Polyurethane Use In Industrial Caster and Wheel Applications for Heavy Duty Casters and Wheels
For most industrial wheel and roller polyurethane applications, the type of material can be chosen on the basis of hardness, load carrying capability, or other standard material properties. If necessary the properties can be altered by adjusting the chemistry during processing. This improves some qualities, but in turn diminishes others. There are some applications for which the selection of polyurethane use in industrial casters requires more consideration. Here are a few examples:
Water Exposure – Not all polyurethane materials can be used in water or in extremely wet environments. For an application such as this, polyether polyurethane must be used as it has excellent hydrolytic resistance. A polyester material will degrade when exposed to excessive moisture. The same is true of extremely warm, humid environments. Polyesters can also be subject to attack by microbial organisms. There are additives which can make the polyester polyurethane less susceptible to attack, but it is best if a more suitable polyurethane material is chosen.
Solvent and Oil Exposure – Just as polyether polyurethanes must be used in water applications, polyester polyurethanes need to be used in applications where the material will be exposed to oil and/or solvents. This is due to polyester’s high degree of oil resistance. Also a polyether material will degrade when exposed to solvents and oil.
Electrostatic Dissipation – In applications such as polyurethane-covered rollers, an electrostatic charge can build up. This can cause significant issues with electrical systems especially in automated systems. An additive can be included during the processing of the polyurethane which would allow the material to dissipate electrostatic charges. This additive will only minimally affect the cost of the polyurethane and the associated physical properties of the material.
Food Grade – Special care must be taken when choosing a polyurethane material for food grade applications. First it must be determined if the polyurethane part will be making contact with wet or dry food. In both cases an MDI polyurethane is required, however not all MDI polyurethanes are suitable for wet food contact. In addition, the catalyst and colorant in the polyurethane must be carefully selected so to ensure that they are also FDA approvable for either wet or dry food contact.
High Performance – In high performance applications such as roller coaster wheels which are subjected to high speeds and high loads, special polyurethanes are used. NDI, PPDI and TODI polyurethanes are most commonly used in these applications. These materials are used because of their excellent dynamic properties and lower heat generation under repetitive load and extended cycle times. These polyurethanes are more difficult to process and are significantly more expensive than other polyurethanes.
The engineering staff of Reaction Industries LLC, a business unit of Caster Concepts, Inc, is skilled in the proper application of polyurethane materials in a variety of uses. To assure a long life cycle for the product, it is important to anticipate all environmental and application issues that might impact the wheel. Call and speak to the applications engineers who will work with you to find the proper polyurethane for your application.