gasket seals | Polyurethane Compounds And Applications
Polyurethane Compounds And Applications
Having become the industry standard for physical
toughness in various components including o-
rings, polyurethane sees active service in
applications requiring resistance to abrasion, tear,
and high tensile strength. Urethanes possess a
unique molecular structure of tight bonds
between soft polyol segments and hard
isocyanate segments, creating a strong but
flexible elastomeric backbone. Polyurethanes are
also unique in that they have a number of
serviceable forms, from low strength liquids to
highly cross-linked thermoplastics. Premiere
urethane product supplier Real Seal commonly
handles the two most often used in the sealing
industry; Thermosetting and Thermoplastic.
Thermosetting polyurethanes possess bonds that are similar to standard elastomeric materials in that
they are non thermally-reversible; that is to say that once they are formed, the bonds cannot be broken
down and then reformed with the addition and subsequent subtraction of heat. Thermosetting
polyurethanes are typically processed in the same manner as other thermosets, being mixed in standard
rubber equipment such as rubber o-rings. Typically molded through compression, transfer, or hot
platen injection molding methods, this class of urethanes also covers those formed through liquid
casting, rotational molding, RIM, and autoclave.
Thermoplastic polyurethanes possess thermally reversible bonds that allow gasket seals, for instance,
to liquefy with the addition of sufficient heat and resolidify upon cooling. Thermoplastic urethanes are
typically formed using injection molding equipment, however, extrusion, thermoforming, vacuum
molding, and hot-knife welding are also possible.
The chemical type of the polyol backbone used when compounding polyurethane material is one of the
two major contributors to its physical properties and relative chemical resistances. There are three
types normally utilized in the production of o-rings and specialty seals:
Polyester Based: The most commonly used, 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. For additional information on polyurethane o-rings and seals, please visit
www.real-seal.com to learn more.
o-rings, rubber o-rings, gasket seals, specialty seals