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Abrasion resistance (extended definition)
Ability of an adhesive to resist degradation due to mechanical wear by hard and rough objects (mechanical erosion) thanks to the ability to dissipate the applied mechanical energy.

Accelerating agent
Syn. Vulcanizing agent

Accelerator (extended definition)
Compounding material used in small amounts with a vulcanizing agent to increase the speed of vulcanization.
Syn. Catalyst

Acid absorber/acceptor
Additive neutralizing and absorbing hazardous acid spills.

Acrylic (extended definition)
Made by the polymerization of acrylic monomers, such as ethyl acrylate and methyl methacrylates.

Acrylonitrile Butadiene Styrene resin, ABS
Common polymer (plastic) with high resistance to heat, low-temperatures and impact, and exibiting excellent surface appearance. Bonds well with many adhesive families.

Activator
Chemicals which can be applied directly to a surface, substrate or mixed with an adhesive to speed up the solidification of an adhesive. Used in small proportions to increase the effectiveness of an accelerator.

Adhesion
Power of an adhesive layer to hold the parts of an assembly together. The two surfaces are held together by interfacial forces which may consist of valence forces or interlocking action. Quantitative tests are available for measuring the adhesive strength under various environmental conditions; measured in units such as psi. (see Bond strength)
Syn. Adherence

Adhesion Promoter
Material used to improve adhesion between materials. May be used in two different modes: by pre-treatment of a substrate, and as a component in adhesive formulation capable of enhancing adhesion durability due to the improvement in substrate wetting and formation of chemical bonds across the film/substrate interface.
Syn. Bonding agent

Adhesive
Material that can be used to adhere or stick one surface to another. (see Adhesion)
Note: Adhesive is the general term and includes among other cement, glue, mucilage and paste.

Adhesive layer
The layer of adhesive between the parts to be stuck together.

Adhesive failure
Separation of two bonded surfaces that occurs within the bonding material. The adhesive separates entirely from the substrate.
Note: Adhesive failure occurs when the adhesive strength of a bonding material is greater than it's cohesive strength. (more about failure mechanisms)

Adhesive tensile
An adhesive is in tensile loading when the acting forces are applied at right angles to the plane of the adhesive.

Adhesive testing
The testing of bonded joints serves two purposes: first in permitting quality control checks to be carried out during the development, production, and processing of adhesives, and second in allowing comparative tests to be conducted on different types of adhesive.(more about adhesive testing)

Adsorption
Not to be confused with absorption, adsorption is the build up of a molecule at a surface. Adsorption generally occurs because different parts of a molecule have an affinity for the two different phase on either side of the interface. (to know more about adsorption mechanism visit the Adhesion Guide)

Aerobic adhesive
Adhesive that sets on contact with the air.

Aging
Exposure of materials to an environment for an interval of time. The change of a material with time under defined environmental conditions, leading to improvement or deterioration of properties (see Weathering)

Alkyd
Formed by the condensation of polyhydric alcohols with polybasic acids. May be regarded as complex polyester (thermoset).

Amide
Organic compound that contains a carbonyl group bound to nitrogen. -CON- (C double bonded to O)

Amino resin
Amino resins are thermo-setting resins manufactured from amino compound and formaldehyde. See also Urea formaldehyde resin, Melamine formaldehyde resin .

Anaerobic adhesive (extended definition)
Specialty adhesive designed to cure on metals in the absence of oxygen. Often known as locking compound or, sealant , it is used to secure, seal and retain turned, threaded, or similarly close-fitting parts. Based on synthetic resins known as acrylics. Primarily used to anchor threaded joints and shafts against breaking free due to vibration.

Anti-blocking agent
Agent used to lessen the adhesion of the surface of products made from the formulation to a like or different surface. Acts by producing a slight roughening of the surface. Are typically finely divided, solid minerals, but some are waxes.

Anti-degradant
Compounding material used to retard deterioration caused by oxidation, ozone, light and combinations.
Note: Antidegradant is a generic term for such additives as antioxidants, antiozonants and UV absorbers/ light stabilizers.

Anti-flex cracking agent
Compounding material used to retard cracking caused by cyclic deformations.

Antioxidant
Compounding material used to retard deterioration caused by oxidation. Usually based on molecules that will scavenge free radicals as they are formed.

Anti-ozonant
Compounding material used to retard deterioration caused by ozone.

Anti-skinning agent
Substance added to a material to prevent or retard the processes of oxidation or polymerization which result in the formation of an insoluble skin on the surface of the material.

Anti-static agent
Additive which increases the surface conductivity of adhesives and which eliminates the accumulation of electrostatic electricity and dirt. Quaternary ammonium salts of organic or fatty acid derivatives are typically used as anti-static agents.

Anti-stick / Anti-tack agent
Additive incorporated in order to reduce tackiness or agglomeration of the material.

Asphalt / Bitumen (extended definition)
Dark brown to black cementitious material, solid or semisolid in consistency, in which the predominating constituents are bitumens which occur in nature as such or are obtained as residue in refining petroleum. The principal ingredient in asphalt is a mastic.