What are Vulcanized O-Rings and Their Applications?

Vulcanized o-rings are made by cutting extruded cord stock and bonding it together, whereas moulded o-rings are compressed or injection moulded as one piece. Vulcanized o-rings make a great choice for fixed sealing applications where moulded o-rings cannot be used because of:

  • Big or non-standard dimensions
  • Only a few pieces are required
  • The application requires an o-ring immediately and you cannot wait for the usual lead times of moulded production.

COR’s in-house production team can make vulcanized o-rings in any size from a range of elastomers.

How are they made?

Two principal steps are involved to make a vulcanized o-ring. These steps include:

  1. A continuous length cord is cut as per the required diameter of the o-ring.
  2. The two ends of the cord are joined together in a mould at a high temperature for a specified period (depending upon the type of elastomer used) by applying a bonding agent. This  bonding process results in creating a strong joint at a molecular level.

Are they Suitable for your Application? 

The most important question you have to ask yourself is if you need an o-ring for a dynamic application (where moving parts come in contact with the o-ring) or a static application (where there are no moving parts coming in contact with the o-ring). If the o-ring will be subjected to moving parts around it, then one must not consider the use of a vulcanized o-ring for their application.  If the equipment or machinery in use is a static one with no moving components, then a vulcanized ring can be the ideal solution for your application. Read about other factors to consider before choosing between vulcanized and moulded o-rings. Contact us for any questions you may have.

Applications:          Static
Pressure:                Up to 1200 psi Max.
Requirements:       24 hours to cure

Their Disadvantages

  • As discussed above, vulcanized o-rings are not suitable to handle dynamic applications as a lot of stress is subjected to them due to the moving components. 
  • If your application needs a large number of o-rings, it would be more cost-effective to use custom moulded o-rings and to create proper tooling for the application. They can get costly for such applications.

Various Application-Specific Options of Vulcanized O-Rings

Vulcanized o-rings are made in various profiles to meet the application-specific requirements. The main features that describe a vulcanized o-ring’s profile include:


  • Type of rubber used
  • Colour
  • Cross Section (CS) of durometer (aka thickness of the cord)

Cord Length (CL)

It is calculated based on the required diameter of the vulcanized o-ring for the application.

Cut Angle

By default, a 90º cut is made where the cord is cut straight from top to bottom. For some applications, a Bevel Cut (45 degrees) angle cut is required. This kind of cut is used to make the joint stronger by having more of elastomer’s surface in contact.

How to find a suitable Cord Length for your Application?

COR has made a simple Cord Length calculation tool, which you can utilize to find the suitable cord Length for your application.

Click here to use our tool.

Industrial Applications

The common use of Vulcanized o-rings includes:

  • Filtration
  • Pharmaceutical
  • To seal flanges or lids (of any shape)

The important aspect is to design the groove properly and then the vulcanized o-ring will work very effectively.

For any application questions, please contact COR’s industry expert team.

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