The advent of polyurethane nearly 50 years ago has impacted many industries and product lines. One area that has impacted significantly is the manufacture of heavy duty industrial casters and wheels. Approximately 80 percent of all heavy duty applications require a polyurethane tire applied to a wheel core. The quality of the material and process is what assures a long life cycle of the product.
I want to share five important facts that you must consider when utilizing polyurethane tire wheels in your industrial applications. If you consider these facts, you will likely have a good experience with polyurethane wheels.
Polyurethane is a very tough material when used properly. However, when used in either high environmental heat applications or applications that generate heat, the durability of polyurethane will be compromised significantly. Most common urethane will not withstand ambient heat above 230 degrees for any longer than 60-90 minutes without causing damage. Internally generated heat (by cyclic deflection of the urethane) in the 250-degree range will liquefy the material within 15 minutes.
Polyurethane used in industrial applications must have properties that exceed the properties of most urethanes used in non-dynamic applications. To get the proper urethane to meet your needs, one must consider the following.
Urethanes that are hot cast (poured at heat levels of 140-170 F and cured in the range of 190-240 F) produce a superior wheel for demanding dynamic applications. Urethanes that are processed and cured at room temperature seldom deliver the physical properties needed in an industrial wheel application.
The common point of failure of the industrial polyurethane wheel is the point where the urethane and the core (steel or cast iron) must bond to support the dynamic application of the wheel. Without proper preparation of the core, proper cleansing of the prepared surface, proper application of the bonding agent, and proper preheating of the core, the probability of premature failure of the bond and wheel increases significantly. And you won’t see these defects when you receive your wheel and put it into application. Choose a manufacturer that follows a quality procedure and is ISO 9001-2000 certified.
The ratio of the isocyanates to the curing agent is a critical part of the manufacture of the desired end product. An improper mixture of the two parts will lead to a material that might appear correct but will never perform in the way it was designed. Stoichiometry is the measurement of the ratio of the two components, and at times when wheel failures occur can be tested in the final product to determine a mode of failure. Many of today’s modern machines include high-tech metering systems and mixers that make the manufacture of a standard stoichiometry mixture a consistent outcome.