Types of Adhesives 140

accelerator

A substance used to speed the curing time of a cyanoacrylate adhesive.

acetic acid

A byproduct of the vulcanization reaction. Silicones cure through vulcanization.

acrylic adhesive

A type of structural adhesive made from acrylic, a manufactured polymer. Acrylic adhesives set rapidly and are very strong due to heavy cross-linking.

acrylic adhesive

A type of structural adhesive made from acrylic, a manufactured polymer. UV-curing acrylics typically cure in less than one minute.

active surface

A surface with ample ions that leave the surface and react with an anaerobic adhesive. Active surfaces enable the fastest curing of an anaerobic adhesive.

additive

An element often mixed with resin to assist in the curing of an adhesive. A toughening agent is an additive.

adhesion

The measure of the bond strength between an adhesive and a surface. Adhesion assists in the curing of a PSA.

adhesive

A nonmetallic material used to join two or more materials together. Adhesives are generally categorized as natural or synthetic.

adhesive bond

The process of binding a material to a surface using any number of adhesive substances.

ambient temperature

The temperature of the atmosphere. Urethane adhesives are sensitive to ambient temperature.

anaerobic adhesive

A type of structural adhesive that can only cure in the absence of oxygen. Anaerobic adhesives are used to make parts that require a tight seal.

benzoyl peroxide

A curing agent typically used to cure two-component acrylics.

blooming

The condensation of evaporated adhesive on a part. Blooming occurs most often with cyanoacrylates.

carrier

The backing material to which pressure-sensitive adhesives stick. The carrier acts as a mode of transport for the adhesive.

catalyst

Also called the curing agent or hardener, the substance that hardens the adhesive when mixed with resin.

catalyst system

The method by which acrylic adhesives cure. Most acrylics cure through a two part catalyst system.

chemical activator

A substance that speeds the polymerization of a cyanoacrylate adhesive.

chemical resistance

A material's ability to withstand exposure to chemicals. Several structural adhesives have strong chemical resistance.

chlorosulphonated polyethylene

A toughening agent that typically assists in the curing of acrylics.

cohesive strength

The internal strength of the adhesive. Epoxies have high cohesive strength.

creep

The deformation of a material that occurs over time due to the presence of a constant load. A PSA must have the ability to resist creep.

cure

To cross-link molecules permanently. Adhesives cure as they solidify.

curing agent

Also called a hardener or catalyst, the substance that hardens the adhesive when mixed with resin.

cyanoacrylate adhesive

A type of structural adhesive made form acrylic, a manufactured polymer. Cyanoacrylates bond with surfaces very quickly.

elastic

Capable of resuming original shape after experiencing temporary deformation. Silicone adhesives are elastic once cured.

elasticity

The measure of a material's ability to reshape itself after it has been stretched or deformed. A rubber band is an example of an object with high elasticity.

elastomer

A formation of a thermoplastic or thermoset that can stretch and then return to its original shape without permanent deformation.

epoxy adhesive

A type of structural adhesive made from epoxy, a manufactured polymer. Epoxy adhesives are strong and resilient and can bond with a variety of surfaces.

glass transition temperature

T_g. The temperature at which a hot melt changes from a brittle, glassy condition to a soft, pliable condition.

hardener

Also called the curing agent or catalyst, the substance that hardens the adhesive when mixed with resin.

heat resistance

A material's ability to withstand heat. Several structural adhesives have strong heat resistance.

hot melt

A thermoplastic, non-structural adhesive that flows when heated and hardens and strengthens as it cools. When applied as a melted liquid, a hot melt immediately adheres to a surface.

impermeable surface

A surface that cannot be penetrated by any element. Urethanes can bond to impermeable surfaces.

inactive surface

A surface that lacks sufficient ions with which to react. An inactive surface requires heat or a primer in order to cure the anaerobic adhesive.

inhibiting surface

A surface with a cover that prevents ions from escaping from the surface and reacting. An inhibiting surface requires heat or a prime rto cure the anaerobic adhesive.

ion

An atom or molecule that gains an electrical charge after it has either lost or gained electrons. Metal ions assist in curing anaerobic adhesives.

isocyanate resin

The resin used to cure urethane adhesives.

joint

The location where an adhesive layer holds two surfaces together.

LED

Light emitting diode. A semiconductor device that emits a narrow spectrum of light in a forward direction.

load

The overall force applied to a material or structure.

low-solvent formulation

An adhesive dissolved in a small amount of petroleum-based solvent. The adhesive cures as the solvent evaporates.

melt temperature

T_m. The temperature of a hot melt during application.

methyl methacrylate

A type of monomer that is odorous and tends to behave unpredictably. Most acrylics are composed of methyl methacrylate monomers.

monomer

A small molecule that joins with other molecules to form a polymer. An acrylic is composed of a monomer.

natural adhesive

Also called an organic adhesive, an adhesive made from naturally occurring living sources, such as plants and animals.

nonstructural adhesive

A synthetic adhesive ideal for applications that do not require high strength or permanent joining. Nonstructural adhesives can be easily unbonded from their surfaces.

one-component formulation

A method used to make an adhesive in which the resin and curing agent are packaged together, already mixed.

organic adhesive

Also called a natural adhesive, an adhesive made from naturally occurring living sources, such as plants and animals.

peel strength

A material's ability to resist forces that attempt to pull an adhesive apart by separating flexible surfaces.

permeable surface

A surface that can be penetrated by an element. Urethanes can bond to permeable surfaces.

photoinitiator

A curing agent typically used to cure UV-curing acrylics.

polar attraction

The process through which a PSA cures. Tack, shear strength, and adhesion enable a PSA to cure.

polymer

A material made of very large molecules. Synthetic adhesives are derived from polymers.

polymerization

A chemical reaction in which molecules are linked together to form large molecules. Most structural adhesives cure through polymerization.

pressure-sensitive adhesive

PSA. A non-structural adhesive that provides instant tackiness to a variety of surfaces. PSAs require minimal pressure to stick to a surface.

primer

A liquid material that is used to coat a surface before the adhesive is applied. Primers improve surface conditions and allow for stronger adhesive bonds.

properties

The characteristics of a material that distinguish it from other materials.

PSA

Pressure-sensitive adhesive. A non-structural adhesive that provides instant tackiness to a variety of surfaces. PSAs require minimal pressure to stick to a surface.

resin

A solid or semi-solid organic material that tends to flow when subjected to stress. Resin is mixed with a curing agent to enable an adhesive to cure.

shear strength

A material's ability to resist forces that can cause the internal structure of the material to slide against itself.

shear stress

A force that can cause the internal structure of a material to slide against itself. A PSA must be able to resist shear stress.

shelf life

The length of time an adhesive can be used for its intended application.

silicone adhesive

A type of structural adhesive made from silicone, a manufactured polymer. Silicone adhesives are durable and have high elasticity.

solvent

A chemical material that can dissolve another material. Adhesives generally are either low-solvent formulations or zero-solvent formulations.

structural adhesive

A durable synthetic adhesive designed to endure the duration of the application without undergoing deformation or unbonding from its surfaces. Structural adhesives can withstand heavy loads.

surface moisture

Water particles that accumulate on a surface. Silicone adhesives often turn yellow because they react with surface moisture.

synthetic adhesive

A man-made adhesive derived from polymers. Synthetic adhesives are produced to have specific chemical characteristics.

T_g

Glass transition temperature. The temperature at which a hot melt changes from a brittle, glassy condition to a soft, pliable condition.

T_m

Melt temperature. The temperature of a hot melt during application.

tack

The property of an adhesive that enables it to bond immediately to a surface.

tackiness

The ability of an adhesive to form an immediate bond with a surface upon contact. Pressure-senstive adhesives provide instant tackiness when applied to a surface.

tensile strength

A material's ability to resist forces that attempt to stretch it or pull it apart.

thermoplastic

A plastic that may be repeatedly heated, shaped, and cooled without damage. Cyanoacrylates are thermoplastic adhesives.

thermoset

A type of plastic that is permanently hardened by cooling. Synthetic adhesives are thermosets.

toughening agent

An additive mixed with resin to assist in the curing of an adhesive.

two-component formulation

A method used to make an adhesive in which the resin and curing agent are packaged separately and mixed prior to or during application.

ultraviolet light

UV light. Light not visible to the naked eye because it consists of wavelengths shorter than those of visible light. Most acrylics used today cure with UV light.

urethane adhesive

A type of structural adhesive made from urethane, a manufactured polymer. Urethane adhesives are highly flexible and are known for their versatility.

UV light

Ultraviolet light. Light that is invisible to the naked eye because it consists of wavelengths shorter than those of visible light. Most acrylics used today cure with UV light.

viscosity

A fluid's resistance to flow. The higher the viscosity, the greater a material's ability to resist flow.

vulcanization

The process by which silicone adhesives cure. Acetic acid is a byproduct of vulcanization.

wetting

The process of spreading an adhesive over a surface. Proper wetting occurs when the adhesive fills all crevices of the surface.

zero-solvent formulation

An adhesive dissolved in a substance such as water. The adhesive cures as the water evaporates.