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Terms and Definitions

 

A

Amount mixed / Dispensed at a time

Specify the amount of material that you wish to mix at one time. For example: you may want to mix enough material to use on one part only or you may want to mix enough to pour several parts at a time. Please specify weight or volume. This has a major impact on the maximum allowable speed of reaction.

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.

B

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 kilo-volts, 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.

C

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.

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):

Water1

Kerosene10

Motor oil (SAE 10)100

Castor oil1,000

Corn syrup10,000

Molasses100,000

Chemical Resistance

Products can be formulated to be resistant to certain chemicals or groups of chemicals in their operating environment. The chemicals present in high concentrations along with the operating temperature of the device are key pieces of information for material selection.

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.

Cure Temperature

The temperature at which the necessary chemical reaction is initialized for the material to solidify.

Cure Time / Temperature

The cure time is the time it takes for the material to solidify and develop its full strength and cured properties. Some materials are cured at room temperature while others require the application of heat to react. Many products will cure faster and develop better properties when cured at elevated temperatures.

There are certain trade-offs involved when products are cured at other than the specified temperatures and therefore, it is important to know both the desired time and the cure temperature available. Specify time in Hours or Minutes and temperature in oC or oF (example: 2Hrs@ 125oC).

Cure Cycle

Is the prescribed periods of time and temperature for a material to develop its stated properties.

D

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.

Dispensing Method

Choose how the material will be mixed in manufacturing.

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.

E

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.

F

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.

G

Gel Time

Gel time is the time required for the material to become firm to the touch. At this point the component may be handled without causing damage however, it may not be subjected to any stress or temperature cycling because it is not fully cured and has not developed full strength.

The gel time is less if the materials were mixed and/or poured at elevated temperatures. Some products have to be heated for ease of processing. It is therefore necessary to know both the processing temperature and the desired time for the material to become firm to the touch at that temperature. Specify the desired time in Hours or Minutes and the temperature in oC or oF (example: 1Hr @ 60oC).

H

Heat Deflection Temperature (HDT)

HDT is defined as the temperature at which a standard test bar with a standard load of 66 or 264psi deflects 0.010". This represents the point where the cured product begins to soften with the application of heat. 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. Specify the temperature and select the scale in the dropdown box.

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.

I

FiIndoor or Outdoor serviceler

Important from the chemistry standpoint. Select Outdoor if the material is exposed directly to the elements. Select Indoor if the compound will not be directly exposed to the elements (example: operates outdoor but contained in a covered container.

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

105°C

B

130°C

F

155°C

H

180°C

L

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.

M

Mix Ratio by Volume

Most commonly applicable if processing by automated dispense equipment. Many dispense machines have fixed cylinder sizes and therefore the mix must meet a certain ratio of resin to hardener by volume. Specify only if a restriction exists. Specify as a ratio (example: 1:1).

Mix Ratio by Weight

The mix ratio by weight represents the weight of component A and the weight of component B to be mixed together to result in a complete reaction.

The mix ratio is determined by the products chemistry but there may be some customer requirements that limit processing to certain ratios. Specify this parameter only if there is such a restriction applicable to the process being considered. Specify using ratios (100:100) or using weights (100grms:10grms).

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.

O

Operating Temperature

The operating temperature of the finished component in service is a major consideration in material selection. Specify the continuous operating temperature and select the temperature scale in the dropdown box.

P

Pot Life

Pot life is the length of time the material remains pourable (useable) after mixing the resin and hardener together. Specify how much time you require to pour or use up all of the mixed material. This is not applicable to single component materials. Specify in Hours or Minutes.

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 (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.

R

Resistivity

The ability of an insulator to resist the flow of electric current through it. It is expressed in ohm-cm.

S

Shore hardness

Most epoxies and polyurethanes fall into the shore A or shore D range with some in the very low end of the Rockwell scale. Some applications, such as rollers, require precise control of the cured hardness. Specify only if known. Specify the number and select the scale from the dropdown list.

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).

T

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 1oC.

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 Cycling Requirements

Thermal cycling takes place when a component transitions from hot to cold (or visa versa) temperatures in a gradual manner, passing through room temperature. Components facing this condition are usually tested and approved based on having passed a certain number of these cycles. It is important to know the following:

 

1. The maximum temperature and the time at that temperature

2. The transition time between the maximum temperature and room temperature.

3. The transition time between room temperature and cold temperature.

4. The lowest temperature and time at the lowest temperature.

5. The number of cycles the unit is required to pass for approval.

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.

V

Viscosity / Temperature (Hardener)

Same as above for the resin. Specify only if restrictions exist. Specify viscosity in Centipoises or Pascal-seconds and temperature in oC or oF.

Viscosity / Temperature (Mixed)

This is a frequently specified requirement. Certain applications, such as impregnating, dictate the maximum viscosity. In most cases, the lower the mixed viscosity the easier it is to de-air the mixed material and it is able to impregnate porous materials better. Viscosity changes drastically with temperature. The higher the temperature the lower the viscosity but the pot life is also reduced. Materials can be formulated to yield low mixed viscosity at room temperature or can be highly filled and sill yield low viscosity at elevated temperatures. Specify only if restrictions exist. Specify viscosity in Centipoises or Pascal-seconds and temperature in oC or oF.

Volume per Part

Provide the estimated amount of material that will be used for one part. May be specified as grams, kilograms, cubic centimetres, ounces, pounds, cubic inches etc.

Volume resistivity

The resistance to the flow of electric current through a 1 cm cube of material. It is expressed as ohm-cm.

Y

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"

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