When casters show signs of damage, the most common way to assess the issue is by examining how much of the tread has worn away. However, on-site there is another entirely different failure mode: even after relatively short service life, the tread begins to feel sticky, soften, develop fine cracks, and may even crumble—so much so that a small piece of material can be easily chipped off with a finger.

Even more puzzling is that some devices, despite being used infrequently, still exhibit this issue.

At this point, the cause may not be “wear” in the conventional sense, but rather the occurrence of… in certain environmental conditions. Hydrolytic aging 。

I. What is “hydrolysis” of caster materials?

Simply put, when certain polymeric materials are exposed to moisture over a long period or remain in a humid environment, their internal chemical structure gradually undergoes changes.

This change is different from the wheel tread being “worn away” by the ground.

Wear typically occurs in the contact zone between the wheel tread and the road surface, whereas hydrolysis is a gradual change in the material’s intrinsic properties; therefore, even when equipment remains idle for extended periods, it may continue to progress.

This is also why some inventory casters appear “almost unused,” yet upon retrieval after a few years, their wheel surfaces are already noticeably degraded.

II. Are all polyurethane casters susceptible to hydrolysis?

It cannot be generalized.

Polyurethane is not a single, rigid material; rather, it comprises a broad family of materials. Depending on the raw-material system, formulation, and manufacturing process, its resistance to hydrolysis can vary significantly.

Therefore, it is not appropriate to conclude outright that “polyurethane wheels cannot be used in wet environments.”

What truly needs to be done is, during the selection phase, to determine whether the casters will be exposed long-term to water, high-humidity environments, cleaning solutions, or steam, and then choose a material system that best suits the actual operating conditions.

Simply telling a supplier, “I want PU wheels,” doesn’t provide sufficient information.

III. Why should high-temperature, high-humidity environments be given greater attention?

Hydrolysis is closely related to environmental conditions.

If casters are exposed to humid environments for extended periods and simultaneously subjected to elevated ambient temperatures, the aging of certain materials may warrant particular attention.

For example, production areas that require frequent rinsing, warehouses that remain damp for extended periods, cleaning equipment, certain food-processing environments, and workplaces where moisture is present should all be clearly specified during the selection process.

Sometimes the casters can handle the mechanical load with no issue; it’s actually the environment that ends up limiting their performance.

IV. What is the difference between hydrolysis and ordinary wear?

Normal wear typically exhibits fairly distinct contact characteristics.

After prolonged rolling between the wheel tread and the ground, the working surface gradually wears down—this is a relatively straightforward form of mechanical wear.

When the material undergoes significant aging, it may manifest as stickiness on the wheel surface, loss of its original elasticity, the appearance of surface cracks, localized chalking, or flaking in chunks.

If the casters have not been subjected to heavy-duty operation yet exhibit extensive material degradation, the scope of investigation should be broadened from “wear” to consider material–environment compatibility.

V. Why might inventory casters also develop issues?

The fact that casters have not been mounted on the equipment does not mean that the material’s condition will never change.

The storage environment of the warehouse is equally important.

If exposed for extended periods to high temperatures, high humidity, direct sunlight, or environments unsuitable for material preservation, certain polymeric materials may still undergo gradual aging.

Therefore, for casters that have been in long-term storage, it is not advisable to rely solely on the integrity of the packaging.

Before putting it back into service, inspect the wheel tread for any obvious stickiness, cracks, hardening, softening, or surface irregularities.

In particular, inventory that has remained stagnant for an extended period warrants a quick review.

6. For equipment that requires frequent cleaning, be sure to ask one more question when selecting it.

Many procurement professionals tell suppliers:

“The equipment is for indoor use.”

However, the condition “indoor” is too broad.

A standard warehouse is indoors, and the food-processing area that requires daily cleaning is also indoors; the requirements for caster materials in these two environments may be entirely different.

Therefore, if the equipment requires frequent cleaning, it is necessary to specify the cleaning frequency, whether water accumulates over long periods, whether detergents are used, and whether the casters remain wet for extended durations.

This information is often more valuable than simply telling the supplier “for indoor use.”

7. If you detect an abnormality on the wheel tread, don’t rush to replace only the same model.

If a batch of casters exhibits similar issues—such as stickiness, cracking, or chipping—the simplest solution is, of course, to replace them with new ones.

However, if the new casters still use the exact same material system and the on-site conditions remain unchanged, similar issues may recur.

A more reasonable approach is to first confirm:

What is the long-term humidity environment of the equipment?

Do you frequently come into contact with water?

Is there a cleaning process?

Is there persistent moisture near the casters?

Are the warehouse storage conditions appropriate?

After confirming these factors, assess whether the wheel‑rim material needs to be adjusted.

Written at the end

Not all caster failures are due to “overuse.”

Some wheels operate at high frequency every day yet maintain stable performance; others, used only sparingly, prematurely degrade due to mismatches between the operating environment and the materials.

This is also a factor that is often overlooked in caster selection:

In addition to asking how much the equipment weighs and what types of flooring it will be used on, you should also inquire about the environmental conditions the casters will encounter each day.

When the wheel surface starts to feel sticky, crack, or even flake off, don’t rush to blame “poor material quality.” Instead, carefully examine the conditions of use and storage—more often than not, this will help you pinpoint the real cause.