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A |
| ABS (Acrylonitrile
Butadiene Styrene Resin): A common polymer (plastic) with high resistance
to heat, low-temperatures and impact. Bonds well with many adhesive families. |
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Accelerator
(also see Catalyst): Usually part B of an adhesive
formula, it causes and/or speeds the resin’s curing process. |
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| 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. |
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| Activators: Chemicals
which can be applied directly to a surface, substrate or mixed with an adhesive
to speed up the solidification of an adhesive. |
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| Adhesion: The bonding
forces between two different materials (e.g. between an adhesive and substrate). |
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| Adhesive: A material
employed to attach one solid to another so that the two solids may function as
a single unit. |
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| Adhesive Failure:
Loss of adhesion between the adhesive and substrate. The adhesive pulls cleanly
away from the substrate. |
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| Aerobic: An epoxy
that requires exposure to oxygen to cure. |
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| 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. |
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| Aqueous: Relating
to or made with water. |
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B |
| Binder: A component
of an adhesive composition which is primarily responsible for the adhesive forces
that holds two bodies together. |
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| Bond: The union
of materials by adhesives. |
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| Bond Line: The space
or gap between two substrates which contain the adhesive. |
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| Bond Strength: The
amount of force a bond can sustain. Measured in Pounds per Square Inch (PSI). |
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C |
| Cartridge: A relatively
rigid container used for storing unmixed adhesives in pre-measured quantities.
Cartridges can either be side-by-side or coaxial. |
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| 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. |
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| Casting: The finished
product of a casting operation. Should not be used as a synonym for molding. |
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Catalyst
(also see Accelerator): A substance which
causes or speeds a chemical reaction. Usually part B of a two-part adhesive. |
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| Centipoise (CPS):
A measure of viscosity (water has a CPS of 1). |
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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. |
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| 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. |
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| Cohesion: The state
in which the particles of a single substance are held together by primary or secondary
valence forces. |
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| Cohesive Failure:
Loss of adhesion as a result of the adhesive rupturing, leaving adhesive on both
substrates involved in the bond. |
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| Cohesive Strength:
The strength which holds a single material’s molecules together. |
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| Composite: A material
which is composed of two or more different substances. |
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| Compression Strength:
An object’s resistance to rupture under inward pressure. |
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Concentric
(also see Coaxial): Sharing the same center. With
regard to cartridges, one part inside the other. |
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| Crazing: Fine cracks
that may extend in a network on or under the surface of or through a layer of
adhesive. |
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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.
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| 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. |
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| 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. |
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| 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. |
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D |
| Delamination: Separation
of layers in a laminate because of adhesive failure. |
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| Dielectric Strength:
The maximum voltage a material can withstand without failure. Measured in volts
per millimeter of thickness (of the material). |
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| Dilatant Fluid:
A fluid whose viscosity increases with increased shear rate. |
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| Durometer: A device
used to determine the hardness of a material. |
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| 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). |
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E |
| 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. |
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| Elongation: The
amount a material will stretch before breaking. It is expressed as a percentage
of the original length. |
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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. |
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| 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. |
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| Exothermic: Pertaining
to a chemical reaction which releases heat. |
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F |
| 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. |
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| Filler: A non-adhesive
substance added to an adhesive to improve its working properties, permanence,
strength and other qualities. |
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| 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. |
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| Formulator: A company
which develops and makes adhesives. |
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| FRP: Fiberglass
Reinforced Plastic. |
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G |
| Gel: A description
of an adhesive as it hardens from liquid to solid. More often a solid than a liquid. |
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Gel
Time: The time (in minutes) required for a specific quantity of mixed resin
and hardener to become unworkable (gelled). |
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| Glass Transition:
The reversible change in a substance from a pliable, rubbery condition to a relatively
hard and brittle condition or vice-versa. |
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| Glue: A hard gelatin
obtained from the hides of animals. |
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H |
| Hardener: A substance
added to an adhesive that promotes curing and controls hardness. Usually Part
B of a two-part adhesive. |
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| Hardness: A material’s
resistance to indentation, scratching or cutting. |
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| Hygroscopic: The
ability to absorb and retain atmospheric moisture. |
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I |
| Impact Strength:
The ability of a material to withstand a shock load. |
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| Inhibitor: A substance
that slows down a chemical reaction to prolong storage or working life. |
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K |
| 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). |
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L |
| Laminate: To unite
layers of materials with an adhesive. |
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| Lap Shear: Shear
stress acting on an overlapping joint. |
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| Linear Shrinkage:
The shrinkage encountered in an adhesive in one direction. |
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| Load: The amount
of force that a body, joint or bond will sustain. Also, the force applied to a
body, joint or bond. |
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| Luer Lock Adapter:
A device used as a connector between a static mixer and an application tool such
as a disposable needle. |
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M |
| Meter Mix and Dispense
Machine (MMD): A machine designed to bring precisely measured volumes of material
together from separate sources for mixing and dispensing. |
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| Methacrylate: A
modified acrylic adhesive. |
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| Mold: The cavity
or matrix into or on which the plastic composition is placed and from which it
takes its form. |
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| 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. |
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N |
| Newtonian Fluid:
A fluid whose viscosity is independent of shear rate. The term is useful in differentiating
between thixotropic and dilatant fluids. |
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| Nylon: A generic
name for a specific family of plastics. |
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O |
| O-Ring: A circular
piece of rubber which fits around the piston to help maintain the seal between
the piston and cartridge wall. |
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| 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. |
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P |
| Peel Strength: The
amount of force required to peel a material off a substrate. |
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| Piston: A disc with
a seal that fits tightly into the back of a cartridge against the contents and
serves to expel the contents. |
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| Plastic: A synthetic
material made from organic compounds. Also can be defined as malleable (i.e. the
ability to be molded into different shapes). |
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| 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.
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| Polymer: A complex
chemical compound made of similar compounds linked together (e.g. acrylics, epoxies,
silicones, urethanes). |
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| Polypropylene: A
typical material from which cartridges are often made. Benefits are low-cost,
durability and flexibility. |
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| 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. |
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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. |
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Potting
(also see Encapsulation): Similar to encapsulating.
That is, filling a container of electrical components with an adhesive to provide
environmental protection. |
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| Primer: A coating
applied to a surface, prior to application of an adhesive, to improve performance
of the bond. |
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| PSI (Pounds Per
Square Inch): A measurement of pressure, shear, compression or tensile strength. |
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| PVC (Polyvinyl Chloride):
A polymer of vinyl chloride used in soft, flexible films for food packing. Also
used in rigid products such as pipes. |
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R |
| 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. |
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| Rheology: The study
of the flow of matter, especially the non-Newtonian flow of liquids and plastic
solids. |
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| Room Temperature:
70°F/21°C. |
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| 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. |
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S |
| Sag: A decrease
in the thickness of a section. |
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| 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. |
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Set: To convert
an adhesive into a fixed or hardened state by chemical or physical action. |
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| Setting
Temperature: The optimal temperature in which to promote the setting of an
adhesive. |
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| Setting Time: The
period of time during which an assembly is subjected to set the adhesive. |
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| Shear: The effect
of forces acting in opposite but parallel directions. |
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| 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). |
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| 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. |
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| 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. |
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| 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. |
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| Solvent: A substance
capable of dissolving another substance. |
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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. |
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| Substrate: Materials
to be bonded together (e.g. wood to wood, wood to metal, metal to metal, etc.). |
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| Synthetic: Something
produced by chemical means that does not occur naturally. |
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T |
| Tack: Adhesive stickiness
on a surface that is not yet completely cured. |
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| Tack Free Time:
The time required for a one-component silicone to cure enough to develop a skin
which is non-tacky. |
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| Tear Strength: The
force required to propagate a tear in a silicone which has been nicked or cut.
Expressed in lbs./in. of width. |
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| Tensile Strength:
The maximum stress a material subjected to stretching can withstand without tearing. |
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| Thermoplastic: A
material which repeatedly softens as temperatures rise and hardens as temperatures
fall. |
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| Thermosetting: A
material in a relatively infusible state. |
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| Thermoset: A material
which hardens when first exposed to high temperatures and pressure but cannot
be remelted without destroying its attributes. |
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| Thixotropic: A material
with paste-like consistency at rest but flows under pressure or agitation (e.g.
cold cream or grease). |
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| Thixotropic Fluid/Liquids:
Fluids/liquids which reduce their viscosity as agitation is increased (e.g. ketchup,
latex paint). |
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U |
| 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. |
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V |
| Viscosity: The resistance
of a fluid to flow (i.e. "thickness"). Measured in centipoise (cps). |
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VISCOSITY
TABLE
Approximate viscosities of common materials
at room temperature - 70°F
|
|
Material |
Viscosity in Centipoise
(cps) |
| Water |
1 CPS |
| Milk
|
3 CPS |
|
SAE 10 Motor Oil |
85-140 CPS |
|
SAE 20 Motor Oil |
140-420 CPS |
|
SAE 30 Motor Oil
|
420-650 CPS |
|
SAE 40 Motor Oil |
650-900 CPS |
|
Castor Oil |
1,000 CPS |
|
Karo Syrup |
5,000 CPS |
|
Honey |
10,000 CPS |
|
Chocolate Syrup |
25,000 CPS |
|
Ketchup |
50,000 CPS |
|
Mustard |
70,000 CPS |
|
Sour Cream |
100,000 CPS |
|
Peanut Butter |
250,00 CPS |
|
Shortening
|
1,200,000 CPS |
|
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| Voids: Gas or air
pockets trapped within a material. |
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| Volatile Organic Compounds
(VOC) : Any organic molecules which evaporate easily. They are often associated
with unpleasant odors or noxious fumes. |
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W |
| Wetting: The coating
of a substrate surface with an adhesive. |
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| Wicking: The flow
of a liquid along a surface into a narrow space (much like capillary action).
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Work-Life
(see also Pot Life): The period of time after an
adhesive has been mixed with its curing agent that it will remain useful or pliable. |
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| Working-Time: Same
as Gel Time. |
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