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Glue 101

 

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Want to brush up on your adhesive knowledge? Here are some commonly used terms in the technology of adhesives. Of course, our glue experts are happy to chat about their favorite subject so feel free to contact us to discuss your specific adhesive needs.

Our FAQ's page is another great resource for learning more about the adhesives you work with everyday!

 


A

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.

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

Accelerators
Substances employed to speed up the cure of adhesives, sealants, potting/encapsulation compounds and impregnates; 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 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/mm2

Aqueous
Related to or based on water containing compositions.

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B

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.

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.

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.

Brookfield Viscosity
Standard measure of viscosity in the hot melt industry, expressed in centipoise at a specific temperature.

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C

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 impregnates; see also "accelerator"; frequently used as the "B" component of a two-part thermosetting adhesive; sealant or potting compound.

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.

Char
Hard, black particles often found in hot melt application equipment, resulting from adhesive or foreign particle degradation.

Chemical Resistance

Ability of solid materials to resist damage by chemical reactivity or solvent action.

Cohesive Strength
Internal strength of an adhesive.

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; thus 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 100°F.

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 accelerator, catalyst, and 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.

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D

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 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.

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E

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 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.

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.

Extinguishing
See also self-extinguishing. Compounds having resistance to burning.

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F

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.

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

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G

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.

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H

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)

Hot Melt Adhesive
Thermoplastic compound which becomes sufficiently fluid when heated to be pourable or spreadable, and cools to form a coating or adhesive bond.

Hot Tack
Cohesive strength of a molten hot melt adhesive which is desired during sealing to hold mated pieces together while a bond is being formed.

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I

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.

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

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J

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

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L

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 board 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.

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M

Methacrylate
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 etc.).

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

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.

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N

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 acry-lonitrile.

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

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O

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

Open Time
Period after an adhesive is applied during which it remains sufficiently molten to affect a bond.

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P

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.

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 styrene's, 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.

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.

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

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 process ability 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.

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 containing usually electronic or electrical components in order to protect them from vibration, shock and/or environmental hazards such as moisture, aggressive chemicals such as fuels and lubricants, heat etc.

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.

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R

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.

Ring & Ball Softening Point
Temperature at which a small steel ball will fall through a disc of hot melt supported in a ring.

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).

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S

Sag
A decrease in the thickness of a polymer section.

Self-Extinguishing
See also extinguishing. Compounds having resistance to burning.

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

Set-Time
Time required to solidify or set the hot melt adhesive once the mating surfaces are compressed.

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. Both one and two component silicone compounds are available.

Skinning
Formation of a viscous and often discolored layer on the surface of hot melt in a melt tank.

Solids Content
The percentage by weight of nonvolatile 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 adhesive strength of an adhesive to be applied to a specific surface.

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T

Tack
Adhesive "stickiness" on an adhesively 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 re-melted 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.

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V

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 laminate.

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W

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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