About Polyurethane Bushings

Bushings are a common approach to provide low friction surfaces for mechanical equipment. While bushings are manufactured from a range of materials, polyurethane bushings have become especially popular in certain applications.

What are Bushings?

Bushings are a type of bearing known as a plain bearing. Rather than use mechanical elements such as a sleeve and metal rollers, a bushing is simply a sleeve inserted in a hole to provide a smooth surface to allow for low-friction movement of a mechanical object, usually a shaft. After being inserted in the hole or housing, the bushing is then secured in some fashion, usually either with retaining ring or a flange that fits in a groove in the housing.

Bushings offer a range of benefits relative to other forms of bearings: they are compact, can be easier to replace than bearings, and can accommodate heavy loads. Bushings are manufactured from a range of materials, including cast iron, bronze and graphite.

Advantages of Polyurethane Bushings

A designer might select one material over another depending on the application at hand and the qualities afforded by the material in question. However, polyurethane bushings have become increasingly popular in recent years due to a range of advantages. For these and other reasons, designers increasingly use polyurethane bushings to extend the reliability and precision of their rotating equipment and systems:

• Highly predictable life cycles. After decades of research, designers can calculate the life span of polyurethane bushings, making reliability and maintenance easy to forecast.
• Cost-effective option. Polyurethane bushings tend to be more affordable than other materials such as bronze or copper.
• Outstanding resistance to corrosion. Polyurethane bearings are not subject to corrosion like cast iron.
• Dry run behavior. Polyurethane bushings can run lubrication-free thanks to the naturally slick surface of polyurethane.
• Easily formed and machined. Many polyurethane bushing manufacturers provide custom machining services to adjust the final product for custom dimensions.

However, use of polyurethane bushings does not come without risks. One concern has to do with cold flow, or warping of the surface material due to extreme loads. Also, elevated heat can cause thermal expansion or softening of the polyurethane bushing, resulting in reduced life and diminished performance. Manufacturers have responded to these concerns with customized formulations for harder, more heat resistant polyurethane; however, these concerns should still be carefully considered before selecting polyurethane bushings for use in a given project.