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Glossary
This page defines commonly used terms in our industry. The terminology listed below may
appear in our datasheets or may be used in a conversation with one of our
Technical Personnel while discussing your application.
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or (978) 439-9841 if you do not find the term that you were looking for!
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A
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- A-Stage
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- An early stage in the reaction of certain thermosetting resins in which the material is
fusible and still soluble in certain liquids. (See also B Stage and C Stage)
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- Abrasion
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- Wearing away by friction.
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- Abrasion Resistance
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- Ability to resist surface wear; term usually applied to adhesive coatings.
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- Accelerator
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- A substance that hastens a reaction or the solidification of an adhesive caused by a
catalyst.
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- Acid
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- A chemical substance usually corrosive to common metals (iron, aluminum, zinc).
Acids are generally divided into two classes: (a) Strong mineral or inorganic acids such as sulfuric, phosphoric,
hydrochloric or nitric, (b) Weak organic or natural acids such as acetic (vinegar),
citric (citrus fruit juices), oxalic and fatty acids (oleic, palmitic, stearic,
etc.).
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- Acidity
-
- A general term applying to substances on the acid side
of neutral-principally the degree of acidity (1 - 7 on the Ph scale, 7 being neutral).
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- Adhesive
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- A substance capable of holding materials together by surface attachment. Note- Adhesive
is the general term and includes among other cement, glue, mucilage and paste. All of
these terms are loosely used interchangeably.
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- Adhesive Batch
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- A homogenous quality of finished adhesive manufactured under
controlled conditions at one tine or representing a blend of several manufactured units of finished adhesives of
the same formulation and processing.
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- Aggregate
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- A hard fragmented material used with an epoxy binder as a flooring or surfacing medium.
Also a coarse filler used as a core for epoxy tools.
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- Aging
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- The change in properties of a material with time under
stated conditions.
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- Alkali
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- A chemical substance which effectively neutralizes acid material so as to form
neutral salts. A base. The opposite of acid. Examples, ammonia and caustic soda.
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- Alkalinity
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- A general term applying to substances on the base side
of neutral-principally the degree of alkalinity (7 - 14 on the Ph scale, 7 being
neutral).
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- Amine
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- Curing agent for epoxy resins that is any of a class of ammonia derivatives. The are
derived from Ammonia (NH3) by replacement of 1, 2 or 3 hydrogen (H) atoms by univalent hydrocarbon radicals (R).
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- Artificial Weathering
-
- The exposure of product to cyclic laboratory conditions involving changes in
temperature, relative humidity, and ultra violet radiant energy, with or without direct
water spray, in an attempt to produce changes in the material similar to those observed
after continuous outdoor exposure. Note- The laboratory exposure conditions are usually
intensified beyond those encountered in actual outdoor exposure in an attempt to achieve
an accelerated effect.
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- ASTM
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- American Society for Testing Materials.
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- B-Stage
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- An intermediate stage in the reaction of certain thermosetting resins in which the
material softens when heated and swells when in contact with certain liquids, but may not
entirely fuse or dissolve. The resin in an uncured thermosetting system, is usually in
this stage. Sometimes referred to as Resistol. ( See also A Stage; and C Stage.)
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- Baking Temperature
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- A temperature above 150°F.(65.6°C). Refers to curing materials at these elevated
temperatures.
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- Binder
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- An adhesive substance, usually of liquid or molten form, used to create adhesion
between aggregates, globules, etc. Distinguished from an adhesive in that it
perfor
ms an internal adhesive function
rather than a surface adhesive function.
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- Bisphenol A
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- A condensation product formed by the reaction of two molecules of phenol with acetone.
This polyhydric phenol is the standard intermediate resin that is reacted with epichlorohydrin in production of epoxy resins.
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- Bisphenol F
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- A higher functionality liquid epoxy resin.
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- Body
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- The consistency of an adhesive; thickness; viscosity.
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- Bond
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- The union of materials by adhesives.
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- Bonding Operation
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- The curing of adhesives applied to details to effect the joining of parts into a
single component.
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- Bonding Procedure
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- All operations connected with bonding, from the prefit of the formed details
through their assembly for final bonding.
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- Bonding Process
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- All operations connected with the manufacture of assemblies whose parts are joined
by adhesives.
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- Bond Strength
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- The unit load applied in tension, compression, flexure, peel, impact, cleavage, or
shear, required to break an adhesive assembly with failure occurring in or near the plane
of the bond. Note-The term adherence is frequently used in place of bond strength.
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- Brookfield Viscosimeter
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- An instrument for measuring the viscosity of formulated adhesives under standard
conditions of temperature, speed and spindle size.
- C-Stage
-
- The final stage in the reaction of certain thermosetting resins in which the material is
relatively insoluble and infusible. Certain thermosetting resins in a fully cured state are in this stage.( See also A Stage; and B Stage.)
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- Cab-O-Sil
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- Trade name for anhydrous silica used as a thixotropic agent for adhesives, usually as a filler.
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- Calorie
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- A thermal unit. A calorie is that amount of heat required to raise the temperature of
one gram of water, one degree centigrade.
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- Cast
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- (1) To form a plastic object by pouring a fluid resin into an open mold where it hardens.
(2) Casting, the finished product.
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- Catalyst
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- A chemical substance added to thermosetting resin adhesives to speed up the cure
time of these adhesives and to increase the cross linking of the synthetic polymer. A catalyst markedly speeds
up the cure of an adhesive when added in minor quantity as compared to the amounts of the primary reactants.
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- Centigrade
-
- A scale of temperature which features 0° and 100° as the freezing and boiling
point of water respectively. To convert centigrade to Fahrenheit multiply by 1.8 and add
32, e.g., (100° x 1.8) + 32 = 212°F.
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- Centipoise
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- 1/100th of a poise; (dyne-sec/cm2); a viscosity
measurement unit.
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- Chalking
-
- Formation of a dry powdery chalk-like appearance or deposit on the surface of a
material. It is due to a breaking down of the material after being exposed to ultraviolet
light, or other weathering.
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- Clarity
-
- Degree of clearness in a cured epoxy system.
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- Closed-Cell Foamed Plastic
-
- A cellular plastic in which there is a predominance of
no interconnecting
cells.
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- Coefficient Of Linear Thermal
Expansion
-
- Once cured, a measure of the change in length of an epoxy system over a given
temperature range. It is expressed in inches per inch per degree C. ASTM D696-44.
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- Coefficient Of Thermal
Expansion (CTE)
-
- Change in a unit of length or volume that accompanies a unit change in temperature.
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- Cohesion
-
- The state in which the particles of a single substance are held together by primary or
secondary valence forces observed in the tendency of the substance to stick to itself. As
used in the adhesive field, the state in which the particles of the adhesive (or the
adhered) are held together.
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- Compressive Modulus
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- The ratio within the elastic limit of compressive stress to corresponding compressive
strain (deformation per original length). It is expressed in pounds per square inch. ASTM
D695-54.
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- Compressive Strength
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- Crushing load at the failure of a specimen divided by the original sectional area of the
specimen.
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- Compressive Strength, Ultimate
-
- The maximum load in pounds that can be carried per square inch of cross section of the
material under test.
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- Conductive
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- Having the quality of power of conducting or transmitting heat, electricity, or static
electricity.
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- Conductivity
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- Reciprocal of volume resistivity. Conductance of a unit cube of any material.
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- Contaminant
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- An impurity or foreign matter present in a bonded assembly which affects its usefulness.
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- Copolymer
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- A polymer formed by the reaction of two or more different monomers.
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- Coverage
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- A measure of the ability of the adhesive to be spread over adherend surfaces;
the total amount of adhesive required per 1000 sq ft of bonded assembly.
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- Cross-Link
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- Tying together large molecules and hence changing the physical properties of material.
Cross-linking usually involves formation of three dimensional molecular network and is
customarily associated with thermosetting resins.
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- Cure
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- To change the physical properties of an epoxy by chemical reaction through
polymerization, usually accomplished in the presence of heat and catalyst, alone or in
combination.
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- Cure Cycle
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- The schedule of time periods at specified temperatures to which a reacting thermosetting
plastic or rubber composition is subjected in order to reach certain specified properties.
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- Cure Period
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- The elapsed time the adhesive bond is required to remain at a specified cure
temperature to produce a cure.
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- Curing Agent
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- A catalytic or reactive agent which when added to resin causes polymerization.
- Density
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- The ratio of a substance’s mass to its volume at a given temperature and pressure.
Example-water at 25°C, 1 atmosphere of pressure =1.0 gr/cm3
= 8.35 lb. Per gallon.
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- Dielectric
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- A nonconductor of electricity; the ability of an adhesive to resist the flow of
electrical current.
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- Dielectric Constant
-
- When electrical energy is applied in a circuit, the insulating material of the
electrical charge and releases it when the current is broken. Capacitance is the ratio of charge absorbed to the
potential (voltage applied). Dielectric Constance is the ratio of an insulator's capacitance to that of dry air.
(1.0). A dielectric constant of 5 means an insulator will absorb 5 times more electrical energy than air. The
ratio of the parallel capacitance of a given configuration of electrodes with the epoxy system as the dielectric,
the capacitance of the same electrode configuration with a vacuum as the dielectric (ASTM D150-5WT).
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- Dielectric Strength
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- The voltage which an insulating material can withstand before breakdown occurs,
expressed in volts per Mil ((ASTM 149-61).
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- Diluent
-
- A reactive or non-reactive additive whose primary function is to lower the viscosity and
extend the material to which it was added.
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- Discoloration
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- Any change from an initial color possessed by a material, either due to environmental or
internal conditions.
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- Dissipation Factor
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- The measure of electrical energy absorbed and lost in the insulating material when
energy is applied in a circuit. 20-3060 has a dissipation factor of .01. This means that
.01% of the energy being stored (capacitance) is lost. Dissipation factor is the ratio of
the resistive component of a capacitor to the capacitive reactance of the capacitor. Also
referred to as Loss Tangent (ASTM D150-59T).
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- Dry
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- To change the physical state of an adhesive of an adherend by the loss of solvent
constituents by evaporation, absorption, or both.
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- Durometer hardness
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- The hardness of a material (usually applied to elastomerics) as measured by a
shore durometer.
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- Elasticity
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- The extensible property of adhesive films or adhesive interfaces to contract and
expand in such a manner as to overcome the differential contraction and expansion rates that the bonded adherend
may exhibit. That property of materials by virtue of which they tend to recover their original size and shape
after deformation. Note-if the strain is proportional to the applied stress, the material is said to exhibit Hookean
or ideal elasticity.
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- Elastomer
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- A material which at room temperature can be stretched repeatedly to at least twice its
original length and, upon immediate release of the stress, will return with force to its
approximate original length.
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- Elongation (%)
Ability of a material to stretch or become longer.-
- Elongation at break
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- Elongation recorded at the moment of rupture of a bonded specimen, expressed as a
percentage of the original length.
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- Encapsulating
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- Enclosing an article (usually an electronic component or the like) in a closed
envelope of plastic by immersing the object in a casting resin and allowing the resin to polymerize it, or if not,
to cool it.
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- Encapsulation
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- Used interchangeably with POTTING. Refers to the enclosure of an item in a substance.
Sometimes used specifically in reference to the enclosure of capacitors or modules.
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- Endotherm
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- Requiring heat to produce reaction.
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- Evacuation
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- The removal of entrained air from an epoxy system by vacuum. Also referred to as
degassing.
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- Exotherm
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- The liberation of heat energy during a chemical reaction (cure). Exotherm is
increased in large masses.
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- Extender
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- An available or relatively inexpensive compatible material which can be added to a
more valuable substance so as to increase the amount of material in useful form. The use of extenders may involve
adulteration under some conditions.
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- Extrude
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- To expel or force through a measured orifice, to pump adhesive onto the adherend
interface; to apply a molten thermoplastic at the adhesive interface.
- Failure, Adhesive
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- The failure at the bond line between substrates and an adhesive; the adhesive separating
entirely from the substrate.
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- Failure, Cohesive
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- Failure within the adhesive under a stress, resulting in a broken bond with all adhered
surfaces still covered with adhesive.
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- Failure, Substrate
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- The failure of the substrate material itself, upon subjecting bonded adhered surfaces to
a stress.
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- Fatigue
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- (1) A condition of stress created by repeated flexing or impact force upon the
adhesive - adherend interface; (2) The failure or decay of mechanical properties after repeated stress applications.
Fatigue tests provide information on the ability of an adhesive to resist the development of cracks which will
bring about failure as a result of continued cyclic bonds.
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- Filler
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- A relatively non-adhesive substance added to an adhesive to make it less costly, or
to improve physical properties, particularly hardness, stiffness, impact strength, workability, permanence, color,
and electrical properties.
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- Film
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- The thin level application of an adhesive or coating to a surface or substrate.
In the plastics industry, an optional term for a thermoplastic material having a thickness not greater than 0.010
inch.
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- Film adhesive
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- An adhesive that has been placed on a carrier or calendared into a thin film
(0.002 to 0.016 inch).
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- Film forming
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- The property or ability of an adhesive substance to cast a dimensionally stable
continuous film. Also refers to the relative strength of a cast adhesive film. Adhesives with good film-forming
characteristics are those which tend to deposit more uniform films of high structural strengths.
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- Fish
eye
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- Small globular mass which has not blended completely into the surrounding material and
is particularly evident in a transparent or translucent material.
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- Flame Retardance
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- The ability of an epoxy system to resist combustion or burning. Some materials tend to
extinguish themselves when subjected to a flame. Such materials are classified as
self-extinguishing. ASTM D790-63.
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- Flash Point
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- The temperature at which the material gives off flammable vapor in sufficient quantity
to ignite momentarily on the application of a flame under specified conditions.
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- Flexural Modulus
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- The ratio, within the elastic limit, of flexural stress to the corresponding strain. It
is expressed in pounds per square inch. ASTM D790-63.
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- Flexural Strength
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- Ability of a material to withstand failure due to bending.
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- Flow
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- Movement of the epoxy during the curing stages before completely cured.
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- Forced Drying Temperatures
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- A temperature between room temperature and 150°F.(65°C).
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- Fusible
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- Capable of being melted or fused together by melting.
- Gallon, U.S
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- A volume equal to 231 cubic inches (3.7853 liters) measured at 25°C. (77°F).
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- Gel
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- The initial jelly-like solid phase that develops during the transition from a
liquid to a solid. Note- In this state the epoxy is soft, flexible, and has no strength.
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- Gelation time
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- That interval of time, in connection with the use of synthetic thermosetting resins,
extending from the introduction of a catalyst into a liquid adhesive system until the interval of gel formation.
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- Glass Transition Temperature
(Tg)
-
- Approximate midpoint of the temperature range over which a material undergoes a phase
change from brittle to rubbery or vice versa.
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- Glue joint
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- The area of a bonded assembly where the adhesive and adherend are in contact.
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- Glue line
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- The adhesive layer between two adherends.
- Hardener
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- A substance or mixture of substances added to an adhesive to promote or control
the curing reaction by taking part in it. The term is also used to designate a substance added to control the
degree of hardness of the cured film.
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- Hardness
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- The resistance of surface indentation usually measured by a prescribed hardness
tester.
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- Heat Distortion (Deflection)
Temperature
-
- The temperature at which a standard test bar (ASTM D-648)deflrcts 0.010 in. under
a stated load of either 66 or 264 psi.. It is not usually considered to be beyond the maximum usable temperature,
but is an indication of the maximum usable temperature when the material is load bearing at a given load. As
the load decreases, the maximum usable temperature will increase.
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- Heat Sink
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- A contrivance for the absorption or transfer of heat away from a critical part or
detail.
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- Humidity (Absolute)
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- The amount of moisture present in the atmosphere expressed in grams per cubic meter.
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- Humidity (Relative)
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- The ratio of the amount of moisture contained in the atmosphere to the amount of
moisture that can be carried in the atmosphere at a given temperature. Relative humidity
is expressed in percent, e.g., 75% R.H. at a given temperature means that the air is 75%
saturated with moisture.
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- Hydrophilic
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- Capable of absorbing water.
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- Hydropholic
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- Capable of repelling water.
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- Hygroscopic
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- A property of absorbing and holding moisture.
- Impact resistance
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- Relative susceptibility of adhesives to fracture by shock, e. g., as indicated by
the energy expended by a standard pendulum-type impact machine in breaking a standard specimen in one blow.
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Impact shock
A stress transmitted to the adhesive interface resulting from the sudden jarring
or vibration of the bonded assembly.
Impact strength
(1)The ability of a material to withstand shock loading; (2) the work done in
fracturing, under shock loading, a specified test specimen in a specified manner.
Impact test
Measures the energy necessary to fracture or break an adhesive joint as a result
of a swinging pendulum or other impact device.
Impregnate
To fill the voids and spaces of an electrical unit with a compound; to provide
liquid penetration into a porous or fibrous material; the dipping or immersion of a fibrous substrate into an
adhesive liquid.
Inorganic
Applies to the chemistry of all elements and compounds not classified as organic
(carbon); matter other than vegetable, such as earthy or mineral matter.
Inorganic pigments
Natural or synthetic metallic oxides, sulfides, etc., calcined during processing at
1200 to 2200°F. They impact heat stability, weathering resistance, color, etc., to adhesives.
Instron
An instrument utilized to determine the tensile and compressive properties of
material.
Insulation Resistance
The ratio of the direct voltage applied to electrodes in contact with an epoxy system to
the total current between them. It is dependent upon both the volume and surface
resistance of the epoxy systems. ASTM D257-61.
Intermittent Operating Or
Service Temperature
The temperature to which the epoxy system can be subjected for short periods of time
without degradation of its properties.
Internal stress
Stress created within the adhesive layer by the movement of the adherends at
differential rates or by contraction or expansion of the adhesive layer.
Izod Impact Strength
A measure of the brittleness of a material. Brittle materials will have low izod
impact values (.15 for example). Tough materials will have high izod impact strengths (.60 for example). The Izod
Impact Test is a destruetive test designed to determine the resistance of an adhesive to the impact of a suddenly
applied force.
- Jig
-
- A clamping device used to immobilize the bonded assembly until complete solidification
of the adhesive film has taken place.
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- Joint
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- The location at which two adherends are held together with a layer of adhesive.
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- Kinetic viscosity
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- The viscosity / density ratio.
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- Lap joint
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- A joint made by placing one adherend partly over another and bonding
together the overlapped portion.
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- Long time exposure
-
- A relative term, found in most military specifications for adhesives, used normally
to designate an exposure period of 192 hours duration to any desired medium or condition.
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- Loss factor
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- The product of the power factor and the dielectric constant.
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- Mandrel
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- The core around which paper, fabric, or resin-impregnated fibrous glass is wound
to form pipes or tubes.
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- Matrix
-
- The part of an adhesive which surrounds or engulfs embedded filler or reinforcing
particles and filaments.
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- Maximum Service Temperature
-
- Highest recommended continuous use temperature based upon thermal endurance and
historical data.
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- Melting point
-
- The temperature at which a resin changes from a solid to a liquid.
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- Migration
-
- A condition of extraction whereby a solvent, be it water or an organic solvent,
selectively dissolves a portion of the adhesive film; the transferal of the plasticizer portion of an adhesive
into the adherend resulting from the attraction of the adherend composition to the plasticizer used in the adhesive
material composition.
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- Miscible
-
- Capable of being mixed; mutually soluble in each other.
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- Modifier
-
- Any ingredient added to an epoxy formulation that changes its properties.
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- Modulus in flexure
-
- The ratio of the flexure stress to the strain in the adhesive over the range for
which this value is constant.
-
- Modulus of elasticity
-
- The ratio of stress to strain in a material that is elastically deformed.
-
- Moisture absorption
-
- The pickup of water vapor from the air by an adhesive. This relates only to vapor
taken from the air by a material and must be distinguished from water absorption which results in a weight gain due
to water pickup by immersion.
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- Moisture Resistance
-
- Having some resistance to high humidity. A moisture resistant adhesive will not be
easily affected by moisture. Will not easily change its chemical and physical properties due to moisture. Should
not be confused with "water proof."
-
- Mold release
-
- A liquid, powder, or other "slip agent" used to prevent adhesion to tools, molds or
substrates during a bonding operation.
- Novolac
-
- A phenolic resin which, unless a source of methylene groups is added, remains
permanently thermoplastic.
-
- Nylon
-
- A generic name for all synthetic polyamides.
-
- OHM Unit
-
- Unit of electrical resistance. Resistance of a circuit in which a potential difference
of one volt produces a current of one ampere.
-
- Opaque
-
- Any material is opaque if no light can be transmitted through it.
-
- Operating Or Service Temperature
-
- The temperature at which an epoxy system can operate continuously without degradation of
its properties.
-
- Orange-Peel
-
- Uneven surface somewhat resembling an orange peel.
-
- Organic
-
- Designating or composed of matter originating in plant or animal life or composed
of chemocals of hydrocarbon origin, either natural or synthetic.
-
- Overlap
-
- A simple adhesive joint in which the surface of one adheremd extends past the
leading edge of another.
-
- Oxidation
-
- The chemical reaction involving the process of combining with oxygen to form an
oxide; the deterioration of an adhesive film due to atmospheric exposure; the breakdown of a hot-melt adhesive due
to prolonged heating and oxide formation.
- Paste
-
- An adhesive composition having a characteristic plastic-type consistency, a high
order of yield value, low bond strength and higher viscosity.
-
- Peel strength
-
- Bond strength of an adhesive in pounds per inch width, using a standard peel test.
-
- Pigment
-
- The fine solid particle, usually inorganic, used in the preparation of colored
products, and substantially insoluble in the vehicle. In contrast, a dye is soluble.
-
- Pit
-
- Small regular or irregular crater in a surface, usually with its width approximately of
the same order of magnitude as its depth.
-
- Poise
-
- A unit of measurement for viscosity, a 100 centipoise = 1 poise; (dyne-sec/cm2);
-
- Polurethanes
-
- Synthetic polymers that may be either thermosetting or thermoplastic and range
from soft and rubber-like to hard and brittle. They are usually made by the action of toluene diisocyanate or
another diisocyanate with poyols, polyethers, polyesters, amines, or other materials containing active hydrogens.
-
- Polyester
-
- A resin formed by the reaction between a dibasic acid and a dihydroxy alcohol, both
organic. Modification with multifunctional acids and/or bases and some unsaturated reactants permits cross linking
to thermosetting resins. Polyesters modified with fatty acids are called alkyds.
-
- Post-cure bonding
-
- Post curing at elevated temperatures after parts have been removed from the
autoclave or press to obtain higher heat-resistant properties of the adhesive bond.
-
- Pot Life
-
- The length of working time of a two component reactive system from the time of the
addition of the curing agent in a specific mass (i.e. 100 grams). It is expressed in
minutes.
-
- Potting
-
- Similar to encapsulating, except that steps are taken to insure complete penetration of
all the voids in the object before the resin polymerizes.
-
- Premix
-
- An adhesive that has all the ingredients mixed to produce a joint and is then sealed
or frozen for preservation until ready for use.
-
- P.S.I.
-
- Pounds per square inch; a unit measure of pressure.
- Qualification tests
-
- An investigation, independent of a procurement action, performed on an adhesive
product to determine whether or not the product conforms to all requirements of the proposed application.
-
- Quality assurance
-
- The function of evaluating product quality and the procedures taken to ensure that
the final product conforms to the specification requirements. It has for its purpose the continuing assurance of
the customer that the product he receives is of, or better than, the quality level he expects.
-
- Quality control
-
- Monitoring and controlling the usefulness of the end product.
-
- Range
-
- The difference between the extreme high and low test values from specimens
cut from one test assembly.
-
- Release agent
-
- A material which is placed on tooling or other objects to prevent the adhesive from
adhering to them during a bonding operation. The agent may be a mineral spray release or a plastic sheeting as
Teflon.
-
- Resin applicator
-
- A device for applying or spreading an adhesive resin system.
-
- Resin content
-
- The amount of resin in a laminate expressed as a percent of total weight or total
volume.
-
- Resin-rich edge
-
- Insufficient reinforcing material at the of the molded laminate.
-
- Resin starved
-
- Describing an area having an insufficient amount of resin.
-
- Resistivity
-
- The ability of a material to resist passage of electrical current either through its
bulk or on a surface. The unit of volume resistivity is the ohm-cm, of surface resistivity, the ohm.
-
- Rheology
-
- Pertaining to viscosity behavior; the viscosity of an adhesive material
under conditions of shear; the plastic flow properties of an adhesive interface.
-
- Room temperature
-
- As used in most specifications for adhesives and adhesive bonding, this term
applies to temperatures within the range of approximately 75°F. +/- 5°F.
- Set
-
- To convert an epoxy into a fixed or hardened state by chemical or physical action
through polymerization.
-
- Setting temperature
-
- The temperature to which an adhesive or an assembly to be subjected to heat or
pressure, or both, in order to set the adhesive.
-
- Setting time
-
- The period or time required for an assembly to be subjected to heat or pressure,
or both, in order to set the adhesive.
-
- Shear Strength
-
- The shear force required to break a specimen divided by its cross-sectional area; the
force being applied parallel to the cross-sectional area.
-
- Shelf life
-
- The period during which the manufacturer guarantees
that an adhesive stored at some
specified temperature will produce specified mechanical properties when used.
-
- Shore A Hardness
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- The reading of a material's hardness on a durometer, the scale of which is 0-100,
used on elastomers and other flexible materials. Consists of a pin point depression into the material, the material
being at least 100 mils thick. A Shore A reading of 80 equal a Shore D reading of 30.
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- Shore D Hardness
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- The reading of a material's hardness on a durometer similar to the Shore A durometer,
the scale of which 0-100, used on rigid and semi-rigid materials. Consist of a pin point depression into the
material. Both the Shore A and Shore D instruments are made by the Shore Instrument Manufacturing Company, Inc.,
Jamaica, NY.
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- Shrinkage
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- The measure of shrinkage occurring during cure of an epoxy system. The term
refers generally to linear shrinkage and is expressed in inches per inch. The decrease in volume, or contraction,
of a material by the escape of any volatile substance, or by a chemical or physical change in the material.
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- Softening Range
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- The range of temperature in which a thermoplastic changes from a rigid to a soft
state.
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- Solids contents
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- The percentage by weight of the nonvolatile matter in an adhesive.
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- Specific Gravity
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- The ratio of the weight of any volume of a mass or substance to the weight of an
equal volume of water at given temperature. The specific gravity of a substance times the density of water equals
the density of the substance. The density of water = 1.00
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- Starved joint
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- A joint which has an insufficient amount of adhesive to produce a satisfactory
bond.
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- Storage life
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- The period of time during which a packaged epoxy or curing agent can be stored
under specific temperature conditions and remain stable for use. Sometimes called shelf life.
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- Stress
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- An applied force or pressure, as tension or shear, exerted on a body which produces a
resultant strain on the material. The ability of material to withstand a stress depends on
the strength of its cohesive force or molecular resistance.
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- Stripper
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- A compound used to remove undesirable foreign material from a surface. Such
compounds should possess good penetration, rinse freely and not attack the substrate.
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- Stripping
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- The removal of undesirable substance from a surface by abrasive or chemical action.
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- Structural adhesive
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- An adhesive having sufficiently high mechanical properties, when cured, that it may
safely be used for bonding parts in assemblies where human lives, valuable equipment, or both, are involved.
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- Substrate
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- A material upon the surface of which an epoxy is spread for any purpose, such as
bonding or coating.
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- Surface Resistivity
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- The resistance to a current flow along the surface of an insulator material.
Measure in ohms/cm.
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- Surface Tension
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- The property of a liquid which causes the surface to pull into the smallest area
for a maximum volume, hence, drops are spherical. The fact that water drops on a wax surface do not spread out due
to surface tension. If a wetting agent were to be added to the water the round droplet would spread out into a film
because of the lowered surface tension.
- Temperature, Curing
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- The temperature to which an adhesive or an assembly is subjected to cure the
adhesive. Note-The temperature attained by the adhesive in the process of setting it may differ from the
temperature of the atmosphere surrounding the assembly.
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- Tensile Modulus
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- A measure of stiffness, i.e., how much a material will bend, stretch or compress
under a given load and still come back to its original size and shape. When measured in compression, it may be
referred to as "compressive modulus". The same thing holds true for tension and flexural
moduli. The modulus will
be given in terms of pounds per inch and may be expressed exponentially, e.g. 8.8 x 104, which
merely means 88,000 psi.
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- Tensile Strength
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- The pulling force necessary to break a given specimen divided by the cross
sectional area. Units given in lbs./in/2 (P.S.I.). It measures the resistance of a material to
stretching without rupture. Normally is not used with reference to elastic materials which recover after elongation.
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- Thermal Conductivity
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- A measure of how rapidly heat is conducted through a material. To convert BTU/sq.
ft./sec./in. to calories/sq. cm./sec./per cm., multiply by 1.2404.
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- Thermal decomposition
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- Breakdown of an adhesive caused by heat.
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- Thermal expansion (Coefficient of)
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- The fractional change in length (some times volume, specified) of a material for a
unit change in temperature. Values for plastics range from 0.01 to 0.2 mils/inch.,°C.
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- Thermal Shock Resistance
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- The ability of a cured system to resist cracking or crazing under conditions of rapid
and continuous thermal change. The 1/4 inch Olyphant Washer test is cycled over a
temperature range of -55°C to +125°C,
this temperature is normally used as the test condition unless otherwise stated.
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- Thermoplastic
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- A material which will repeatedly soften when heated and harden when cooled.
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- Thermosetting
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- Describes the property of an epoxy, to set or become rigid and non-meltable when
heated with or without pressure.
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- Thixotropy
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- The property of certain gelatin systems of becoming fluid on agitation, and
coagulating again when left at rest. This type material is called thixotropic
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- Time, Curing
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- The period of time during which an assembly or part may be subjected to heat or
pressure, to cure the epoxy. It is the time between the addition of curing agent to the
resin, and completed polymerization.
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- Trowel
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- To spread a high-viscosity adhesive material by spatula, knife, spreader bar, etc.
- Undercure
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- Results of a shortened cure cycle or the applied temperature is not sufficient to
polymerize the adhesive.
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- Unfilled
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- No non-adhesive substance added to an adhesive.
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- Usable life
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- The maximum number of minutes or hours allowed to elapse between the time an
adhesive is sampled for quality-assurance evaluation testing and the time the adhesive is cured.
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- Vapor degreasing
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- A cleaning process that employs the hot vapors of a chlorinated solvent to remove
soils-particularly oils, grease and waxes.
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- Viscosity
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- A measure of the fluidity of a liquid as determined by its internal fluid friction.
The property of resistance to flow exhibited within the body of a fluid. The ratio of the shear stress existing
between laminae of moving fluids and the rate of shear between these laminae; internal frictional resistance of an
adhesive to flow (directly proportional to the applied force). Usually measured in centipoise.
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- 1 cps = Water
- 400 cps = #10 Motor Oil
- 1,000 cps = Castor Oil
- 3,500 cps = Karo Syrup
- 25,000 cps = Hersheys Chocolate Syrup
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- Viscosity coefficient
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- The shearing stress tangentially applied that will induce a velocity gradient.
A material has a viscosity of one poise when a shearing stress of 1 dyne/cm2 produces a velocity
gradient of 1 cm/sec2.
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- Volatiles
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- Gaseous materials in an adhesive formulation that are driven off or liberated
during the curing reaction.
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- Volume Resistivity
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- The ratio of the electrical resistance through a cross section A divided by the
length through which the current flows. Measured in ohms/cm.
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- Volume Shrinkage (%)
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- Amount of dimensional change during cure.
- Water Absorption
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- Ratio of the weight of water absorbed by an adhesive to the weight of the same
material in a dry condition.
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- Waviness, Surface
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- Wave-like unevenness, or out-of-plane in a surface.
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- Wetting
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- The relative ability of a liquid adhesive to display interfacial affinity for an
adherend and to flow uniformly over the adherend surface. The more viscous a fluid, and the higher its surface
tension, the more difficult it is for the liquid to "wet" materials. Wetting agents are added to help
reduce surface tension, or viscosity and improve wetting properties.
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- Working
Life
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- The period of time during which an epoxy after mixing with a curing agent, remains
workable.
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- Working time
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- A measure of the interval of time during which an adhesive may be effectively
applied to the adherend surface before adhesive setting retards flow and application properties of the adhesive.
- X axis
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- The horizontal directional flow of an adhesive or the horizontal directional
flow of electricity through a conductive material or device.
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- Y axis
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- The vertical directional flow of an adhesive or the vertical directional
flow of electricity through a conductive material or device.
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- Yellowing
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- A color change in an unpigmented system, usually due to exposure to Ultraviolet
rays or other weathering conditions.
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- Yield Strength
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- The load in pounds per square inch where the material under test begins to change
dimensions and will not completely recover when the load is removed. Yield strength will normally be lower
than ultimate strength. Generally speaking, the more rigid a material is, the closer will be yield and ultimate
strengths. Furthermore, the more resilient a material is, the greater the spread between yield and ultimate
strengths.
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- Young's modulus
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- The ratio of the tensile stress to tensile strain below the proportional limit.
- Z axis
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- The third axis in a three dimensional configuration. The Z axis often refers to
the height or thickness of a conductive material or device.
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