Accelerator (also see catalyst): Usually part B of
an adhesive formula, it causes and/or speeds the resin’s
curing process.
Acrylic: A
semi-rigid, two-component adhesive which bonds to a large
variety of substrates. Acrylics
are
known for their environmental resistance, fast setting
time and flame retardant properties.
Activators: Chemicals which can be applied directly
to a surface, substrate or mixed with an adhesive to
speed up the solidification of an adhesive.
Adhesion: The bonding forces between two different materials
(e.g. between an adhesive and substrate).
Adhesive: A material employed to attach one solid to
another so that the two solids may function as a single
unit.
Adhesive Failure: Loss of adhesion between the adhesive
and substrate. The adhesive pulls cleanly away from the
substrate.
Aerobic: An epoxy that requires exposure to oxygen to
cure.
Anaerobic: A one-part sealant/adhesive that cures only
in the absence of oxygen. Designed for locking screws,
nuts, bolts or retaining bearings, shafts, etc.
Aqueous: Relating to or made with water.
Binder: A component of an adhesive composition which
is primarily responsible for the adhesive forces that
holds two bodies together.
Bond: The union of materials by adhesives.
Bond Line: The space or gap between two substrates which
contain the adhesive.
Bond Strength: The amount of force a bond can sustain.
Measured in Pounds per Square Inch (PSI).
Cartridge: A relatively rigid container used for storing
unmixed adhesives in pre-measured quantities. Cartridges
can either be side-by-side or coaxial.
Cast: To form a plastic material into a definite shape
by pouring it into a mold and letting it harden without
applying external pressure. Can be accomplished with
or without application of external heat either before
or after pouring.
Casting: The finished product of a casting operation.
Should not be used as a synonym for molding.
Catalyst (also see accelerator): A substance which causes
or speeds a chemical reaction. Usually part B of a two-part
adhesive.
Centipoise (CPS): A measure of viscosity (water has
a CPS of 1).
Coaxial (also see concentric): Sharing the same axis.
When referring to cartridges, one part is contained inside
the other part, as opposed to side-by-side.
Coefficient of Thermal Expansion: A measure of the tendency
of an adhesive to expand with a temperature increase
or contract with a temperature decrease. A higher number
means a larger change up and down as the temperature
rises and falls respectively.
Cohesion: The state in which the particles of a single
substance are held together by primary or secondary valence
forces.
Cohesive Failure: Loss of adhesion as a result of the
adhesive rupturing, leaving adhesive on both substrates
involved in the bond.
Cohesive Strength: The strength which holds a single
material’s molecules together.
Composite: A material which is composed of two or more
different substances.
Compression Strength: An object’s resistance
to rupture under inward pressure.
Concentric (also see coaxial): Sharing the same center.
With regard to cartridges, one part inside the other.
Crazing: Fine cracks that may extend in a network on
or under the surface of or through a layer of adhesive.
Cure (also see setting): To change the physical properties
of a material by chemical reaction through condensation,
polymerization or vulcanization. Usually accomplished
by the action of heat and catalysts, alone or in combination
with or without pressure. Often referred to as hardening
or setting.
Cure Inhibition: A poisoning of the catalyst in an addition
cure product, such that there is a lack of a complete
cure, usually at the interface of the adhesive and the
other material.
Curing Agent: A chemical which reacts with an adhesive
polymer to cause solidification. Approximately equal
amounts of adhesive resin and curing agent are mixed
together to form a solid adhesive. Usually Part A of
a two-part adhesive.
Cyanoacrylate: A one-part adhesive that cures instantly
on contact with mated surfaces. High strength, excellent
adhesion to a wide variety of substrates, especially
plastics. Poor shock resistance super glue.
Delamination: Separation of layers in a laminate because
of adhesive failure.
Dielectric Strength: The maximum voltage a material
can withstand without failure. Measured in volts per
millimeter of thickness (of the material).
Dilatant Fluid: A fluid whose viscosity increases with
increased shear rate.
Durometer: A device used to determine the hardness of
a material.
Durometer Hardness: A measure of the hardness of a material
as measured by a durometer. The resultant numerical rating
of hardness in Shore A softer material (30 or 40) to
higher numbered, harder material (80 to 90).
Elastomer: A synthetic rubber, plastic or other polymer
which can be stretched to at least twice its original
length then return to its original shape with force.
The ability to return to its original shape is called
memory.
Elongation: The amount a material will stretch before
breaking. It is expressed as a percentage of the original
length.
Encapsulate (also see potting): The process to surround
and enclose an object in an adhesive. Often used in the
electronic industry to protect sensitive components.
Epoxy: A two-component adhesive with high strength and
low shrinkage during cure. Epoxies are tough and known
for their resistance to chemical and environmental damage,
as well as their usefulness as structural adhesives.
Some formulations are used as potting agents, while others
are useful as thermal or electrical conductors.
Exothermic: Pertaining to a chemical reaction which
releases heat.
Filled: An adhesive which contains particles not part
of the chemical formula for the purpose of changing properties
such as electrical conductivity or increasing volume.
Filler: A non-adhesive substance added to an adhesive
to improve its working properties, permanence, strength
and other qualities.
Fixture Time: The time at which an adhesive will hold
a part in place. Fixture time is application specific
and varies greatly depending on such parameters as part
size and configuration, part weight, the particular adhesive
used, thickness, temperature and relative humidity.
Formulator: A company which develops and makes adhesives.
FRP: Fiberglass Reinforced Plastic.
Gel: A description of an adhesive as it hardens from
liquid to solid. More often a solid than a liquid.
Gel Time: The time (in minutes) required for a specific
quantity of mixed resin and hardener to become unworkable
(gelled).
Glass Transition: The reversible change in a substance
from a pliable, rubbery condition to a relatively hard
and brittle condition or vice-versa.
Glue: A hard gelatin obtained from the hides of animals.
Hardener: A substance added to an adhesive that promotes
curing and controls hardness. Usually Part B of a two-part
adhesive.
Hardness: A material’s resistance to indentation,
scratching or cutting.
Hygroscopic: The ability to absorb and retain atmospheric
moisture.
Impact Strength: The ability of a material to withstand
a shock load.
Inhibitor: A substance that slows down a chemical reaction
to prolong storage or working life.
Kelvin (K): A scale of temperature which has the same
increments as Celsius but starts at absolute zero (-273.15°C
or -459.67°F).
Laminate: To unite layers of materials with an adhesive.
Lap Shear: Shear stress acting on an overlapping joint.
Linear Shrinkage: The shrinkage encountered in an adhesive
in one direction.
Load: The amount of force that a body, joint or bond
will sustain. Also, the force applied to a body, joint
or bond.
Luer Lock Adapter: A device used as a connector between
a static mixer and an application tool such as a disposable
needle.
Meter Mix and Dispense Machine
(MMD): A machine designed
to bring precisely measured volumes of material together
from separate sources for mixing and dispensing.
Methacrylate: A modified acrylic adhesive.
Mold: The cavity or matrix into or on which the plastic
composition is placed and from which it takes its form.
Motionless Mixer (also see static
mixer): A device which
uses passive (unmoving) means to combine two or more
substances. Commonly found attached to cartridge systems
or meter mix equipment.
Newtonian Fluid: A fluid whose viscosity is independent
of shear rate. The term is useful in differentiating
between thixotropic and dilatant fluids.
Nylon: A generic name for a specific family of plastics.
O-Ring: A circular piece of rubber which fits around
the piston to help maintain the seal between the piston
and cartridge wall.
Outgassing: A response to extreme conditions (e.g. high
heat or the presence of a vacuum) to which the part is
exposed. No relationship to by-products of the cure.
Peel Strength: The amount of force required to peel
a material off a substrate.
Piston: A disc with a seal that fits tightly into the
back of a cartridge against the contents and serves to
expel the contents.
Plastic: A synthetic material made from organic compounds.
Also can be defined as malleable (i.e. the ability to
be molded into different shapes).
Plunger: A rod which is part of a dispensing tool and
is used to force the piston (and thus the contents of
the cartridge) to the front and through the nose of the
cartridge.
Polymer: A complex chemical compound made of similar
compounds linked together (e.g. acrylics, epoxies, silicones,
urethanes).
Polypropylene: A typical material from which cartridges
are often made. Benefits are low-cost, durability and
flexibility.
Polyurethane: A one or two-part structural adhesive
with excellent flexibility and durability. Cure requires
a catalyst, heat or air evaporation. Short shelf-life
with hydroscopic tendencies (water absorption). Excellent
for potting or where flexibility is required. Good for
bonding plastic substrates. Generally slower cure with
more complicated handling and curing procedures.
Pot Life (also see work life): The length of time an
adhesive remains usable for mixing. Usually an important
factor with adhesives mixed together that begin curing
almost immediately.
Potting (also see encapsulation): Similar to encapsulating.
That is, filling a container of electrical components
with an adhesive to provide environmental protection.
Primer: A coating applied to a surface, prior to application
of an adhesive, to improve performance of the bond.
PSI (Pounds Per Square Inch): A measurement of pressure,
shear, compression or tensile strength.
PVC (Polyvinyl Chloride): A polymer of vinyl chloride
used in soft, flexible films for food packing. Also used
in rigid products such as pipes.
Resin: A class of solid or semi-solid organic products
of natural and synthetic origin, generally of high molecular
weights with no definite melting point. Resins are generally
water-insoluble and have little or no tendency to crystallize.
However, certain resins, such as some polyvinyl alcohols
and polyacrylates, are readily dispersible in water.
Others, such as polyamides and polyvinylidene chloride,
are readily crystallized.
Rheology: The study of the flow of matter, especially
the non-Newtonian flow of liquids and plastic solids.
Room Temperature: 70°F/21°C.
RTV (Room Temperature Vulcanizing): The tendency of
an RTV adhesive to vulcanize (i.e. cure) at room temperature.
Changes from a liquid/paste state to a solid, flexible
rubber.
Sag: A decrease in the thickness of a section.
Sealant: A material which adheres to two adjoining parts
of an assembly and prevents the passage of gases, dust,
liquids, etc. into or out of the assembly at that point.
Set: To convert an adhesive into a fixed or hardened
state by chemical or physical action.
Setting Temperature: The optimal temperature in which
to promote the setting of an adhesive.
Setting Time: The period of time during which an assembly
is subjected to set the adhesive.
Shear: The effect of forces acting in opposite but parallel
directions.
Shear Strength: The maximum shearing force, per unit
area, an adhesive bond will endure before failure. A
shearing force on an adhesive bond is created when the
two substrates adhered together are forced in opposite
directions in the same plane as the bond. Usually expressed
in pounds per square inch (psi).
Shelf-Life: The usable storage time of a material. Most
adhesives have a shelf-life of 6 to 12 months. The shelf-life
of an adhesive may be increased by refrigeration and
is usually shortened by exposure to heat.
Silicone: Any member of a family of polymeric products
whose molecular backbone is made up of alternating silicon
and oxygen atoms and which has pendant hydrocarbon groups
attached to the silicon atoms. Used primarily as a sealant,
silicone is known for its ability to withstand large
variations in temperature (-100°F to +600°F).
Silicone is reliable and is relatively easy to handle.
Solids Content: The non-solvent content of an adhesive
by weight, expressed as a percentage. 100% solids means
there are no additives. 75% solids has 25% solvents.
Solvent: A substance capable of dissolving another substance.
Static Mixer: A device which consists of a series
of internal baffles or elements within a plastic tube.
As
adhesive components are forced through the mixer, the
components are repeatedly divided and recombined, thus
creating a complete and uniform mixture. Most static
mixers attach in one of two ways: a "bell-mouth" type
which requires a retaining nut or a "twist-and-lock" (bayonet)
type which requires no additional hardware.
Substrate: Materials to be bonded together (e.g. wood
to wood, wood to metal, metal to metal, etc.).
Synthetic: Something produced by chemical means that
does not occur naturally.
Tack: Adhesive stickiness on a surface that is not yet
completely cured.
Tack Free Time: The time required for a one-component
silicone to cure enough to develop a skin which is non-tacky.
Tear Strength: The force required to propagate a tear
in a silicone which has been nicked or cut. Expressed
in lbs./in. of width.
Tensile Strength: The maximum stress a material subjected
to stretching can withstand without tearing.
Thermoplastic: A material which repeatedly softens as
temperatures rise and hardens as temperatures fall.
Thermosetting:
A material in a relatively infusible state.
Thermoset: A material which hardens when first exposed
to high temperatures and pressure but cannot be remelted
without destroying its attributes.
Thixotropic: A material with paste-like consistency
at rest but flows under pressure or agitation (e.g. cold
cream or grease).
Thixotropic Fluid/Liquids: Fluids/liquids which reduce
their viscosity as agitation is increased (e.g. ketchup,
latex paint).
Urethane: A flexible, two-part structural adhesive known
for its durability. Urethanes make good potting compounds
and bond well to plastics. Generally a slower cure process
than other adhesive formulations.
Viscosity: The resistance of a fluid to flow (i.e. "thickness").
Measured in centipoise (cps).
