| AGING |
The change of a material with time under defined
conditions, leading to either an improvement or deterioration of
properties. |
| AMBIENT TEMPERATURE |
The temperature of of the surrounding air or other medium
in contact with the specimen. |
| ARC RESISTANCE |
The time required for an electrical arc to establish a
conductive (carbon) path in a specimen. |
| BOND STRENGTH |
The amount of adhesion between two substrates. The overall
bond strength is governed by the weakest component in the bonded
structure. |
|
B.I.L.
(Basic Impulse Level) |
Also called "basic Insulation level" - an insulation level, expressed in
kilovolts, at which electrical equipment will withstand a simulated
lightening wave which reaches its peak in 1.2 microseconds and decays to
half of the peak value in 50 microseconds. |
| BREAKDOWN VOLTAGE |
The magnitude of the voltage required to cause an
insulating material to fail. The published figures must be referenced to
the thickness of the specimen under test. Usually, the thinner the
specimen the higher the volts/mil because there are less impurities in the
thinner specimen. |
| CASTING |
A manufacturing procedure where components are placed into
moulds and the moulds are then filled with a thermoset material. After
cure, the parts are removed from the moulds for service.
Diagram |
| CATALYST |
The material that starts or speeds up a given reaction.
Some times referred to simply as "Hardener". A catalyst could also be part
of a hardener to further increase the speed of reaction. |
|
CENTIPOISE |
The unit used to express viscosity (the thickness of a
liquid). Examples:
|
LIQUID: |
VISCOSITY IN CENTIPOISE
(cps): |
| Water |
1 |
| Kerosene |
10 |
| Motor oil (SAE 10) |
100 |
| Castor oil |
1,000 |
| Corn syrup |
10,000 |
| Molasses |
100,000 |
|
|
COEFFICIENT OF THERMAL EXPANSION |
The relative change in length of a material per degree of temperature
change at constant pressure. CTE values are lower when materials are below
their glass transition temperature as compared to when they are above it. |
| COMPRESSIVE STRENGTH |
The amount of compressive load at failure of a specimen in
relation to its cross-sectional area. |
| CONDUCTIVITY |
The amount of electric current passing through a unit cube
of a material. Epoxies and Polyurethanes are considered insulators thus
their conductivity is very low. |
| CORONA |
A visible or invisible arc or arcs that develop in a
material do to the surrounding voltage gradient exceeding a certain
threshold value. Corona usually develops in areas of trapped air that is
ionized by the voltage surrounding it. |
| CORONA RESISTANCE |
The length of time it takes an existing arc to develop a
conductive path by carbonizing the material. Once the material is
carbonized (burned), the arc is extinguished in that area because the
surface carbon is conductive. |
|
CROSS-LINKING |
The coupling of the molecules into a three dimensional structure as a
result of the reaction between the resin and the hardener. |
|
CROSS-LINK DENSITY |
The number of effective cross-links per unit volume. As a rule, the higher
the cross-link density the harder the cured product. |
| CURE TEMPERATURE |
The temperature at which the necessary chemical reaction
is initialized for the material to solidify. |
| CURE TIME |
From the start of the reaction to the time when the
specified properties are realized. |
| CURE CYCLE |
Is the prescribed periods of time and temperature for a
material to develop its stated properties. |
| DEGREE OF CURE |
Relates to the percentage of the stated properties reached
through the curing process. Some products are extremely brittle after
gellation but become quite tough and flexible after full cure. |
| DENSITY |
The weight per unit volume of a material. (grams/cm3) |
| DIELECTRIC |
An insulating material (liquid, solid or gas). |
| DIELECTRIC CONSTANT |
The capacitance developed by an insulating material placed
between two electrodes as compared to only air between the same
electrodes. |
|
DIELECTRIC STRENGTH |
The maximum voltage a given thickness of an insulating
material can withstand without breaking down. It is usually expressed in
volts/mil. As a rule, the thicker the specimen being tested the lower the
volts/mil due to the increased number of impurities present. At the same
time, the thicker specimen will withstand a higher voltage although the
volts per mil is slightly lower. |
|
DISSIPATION FACTOR |
Dissipation factor is the ratio of the equivalent series resistance to the
reactance in a dielectric device. The dissipation factor will be different
at various frequencies, test temperatures and test conditions. This
test would be a rough indication of the efficiency of a capacitive
dielectric. The typical test conditions are: 10kHz and 100kHz at 300C.
ASTM D150 |
| DIPPING |
Immersing a component in a material for the purposes of
penetrating its components usually for the purposes of insulation or
environmental protection. |
|
POWER FACTOR (PF) |
Power factor is the ratio between the power applied to a device and the
power output (exiting from) from the device. It is an indication of how
much power is lost while transiting the dielectric components of the
device. |
| EXOTHERM |
The amount of heat generated as a result of the chemical
reaction. High exotherm usually increases the speed of reaction even
further and results in increased shrinkage. |
| ELONGATION |
The % increase in the length of a material being stretched
just before it breaks. |
|
ENCAPSULATING |
Enclosing a component in a plastic. The finished component
is free standing, with the plastic forming the outside surfaces. |
| FILLER |
The substance added to formulations to obtain certain
desired properties. Depending on the type fillers can be highly abrasive or
only slightly abrasive. |
| FLEXURAL STRENGTH |
The load a product is able to withstand before it brakes
while bending. Usually expressed as Pounds/in2. |
| GEL TIME |
The period of time it takes the material to begin its
irreversible solidification. Gel time is usually measured from the time of
mixing or, in the case of single component materials, from the time of
first applying heat or other curing mechanism. |
| HEAT DISTORTION TEMPERATURE |
The temperature at which a standard test bar
with a standard load of 66 or 264psi deflects 0.010". Its importance is
application dependent. For example: this property is less important if the material is not weight bearing
or there is little force present while operating beyond its HDT, otherwise
it is a critical consideration. |
| IMPACT STRENGTH |
The ability of a material to withstand impact without
damage. |
| IMPREGNATE |
To fill the voids and spaces. |
|
INSULATION CLASS |
The maximum temperature at which electrical equipment can be operated to
yield an average life of 20,000 hours, designated by the letters A, B, F
and H as follows:
|
Insulation Class: |
Temperature Rating: |
|
A |
1050C |
|
B |
1300C |
|
F |
1550C |
|
H |
1800C |
|
|
LINEAR SHRINKAGE |
The reduction in linear dimension that occurs in materials during the
process of solidification (cross linking), expressed as a percentage of
the original dimension. |
|
MODULUS |
Refers to the stiffness of a material and is defined as Load/Change in
shape when loaded. It is expressed in p.s.i. or MPa. A material can be
loaded in tension (Tensile Modulus), flexion or bending (Flexular
Modulus), compression, torsion etc. |
| MOISTURE RESISTANCE |
The ability of a cured material to resist absorbing
moisture. |
| POT LIFE |
The period of time, after mixing or the application of
heat, that the material remains useable (pourable) in the particular
application. |
| POST CURE |
The required extra cure time/temperature to develop the
full cured properties. In some cases the recommended post cure consists of
step curing at different temperatures for different periods of time. |
| POTTING |
A manufacturing method where components are placed into
containers and the containers are filled with a thermoset material. The
containers remain an integral part of the assemblies in service.
Diagram |
| POWER FACTOR |
Is the reflection of the electrical losses (in the form of
heat) at a specified frequency in an insulating material. |
| RESISTIVITY |
The ability of an insulator to resist the flow of electric
current through it. It is expressed in ohm-cm. |
|
SHORE HARDNESS |
Is the measured hardness of a cured material. Softer
products are on the shore A scale, harder materials are on the shore D and
Rockwell scales. Click here for
Hardness Equivalent Chart
|
Hardness Cross Reference |
|
Shore A |
Shore D |
Rockwell M |
| 50 |
10 |
- |
| 70 |
15 |
- |
| 90 |
32 |
- |
| 100 |
45 |
- |
| - |
74 |
- |
| - |
78 |
32 |
| - |
82 |
63 |
| - |
86 |
95 |
| - |
90 |
125 |
|
Practical Hardness Reference |
|
Shore A |
Shore D |
Feels like: |
|
25-30 |
- |
White eraser |
|
35-45 |
- |
Pink eraser |
|
45-55 |
- |
Rubber stamp |
|
55-65 |
- |
Hard eraser |
|
65-75 |
- |
Medium rubber |
|
75-85 |
25-30 |
Rubber shoe sole |
|
85-95 |
30-40 |
Rubber Roller |
|
95-100 |
40-50 |
Garden hose |
|
- |
50-60 |
Hard book cover |
|
- |
60-65 |
Wood desk top |
|
- |
65-70 |
Moulded plastic |
|
- |
70-75 |
Wood yard stick |
|
- |
75-80 |
White board |
|
| SPECIFIC GRAVITY |
The mass per unit volume of a material divided by the mass
of the same volume of water at a standard temperature. Expressed in
grams/cm3. |
| SURFACE RESISTIVITY |
The resistance to the flow of electric current on the
surface of a specimen (between opposite edges). |
| TENSILE STRENGTH |
The pulling force required to break a standard size
specimen. Expressed in pounds/in2. |
| TENSILE
LAP SHEAR STRENGTH |
A measure of
adhesive strength defined as the force required to break an adhesive
junction in the form of a lap joint when a shear stress is applied to it.
A lap joint is made by placing one substrate over another and bonding the
overlapped sections together. |
| THERMAL CONDUCTIVITY |
The ability of a material to conduct heat. The amount of
heat that passes through a specimen of a material in a period of time
until the difference in temperature between the two surfaces is 10C. |
| THERMAL CYCLE |
One or more gradual changes in the temperature of the
medium in which the device operates. Always involves a transition time
from hot to cold. |
| THERMAL SHOCK |
A sudden and marked change in the temperature of the
medium in which the device operates. There is no transition time, the
change is directly from hot to cold. |
| THERMOSET |
A product that is, once solidified, is very difficult or
impossible to re-liquefy. As opposed to Thermoplastic materials that may
be re-liquefied usually by the application of heat. |
|
THERMOPLASTIC |
A polymer
that is solid at room temperature or at another specified temperature but
may be liquefied repeatedly when heated above that temperature. Unlike
Thermosets which undergo a chemical change to form a three dimensional
network, thermoplastic polymer molecules generally remain linear and
separate after processing. |
| THIXOTROPIC |
Materials that have the ability to cling and build on
surfaces. This property does not directly relate to viscosity. Examples of
this are shaving cream, whipped cream etc. |
| VISCOSITY |
Is the measure of a liquid materials ability to flow. It
is usually expressed in centipoises. (See Centipoise above) |
| VOLUME RESISTIVITY |
The resistance to the flow of electric current through a 1
cm cube of material. It is expressed as ohm-cm. |
| YELLOW
CARD |
A category of
products that have been tested and certified by Underwriters
Laboratories Inc.® based on their use and intended
application. UL® recognized systems and
components are listed yearly in the Recognized Components Directory and
documented by the so-called "yellow card" |
| |
|
