Polyurethane Industry Words | Technical Terms Glossary

Glossary

We might use some intimidating language, but the meanings are simple - here are some definitions in case you forget

Additives	A substance that is added to a polyol component to alter the properties, usually in a relatively small percentage. Examples are: degassing agents, moisture scavengers, surfactants, adhesion promoters and etc.
Adhesive	A substance used to join two or more materials.
Aliphatic	A type of polyurethane that does not contain carbon atoms arranged in aromatic (benzene) ring structures. As compared to aromatic, products based on aliphatic polyurethane have superior resistance to UV weathering, and better color and gloss retention.
Ambient Temperature	The surrounding air temperature.
Aromatic	A type of polyurethane that contains some carbon atoms arranged in aromatic (benzene) ring structures. As compared to aliphatic, products based on aromatic polyurethane are usually tougher, but have less resistance to UV weathering, and lesser color and gloss retention.
Catalyst	An ingredient used to increase the speed of a chemical reaction.
Compression Set	Measures the resistance of material to permanent deformation.
Curative	A compound that completes a polymer reaction.
Cure	A material bond by permanently cross-linking its molecules.
Cure Time	A term which refers to the completeness of the chemical reaction. At 100% completion the polyurethane should have reached 100% of its maximum physical properties attainable.
Demold Time	The fasted time a cured part can be removed from the mold.
Density	Density equals the mass of the substance divided by its volume.
Discoloration	Any change from the initial color.
Durometer	One of several measures of the hardness of a material.
Elasticity	The measure of a material’s ability to reshape itself after it has been stretched or deformed.
Elastomer	Polyurethane that has “rubber” like characteristics which resist and recover from deformation produced by force.
Elongation	The percent of its original length to which a sample will stretch before breaking.
Filled System	Polyurethane with filler
Flammability	Relative ability of a material to support combustion as expressed by its flash point.
Flash Point	The lowest temperature of a material at which it gives off vapors sufficient to form an ignitable mixture with air near its surface.
Gel	The initial semisolid phase that develops during the formation of a resin from a liquid.
Gel Time	The “working time” from the initial mixing of the urethane raw material components to the solidification of the material.
Glass Transition Temperature	The temperature region where the polymer transitions from a hard, glassy material to a soft, rubbery material.
Green Strength	The ability to be handled before it has completely cured.
Hydrophilic	An affinity for water
Hydrophobic	Water repellent
Ignition Temperature	The minimum temperature to which a solid, liquid, or gas must be heated in order to initiate or cause self-sustained combustion independent of the heating element.
Isocyanate (ISO)	Chemical compounds having one or more reactive NCO groups.
MDI	An acronym for 4,4′ diphenylmethane diisocyanate, a common raw material used in the production of polyurethane elastomers.
Mix Ratio	Expresses the proper proportion (either by weight or volume) of POLY and ISO to be combined before pouring.
Moisture Cure	Prepolymers that are formulated to cure on exposure to moisture either in the substrate or atmosphere.
NCO%	A measure of the isocyanate content of a prepolymer or other isocyanate-containing compound measured as the weight percent of unreacted isocyanate groups in the material. Value is used to determine proper mix ratio of polyurethane system components.
One-Component System	Systems that cure either by water vapour reacting.
Open Time	The time after adhesive is applied during which a serviceable bond can be made.
Plasticizers	Chemicals used as additives that generally serve to increase the flexibility and lower the viscosity and hardness.
Polyol	An alcohol with more than two reactive hydroxyl groups per molecule.
Polyurea	A type of elastomer that is derived from the reaction product of an isocyanate component and a synthetic resin blend component. The isocyanate can be aromatic or aliphatic in nature.
Polyurethane	A compound based on the reaction of various isocyanates and polyol resins.
Post Curing	A secondary period of curing a cast part at elevated temperature, once it has reached its “green strength” which promotes the completion of the chemical reaction.
Pot Life	The amount of time available to work with a product before it begins to gel.
Potting	The process of encapsulating a device by pouring a casting compound into a cavity in which the device has been fixed and curing the compound in place.
Prepolymer	Formed by combining an excess of diisocyanate with polyol.
Resilience	The ability of a substance or object to spring back into shape.
Resin	Any natural or synthetic organic compound consisting of a noncrystalline or viscous liquid substance.
Shelf Life	The period of time during which a product can be stored under specified temperature conditions and remain suitable for use.
Shore Hardness	Measure of hardness based on the shore scale.
Specific Gravity	The ratio of the weight on any volume of a substance to the weight of an equal volume of another substance taken as standard at a constant or stated temperature.
Surfactants	An additive that either helps or hinders the formation and stabilization of bubbles.
TDI	An acronym for toluene diisocyanate, a common raw material used in the production of polyurethane elastomers.
Tear Strength	The maximum force required to tear a specimen, the force acting substantially parallel to the major axis of the test specimen.
Tensile Strength	The force necessary to rupture a material sample divided by the sample’s original cross sectional area.
Thermal Conductivity	Ability of a material to conduct heat.
Thermoplastic	A type of polymer that can be melted and reformed by application of heat.
Thermoset	A type of polymer that cannot be melted and reformed by application of heat.
Thixotropic	Having the property of decreasing viscosity with increasing shear stress. A coating is thixotropic if it thins with stirring or pumping but thickens back up when movement ceases.
TrioI	A polyol characterized by having three reactive hydroxyl (OH) groups.
Two-Component System	Polyurethane formed by the mixing and the reaction of two different materials.
Unfilled System	Polyurethane without filler.
Viscosity	The thickness or resistance to flow of a liquid. Viscosity generally decreases as temperature increases.
Working Time	The time period during which an adhesive must be used after its container has been opened or, in the case of two-part curing adhesives, after it has been mixed.