Glossary
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A-Stage
An early stage in the reaction of certain thermosetting resins in which the material is fusible and still soluble in certain liquids.
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.
Amine
Curing agent for epoxy resins that is any of a class of ammonia derivatives. They are derived from Ammonia.
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.
Brookfield Viscometer
An instrument for measuring the viscosity of adhesives under standard conditions of temperature.
C-Stage
The final stage in the reaction of certain thermosetting resins in which the material is relatively insoluble and infusible. Certain thermosetting resins in a fully cured state are in this stage.
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.
Centigrade
A scale of temperature which uses 0º and 100º as the freezing and boiling point of water respectively. To convert centigrade to Fahrenheit, multiply by 1.8 and add 32.
Centipoises
A unit of viscosity (with water as the standard = 1.0) for indicating the fluidity or flow property of a liquid at room temperature. 1/100 of a poise.
Chalking
Formation of a dry powdery chalk-like appearance or deposit on the surface of a material. It is due to a breaking down of the material after being exposed to ultraviolet light, or to other weathering.
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.
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 (or insulator) to the capacitance of air. A dielectric constant of 4 means an insulator will absorb 4 times more electrical energy than air.
Dielectric Strength
The maximum electrical voltage which an insulating material can withstand without breakdown (conducting electricity). Expressed in volts/mil.
Diluent
A reactive or non-reactive additive whose primary function is to lower the viscosity and extend the material to which it was added.
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.
Doming
Application of a clear doming material (urethane or epoxy) to the surface of labels, nameplates or decals for the purpose of creating a clear raised (“domed”) surface. Used to enhance and protect the appearance of these products. (See also “Scripting”)
Elasticity
That property of materials to tend to recover their original size and shape after deformation. If the strain is proportional to the applied stress, the material is said to exhibit Hookean or ideal elasticity.
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.
Evacuation
The removal of entrained air from an epoxy system by vacuum. Also referred to as degassing.
Exotherm
The amount of heat given off by a chemical reaction, proportional to the mass.
Extender
An available or relatively inexpensive compatible material which can be added to a more valuable substance so as to increase the amount of material in useful form. The use of extenders may involve adulteration under some conditions.
Failure, Adhesive
The failure at the bond line between substrates and an adhesive; the adhesive separating entirely from the substrate.
Failure, Cohesive
Failure within the adhesive under a stress, resulting in a broken bond with all adhered surfaces still covered with adhesive.
Failure, Substrate
The failure of the substrate material itself, upon subjecting bonded adhered surfaces to a stress.
Filler
An inert material added to a formulated system to improve properties and/or decrease cost.
Fisheye
Small globular mass which has not blended completely into the surrounding material and is particularly evident in a transparent or translucent material.
Flame Retardant
The property of a material that extinguishes a flame once the source of heat has been removed.
Flexural Strength
Ability of a material to withstand failure due to 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.
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 Resistance
The ratio of the direct voltage applied to electrodes in contact with an epoxy system to the total current between them. It is dependent upon both the volume and surface resistance of the epoxy systems. ASTM D257-61.
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. Also known as the brittleness of a material. Brittle materials will have low izod impact values (.15 for example). Tough materials will have high izod impact strengths (.60 for example).
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 in a static or dynamic mixer and dispenses the mixture.
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.
Orange Peel
Uneven surface somewhat resembling an orange peel.
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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 and .
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 of dispensing an insulating material into a container. Typically, 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. The unit of volume resistivity is the ohm-cm, of surface resistivity, the ohm.
Scripting
A process in which a clear doming material (urethane or epoxy) is applied to labels, decals or nameplates that feature scripted lettering, graphics or symbols. XYZ automation is often used to control the deposition path of the doming material.
Shelf Life
The amount of time a material may remain useable in its original containers.
Shore Hardness
The reading of a material’s hardness on a durometer similar to the Shore A durometer. The scale of 0-100 is used on rigid and semi-rigid materials. Consists of a pin point depression into the material. Both the Shore A and Shore D instruments are made by the Shore Instrument Manufacturing Company, Inc., Jamaica, NY.
Silicone
Polymeric materials composed of molecules of silicon and oxygen.
Solvent
A liquid substance which dissolves other substances.
Specific Gravity
The ratio of the weight of any volume of a mass or substance to the weight of an equal volume of water at given temperature. The specific gravity of a substance times the density of water equals the density of the substance.
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.
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. See “Common Viscosities.”
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.
Wetting
The thorough impregnation of a material by a liquid. The more viscous a fluid, and the higher its surface tension, the more difficult it is for the liquid to “wet” materials. Certain additives can reduce surface tension or viscosity and improve wetting properties, allowing the material to flow out more.
Working Time
(Work Life) See Pot Life
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