Urethane Glossary

Use this glossary of commonly used terms related to urethane to better understand urethane, how it is made and its properties.

Cast - Forming products by pouring fluid urethane into the cavity of an open mold.

Durometer - The hardness of a non-metallic product or the gauge used to measure the hardness. The two most common durometer scales, using slightly different measurement systems, are the ASTM D2240 type A and type D scales. The A scale is for softer plastics, while the D scale is for harder ones. Each scale results in a value between 0 and 100, with 0 being the softest and 100 being the hardest. Also see Shore Hardness.

Elastomer - Polymers that at room temperature can be stretched repeatedly to at least twice their original length, and as soon as the stress is released, will snap back to their approximate original length.

Gel Time - The "working time" from when the raw urethane components are first mixed to when they become solid at a given temperature and mass.

Pigment - A coloring agent.

Plasticiser - An additive that makes a compound softer or more pliable.

Polyester - A chemical building block that provides good resistance to solvents as well as good mechanical properties in the final elastomer.

Polyether - A chemical building block sometimes used in place of polyester and provides exceptional resilience and hydrolytic stability.

Polymer - A solid polyurethane rubber resulting from the chemical reaction of a prepolymer with a curative.

Polyol - A substance containing several hydroxyl groups.

Polyurethane (Urethane) - This is the polymer prepared by reacting a prepolymer with a curative. Sometimes misspelled eurothane, urathane, urithane, and urothane, its correct spelling is URETHANE.

Prepolymer - Used in the production of polyurethane cast parts, prepolymers give the ability to tailor formulations for specific physical properties, such as tear strength, abrasion resistance, and compression set.

Primer - The first coat of paint applied to a surface to help it bond well with another material.

Shore Hardness - A method of determining the hardness or durometer of a material using a pointed gauge. Soft materials are measured with Shore A and 00 and 000, and harder materials are measured with Shore D.

Stoichiometry - The part of chemistry that studies amounts of substances involved in reactions. In polyurethane chemistry, the term defines the ratio of hydroxyl groups to isocyanate groups in a reaction mixture.

Tear Strength (Split Strength) - An elastomer's resistance to abrasion, tears and gouging.

Thermoset - A type of polymer that cannot be melted and reformed by applying heat. 

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