Glossary of Terms

Accelerators -

Substances employed to speed up the cure of adhesives, sealants, potting/encapsulation compounds and impregnants; See also ‘catalyst’.

 

Acrylics -

A family of thermoplastic synthetic resins based largely on acrylic esters with a wide range of performance properties; acrylic resins are often recognized for their superior optical clarity, strength and high durability; acrylic adhesives are available which feature remarkable adhesion to many different substrates and quick cure times; limited resistance to elevated temperatures and/or chemical exposure are factors to be considered when selecting such adhesives, sealants, etc. for specific applications.

 

Adhesion -

The state in which two surfaces are held together by interfacial forces which may be chemical or mechanical in nature or both; frequently called bonding.

 

Adhesive -

A substance with the capability of holding two surfaces together by either chemical or mechanical interfacial forces or combinations thereof; bonding agent.

 

Adhesive strength -

The strength with which two surfaces are held together with an adhesive, also known as the bond strength; quantitative tests are available for measuring the adhesive strength under various environmental conditions; measured in units such as psi or N/mm2

 

Bonding -

The assembly of materials by means of adhesives; may be carried out at ambient or at elevated temperatures for specified time periods.

 

Bond strength -

See "adhesive strength". Specific measurements include the load applied in tension, compression, flexure, peel, impact or shear needed to break an adhesive assembly with failure noted in or near the plane of the bond.

 

Break-

Failure of an adhesively bonded assembly when subjected to excessive loads and/or hostile environmental conditions such as exposure to excessively high or low temperatures, aggressive solvents etc; failures can also occur as the results of inadequate joint design or contamination of the surfaces to be bonded by oils, grease, particulates and so on. It can also result from insufficient adhesive application to a joint.

 

Catalyst -

A chemical substance employed to speed up the cure of adhesives, sealants, potting/encapsulation compounds and impregnants; see also "accelerator"; frequently used as the "B" component of a two-part thermosetting adhesive; sealant or potting compound.

 

Curing -

The process which changes the properties of a material by chemical reactions; it frequently involves a physical change from the liquid to the solid state; often called hardening or setting; fully cured materials exhibit maximum physical, thermal and chemical properties in use.

 

Cyanoacrylates -

A family of exceptionally fast curing so called "instant glue" adhesives with the capability of quick bonding to a wide range of metallic and non-metallic substrates; special primers are also available for certain difficult-to-bond to substrates.

 

Epoxy -

A most versatile group of thermosetting polymers for adhesive, sealant, coating, potting/encapsulation, impregnation and coating uses; can be two component room temperature curing or one part heat curing compositions; feature high physical strengths, superior resistance to chemical and/or environmental damage and excellent dimensional stability; widely employed for structural adhesive applications and as electrical insulation materials; special formulations are available which feature high electrical and/or thermal conductivity; remarkably wide service temperature range.

 

Fillers -

Relatively non-adhesive substances added to an adhesive composition to improve ease of application and/or some specific performance property such as strength, durability, hardness, dimensional stability or other characteristics.

 

Hardener -

A substance or mixture of substances added to an adhesive composition to promote the curing reaction; hardeners become part of the cured adhesive compound (see also catalyst)

 

Inhibitor -

A substance which is added to slow down the rate of a chemical reaction; they are at times useful to prolong the storage or working life of certain types of adhesives.

 

Joint -

The location at which two or more adherends are held together with a layer of adhesive (see also bond).

 

MSDS -

Material Safety Data Sheet

 

Paste -

An adhesive composition having the characteristic plastic-like consistency of a paste i.e. a high order of yield value compared to a liquid.

 

Polymer -

A complex compound made up by the reaction of simple molecules having functional groups which permit their combination to proceed to a high molecular weight given appropriate reaction conditions; polymers may be formed by addition or condensation reactions; addition polymers include acrylics, ABS, nylons and styrenics, condensation polymers are epoxies, phenolics and silicones.

 

Polyurethane -

A family of rigid and flexible plastics characterized by the utilization of the urethane group in their manufacture; many polyurethane products exhibit high flexibility and abrasion resistance after cure; special polyurethane based adhesive formulations are available.

 

Pot life -

The period of time an adhesive or potting compound remains useful after adding an accelerator, catalyst or exposure to curing conditions.

 

Primer -

A formulated coating applied to a surface prior to the application of an adhesive in order to enhance the strength of the bond.

 

PVC -

Polyvinylchloride; polymer family based on vinyl chloride monomer used in diverse applications such as flexible films for packaging or rigid pipe.

 

Resin -

1) A solid, semi-solid or pseudo solid organic material with no definite melting point usually comprised of high molecular weight material; when subjected to stress a resin typically tends to flow; 2) in adhesives, sealants, etc., resins are the basic raw materials from which these compositions are made.

 

Sag -

A decrease in the thickness of a polymer section.

 

Shear strength -

The ability of a plastic material to withstand shear stresses.

 

Silicones -

A family of polymeric materials containing the Si-O chemical group in their structure; the most widely used silicones are elastomeric adhesives and sealants capable of service over the exceptionally wide temperature range of –100°F to over 500°F. Both one and two component silicone compounds are available.

 

Solids content -

The percentage by weight of non-volatile material in an adhesive or sealant.

 

Spread -

The quantity of adhesive per unit joint area applied to an adherend, generally expressed in pounds of adhesive per thousand square feet of joint area.

 

Squeeze out -

The amount of adhesive pressed or squeezed out at the bond line of a joint due to pressure applied to the adherends.

 

Substrate -

The basic surface upon which the adhesive is applied and to which it is expected to adhere.

 

Surface preparation -

Physical and/or chemical pre-treatments to enhance the adhesive strength of an adhesive to be applied to a specific surface.

 

Tack -

Adhesive "stickiness" on an adhesively coated surface that is yet not completely dry; the property of an adhesive that permits it to form a bond of measurable strength immediately after the adhesive and the adherends have been brought into direct contact by application of low pressure.

 

TDS -

Technical Data Sheet

 

Tensile strength -

The maximum stress a material can be subjected to without tearing when stretched under tensile load.

 

Thinners -

Volatile liquids added to adhesives to modify their consistency and enhance flow.

 

Viscosity -

The resistance of a fluid to flow; the ratio of shear stress between laminae of moving fluid and the rate of shear between these laminae.