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What is Urethane Rubber Used for?

Y. Chen
Y. Chen

Exclusively used in industrial production applications, urethane is a family of rubbers and plastics materials that are used for making molds. Urethane rubber is widely known for its tough properties, being abrasion-resistant, economical, relatively simple to mix and apply, and flexible once it is formed into a mold. The molds are then used in industrial design projects, such as sculpture replication or stamping designs into concrete. This makes urethane rubber one of the most economical mold rubber products ever to be utilized.

In the urethane family, this rubber is considered to be one of the more tensile, durable, and cheap materials to work with when compared to silicone. While silicone does not need a spray-on mold release agent, it is not as resistant to abrasion and is therefore used in more delicate casting processes. Not only does urethane rubber have a high tear strength, but it is reusable, retains its shape, and comes in a range of malleabilities.


When used in conjunction with sealant and a release agent, this type of rubber can be poured, brushed, and sprayed onto an assortment of hard materials for casting purposes. It develops a viscosity similar to water when in liquid form, making it easy to apply. In addition, it has good cohesion when mixed with other forms of urethane rubber and incorporates well with fibers and foams, resulting in a more textured mold when needed.

A typical casting of a sculpture, for example, proceeds as follows:

  1. The model to be cast is sealed at least twice with a sealant. This is especially important for models of porous properties; stone, wood, or water- or sulfur-based clay sculptures need to be coated. The sealant layer must be allowed to harden before the next step.

  2. A release agent is applied to the sealed model.

  3. The person doing the casting must mix and apply the rubber by either brushing, spraying, or pouring it on the model. If tweaks to the mold are necessary, they must be done before the rubber hardens completely.

  4. The model is demolded by separating the mold from it. A precise and accurate impression of the model should now be indented into the urethane rubber mold.

  5. The resultant mold is now ready for reuse. A release agent must be applied to the inside before casting additional models.

Discussion Comments


Does anyone have a recommend material for dampening noise at the mounting point for a plastic fan housing?


Have been asked by a customer to price a chain to manufacture large rubber "o" rings. He suggest a mixing head for the rubber compound, a conveyor to carry it through a caliber to make sheets of a certain thickness, then to place the sheets in a mold to be cut and vulcanized. I am not convinced by this procedure, and would like to offer an alternative. Anyone willing to help?


Urethane rubber also refers to solid urethane that is processed like other rubbers (e.g., natural rubber) on industrial mixing equipment like rubber mills, internal mixers, and extruders. The 'raw' urethane rubber is mixed with curatives, typically sulfur or peroxide, along with reinforcing fillers and process aids, the resulting material having the consistency of chewing gum. This is then cured or vulcanized under heat and pressure, typically in a mold, to give a finished part such as a shoe sole, o-ring or roller.

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