Glossary

Glossary of polymer-related technical terms.

A-stage

The early stage in the reactions of certain thermosetting polymers wherein the material is still quite soluble in various liquids and flowable at elevated temperatures; readily formable into specific configurations.

ABS

Acrylonitrile Butadiene Styrene Resins—versatile, widely employed thermoplastic polymer compositions with moderate resistance to heat, low temperatures and chemicals; bonds readily to many different adhesive materials.

Accelerators

Substances employed to speed up the cure of adhesives, sealants, potting/encapsulation compounds and impregnants.

See also: Catalyst, Curing agent
Acetal

Acetal resins based on formaldehyde are high performance engineering plastics with superior abrasion resistance and toughness; may require pretreatments to enhance adhesion properties.

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 assembly

An adhesive which can be employed to bond parts together such as in the manufacture of aircraft and automotive components, electronic circuitry, medical devices, furniture and many other structures or goods.

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/mm

See also: Bond strength
Aqueous

Related to or based on water containing compositions.

B-stage

The intermediate stage in the reaction of certain thermosetting polymers wherein the material can still be softened when heated or swelled in contact with certain liquids but cannot be completely fused or dissolved; B-staged resins generally permit some degree of formability or shaping into certain specific configurations.

Bond 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.

See also: Adhesive strength
Bonding

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

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.

C-stage

The final stage in the reaction of certain thermosetting polymers wherein the material becomes largely insoluble and infusible; the attainment of the C-stage signals achievement of completeness of the cure of these products and realization of their optimum strength and other pertinent performances characteristics.

Cartridge

A rigid container employed to store unmixed adhesive compositions in pre-measured amounts; cartridges may feature a side-by-side or coaxial configuration.

Catalyst

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

See also: Accelerators, Curing agent, Hardener
Composite

A material made up of two or more different substances, each having its own properties, combined to form a third substance with its own specific performance properties. For example, epoxy or polymer type resins can be combined with glass or graphite fibers to create higher strength glass or graphite fiber reinforced laminates with enhanced toughness, dimensional stability, etc.

Crazing

Fine cracks that may extend in a polymer network on, or under the surface of or through a layer of an adhesive or substrate.

Creep

Dimensional change that can occur with time with a material under load, following instantaneous or rapid deformations especially after repeated cycling; creep at ambient temperatures is often called cold flow.

Cryogenic

Applicable to very low temperature conditions such as liquid nitrogen and below; usually referred to temperatures below 77K.

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.

Curing agent
See also: Accelerators, Catalyst, Hardener
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 nonmetallic substrates; special primers are also available for certain difficult-to-bond to substrates.

Diluents

Ingredients usually added to an adhesive composition to decrease the concentration of the active bonding materials so as to achieve enhanced flow properties, or to reduce cost.

Drying

To change the physical state of an adhesive on an adherend surface by evaporation of the solvent components of the adhesive composition; drying can also be accomplished by absorption of the solvent components on the adherend surface.

Elastomer

A polymeric material which at ambient temperatures can be stretched to at least twice its original length by a deforming force and then returns to its original length upon removal of that force; elastomers can be synthetic or natural materials (rubbers).

Epoxy

A 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 that feature high electrical and/or thermal conductivity; remarkably wide service temperature range.

Exothermic

Chemical reactions which release heat; the opposite of endothermic reactions which require heat to proceed.

Extenders

Ingredients frequently having some adhesive property, added to an adhesive composition in order to reduce the cost of the amount of the primary adhesive component required per unit of bond area.

See also: Modifier
Extinguishing

Compounds having resistance to burning.

See also: Self-extinguishing
Failure, adhesive

Breakage of an adhesive bond such that the separation takes place at the adhesive/adherend interface.

Failure, cohesive

Breakage of an adhesive bond such that the separation takes place within the adhesive bond layer.

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.

See also: Modifier
Fillet

That portion of an adhesive which fills the corner or angle formed where two adherends are joined.

Flow

Movement of an adhesive compound during application and the bonding process, prior to the onset of cure.

FRP

Fiber reinforced plastics.

Gelation

Description of the process wherein an initially liquid composition thickens and changes from liquid to solid state; formation of a solid polymer network from a liquid.

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, Curing agent
Impregnation

The process of embedding a reactive liquid into a porous substrate in order to change its properties.

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.

Synonyms: bond
Joint, lap

A joint made by placing one adherend partly over another and then bonding together the overlapped portions.

Joint, starved

A joint that has an insufficient amount of adhesive to produce a satisfactory bond.

Laminate

A product made by bonding together two or more layers of material with adhesive.

Load

The amount of force that a body, joint or bond can sustain; the force applied to a body, joint or bond.

Luer Lock

A device used as a connector between a static mixer and a hose or application tool such as a disposable needle.

Methacrylates

A family of high performance thermoplastics featuring superior optical clarity, abrasion resistance and good physical strength properties; the term is also used to describe certain modified acrylic adhesives.

Modifier

Any inert chemical ingredient added to an adhesive compound that changes its properties.

See also: Extenders, Fillers
Monomer

A simple chemical building block with reactivity, to make the formation of a polymer possible.

Motionless mixers

Devices which employ passive (unmoving) means to combine and mix two or more substances; commonly found attached to cartridge systems or meter mix equipment; frequently called static mixers.

Neoprene elastomers

Synthetic rubbers with superior resistance to heat and many aggressive chemicals based on chloroprene.

Nitrile elastomers

Synthetic rubbers featuring excellent resistance to oils, fuels, etc. over a wide range of temperatures; based on butadiene acrylonitrile.

Nylon plastics

Tough thermoplastics polyamide based resins with superior physical strength properties, toughness and environmental resistance, usually employed as molding compounds.

O-ring

A circular disc of rubber which fits snugly around the piston to help maintain a seal between piston and cartridge wall.

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.

Peel strength

An adhesive's resistance to be stripped from a bonded joint, usually with the stripping force applied at a predetermined angle and rate.

Penetration

The entering of an adhesive into an adherent, measured by the depth of the penetration achieved in a given time.

Piston

A disc which fits tightly into the back of a cartridge against its content.

Plastic

1) A synthetic polymeric material made up from organic compounds. 2) A malleable consistency material capable of being pushed into different shapes.

Plasticizer

An ingredient incorporated into an adhesive composition that enhances flow, deformation and flexibility; the addition of plasticizers also tends to reduce melt viscosity, tensile strength properties and elastic moduli while increasing toughness and impact strength.

Plunger

A rod or stick which forces the piston and thus the contents of the cartridge to the front and through the opening.

Polyethylene

A family of thermoplastics mainly based on ethylene monomer widely used in injection molding, extrusion and calendering processes to produce various plastic products including also films, sheets and fibers.

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.

Polymerization

The process involving chemical reactions leading to the formation of the large molecules known as the high molecular weight materials also called polymers.

Polypropylene

A family of thermoplastic products mainly based on propylene monomers; they generally feature a higher degree of heat resistance and enhanced stiffness compared to polyethylene plastics.

Polystyrene

A group of commodity plastics produced chiefly of styrene monomers; easy processability especially popular for manufacturing injection molded parts at moderate cost.

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.

Post cure

A treatment usually involving the application of heat which is applied to an adhesive assembly following initial cure; its purpose is to modify certain specific joint properties such as heat resistance, chemical inertness, etc.

Pot life

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

Potting

The process of filling a cavity or space usually containing electronic or electrical components in order to protect them from vibration, shock and/or environmental hazards such as moisture, heat and aggressive chemicals such as fuels and lubricants.

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.

Rheology

The study of the flow properties of different materials especially of non-Newtonian liquids and plastics; non-Newtonian materials are substances where the flow is not proportional to the stress applied.

Rosins

Resins obtained as a residue from the distillation of turpentine derived from the sap of pine trees (gum resin) or from an extract of the stumps and other parts of the tress (wood resins).

Sag

A decrease in the thickness of a polymer section.

Self-extinguishing

Compounds having resistance to burning.

See also: Extinguishing
Setting

The hardening or solidification of an initially liquid plastic material by chemical and/or physical action.

Shear strength

The ability of a plastic material to withstand shear stresses.

Shortness

A qualitative term describing the characteristic of a polymeric material that does not string or otherwise form filaments or threads during application.

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.

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 pretreatments to enhance the strength of an adhesive to be applied to a specific surface.

Tack

Adhesive stickiness on a coated surface that is to yet not completely dried; 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.

Tensile strength

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

Thermoplastic

Polymeric materials which will repeatedly soften and flow as the temperature is increased and harden as the temperature falls.

Thermosetting

Polymeric materials which harden when exposed to high temperatures and pressures but cannot be softened or remelted upon further heating; the hardening of polymeric materials upon heating is due to a largely irreversible chemical reaction.

Thinners

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

Thixotrophy

The property of certain adhesive compositions to thin upon isothermal agitation and to thicken upon subsequent resting, i.e. cessation of the agitation.

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.

Wetting

The coating of a substrate surface with an adhesive.

Wicking

The flow of an adhesive into a tightly restricted opening.

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