TPU Material Classification and Performance Analysis: Helping You Find the Best Application

Polyurethane thermoplastic elastomers (TPUs) are high-performance polymer materials synthesized via the reactive polymerization of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), macromolecular polyols, and chain extenders. They exhibit outstanding wear resistance, oil resistance, and excellent elasticity, with a mainstream hardness range of 55A to 72D, making them stand out in a wide variety of applications.

From the perspective of chemical structure, TPU can be finely classified into various types based on the differences between the hard segments and soft segments in its molecular chains.

I. Classification of TPU’s Chemical Structure

The mainstream classification of TPUs is primarily based on their soft and hard segment structures. Next, we will provide a detailed introduction to several major TPU categories and their respective characteristics, as shown in the figure below:

I. Classification of TPU’s Chemical Structure

There are various ways to classify TPU, and one of the mainstream approaches is to categorize it based on the type of diisocyanate used in its hard segments. Specifically, it can be divided into the following two categories:

First, there are aromatic TPU materials, in which the hard segments predominantly utilize aromatic diisocyanates, such as diphenylmethane diisocyanate (MDI). Second, there are aliphatic TPUs, whose hard segments mainly employ aliphatic diisocyanates, like hexamethylene diisocyanate (HDI).

In addition, TPU classification can also be based on the structure of its soft segments. Specifically, these include polyester-based TPUs, polyether-based TPUs, polycaprolactone-based TPUs, polycarbonate TPUs, and certain TPUs equipped with other specialized functional groups. These classification methods help us gain a deeper understanding of TPU’s performance and characteristics.

Classification of Soft Segment Structures in TPU

The classification of TPU is not limited solely to the type of diisocyanate used in the hard segments; the structure of the soft segments also serves as an important basis for classification. Depending on the nature of the soft segments, TPU can be categorized into polyester-based, polyether-based, polycaprolactone-based, polycarbonate-based, and certain types featuring other specialized functional groups. This classification approach is of great significance for gaining a deeper understanding of TPU’s properties and characteristics.

II. By classifying the soft segments of TPUs, we will conduct an in-depth analysis of the properties of five types of polyurethanes.

The soft-segment structure of TPU is one of the key factors influencing its performance. By virtue of differences in their soft segments, TPUs can be categorized into five major types: polyester-based, polyether-based, polycaprolactone-based, polycarbonate-based, and those featuring specific functional groups. Each type of TPU exhibits unique physical and chemical properties, enabling it to play distinct roles in various application fields. Therefore, understanding and mastering the classification of TPU soft segments is crucial for gaining a comprehensive grasp of polyurethane materials and making informed, rational selections when choosing them.

1. Polyester-based TPU

Polyester-based TPU uses polyester as its soft segment, such as polybutylene adipate (BDO-PA). Its most notable characteristics are high strength and excellent wear resistance. Nevertheless, its hydrolysis resistance is relatively low. For this very reason, polyester-based TPU shines in applications that demand high wear resistance, such as the manufacture of shoe soles and conveyor belts. Currently, this type of TPU dominates the market, accounting for approximately 68% of the market share.

Polyester-based TPU granules

Performance Highlights: Polyester-based TPU granules excel in strength, oil resistance, and thermal-oxidative stability, surpassing polyether-based TPU. In addition, they also demonstrate remarkable tensile properties, flexural performance, abrasion resistance, as well as resistance to solvents and high temperatures.

Shortcomings: However, polyester-based TPU granules have relatively poor water resistance and are prone to degradation under the attack of water molecules, leading to chain scission. Moreover, the acids generated during hydrolysis can further accelerate the hydrolysis process.

Wide-ranging applications: Despite the aforementioned drawbacks, polyester-based TPU granules continue to find extensive use in numerous fields. For instance, they can be employed in the manufacture of shoe sole components, coated plastics, blended and modified materials, as well as mobile phone cases, injection-molded wheels, sports protective gear, and mechanical equipment. Moreover, they are also widely used in the production of films, pipes, wires and cables, conveyor belts, elastic cords, straps, air cushions, and shoe accessories.

Wear Resistance of Polyester-Based TPU in Sole Applications

Polyester-based TPU granules play a crucial role in shoe sole manufacturing. Their outstanding abrasion resistance makes shoe soles more durable. In addition, polyester-based TPU boasts excellent tensile and flexural properties, further enhancing the elasticity and comfort of shoe soles. These characteristics make polyester-based TPU an ideal choice for shoe sole production and it is widely used in various types of shoe sole components.

Polyester-based TPU phone case

Polyester-based TPU material also demonstrates its unique advantages in the field of phone cases. Not only does this material exhibit exceptional abrasion resistance, effectively protecting the phone’s exterior from wear and tear, but it also boasts outstanding impact-absorbing capabilities, providing extra protection for your phone. Moreover, the softness and elasticity of polyester-based TPU make phone cases more comfortable and durable, making them an ideal choice for smartphone users.

Advantages of TPU Material in Caster Applications

TPU, a material boasting exceptional wear resistance and high tensile and flexural strength, also demonstrates its unique advantages in caster applications. Its outstanding wear resistance ensures that casters remain durable and long-lasting, effectively reducing the frequency of replacements. Meanwhile, its high tensile and flexural strength guarantees that casters can maintain stability even in a variety of challenging environments, resisting damage with ease. As a result, TPU has become the ideal material choice for caster manufacturing.

2. Polyether-based TPU

These TPU grades use polyethers as soft segments; common examples include polytetramethylene ether glycol (PTMEG) and polyethylene glycol (PEG). Their notable characteristics include excellent hydrolysis stability and resistance to microbial degradation. For this reason, polyether-based TPUs have found widespread application in scenarios that demand exceptional resistance to hydrolysis and microbial attack. Although their market share is smaller compared to polyester-based TPUs—accounting for only about 20-30%—the range of applications for polyether-based TPUs continues to expand, and the upward trend is evident. Among the brands producing TPUs on the market, most offer polyether-based products.

TPU raw material pellets

Polyether-based TPU, thanks to the easy rotation of its ether groups, exhibits excellent flexibility and outstanding low-temperature performance. It also boasts superior resistance to hydrolysis and mold growth, and does not contain ester groups that are prone to hydrolysis. However, this material’s mechanical strength and oil resistance are only average, and its heat resistance is relatively poor. Despite these limitations, polyether-based TPU has found applications in a variety of fields, including fire hoses, wires, films, V-belts, and animal identification ear tags. On the market, numerous well-known brands such as BASF, Covestro, Lubrizol, and Huntsman, as well as domestic brands like Wanhua, HuaFeng, Taiwan Kunzhong, and Daitong Resin, have all introduced polyether-based TPU products.

Flexibility and Hydrolysis Resistance of Polyether-Based TPU in Watch Strap Applications

Polyether-based TPU, with its unique ether-based structure, boasts exceptional softness and excellent resistance to hydrolysis, giving it significant advantages in watch strap manufacturing. This material is not only easy to process and mold but also highly resistant to harsh environmental conditions, ensuring long-term stability. As a result, polyether-based TPU has become the ideal choice for watch strap production and is widely used in various types of watch strap products.

Flexibility and Hydrolysis Resistance of Polyether-Based TPU in Car Cover Films

Polyether-based TPU, with its unique ether-based structure, exhibits exceptional flexibility and resistance to hydrolysis, making it an ideal choice for the manufacture of car wrap films. This material is not only easy to process and mold but also maintains long-term stability even in harsh environments, effectively resisting chemical degradation such as hydrolysis. As a result, polyether-based TPU is increasingly being adopted in the field of car wrap films, helping to enhance both the durability and aesthetic appeal of these products.

The flexibility and mold resistance of TPU in animal identification ear tags

TPU material, with its exceptional flexibility and resistance to mold, plays a crucial role in the manufacture of animal identification ear tags. Not only is this material easy to process and mold, but it also effectively resists the attack of microorganisms such as mold, ensuring that the ear tags maintain their original performance and appearance over long-term use. As a result, TPU has become the ideal choice for manufacturing animal identification ear tags, significantly enhancing the durability and practicality of these products.

3. Polycaprolactone-based TPU

Polyester-based TPU demonstrates advantages in the manufacture of animal identification ear tags thanks to its unique properties. This TPU uses polycaprolactone as its soft segment, combining the dual benefits of polyethers and polyesters. It boasts both excellent hydrolysis resistance and outstanding abrasion resistance, making it stand out in applications that demand comprehensive performance. Although polyester-based TPU accounts for a relatively small share of the market and is slightly more expensive, its superior performance still makes it an ideal choice for manufacturing animal identification ear tags.

Polycaprolactone-based TPU granules

PCL-based TPU demonstrates significant advantages in terms of performance, boasting outstanding overall properties and promising broad prospects for future development. This material finds extensive applications across multiple industries, including seals and gaskets—such as high-end oil seals and airtight sealing rings—as well as mechanical components, diaphragms, spinning wheels, and footwear and sports equipment. Moreover, the healthcare sector also benefits from its use, particularly in the manufacture of catheters and medical devices. It is worth noting that internationally renowned brands like Lubrizol, Huntsman, and Covestro, as well as domestic companies such as Meirui New Materials and Taiwan Datong Resin, are all dedicated to the production of PCL-based TPU.

Application of Polycaprolactone-Based TPU in Oil Seals

Polyester-based TPU demonstrates particularly outstanding performance in the field of oil-seal rings. Its exceptional wear resistance, oil resistance, and excellent elasticity make it an ideal choice for manufacturing high-end oil seals. Moreover, its superior overall performance provides strong support for innovation in a variety of fields, including mechanical components, diaphragms, spinning wheels, as well as footwear and sports equipment.

Application of Polycaprolactone-Based TPU in Medical Membranes for Bacterial Barrier Protection

Polyester-based TPU also demonstrates its unique advantages in the medical field. Its outstanding bacterial barrier performance has earned it a prominent place in the manufacture of medical membranes. This material not only effectively blocks bacteria but also maintains excellent elasticity and durability, providing strong assurance for medical safety.

Applications of TPU in Medical Catheters

Polyester-based TPU finds extensive applications in the medical field, one of which is in medical catheters. This material plays a crucial role in catheter manufacturing by offering exceptional flexibility and durability, while also effectively preventing bacterial intrusion. Thanks to its outstanding performance, medical catheters are now safer and more reliable, providing strong support for patients throughout their treatment process.

4. Polycarbonate-based TPU

Polycarbonate-based TPU plays a critical role in specific applications thanks to its unique properties. In this type of TPU, polycarbonate serves as the hard segment, endowing it with exceptional transparency and weather resistance. At the same time, it also exhibits outstanding chemical resistance, mechanical performance, and resistance to aging, oils, and hydrolysis. For these reasons, polycarbonate-based TPU has found widespread use in fields such as medical devices and optical products—areas that demand high transparency and chemical resistance. Although its market share remains relatively small and commercial applications are somewhat limited, its importance in specialized sectors cannot be overlooked.

Polycarbonate-based TPU plays a critical role in a wide range of fields, with applications that are both extensive and diverse. This type of TPU is not only used in high-end sectors such as medical and defense industries but also finds widespread use in everyday products like footwear materials and food packaging. Meanwhile, it also excels in optical applications—for instance, its use in optically transparent films for electronic devices such as displays and touchscreens vividly demonstrates the unique value and broad applicability of polycarbonate-based TPU.