Premiere Urethane Components Applications

Becoming the industry standard for physical toughness, polyurethane sees active service in applications requiring resistance to abrasion, tar, and high tensile strength. Urethane possess a unique molecular structure of tight bonds between soft polyol segments and hard isocyanate segments, creating a strong but flexible elastomeric backbone in gasket seals and other seal systems. Polyurethanes are also unique in that they have a number of serviceable forms, from low strength liquids to highly cross-linked thermoplastics.

Real Seal commonly handles the two most often used in the sealing industry; Thermosetting and Thermoplastic. The chemical type of the polyol backbone used when compounding polyurethane material is one of the two major contributors to a specialty seals physical properties and relative chemical resistances, for instance. These are three types normally utilized:

Polyester Based: The most commonly used in silicone seals and other seal systems, providing excellent mechanical properties with resistance to hydrocarbon oils and hydraulic oils. Most urethane seals are based on polyesters.

Polyether Based: Compounded for better hydrolytic stability and good low temperature properties while maintaining the other excellent properties that urethane possesses.

Polycaprilactone Based: A subgroup of polyesters, polycaprilactones impart some of the hydrolysis resistance and low temp properties of the polyethers to the outstanding oil resistance and mechanical properties of polyesters.

The other major contributor to the physical properties of urethane is the curative used. Millable gum urethanes may employ standard peroxide and sulphur cure systems similar to other elastomers, but thermoplastic and higher performance thermosetting materials employ isocyanate cure systems. These may be of several basic types:

MDI – Methylene bis-(4-phenylisoyanate) is commonly known as MDI and is the second most common curative. Most often used in the thermoplastic materials.

TDI – 2,4-tolyene diisocyanate is known as TDI. Used in specialty millable gums and some casting systems as well as in most foam urethane materials; the most commonly used urethane curative in the world.

TODI – 3,3’-Dimethyldiphenyl-4,4’ diisocyanate is known as TODI. Imparts excellent heat resistance properties along with superior mechanical properties. For additional information, visit www.real-seal.com/ to learn more.