Glossary of Adhesive Terms

A

Accelerator, Activator
Terms used to describe the materials which initiate the polymerization needed to cure anaerobic, cyanoacrylate and modified acrylic adhesives.
Adhesive
Substance for bonding, sticking or holding things together.
Adhesive, Anaerobic
An adhesive which only cures when air is excluded.
Adhesive, Cyanoacrylate
Group of adhesives which show "instant" cure properties and bond to a wide variety of substrates. Cure is by contact with alkaline materials. Weak alkaline materials, such as water, cause the cure to start.
Aging, Heat
Strength measured at room temperature after some period of aging at elevated temperature.
Ambient Conditions
Temperature, humidity, sunlight, etc., which exist in the area surrounding the bond, normally room temperature, atmospheric pressure, daylight, etc.
Anaerobic Adhesive
An adhesive which only cures when air is excluded.
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B

Bond
Interface of the adhesive and the substrate.
Breakaway Torque
Measure of force needed to initiate movement of an unseated fastener in a loosening direction.
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C

Cohesive Failure
Condition of bond failure in which the adhesive falls apart.
Conditions, Ambient
Temperature, humidity, sunlight, etc., which exist in the area surrounding the bond, normally room temperature, atmospheric pressure, daylight, etc.
Cure Speed
Time needed for an adhesive to reach full strength.
Cyanoacrylate Adhesive
Group of adhesives which show "instant" cure properties and bond to a wide variety of substrates. Cure is by contact with alkaline materials. Weak alkaline materials such as water, cause the cure to start. Commonly referred to as "super glue."
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E

Exotherm
Exothermic materials give off heat when they cure. When large quantities cure all at one time, the amount of heat given off (the exotherm) can be high enough to melt plastic containers.
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F

Failure, Cohesive
Condition of bond failure in which the adhesive falls apart.
Failure, Substrate
Condition of bond failure in which the substrate falls apart. The cohesive strength of the adhesive and the adhesive forces between the adhesive and substrate exceed the internal strength of the material being bonded.
Fill, Gap
Ability of an adhesive to fill the space between substrates and hold the substrates in place.
Fixture Time
Time needed for adhesive to reach sufficient strength to allow pieces to be handled and moved.
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G

Gap Fill
Ability of an adhesive to fill the space between substrates and hold the substrates in place.
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H

Heat Aging
Strength measured at room temperature after some period of aging at elevated temperature.
Hot Strength
Strength measured at elevated temperature.
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I

Impact Strength
Resistance to sharp, intense blows or force.
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L

Lap Shear
Test to measure resistance to shear stress by bonding the ends of flat bars in an overlapping position.
Locking Torque
Test designed to measure breakaway and prevailing torque of a threaded piece coated with thread locking adhesive.
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M

Monomer
Chemical which can be reacted to join and form polymers.
MRO
Maintenance, repair and overhaul.
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O

OEM
Original equipment manufacturer.
Open Time
Time during which the adhesive remains active without curing after being applied to the substrate.
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P

pH
Measure of acidity. A pH of 1 would be very acidic. A pH of 7 is neutral. A pH of 10 is very alkaline.
Polymers
Substance made up of many units such as polyethylene, polystyrene, etc.
Prevailing Torque
Measurement of average force needed to provide continuing movement, after unseating, through first full turn.
Primer, Surface
A surface primer is a coating that changes the character of a surface so that an adhesive or coating will adhere to it more effectively.
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R

Rheology
Special consideration of viscosity. Considers the effect of such things as stickiness and sensitivity to shear on viscosity.
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S

Shear, Lap
Test to measure resistance to shear stress by bonding the ends of flat bars in an overlapping position.
Shear, Static
Test to measure resistance to shear stress by bonding a pin within a collar or ring.
Speed, Cure
Time needed for an adhesive to reach full strength.
Static Shear
Test to measure resistance to shear stress by bonding a pin within a collar or ring.
Strength, Hot
Strength measured at elevated temperature.
Strength, Impact
Resistance to sharp, intense blows or force.
Substrate
Material which is being joined or bonded.
Substrate Failure
Condition of bond failure in which the substrate falls apart. The cohesive strength of the adhesive and the adhesive forces between the adhesive and substrate exceed the internal strength of the material being bonded.
Surface Primer
A surface primer is a coating that changes the character of a surface so that an adhesive or coating will adhere to it more effectively.
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T

Thermoplastic
A thermoplastic material will soften when exposed to high temperature. It literally becomes plastic when heated. Usually, removing the heat restores the original strength.
Thermoset
Products that will only cure when exposed to heat are described as thermoset resins. After they are cured, subsequent heat exposure will have little or no effect on the properties of the cured resin.
Thixotropy
Term which describes the flow character of a liquid or paste. Liquids that are thixotropic flow under shear but flow less when the shear is removed. Best example is ketchup.
Time, Fixture
Time needed for adhesive to reach sufficient strength to allow pieces to be handled and moved.
Time, Open
Time during which the adhesive remains active without curing after being applied to the substrate.
Torque, Breakaway
Measure of force needed to initiate movement of an unseated fastener in a loosening direction.
Torque, Locking
Test designed to measure breakaway and prevailing torque of a threaded piece coated with thread locking adhesive.
Torque, Prevailing
Measurement of average force needed to provide continuing movement, after unseating, through first full turn.
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V

Viscosity
Measure of fluid thickness or resistance to flow expressed in poise or centipoise. Water is one centipoise. Thicker fluids have higher numbers. 30 weight oil has a viscosity of 400 centipoise (cps).
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