Hydrolysis resistance of TPU refers to its ability to resist “attack” by moisture and prevent performance degradation. This capability is determined by the chemical structure and additives of TPU, and is a key indicator for evaluating its long-term reliability in humid or underwater environments.

Decisive Factor: Polyester-based vs. Polyether-based TPU

The fundamental difference in hydrolysis resistance comes from the “soft segment” structure within the molecular chain.

• Polyester-based TPU: The ester bonds in the molecular chain are susceptible to hydrolysis, leading to significant performance degradation in hot and humid environments. Therefore, it has inherently poor hydrolysis resistance.
• Polyether-based TPU: The ether bonds in the molecular chain are stable and resistant to hydrolysis, offering excellent hydrolysis resistance. This makes it the preferred choice for underwater or high-humidity applications.

In short: For applications requiring prolonged contact with water or humid environments, polyether-based TPU should be prioritized.

Core Evaluation Indicators

Hydrolysis resistance is typically assessed through accelerated aging tests, focusing on the following key parameters:

• Tensile Strength Retention Rate: The percentage of tensile strength retained after aging compared to the original value. Higher retention indicates better hydrolysis resistance; the industry typically requires ≥80%.
• Change in Elongation at Break: Measures the change in material flexibility. Smaller changes indicate more stable performance.
• Change in Hardness: Reflects changes in surface hardness. Smaller changes indicate better stability of the bulk material.
• Visual Appearance: Observe whether the sample surface shows signs of degradation such as cracking, blistering, or chalking.

Test Methods and Standards

Hydrolysis resistance is evaluated through accelerated aging tests. Main standards include:

• ISO 4611: International standard for湿热 aging of plastics.
• ASTM D570: Standard test method for water absorption of plastics.
• DIN 53366: Used for classifying hydrolysis stability of materials.

Typical test conditions are 70°C / 95% Relative Humidity (RH) for hundreds to thousands of hours, with periodic sampling to monitor performance changes.

Methods to Improve Hydrolysis Resistance

If the hydrolysis resistance of polyester-based TPU is insufficient, the following methods can be employed:

1. Add Hydrolysis Stabilizers: One of the most effective methods is adding polycarbodiimide (PCD) or other anti-hydrolysis agents. These “repair” broken molecular chains and delay degradation.
2. Optimize Molecular Structure: Selecting polyester polyols with higher molecular weight, longer chains, or branched structures can also improve hydrolysis stability to some extent.

Summary and Selection Recommendations

• Key Choice: In humid environments, prioritize polyether-based TPU.
• Evaluation Basis: Quantitatively assess different TPU grades by comparing tensile strength retention rates and other data from aging tests.
• Balance is Key: Recognize that polyether-based TPU may have slightly lower mechanical strength and heat resistance compared to polyester-based grades. A balance between hydrolysis resistance and mechanical properties must be achieved.

Understanding these parameters will help you select the right TPU material for your product, ensuring long-term reliability in its target environment.

About Yantai Linghua New Material Co., Ltd.

Yantai Linghua New Material Co., Ltd. possesses solid R&D and production capabilities in the field of polyether-based TPU. As a professional TPU supplier, established in 2010, the company has grown into a full-industry-chain enterprise integrating raw material trade, material R&D, and production and sales.

Its polyether-based TPU products, based on the ether bond structure in the molecular chain, impart the material with excellent hydrolysis resistance, superior low-temperature performance (down to -40°C and below), and outstanding resistance to mildew. Additionally, the products feature high mechanical strength, good abrasion resistance, and excellent processability, while complying with international quality requirements including REACH, RoHS, and FDA. Leveraging these properties, Linghua New Materials’ polyether TPU products are widely used in wire and cable, automotive components, fire hoses, tubes and pipes, and footwear – industrial and consumer applications demanding high weather resistance and long-term stability.

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Company Name: Yantai Linghua New Material Co., Ltd.
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Address:Floor 12, Yeda Zhigu Comprehensive Center Building, No. 300 Changjiang Road, Yantai ETDZ, FTZ Yantai Area
City: Shandong
Country: China
Website: https://www.ytlinghua.com/