Over the years, metals have demonstrated their worth and have long been used to manufacture machinery components such as bushings and bearings. They do, however, have certain flaws. Although extraordinarily strong, metals are more susceptible to corrosion, dust and dirt than their plastic counterparts. They also require external lubrication, as their coefficient of friction is not low enough and tends to increase with wear. Unlike metals, plastics have an incredibly low and stable coefficient of friction.
Thanks to advances in technology, high-performance polymers are now regarded as highly specialized, state-of-the-art materials that are better adapted to their environment than their metal predecessors. The main advantages of plastic bushings are
- High tolerance to stress
- Elasticity and flexibility
- Self-lubrication, eliminating the need for external lubricants
- Excellent impact absorption
- Noise reduction
- Excellent resistance to wear thanks to their low coefficient of friction
- Incomparable lightness
- Superior service life
- Reduced maintenance needs
Applications that require high-performance plastics
Metals are often plagued by corrosion, which causes a rapid deterioration and a lost of key properties. Corrosion also increases the coefficient of friction, resulting in premature wear. In contrast, high-performance plastics are designed to withstand harsh environments. Here is a list of applications that can benefit from their use:
In food environments, grease and lubricants are seldom used because they increase the risk of contamination. Fortunately, self-lubricating performance plastics eliminate the need for external lubrication.
Performance plastics are better suited to highly humid environments because they do not deteriorate as a result of contact with water or moisture. Thanks to their excellent chemical resistance, plastics never rust or prematurely degrade.
Performance plastics are also a wise choice for applications where high friction is present, as they improve fluidity and reduce the frequency of maintenance. In cases like these, a polymer whose resin is naturally enriched with oil or wax is often the best solution because its self-lubricating property eliminates the need for grease or oil. Moreover, the coefficient of friction of plastics is always stable even when subjected to wear, making them preferable to metals.
Plastics have the ability to absorb impacts and regain their shape thanks to their excellent elasticity. Polymer materials also reduce vibrations.
Plastic bushings and bearings are a very advantageous solution for applications that generate high levels of noise, as they tend to be much quieter than their metal equivalents.
Polymers are also a superior choice for environments where dust and particles tend to damage the bearings or make them less efficient.
Choosing the right plastic
Nylons are part of a family of plastics with interesting mechanical properties such as a low coefficient of friction and a high resistance to wear. For this reason, they are ideal for applications where high speeds and high levels of friction are present. They are, however, less suitable for humid or wet environments because their moisture absorption rate is higher than that of other performance plastics. For environments with wide moisture variations, acetal is a better choice.
PTFE is a very resistant plastic with an extremely low coefficient of friction, making it extremely slippery. It is known for its impressive thermal resistance, retainaing its mechanical properties even in temperatures ranging from -400 °F to 500 °F. For demanding applications, PTFE bushings are a strong and durable choice.
Acetal is fairly comparable to plastics of the nylon family in terms of mechanical properties. It is, however, harder and stiffer. Acetal is also known for its low rate of moisture absorption, making it an ideal material for applications where water is present.