TPU Hydrolysis Resistance Explained: Why Some Polyurethane Tubes Last Years Longer

Failures of pneumatic automation tubing do not have to be caused by overpressure. Often, failures are the result of gradual degradation of tubing in the environment over time. One of the major factors is the chemical breakdown by moisture. The hydrolysis resistance of TPU is crucial for the use of polyurethane tubing in order to guarantee the mechanical strength of the tubing in humid environments, outdoors or in wet environments within production. For engineers and purchasing departments, the use of hydrolysis resistant polyurethane tubing can be crucial for the reliability of their automation systems and for the maintenance interval and total cost of ownership.

Why does TPU hydrolysis resistance matter for pneumatic tubing in real applications?

Resistance to hydrolysis of TPU is critical as pneumatic tubing is usually exposed to water, to humidity of the compressed air and to changes in temperature.

How does hydrolysis affect flexible pneumatic tubing performance?

Hydrolysis is the chemical reaction where water breaks down the long polymer chains of polyurethane. Flexible pneumatic hose is particularly prone to this degradation. As hydrolysis progresses, the hose will lose its flexibility and develop surface cracks. It will also be unable to withstand pressures and may harden or become brittle, leading to leaks or burst failures. In automated systems, this can cause significant problems.

Why is this important in industrial pneumatic systems?

In continuous air supply systems used in factories even minor damage to tubing can affect the precision of the actuator and its cycle stability. Equipment like for example robotic arms, assembly lines and packaging machines are dependent on a stable air supply. Already a small hydrolysis can cause problems with the air supply, such as instable air flow, which can lead to imprecise positioning of the equipment or even a complete break down.

What causes polyurethane tubing degradation in humid environments?

Moisture is the main cause for the degradation of polyurethane, but alone it is not responsible for the degradation.

Why do temperature and humidity accelerate TPU breakdown?

In warmer, more humid production environments the higher temperature in combination with higher humidity accelerates the degradation of the material’s molecular chains. Water molecules penetrate into the material quickly, in particular when the tubing is under constant pressure. This speeds up the aging process of the material significantly. As a result the service life of polyurethane tubing is greatly reduced.

How do chemicals and compressed air quality contribute?

Industrial compressed air can contain a mixture of oil mist, cleaning solvents or other industrial chemicals. These chemicals can leach from TPU materials and increase the rate of hydrolysis. The air treatment as well as the tubing selection therefore plays a significant role.

How do polyether TPU and polyester TPU differ in hydrolysis resistant polyurethane performance?

The base chemistry of the TPU is the major factor that will affect hydrolysis resistance.

Why is polyether TPU more hydrolysis resistant?

Polyether TPU generally provides stronger hydrolysis resistance because its molecular structure is less vulnerable to water-induced chain scission. This makes it suitable for TPU tubing for humid factories, marine environments, or applications involving frequent washdowns.

What are the limitations of polyester TPU?

A polyester based TPU will have higher mechanical strength and better abrasion resistance than a similar Hydrogenated polyurethane. However it will have less resistance to hydrolysis. Therefore, although polyester based polyurethane tubing will withstand long term humid exposure, it will degrade faster than its hydrogenated counterpart especially when elevated temperatures are also present. In dry or controlled environments polyester TPU would however be a suitable alternative.

How does hydrolysis impact TPU tubing lifespan under pressure and temperature stress?

Hydrolysis can cause failure, but it is not a singular factor. It interacts with other factors such as pressure and temperature and together they can cause failure to accelerate.

How does pressure stress influence material aging?

Combining the TPU pressure rating with long-term internal pressure is driving the material into mechanical stress. Whilst the material is in this stressed state, hydrolysis can enable micro-cracks to open up much faster. This will reduce the service life of such tubing and pose the risk of leakage in pneumatic circuits.

How does cyclic temperature variation worsen degradation?

The multiple heating and cooling cycles cause the polyurethane hose tubing to expand and contract. This contraction and expansion allows moisture to penetrate deeper into the tubing material which in turn accelerates the hydrolysis reaction. This is particularly a problem where the fluid system is exposed to the outdoors or experiences seasonal temperature changes.

How should buyers select hydrolysis resistant pneumatic tubing for industrial systems?

Tubing selection is a compromise between chemical resistance, mechanical characteristics and other plant characteristics.

What technical parameters should be evaluated?

To make the right choice when buying tubing, Shore hardness of the TPU grade, hydrolysis resistance rating, pressure, wall thickness, bend radius and operating temperature have to be matched. In addition the compatibility of the tubing with fittings and connectors has to be checked in order to avoid leakage in the long run.

What application scenarios require hydrolysis resistant tubing?

If hydrolysis resistance is required for components that are to be used in food processing lines, for filling beverages, in very humid automation facilities, in pneumatic washing facilities or in outdoor applications, a special polyurethane is recommended for these applications. In all these cases there is a constant and unavoidable exposure to moisture and in such cases the choice of a suitable material is critical.

Which supplier can support polyurethane pneumatic tubing projects?

Yantai Aisili nouveau matériel Co., Ltd. is a Chinese manufacturer of polyurethane pneumatic tubing as well as of multi-material flexible tubing systems for industrial applications. The company offers a wide range of tubing materials with different hydrolysis resistance. Depending on humidity and temperature as well as on the requirements of the compressed air system, there are suitable tubing materials. The tubing is used in industrial automation, in pneumatic control systems as well as in production of other equipment which requires a stable airflow. As a supplier for procurement teams Yantai Aisili New Material Co., Ltd. also offers support for material selection, specifies required technical data and offers customized products for the respective applications. For a final specification decision, however, the buyer should compare the technical data, allowed working pressure as well as system compatibility.

Conclusion

TPU hydrolysis resistance is a key factor that determines the long-term reliability of polyurethane pneumatic tubing in humid and demanding environments. Hydrolysis gradually weakens material structure, affecting flexibility, pressure stability, and overall system performance. Polyether TPU generally provides stronger resistance compared to polyester TPU, making it more suitable for wet or moisture-prone applications. However, material selection should always consider pressure, temperature, and air quality conditions together. Proper tubing selection helps extend service life, reduce maintenance frequency, and improve pneumatic system stability.

FAQs

1. What is TPU hydrolysis resistance?

This property of polyurethane describes its time-stable resistance to water.

2. Why does polyurethane tubing degrade in humid environments?

Moisture enters into the material, and breaks the polymer chains, particularly under elevated temperature and/or pressure.

3. Which TPU type has better hydrolysis resistance?

Based on our experience, in humid environments Polyether TPU performs generally better than Polyester TPU.

4. Can hydrolysis affect TPU pressure rating?

Yes, degradation of materials also reduces the structural strength. Over time this leads to a reduction in the effective pressure resistance.

5. How can buyers extend polyurethane tubing lifespan?

Use of hydrolysis resistant materials, control of air, correct pressure and temperature.