Plastic bushings are now designed to handle high speeds, loads, temperatures, caustic chemicals and a wide array of other application factors.
Here are the top four reasons for replacing PTFE-lined bushings with plastic bushings, which offer more design flexibility.
A PTFE-lined bushing is comprised of a metal shell and a very thin polymer coating (PTFE) applied to the inside. These types of bushings typically have a maximum wear surface of 0.06 millimeters (0.002 inches), but as the PTFE coating is stripped off during operation, the metal shell becomes exposed. This creates a metal-on-metal effect between the bushing and the shaft and can cause serious damage. This problem is common when high edge loads or oscillating movements are present.
In comparison, plastic bushings are comprised of advanced synthetic compounds, which contain solid lubricants embedded in millions of tiny chambers throughout the material.
During operation, lubricant is transferred onto the shaft to help lower the coefficient of friction and wear, and unlike PTFE-lined bushings, plastic bushings eliminate the danger of metal-on-metal contact. This is huge benefit since the acceptable amount of wear can be determined by the type of application (unlike the PTFE-lined bushing, which will fail if the wear rate surpasses 0.06 millimeters).
For example, igus®' lifetime calculator uses a preset wear rate of 0.25 millimeters (0.01 inches), but the user can easily increase or decrease this number to meet the wear limit acceptable for the particular application.
Almost any of igus®’ iglide® plastic bushings can replace a PTFE-lined bushing. One of the most popular is iglide® G300.
iglide® G300 is ideal for demanding applications with medium to high loads, average surface speeds, and moderate temperatures. It is available as a sleeve bushing, flange bushing or thrust washer.
PTFE-lined bushings weigh more than plastic bushings. When using a heavier bushing, no matter what material it is comprised of, more energy is required for the bushing to operate. This can be troublesome, especially in automotive, aerospace, recreational vehicle, and bicycle applications.
In contrast, plastic bushings are lightweight, which helps decrease fuel consumption and carbon dioxide output. The reduced weight can also help reduce carbon dioxide output, lower masses and subsequently, lower energy consumption.
In a weight comparison, an iglide® plastic bushing weighs approximately 80 percent less than a PTFE-lined bushing.
The metal shell of a PTFE-lined bushing is not ideal for applications where water or caustic chemicals are present. In these types of applications, PTFE-lined bushings can rust, corrode, contaminate sensitive areas, and ultimately fail. Since plastic bushings are made solely of high-performance polymers, they offer both corrosion- and chemical-resistance and operate unaffected in those types of environments.
The trend towards the increasing use of biofuels and biodiesels creates problems when using PTFE-lined bushings; after limited exposure to moisture, parts of the bushing’s metal shell can begin to peel off.
However, these types of applications open new doors for plastic bushings. Since they are corrosion-resistant, plastic bushings remain unaffected despite the fact that biodiesel has the tendency to absorb a great deal of water.
igus® has developed iglide® H370 and iglide® T500, which can both be used in biodiesel applications. These bearings are specifically designed for demanding, highly technical applications.
iglide® H370 is ideal for underwater applications and can handle chemicals, high loads and temperatures up to 392 degrees Fahrenheit.
iglide® T500 is also extremely resistant to chemicals and can be used in continuous temperatures up to 482 degrees Fahrenheit. This bushing was also specially designed so that its wear resistance actually increases when exposed to high temperatures.