Standard Glossary of Terms Relating to Adhesives

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A

A-Stage
an early stage in the reaction of certain thermosetting resins in which the material is fusible and still soluble in certain liquids. (See also B-stage and C-stage)
Abhesive
a material which is adhesive resistant and applicable as a surface coating or release agent
Adhere
to cause two surfaces to be held together by adhesion.
Adherend
a body which is held to another body by an adhesive.
Adhesion
the stage in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking addition, or both.
Adhesion, mechanical
adhesion between surfaces in which the adhesive holds the parts together by interlocking action.
Adhesion, specific
adhesion between surfaces which are held together by valence forces of the same type as those which give rise to cohesion.
Adhesive
a substance capable of holding materials together by surface attachment. Note: adhesive is a general term and includes among others cement, glue, mucilage, and paste. All of these terms are loosely used interchangeably.
Adhesive, assembly
an adhesive that can be used for bonding parts together, such as in the manufacture of a boat, airplane, furniture, and the like. Note: The term assembly adhesive is applied to adhesives used in fabricating finished structures or goods, or subassemblies thereof, as differentiated from adhesive used in the production of sheet materials for sale as such, for example, plywood or laminates.
Adhesive, anaerobic
an adhesive that cures spontaneously in the absence of oxygen, the curing being inhibited by the presence of oxygen and catalyzed by metallic ions.
Adhesive, contact
an adhesive that is apparently dry to the touch and which will adhere to itself instantaneously upon contact; also called contact bond adhesive or dry bond adhesive.
Adhesive, dispersion (or emulsion)
a two phase system with one phase (the adhesive material) in a liquid.
Adhesive, encapsulated
an adhesive in which the particles or droplets of one of the relative components are enclosed in a protective film (microcapsules) to prevent cure until the film is destroyed by suitable means.
Adhesive, film
an adhesive in film form with or without a carrier, set by means of heat and/or pressure.
Adhesive, foamed
an adhesive, the apparent density of which has been decreased substantially by the presence of numerous gaseous cells dispersed through its mass.
Adhesive, gap filling
an adhesive subject to low shrinkage in setting, can be employed as a sealant.
Adhesive, heat activated
a dry adhesive film that is rendered tacky or fluid by application of heat or heat and pressure to the assembly.
Adhesive, heat sealing
a thermoplastic film adhesive which is melted between the adherend surfaces by heat application to one or both of the adjacent adherend surfaces.
Adhesive, hot melt
an adhesive that is applied in a molten state and forms a bond on cooling to a solid state.
Adhesive, latex
an emulsion of rubber or thermoplastic rubber in water.
Adhesive, multiple layer
a film adhesive usually supported with a different adhesive composition on each side; designed to bond dissimilar materials such as the core to face bond of a sandwich composite.
Adhesive, one component
an adhesive material incorporating a latent hardener or catalyst activated by heat. Usually refers to thermosetting materials, but also describes anaerobic, hot melt adhesive, or those that depend on solvent loss for adherence. Thermosetting one component adhesives require heat to cure.
Adhesive, pressure sensitive
a viscoelastic material which in solvent free form remains permanently tacky. Such materials will adhere instantaneously to most solid surfaces with the application of very slight pressure.
Adhesive, solvent
an adhesive having a volatile organic liquid as a vehicle. Note: This term excludes water based adhesive.
Adhesive, structural
an adhesive of proven reliability in engineering structural applications in which the bond can be stressed to a high proportion of its maximum failing load for long periods without failure.
Adhesive, two component
an adhesive supplied in two parts which are mixed before application. Such adhesives usually cure at room temperature.
Adsorption
the action of a body in condensing and holding gases and other materials at its surface.
Aging, accelerated
a set of laboratory conditions designed to produce in a short time the results of normal aging. Usual factors include temperature, light, oxygen, water and other environments as needed.
Amorphous phase
noncrystalline; most plastics are amorphous at processing temperature. Many retain this strength under normal temperatures.
Amylaceous
pertaining to, or of the nature of, starch; starchy.
Assembly
a group of materials or parts including adhesive, which has been placed together for bonding or which has been bonded together.

B

B-stage
an intermediate stage in the reaction of certain thermosetting resins in which the materials soften when heated and swell when in contact with certain liquids, but may not entirely fuse or dissolve. The resin in an uncured thermosetting adhesive is usually in this stage. (See also A-stage and C-stage).
Backing
the flexible supporting materials for an adhesive. Pressure sensitive adhesives are commonly backed with paper, plastic films, fabric, or metal foil while heat curing thermosetting adhesives are often supported on glass cloth backing.
Binder
a component of an adhesive composition that is primarily responsible for the adhesive forces that hold two bodies together.
Blister
an elevation of the surface of an adherend, somewhat resembling in shape a blister on the human skin; its boundaries may be indefinitely outlined and it may have burst and become flattened.
Blocked curing agent
a curing agent or hardener rendered unreactive, which can be reactivated as desired by physical or chemical means.
Blocking
an undesired adhesion between touching layers of material, such as occurs under moderate pressure during storage or use.
Body
the consistency of an adhesive which is a function of viscosity, plasticity, and rheological factors.
Bond, n
the union of materials by adhesives.
Bond strength
the unit load applied in tension, compression, flexure, peel, impact, cleavage, or shear, required to break an adhesive assembly with failure occurring in or near the plane of the bond. Note: The term adherence is frequently used in place of bond strength.

C

Caul
a sheet of materials employed singly or in pairs in hot or cold pressing of assembles being bonded.
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 adhesive layer are in this stage. (See also A-stage and B-stage)
Catalyst
a substance that markedly speeds up the cure of an adhesive when added in minor quantity as compared to the amounts of the primary reactants.
Cohesion
the state in which the particles of a single substance are held together by primary or secondary valence forces. As used in the adhesive field, the state in which the particles of the adhesive (or the adherend) are held together.
Cold pressing
a bonding operation where an assembly is subjected to pressure without heat.
Collagen
the protein derived from bone and skin used to prepare animal glue and gelatin
Condensation
a chemical reaction in which two or more molecules combine with the separation of water or some other simple substance. If a polymer is formed, the process is called poly condensation.
Consistency
that property of a liquid adhesive by virtue of which it tends to resist deformation. Note: Consistency is not a fundamental property but is comprised of viscosity, plasticity, and other phenomena.
Contact bonding
the deposition of cohesive materials on both adherend surfaces and their assembly under pressure.
Corrosion
the chemical reaction between the adhesive or contamination and the adherend surfaces, due to reactive compounds in the adhesive film, leading to deterioration of the bond strength.
Coverage
the spreading power of an adhesive over the surface area of the adherend.
Crazing
fine cracks that may extend in a network on or under the surface of or through a layer of adhesive.
Creep
the dimensional change with time of a material under load, following the initial instantaneous elastic or rapid deformation. Creep at room temperature is sometimes called cold flow.
Cross linking
the union of adjacent molecules of uncured adhesive by catalytic or curing agents.
Crystallinity
a state of molecular structure in some polymers denoting uniformity and compactness of the molecular chains.
Cure
to change the physical properties of an adhesive by chemical reaction, which may be condensation, polymerization, or vulcanization; usually accomplished by the action of heat and catalyst, alone or in combination with or without pressure.

D

Delamination
the separation of layers in a laminate because of failure of the adhesive, either in the adhesive itself or at the interface between the adhesive and the adherend.
Dextrin
a water based product derived from the acidification and/or roasting of starch.
Dielectric curing
the use of a high frequency electric field through a joint to cure a synthetic thermosetting adhesive. A curing process for wood and other nonconductive joint materials.
Diluent
an ingredient usually added to an adhesive to reduce the concentration of bonding materials.
Doctor-bar or blade
a scraper mechanism that regulates the amount of adhesive on the spreader rolls or on the surface being coated.
Doctor roll
a roller mechanism that is revolving at different surface speed, or in opposite directions, resulting in a wiping action for regulating the adhesive supplied to the spreader roll.
Dry
to change the physical state of an adhesive or an adherend by the loss of solvent constituents by evaporation or absorption, or both.

E

Elasticity, modulus of
the ratio of stress to strain in elastically deformed materials.
Elastomer
a macromolecular material which, at room temperature, is capable of recovering substantially in size and shape after removal of a deforming force.
Epoxy
a resin formed by combining epichlorohydrin and bisphenols. Requires a curing agent for conversion to a plastic-like solid. Has outstanding adhesion and excellent chemical resistance.
Exothermic
a chemical reaction that gives off heat.
Extender
a substance, generally having some adhesive action, added to an adhesive to reduce the amount of the primary binder required per unit area.

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.
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