Jump to a letter: A — B — C — D — E — F — G — H — I — J — L — M — N — P — R — S — T — V — W — Y

S

Sagging

run or flow-off of adhesive from an adherend surface due to application of excess or low viscosity material.

Sandwich panel

an assembly composed of metal skins (facings) bonded to both sides of a lightweight core.

Sealant

a gap filling material to prevent excessive absorption of adhesive, or penetration of liquid or gaseous substances.

Self-vulcanizing

pertaining to an adhesive that undergoes vulcanization without the application of heat.

Service conditions

the environmental conditions to which a bonded structure is exposed., e.g., heat, cold, humidity, radiation, vibration, etc.

Set

to convert an adhesive into a hardened sate by chemical or physical action, such as condensation, polymerization, oxidation, vulcanization, gelation, hydration, or evaporation of volatile constituents.

Shear, tensile

the apparent stress applied to an adhesive in a lap joint.

Shrinkage

the volume reduction occurring during adhesive curing, sometimes expressed as percentage volume or linear shrinkage; size reduction of adhesive layer due to solvent loss or catalytic reaction.

Sizing

the process of applying a material on a surface in order to fill pores and thus reduce the absorption of the subsequently applied adhesive or coating or to otherwise modify the surface properties of the substrate to improve the adhesion. Also, the materials used for this purpose. The latter is sometimes called size.

Slippage

the movement of the adherends with respect to each other during the bonding process.

Solids content

the percentage of weight of the nonvolatile matter in an adhesive. Note: The actual percentage of the nonvolatile matter in an adhesive will vary considerably according to the analytical procedure that is used. A standard test method must be used to obtain consistent results.

Solvent cement

an adhesive utilizing an organic solvent as the means of depositing the adhesive constituent.

Solvent reactivating

the application of solvent to a dry adhesive layer to regenerate its wetting properties.

Solvent welding

the process of joining articles made of thermoplastic resins by applying a solvent capable of softening the surfaces to be joined and pressing the softened surfaces together. Adhesion is attained by means of evaporation of the solvent, absorption of the solvent into the adjacent materials and/or polymerization of the solvent cement.

Spread

the quantity of adhesives per unit joint area applied to an adherend, usually expressed in points of adhesive per thousand square feet of joint area. (1) Single spread refers to application of adhesive to only one adherend of a joint. (2) Double spread refers to application of adhesive to both adherends of a joint.

Stabilizer

an adhesive additive which prevents or minimizes change in properties, e.g.., by adherend absorption, demulsification, or rapid chemical reaction.

Storage life

the period of time during which a packaged adhesive can be stored under specified temperature conditions and remain suitable for use. Sometimes called Shelf Life.

Strength, cleavage

the tensile load expressed in force per unit of width of bond required to cause cleavage separation of a test specimen of unit length.

Strength, dry

the strength of an adhesive joint determined immediately after drying under specified conditions or after a period of conditioning in the standard laboratory atmosphere.

Strength, fatigue

the maximum load that a joint will sustain when subjected to repeated stress application after drying, or after a conditioning period under specified conditions.

Strength, impact

the ability of an adhesive material to resist shock by a sudden physical blow direct against it. Impact shock is the transmission of stress to an adhesive interface by sudden vibration or jarring blow of the assembly, measured in work units per unit area.

Strength, lap joint

the force necessary to rupture an adhesive joint by means of stress applied parallel to the plane of the bond. Also referred to as tensile-shear strength.

Strength, peel

the force per unit width necessary to bring an adhesive to the point of failure and/or to maintain a specified rate of failure by means of a stress applied in a peeling mode.

Strength, shear

the resistance of an adhesive joint to shearing stresses; the force per unit areas sheared, at failure.

Strength, tensile

the resistance of an adhesive joint to tensile stress; the force per unit area under tension, at failure.

Strength, wet

the strength of an adhesive joint determined immediately after removal from a liquid in which it has been immersed under specified conditions of time, temperature, and pressure.

Stringiness

the property of an adhesive that results in the formation of filaments or threads when adhesive transfer surfaces are separated. Note: Transfer surfaces may be rolls, picker plates, stencils, etc.

Structural bond

a bond, which stresses the adherend to the yield point, thereby taking full advantage of the strength of the adherend. On the basis of this definition, a dextrin adhesive used with paper (e.g., postage stamps, envelopes, etc.) and which causes failure of the paper, forms a structural bond. The stronger the adherend, the greater the demands placed on the adhesive. Thus, few adhesives qualify as "structural" for metals. A further requirement for a structural adhesive is that it be able to stress the adherend to its yield point after exposure in its intended environment.

Substrate

a material upon the surface of which an adhesive containing substance is spread for any purpose, such as bonding or coating. A broader term than adherend.

Surface preparation

a physical or chemical preparation, or both, of an adherend to render it suitable for adhesive joining.

T

Tack

the property of an adhesive that enables it to form a bond of measurable strength immediately after adhesive and adherend are brought into contact under low pressure.

Tack range

the period of time in which an adhesive will remain in the tacky dry condition after application to an adherend, under specified conditions of temperature and humidity.

Tackifier

an additive intended to improve the stickiness of a cast adhesive film; usually a constituent of rubber based and synthetic resin adhesives.

Tape

a film form of adhesive which may be supported on carrier material.

Teeth

the resultant surface irregularities or projections formed by the beading of filaments or strings which may form when adhesive bonded substrates are separated.

Temperature, curing

the temperature to which an adhesive or an assembly is subjected to cure the adhesive.

Temperature, drying

the temperature to which an adhesive on an adherend or in an assembly or the assembly itself is subjected to dry the adhesive.

Temperature, maturing

the temperature, as a function of time and bonding condition, that produces desired characteristics in bonded components.

Temperature, setting

the temperature to which an adhesive or an assembly is subjected to set the adhesive.

Test, destructive

tests involving the destruction of assemblies in order to evaluate the maximum performance of the adhesive bond.

Test, nondestructive

inspection tests for the evaluation of bond quality without damaging the assembly, e.g., ultrasonic, visual inspection, etc.

Thermoplastic, n

a material that will repeatedly soften when heated and harden when cooled.

Thermoset, n

a material that will undergo or has undergone a chemical reaction by the action of heat, catalyst, ultraviolet light, etc., leading to a relatively infusible state.

Thinner

a volatile liquid added to an adhesive to modify the consistency or other properties. (See also diluent and extender)

Thixotropy

the property of adhesives systems to thin upon isothermal agitation and to thicken upon subsequent rest.

Time, assembly

the time interval between the spreading of the adhesive on the adherend and the application of pressure or heat, or both, to the assembly.

Time, curing

the period of time during which an assembly is subjected to heat or pressure, or both, to cure the adhesive. (See also time, joint conditioning and time, setting)

Time, drying

the period of time during which an adhesive on an adherend or an assembly is allowed to dry with or without the application of heat or pressure, or both. (See also time, curing; time, joint conditioning; and time, setting)

Time, joint conditioning

the time interval between the removal of the joint from the conditions of heat or pressure, or both, used to accomplish bonding and the attainment of approximately maximum bond strength. Sometimes called joint aging time.

Time, setting

the period of time during which an assembly is subjected to heat or pressure, or both, to set the adhesive. (See also time, curing; time, joint conditioning; and time, drying)

V

Vehicle

the carrier medium (liquid) for an adhesive material which improves its ease of application to adherends; solvent component of an adhesive.

Viscosity

the ratio of the shear stress existing between laminae of moving fluid and the rate of shear between these laminae. Note: A fluid is said to exhibit Newtonian behavior when the rate of shear is proportional to the shear stress. A fluid is said to exhibit non-Newtonian behavior when an increase of decrease in the rate of shear is not accompanied by proportional increase or decrease in the shear stress.

W

Weld bonding

a process in which a joint is formed by spot welding through an uncured adhesive bond line, or by flowing an adhesive into a spot-welded joint.

Wetting

a surface is said to be completely wet by a liquid if the contact angle is zero, and incompletely wet if it is a finite angle. Surfaces are commonly regarded as unwettable if the angle exceeds 90 degrees.

Working life

the period of time during which an adhesive, after mixing with catalyst, solvent or other compounding ingredients, remains suitable for use.

Y

Yield value

the stress (either normal or shear) at which a marked increase in deformation occurs without an increase in load.

The following sources were used in compiling this Glossary:

• ASTM D 907, "Standard Definitions of Terms Relating to Adhesives," American Society for Testing and Materials, Conshohocken, PA.
• ASTM C717, "Terminology of Building Seals and Sealants," American Society for Testing and Materials, Conshohocken, PA.
• MIL-HDBK-691B, Military Standardization Handbook, Adhesive Bonding, Department of Defense, Washington, DC.
• Panek, J.R. and Cook, J.P., Construction Sealants and Adhesives, John Wiley & Sons, New York, 1991.
• Sharpe, L.H., "Fundamentals of Adhesives and Sealants Technology," Adhesives and Sealants, vol. 3, Engineered Materials Handbook Series, ASM International, 1990.