How do polyurethane casters compare to rubber casters in terms of oil resistance and corrosion resistance?

Oil and Corrosion Resistance Comparison between Polyurethane and Rubber Casters
In terms of oil resistance and corrosion resistance, polyurethane casters generally outperform ordinary rubber casters. However, their suitability for different applications varies and needs to be determined based on the specific media type. A specific comparison is as follows:

1. Oil Resistance: Polyurethane casters are more suitable for environments with low to medium concentrations of oil.

In terms of oil resistance, polyurethane casters are significantly better than ordinary rubber casters such as natural rubber and styrene-butadiene rubber, but weaker than specialty oil-resistant rubbers (such as nitrile rubber and fluororubber).

Polyurethane casters: Their molecular structure does not contain weakly polar groups that are easily dissolved by oils and fats. They can withstand short-term or long-term contact with low to medium concentrations of mineral oil and vegetable oils (such as machine tool lubricants and cooking oils). For example, in a machine shop, polyurethane casters lightly lubricated with lubricant will not swell, soften, or break after prolonged rolling. Only minor oil stains may form on the surface, which can be restored after cleaning. However, prolonged contact with highly concentrated solvent-based oils like gasoline and diesel can cause the tread to slightly harden, affecting its elasticity (without significant corrosion damage).

Ordinary rubber casters: Materials like natural rubber and styrene-butadiene rubber contain a large number of unsaturated bonds, making them susceptible to swelling reactions with oils and greases. Contact with lubricants and engine oils can soften and become sticky in the short term. Over time, the tread can deform, crack, or even separate from the wheel hub, completely losing its load-bearing capacity. Even nitrile rubber (a moderately oil-resistant rubber) offers only comparable oil resistance to basic polyurethane and offers far less wear resistance.

Specialized fluororubber casters are only recommended for long-term use with highly concentrated solvent-based oils (such as aviation kerosene and industrial gear oil). In these cases, neither polyurethane nor ordinary rubber is the optimal solution.

2. Corrosion Resistance: Polyurethane casters are more resistant to weak acids and bases, while rubber casters are susceptible to chemical attack.

Polyurethane casters are generally more resistant to weak acids, bases, and common corrosive substances than ordinary rubber casters, but neither can withstand strong corrosive media.

Polyurethane casters can withstand weak acid and base environments with a pH of 4-9 (such as diluted dishwashing liquid and hydrochloric acid/sodium hydroxide solutions below 5%). The tread will not bulge or decompose during daily cleaning or light chemical exposure. For example, in food processing plants, cleaning polyurethane casters with a weak alkaline cleaner will not discolor or show signs of corrosion. However, polyurethane casters will swell and peel when exposed to concentrated acids (such as 30% sulfuric acid), concentrated bases (such as 20% sodium hydroxide), or strong solvents (such as acetone and toluene). Therefore, contact should be avoided.

Ordinary rubber casters: Materials like natural rubber and neoprene have poor chemical stability. Contact with weak acids and bases (such as vinegar and soapy water) can easily cause surface aging and hardening. Contact with mild chemical reagents (such as diluted alcohol or 5% acetic acid) can cause the tread to crack in a short period of time and even release harmful substances, making them completely unsuitable for applications with corrosion risks. Even EPDM, which offers excellent chemical resistance, has corrosion resistance comparable to polyurethane, and exhibits even weaker elasticity and wear resistance.

In summary, in general applications with low to medium concentrations of oil and weak acids and bases (such as machine shops, food factories, and general clean environments), polyurethane casters offer superior oil and corrosion resistance compared to ordinary rubber casters, making them a better choice. Ordinary rubber casters can be used as a low-cost alternative only when the application is oil-free, corrosion-free, and requires extreme elasticity (such as shock absorption and cushioning).