastic which will repeatedly flow under the application of heat and pressure. |
Thermoset |
A plastic material that is capable of being changed into a non-melting or insoluble
product by heat or chemical means. |
Thixotropic |
Describes materials that will not flow unless agitated or forced through an orifice. Shear
thinning. |
Thixotropy |
False body. The property of a paste or fluid to thicken or set up to a paste or a
semi-gel when allowed to stand. Agitation breaks it down but further standing will again
permit a viscosity rise. |
Urethane |
A polymeric material that is formed by the use of an
Isocyanate base chemical. |
Vapor Degreasing |
A chemical method for cleaning surfaces of contaminants. |
Varnish |
A thin coating material that may be one or two package in nature and often contain
solvents. |
Viscosity |
A measure of the resistance of a fluid to flow or the internal friction within the body of
fluid. Measured in Centipoises or Pascal seconds. |
Volume Resistivity |
The resistance of a material to the flow of electric current through itself. Measured in
ohms/centimeter. |
Water Absorption |
The ratio of the weight of water absorbed by a material to the weight of the dry
material. |
Working Time |
(Work Life) See Pot Life |
