Glossary of Terms
ABRASION RESISTANCE: Ability of material to withstand mechanical actions such as rubbing, scraping, etc.
ADDITIVES: Materials combined with prepolymer and curative (e.g., plasticizers, fillers, and stabilizers) to modify the properties of the polyurethane product.
ADHESIVE: A layer of paint-like material which interfaces between urethane and another material to promote strong bonding.
BASHORE REBOUND: An ASTM test for the resiliency of a material.
BLOWING AGENT: An additive that decomposes during the curing process to yield a large volume of gas to create the cells in foamed urethane.
CATALYST: An additive that accelerates the reaction rate or setup time of urethane.
CENTRIFUGAL MOLDING: A process in which the mold is spun to force the material into a shape.
CLOSED CELL FOAM: Cellular urethane material composed of cells that do not allow gases or fluids to pass to adjacent cells.
COEFFICIENT OF FRICTION (COF): The resistance to motion between two contacting surfaces. It is expressed as: COF = F/N, where F = the force required to move an object and N = the ‘normal force’ between the two surfaces.
COMPRESSION LOAD DEFLECTION (CLD): The force required to deflect an object a precise distance expressed as a percentage.
COMPRESSION MOLDING: Formation of a rubber or plastic article to a desired shape, by either placing the raw mixture in a specially designed cavity or bringing it into contact with a contoured metal surface under pressure.
COMPRESSION SET: The difference between the original size and the final size of a molded product, expressed as a percentage after being compressed.
CONDUCTIVE OR ANTISTATIC AGENT: A polymer additive that raises the conductivity of the material or dissipates static.
CONDUCTIVITY: A measure of the ability of a material to conduct electrical current. It is the reciprocal of resistivity.
CURE TIME: Length of time a liquid urethane compound must remain in the mold before it can be removed as a solid elastomer.
DENSITY: Weight per unit volume of a substance.
DISPERSION: A uniform mixture of liquid and solid particles.
DUROMETER: A measurement of an elastomer’s hardness. (Usually measured on Shore, Asker, or JIS scales).
ESD Management: Electrostatic dissipation (e.g., electrical grounding).
ELASTICITY: The ability of a material to resume its original size and shape after the force that caused its deformation has been removed.
ELASTOMER: Any polymer having elastic properties.
ELONGATION: Measurement of stretch under load.
EXOTHERM: Heat given off in a chemical reaction.
FILLERS: Solids added to a polymer to enhance physical properties or displace the polymer.
HYDROLYTIC STABILIZERS: Chemical additives that reinforce resistance to water.
HYSTERESIS: The heat produced from stress and strain of cyclic loads on a material.
INTEGRAL SKIN FOAM: Urethane foam with a cellular core structure and a relatively nonporous film skin.
MDI (Diphenylmethane 4.4 Diisocyanate): A chemical building block of polyurethane.
MICROCELLULAR: Urethane chemically or mechanically blown to produce a density lower than the solid material.
MODULUS: Coefficient of elasticity representing the ratio of stress to strain as the material is deformed under dynamic load. It defines the softness or stiffness of the material.
OPEN CAST: A process of pressureless molding.
OPEN CELL FOAM: Foamed or cellular material with interconnecting cells that allow liquids or gases to pass through.
PARTING LINE: The line formed by the mating surfaces of a mold.
POLYESTER RESIN: A chemical constituent of MDI and TDI reacted with polyethers. They are stable with heat and humidity.
POLYMER: A macromolecule formed by the chemical union of five or more identical combining units called monomers.
POLYURETHANE (Urethane Elastomer): The polymer prepared by reacting a diisocyanate with a polyhydroxyl-terminated compound.
PPDI (Para-phenylene Diisocyanate): The resin (created by reacting diisocyanate and polyol or polyamine) which is a conveniently stable building block of polyurethane.
PREPOLYMER: The resin (created by reacting diisocyanate and polyol or polyamine) which is a conveniently stable building block of polyurethane.
REBOUND: Measurement of how a material returns or absorbs energy.
REVERSION: A urethane’s loss of physical integrity due to excessive heat and humidity.
SEMI-CONDUCTIVITY: The ability of a material to partially conduct electric current.
STRESS AND STRAIN: Stress is a force or load. Strain is the percentage change under load.
SURFACE FINISH: The degree of roughness of a surface. Usually expressed as the average height of surface imperfections.
SURFACE RESISTIVITY: The ratio of the potential gradient parallel to the current along the surface, to the current per unit width of surface. The most important factor in this measurement is the presence of moisture, which will significantly lower the surface resistance.
TDI (Toluene Diisocyanate): A chemical building block of polyurethane.
TEAR STRENGTH: The resistance of a material to a shearing force or tension.
TENSILE STRENGTH: A measure of the force required to stretch a material until it breaks.
THERMOPLASTIC URETHANE: Polymers (formed by the reaction of bifunctional polyols with diisocyanates) which can be melted and reformed.
THERMOSET URETHANE: Polymers formed by reacting diisocyanate and hydroxy or amines to form a cross-linking polyurethane, which cannot be melted and reformed.
TRIBOCHARGE MANAGEMENT: The generation of a charge or conductivity in relation to motion or friction (e.g., toner charge regulation).
VOLUME RESISTIVITY (OHM-CM): The electrical resistance offered by a material to the flow of direct current. Also called specific resistance, it is an intrinsic property of bulk (not thin-film) material. In the COS system (SI), the unit of resistivity is the ohm-cm. Resistance is expressed in ohms and the sample dimensions in meters.