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Welcome to PK Industries
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GLOSSARY
This
page defines commonly used terms in our industry. The terminology listed below
may appear in our Technical Bulletins or may be used in a conversation with one
of our Technical Personnel while discussing your application.
Send
mail to sales@pkindustries.net if you do not find the term that you were looking for!
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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.
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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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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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The
change of a material with time under defined environmental conditions,
leading to improvement or deterioration of properties.
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Curing
agent for epoxy resins that is any of a class of ammonia derivatives. The
are derived from Ammonia (NH3).
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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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American
Society for Testing Materials.
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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.
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A
temperature above 150°F.(65.6°C). Refers to curing materials at these
elevated temperatures.
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The
union of materials by adhesives.
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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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An
instrument for measuring the viscosity of formulated adhesives under
standard conditions of temperature.
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Internal
void or a trapped globule of air or other gas.
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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.
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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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A
substance which 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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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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1/100th
of a poise; (dyne-sec/cm2); a viscosity measurement unit.
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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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Degree
of clearness in a cured epoxy system.
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A
cellular plastic in which there is a predominance of noninterconnecting
cells.
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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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Change
in a unit of length or volume that accompanies a unit change in temperature.
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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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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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Crushing
load at the failure of a specimen divided by the original sectional area of
the specimen.
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The
maximum load in pounds that can be carried per square inch of cross section
of the material under test.
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Having
the quality of power of conducting or transmitting heat, electricity, or
static electricity.
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Reciprocal
of volume resistivity. Conductance of a unit cube of any material.
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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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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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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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A
catalytic or reactive agent which when added to resin causes polymerization.
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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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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.
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The
voltage which an insulating material can withstand before breakdown occurs,
expressed in volts per Mil.
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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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Medium
used to apply epoxy to pieces or units. Squeeze bottles, syringes, needles,
and meter mix equipment are all examples.
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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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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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Showing
a symmetrical distortion of a flat or curved section of an object so that as
normally viewed. Term often used when clear "epoxy domes" are
applied to labels, pins, magnets, key tags, etc.
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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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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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Ability of a material to stretch or become longer.
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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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The
removal of entrained air from an epoxy system by vacuum. Also referred to as
degassing.
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The
liberation of heat energy during a chemical reaction. Exotherm is increased
in large masses.
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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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The
failure at the bond line between substrates and an adhesive; the adhesive
separating entirely from the substrate.
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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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The
failure of the substrate material itself, upon subjecting bonded adhered
surfaces to a stress.
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A
substance, often inert, added to a system to improve properties and/or
decrease cost.
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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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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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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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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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Ability
of a material to withstand failure due to bending.
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Movement
of the epoxy during the curing stages before completely cured.
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A
temperature between room temperature and 150°F.(65°C).
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Capable
of being melted or fused together by melting.
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A
volume equal to 231 cubic inches measured at 25°C. (77°F).
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A
system of color standards based upon stable solutions of ferric chloride
used in the evaluation of resins, lacquers, oils and varnishes. The Gardner
Scale can be correlated roughly with other color standards such as FAC,
ASTM, NPA and Lovibond.
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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.ib
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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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That
property of the cured epoxy or any other material which causes it to reflect
light.
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A
substance or mixture of substances added to an epoxy resin to promote or
control the curing reaction by taking part in it.
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The
temperature at which a material softens enough to distort under a given
load. 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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Any
device that absorbs and draws off heat from a hot object, thereby
neutralizing the extreme temperature.
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The
amount of moisture present in the atmosphere expressed in grams per cubic
meter.
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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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A
property of absorbing and holding moisture.
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To
fill the voids and spaces of an electrical unit with a compound. (This does
not imply complete fill or complete coating of the surfaces by a hole-free
film).
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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.
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The
temperature to which the epoxy system can be subjected for short periods of
time without degradation of its properties.
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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).
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Highest
recommended continuous use temperature based upon thermal endurance and
historical data.
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Any
ingredient added to an epoxy formulation that changes its properties.
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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."
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Unit
of electrical resistance. Resistance of a circuit in which a potential
difference of one volt produces a current of one ampere.
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Any
material is opaque if no light can be transmitted through it.
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The
temperature at which an epoxy system can operate continuously without
degradation of its properties.
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Uneven
surface somewhat resembling an orange peel.
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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.
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Small
regular or irregular crater in a surface, usually with its width
approximately of the same order of magnitude as its depth.
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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.
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Similar
to encapsulating, except that steps are taken to insure complete penetration
of all the voids in the object before the resin polymerizes.
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Pounds
per square inch; a unit measure of pressure.
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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.
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To
convert an epoxy into a fixed or hardened state by chemical or physical
action through polymerization.
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The
shear force required to break a specimen divided by its cross-sectional
area; the force being applied parallel to the cross-sectional area.
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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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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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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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The
range of temperature in which a thermoplastic changes from a rigid to a soft
state.
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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.
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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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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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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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The
removal of undesirable substance from a surface by abrasive or chemical
action.
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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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The
resistance to a current flow along the surface of an insulator material.
Measure in ohms-cm.
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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.
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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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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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A
measure of how rapidly heat is conducted through a material.
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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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Describes
the property of an epoxy, to set or become rigid and non-meltable when
heated with or without pressure.
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False
body. The property of a paste or fluid to thicken or set up to a paste or
semi-gel when allowed to stand. Agitation breaks it down but further
standing will again permit a viscosity rise.
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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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The
property of resistance to flow exhibited within the body of a fluid. Usually
measured in centipoise.
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1
cps = Water
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400
cps = #10 Motor Oil
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1,000
cps = Castor Oil
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3,500
cps = Karo Syrup
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25,000
cps = Hersheys Chocolate Syrup
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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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Amount
of dimensional change during cure.
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%
by weight water absorbed by material in 24 Hours @ RT
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Wave-like
unevenness, or out-of-plane in a surface.
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The
thorough impregnation of a material by a liquid. The more viscous a fluid,
and the higher its surface tension, the more difficult it is for the liquid
to "wet" materials. Certain additives, for example, water
softeners, reduce surface tension, or viscosity and improve wetting
properties, allowing the material to flow out more.
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The
period of time during which an epoxy after mixing with a curing agent,
remains workable and suitable for use.
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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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