Glossary of Terms

Adhesive Substance used to join two or more materials.
Additive Component generally used in small quantities that does not participate in the chemical reaction but changes the properties of the final product or the production process (pigments, antifoams, flame retardants,...)
Aliphatic Product/polyurethane that does not contain benzene ring molecules (aromatic structure) in its composition. Characterized by better UV resistance and better discoloration resistance than aromatic polyurethanes.
Aromatic Polyurethane that contains molecules with aromatic rings in its composition.
Catalyst Component used to increase the speed of a chemical reaction.
Renewable content Amount of carbon of animal or vegetable origin present in a product and determined according to the ASTM D6866 standard.
Curing The process that leads to the formation of a polymer with fully consolidated final properties. In the case of prepolymers, it refers to the reaction with water in 1-component (1K) systems or with crosslinking agents in 2-component (2K) systems, reflecting their drying process.
Density Ratio of the mass to volume of a material.
Aqueous polyurethane dispersion (PUD) Polyurethane product, in which particles are dispersed in water.
Elastomer Material that behaves like rubber, i.e., that resists and recovers from imposed deformations.
Hydrophilic That has an affinity for water.
Hydrophobic That repels water.
Hydrolysis The breaking down reaction of molecules carried out by the action of water and which is normally associated with the degradation of materials.
Isocyanate Chemical group (NCO) that is characterized by being reactive with several other chemical groups. It is also the generic name for the group of substances that have one or more NCO groups in their molecule.
Abbreviation for diphenylmethane diisocyanate, one of the isocyanates used in the synthesis of polyurethanes.
Monomer The structural unit of a polymer, so it usually refers to the raw materials used in polymer synthesis. The consecutive reaction between monomers (small molecules) results in the formation of polymers (high molecular weight molecules).
Free monomer Residual amount of monomer that did not react during production and remains free in the final product. In the case of prepolymers, this usually refers to free TDI or MDI. This value determines the toxicological classification of the products and justifies the need for safety measures when handling them.
NCO Chemical formula of the isocyanate functional group, which is composed of nitrogen (N), carbon (C) and oxygen (O).
Plasticizers Additives typically used to increase the flexibility of the polymer and decrease its hardness. In the case of prepolymers, it may also lead to a reduction in viscosity.
Polyol Chemical compound that has more than one reactive hydroxyl group attached to the molecule.
Polyurethane Polymer that has urethane groups in its composition and results from the reaction of isocyanates with polyols.
Polyurea Polymer that has urea groups in its composition and results from the reaction of isocyanates with amines.
Pot-life Time available to use a prepolymer before it starts to gel (dry out).
Pre-polymer Intermediate compound between monomers and the final polymers. In the case of polyurethanes, it is the product that results from the reaction between a polyol and a polyisocyanate but still has isocyanate groups available for further reaction.
PU Abbreviation for polyurethane.
Reactivity It reflects the reaction speed of a given substance/compound. In the case of prepolymers, it refers to the speed at which the curing process takes place.
TDI Abbreviation for toluene diisocyanate, one of the isocyanates used in the synthesis of polyurethanes. 
Curing time Time required for the curing reactions to be completed and the polymer to consolidate its mechanical properties.
Extractables content The amount of non-reactive substances in a polymer composition. As these substances are not incorporated into the polymer matrix, they can migrate out of the polymer or be extracted using solvents.
NCO content Quantifies the percentage, by mass, of isocyanate groups in a prepolymer.
Urea Chemical group (-NH(COO)2-) that characterizes polyureas.
Urethane Chemical group (-NHCOO-) that characterizes polyurethanes.
Viscosity Property that characterizes the resistance that fluids have to flow. The higher the viscosity, the lower its fluidity.