When choosing wheelchair tires, safety always comes first. Following our previous article exploring the potential slip hazards of PU tires on wet roads, this article will reveal another, more subtle, and potentially more long-term, Achilles' heel of PU tires.
Before we delve into this potential safety hazard, let's first take a comprehensive look at the characteristics of PU tires:
Advantages and Disadvantages of Polyurethane (PU) Tires
advantage:
No inflation required, puncture-proof: Solid design, no risk of blowout or air leakage.
Low maintenance: No need to check tire pressure, eliminating the daily hassle of daily maintenance.
High load-bearing capacity and wear resistance: The material is strong and resistant to initial wear.
shortcoming:
Not anti-slip: The material is hard and the surface is slippery, so the grip on wet roads is poor.
Not resistant to hydrolysis (the focus of this article): In a humid environment, it will undergo an irreversible chemical reaction with water molecules, causing the tire to decompose, soften, and become sticky from the inside, posing a hidden safety risk.
Aging and brittleness: After long-term use, it will become hard and crack, affecting comfort and safety.
Today, we focus on this fatal flaw that can "silently corrode" the tire structure and cause "sticky hands" problems: hydrolysis resistance.
Hypothetical event: The potential danger behind "sticky" tires
Imagine a user living in a coastal city in southern China, where the climate is warm and humid year-round, with the rainy season lasting endlessly. He bought a wheelchair with PU tires for an elderly family member and has been using it for over a year. At first, everything seemed normal.
However, in recent months, especially after the long rainy season, he'd noticed the tires had become sticky while cleaning his wheelchair, as if coated with an indelible glue. He'd assumed it was some kind of dirt, but no matter how hard he scrubbed, the stickiness wouldn't go away. Then one day, when he applied a little pressure, his fingernail dug into the tire's surface, peeling off a small piece of material like wet dough, revealing the soft, mushy interior.
This sight made him break out in a cold sweat. He realized that it wasn't just dirt on the surface, but rather the tire's inherent rotting. If it weren't for this accidental discovery, if the elder had continued to use this wheelchair, the tire would likely have suddenly disintegrated at some point, causing the wheelchair to lose control or even tip over, with disastrous consequences.
Why do PU tires "rot"?
Behind this dangerous scene is the chemical defect that PU material cannot overcome - hydrolysis.
Chemical Principle: Polyurethane (PU) contains "ester" bonds in its molecular chains, which undergo irreversible cleavage when exposed to water molecules. Simply put, water continuously breaks down the molecular structure of PU.
Environmental acceleration: Whether it is the ubiquitous humidity in the air, rain, or liquid water during cleaning, they will continuously "attack" PU tires. In the humid environment of the south, this decomposition process is greatly accelerated.
The consequences of hydrolysis are catastrophic: the tire begins to lose strength and toughness from the inside out, gradually becoming soft and sticky, and ultimately completely losing its load-bearing capacity. This is a "silent corrosion" from the inside out. The appearance may only be slightly abnormal, but the safety line has already collapsed.
How to get rid of the problem of "sticky hands"? TPE tires are a better choice
So, how can we avoid this potential crisis caused by material decomposition from the root? The answer lies in choosing a tire with extremely stable chemical properties.
Let's return to that hypothetical scenario. If the user had chosen TPE (thermoplastic elastomer) tires for their elderly parent, the tires would not be in the same condition after more than a year of use, even with the same humid rainy season and frequent cleanings. When they cleaned the wheelchair, the surface of the TPE tires would remain smooth and tough, and after wiping, they would be dry and clean, without any stickiness at all. This is because:
The chemical structure of TPE material is inherently resistant to hydrolysis. Its molecular chains are extremely stable and do not react chemically with water. This means that no matter how humid the environment or how it is washed, TPE tires will maintain their factory-fresh physical properties and structural strength.
For users in humid environments, choosing TPE tires means choosing long-term peace of mind. They no longer need to worry about tires quietly "rotting" due to weather or routine maintenance, and the "sticky" problem and safety hazards caused by material hydrolysis are fundamentally eliminated.
Conclusion: PU tires' inability to resist hydrolysis makes them a slow but certain safety threat in wet environments. In the next article, we will explore the inevitable fate of PU tires, even in dry environments: aging and brittleness.