Density The weight per unit volume of a material. Measured in pounds/gallon, or kilograms/liter. Specific gravity is the density in kilograms/liter.
Dielectric Constant The ratio of the capacitance of a material (or insulator) to the capacitance of air. A dielectric constant of 4 means an insulator will absorb 4 times more electrical energy than air.
Dielectric Strength The maximum electrical voltage which an insulating material can withstand without breakdown (conducting electricity). Expressed in volts/mil.
DiluentA reactive or non-reactive additive whose primary function is to lower the viscosity and extend the material to which it was added.
Dipping The process of coating or impregnating of insulating materials by immersion into the uncured material.
Dissipation Factor The measure of the loss of power which takes place in virtually all dielectric materials, usually in the form of heat. It's expressed as the ratio of the resistive (loss) component of the current to the capacitive component of current and is equal to the tangent of the loss angle.
DomingApplication of a clear doming material (urethane or epoxy) to the surface of labels, nameplates or decals for the purpose of creating a clear raised (“domed”) surface. Used to enhance and protect the appearance of these products. (See also
“Scripting”)
Elasticity
That property of materials to tend to recover their original size and shape after deformation. If the strain is proportional to the applied stress, the material is said to exhibit Hookean or ideal elasticity.
Elongation
The increase in length of a material when stress in tension. Measured as a percentage increase over the unstressed material.
Embedment
The enclosure of an electronic, electrical, or electromechanical device in a resin matrix. Most commonly, the embedding matrix is composed of a thermosetting polymer than can be converted from a liquid to a solid by heat, chemical reaction and/or a combination of these. The device is buried or encased in the liquid, which then forms a protective shell when the liquid hardens.
Encapsulating
Enclosing an article in a closed envelope of a material.
Epoxy Resins
A specific type of chemical structure based on ethylene oxide.
Evacuation
The removal of entrained air from an epoxy system by vacuum. Also referred to as degassing.
Exotherm
The amount of heat given off by a chemical reaction, proportional to the mass.
Extender
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.
Failure, Adhesive
The failure at the bond line between substrates and an adhesive; the adhesive separating entirely from the substrate.
Failure, Cohesive
Failure within the adhesive under a stress, resulting in a broken bond with all adhered surfaces still covered with adhesive.
Failure, Substrate
The failure of the substrate material itself, upon subjecting bonded adhered surfaces to a stress.
Filler
An inert material added to a formulated system to improve properties and/or decrease cost.
Fisheye
Small globular mass which has not blended completely into the surrounding material and is particularly evident in a transparent or translucent material.
Flame Retardant
The property of a material that extinguishes a flame once the source of heat has been removed.
Flexural Strength
Ability of a material to withstand failure due to bending.
