Publish Time: 2025-06-30 Origin: Site
TPU (Thermoplastic Polyurethane) is a type of thermoplastic elastomer composed of diisocyanates, polyols, and chain extenders, forming a multiphase block copolymer.
The American company Goodrich Chemical (now renamed Lubrizol) first registered the TPU brand "Estane" in 1958. Over the past 60 years, more than 20 commercial brands have emerged worldwide, each with several product series.
Current TPU raw material manufacturers include BASF, Covestro, Lubrizol, Huntsman, Wanhua Chemical, Shanghai Heng'an, Ruihua, Asahi Kasei, etc.
As a high-performance elastomer, TPU has a wide range of downstream applications in daily necessities, sports goods, toys, decorative materials, such as footwear, hoses, cables, and medical devices.
However, common TPUs are divided into two types: polyether-based and polyester-based. Different types of TPU need to be selected according to specific application requirements. For example, if high hydrolysis resistance is required, polyether-based TPU is more suitable than polyester-based TPU.
Therefore, today we will discuss the differences between polyether-based TPU and polyester-based TPU, and how to distinguish them. The following will elaborate on four aspects: raw material differences, structural differences, performance comparison, and identification methods.
I. Raw Material Differences
Many people are familiar with the concept of thermoplastic elastomers, which are characterized by containing both soft segments and hard segments, providing flexibility and rigidity to the material respectively.
TPU also has soft and hard segments, and the difference between polyether-based TPU and polyester-based TPU lies in the soft segments, which can be seen from the raw materials:
Polyether-based TPU: 4,4'-Diphenylmethane diisocyanate (MDI), polytetrahydrofuran (PTMEG), 1,4-butanediol (BDO), with MDI accounting for about 40%, PTMEG about 40%, and BDO about 20%.
Polyester-based TPU: 4,4'-Diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO), adipic acid (AA), with MDI accounting for about 40%, AA about 35%, and BDO about 25%.
We can see that the soft segment raw material for polyether-based TPU is polytetrahydrofuran (PTMEG); for polyester-based TPU, it is adipic acid (AA), which reacts with butanediol to form polybutylene adipate as the soft segment.
II. Structural Differences
The molecular chain of TPU has an (AB)n block linear structure, where A is a high molecular weight (1000-6000) polyester or polyether, B is generally butanediol, and the chemical structure between AB segments is diisocyanate.
According to the structure of A, TPU can be divided into polyester, polyether, polycaprolactone, polycarbonate types, etc. The most common ones are polyether-based TPU and polyester-based TPU.
As can be seen from the figure above, both polyether-based TPU and polyester-based TPU have linear molecular chains as a whole. The main difference lies in whether the soft segment is polyether polyol or polyester polyol.
III. Performance Comparison
Polyether polyols are alcoholic polymers or oligomers containing ether bonds in the main molecular chain and hydroxyl groups at the end. Due to the low cohesive energy of the ether bonds in their structure, they are easy to rotate.
Therefore, polyether-based TPU has excellent low-temperature flexibility, hydrolysis resistance, mildew resistance, UV resistance, etc., with good hand feel, but relatively poor peel strength and tensile strength.
The ester groups with strong covalent bond energy in polyester polyols can form hydrogen bonds with hard segments, acting as elastic cross-linking points. However, polyesters are susceptible to water molecule attack leading to breakage, and the acids generated by hydrolysis can further catalyze polyester hydrolysis.
Therefore, polyester-based TPU has excellent mechanical properties, wear resistance, tear resistance, chemical resistance, high temperature resistance, and easy processing, but poor hydrolysis resistance.
IV. Identification Methods
Regarding which TPU is better, it can only be said that it should be selected according to product property requirements.
For good mechanical properties, choose polyester TPU; if considering cost, density, and product usage environment, such as water amusement products, polyether-based TPU is more suitable.
However, when selecting or accidentally mixing up the two types of TPU, they have no obvious difference in appearance, so how to distinguish them?
There are many methods, such as chemical color reaction, gas chromatography-mass spectrometry (GCMS), mid-infrared spectroscopy, etc., but these methods have high technical requirements and take a long time.
Is there a relatively simple and quick identification method? The answer is yes, such as the density comparison method.
This method only requires a density tester. Taking a high-precision rubber densitometer as an example, the measurement steps are:
1. Place the product on the measuring platform, display the product weight, press ENTER to memorize.
2. Place the product in water to display the density value.
The entire measurement process takes about 5 seconds, and then distinguish according to the principle that polyester TPU has a higher density than polyether TPU. The specific density ranges are: polyether-based TPU - 1.13-1.18g/cm³; polyester-based TPU - 1.18-1.22g/cm³.
The above is a detailed explanation of the differences between polyether-based TPU and polyester-based TPU. If you have different opinions or supplements, welcome to join the group to discuss!