Adhere – When materials stick or cling to one another.
Aging – When a material undergoes physical changes over time.
Back-Up Ring – A hard ring that is placed in the gland between the o-ring and the groove walls in order to prevent extrusion.
Batch – The resulting product from a mixing operation.
Cell – A small cavity that is surrounded either completely or partially by walls.
Elastomer – Any of the various materials that are elastic and resemble rubber. Elastomers can be used instead of springs as energizers.
Energizer – A device used in some o-rings that acts to retain the ring’s natural shape. Often, either a spring or an elastomer serve as the energizer at the core of the o-ring.
Friction – The resistance to motion when two or more surfaces rub against one another.
Gland – Cavity into which an o-ring is installed, which also has the groove and mating surface of the second part.
Inside Diameter – The size measured from any inner point of an o-ring to the inner location on the direct opposite side, creating a straight line.
Lubricity – The slippery, lubricated qualities an o-ring material has.
Memory – A material’s tendency to resume its original shape after deformation.
Mil-Spec – O-rings that meet and/or surpass standards of the United States military.
Off-Register – When a mold is misaligned and causes an out-of-round cross section of an o-ring.
Outside Diameter – The size measured from an outside point of an o-ring to that same point on the direct opposite side, creating a straight line.
Overflow Groove – A groove around the mold cavity of an o-ring that is used to accept excess material from the cavity in order to create a better fit.
Parting Line – A line outside of o-rings that is left-over from when the two mold plates met.
Polyurethane – Any of various resins that vary in flexibility and are used in chemical resistant coatings, foams and adhesives.
Squeeze – Cross-section compression of an o-ring gland assembly that shows between the surface of the groove bottom and surface of the mating metal part.
Vulcanized – Improved strength, lubricity and resiliency by combining sulfur and/or other additives with both heat and pressure.
Water Swell – The bulging or increased size of an o-ring due to water intake.