It is impossible to distinguish between polyester-based TPU (Ester) and polyether-based TPU (Ether) simply by their appearance. Both appear as transparent or white, irregularly shaped spherical or columnar particles. To differentiate them, you can look at the following points:
1. Differences in raw materials and formulations;
2. Molecular weight distribution and factors influencing the differences;
3. Different mechanical properties;
4. Differential hydrolytic stability;
5. Differences in antimicrobial performance;
6. Prices differ.
 

1. The raw materials and formulations used in the production of polyester-based TPU differ from those used for polyether-based TPU.
The primary raw materials for the production of polyether-type TPU (Ether) include 4,4'-diphenylmethane diisocyanate (MDI), polytetramethylene ether glycol (PTMEG), and 1,4-butanediol (BDO). Among these, MDI accounts for approximately 40%, PTMEG for about 40%, and BDO for roughly 20%.
The main raw materials for the production of polyester-based TPU (ester) include 4,4'-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO), and adipic acid (AA). Among these, MDI accounts for approximately 40%, AA for about 35%, and BDO for roughly 25%.
 

II. Molecular Weight Distribution and Influencing Factors Differentiating Polyester-Based TPU from Polyether-Based TPU
The relative molecular mass distribution of polyethers follows the Poisson probability equation and exhibits a relatively narrow molecular weight distribution; in contrast, the relative molecular mass distribution of polyester diols conforms to the Schulz-Flory “most probable distribution” and shows a broader molecular weight distribution.
The molecular weight of the soft segment significantly influences the mechanical properties of polyurethanes. Assuming that the polyurethane molecules have the same molecular weight, if the soft segment is a polyester, the strength of the polyurethane elastomer will increase as the molecular weight of the polyester diol rises. On the other hand, if the soft segment is a polyether, the strength of the polyurethane elastomer will decrease with increasing molecular weight of the polyether diol, while its elongation at break will increase. This is because polyester-based soft segments themselves are highly polar and exhibit high structural regularity when their molecular weight is large, which is beneficial for enhancing strength. In contrast, polyether-based soft segments are less polar; as their molecular weight increases, the relative content of the hard segments in the polyurethane decreases, leading to a decline in strength.
 

III. Differences in Mechanical Properties Between Polyester-Based TPU and Polyether-Based TPU
The soft segments of polyethers, polyesters, and other polymers are composed of polyol oligomers. In polyurethane elastomers, the soft segments account for the majority of the material. The properties of polyurethanes prepared from different polyol oligomers combined with diisocyanates vary considerably. Polyurethane elastomers and foams made using highly polar polyesters as soft segments exhibit superior mechanical performance. This is because polyesters contain highly polar ester groups; within such polyurethanes, not only can hydrogen bonds form between hard segments, but also the polar groups on the soft segments can partially form hydrogen bonds with the polar groups on the hard segments. As a result, the hard phases are more uniformly dispersed throughout the soft phase, acting as elastic crosslinking points. At room temperature, certain polyesters can crystallize in the soft segment, which may affect the overall performance of the polyurethane. Polyester-based polyurethanes generally have higher strength, oil resistance, and thermal-oxidative stability than PPG-based polyether polyurethanes; however, their resistance to hydrolysis is inferior to that of polyether-based polyurethanes.
 

IV. The Difference Between Polyester-Based TPU and Polyether-Based TPU in Terms of Hydrolytic Stability
After being protected with carbodiimide, polyester-based thermoplastic polyurethane elastomers exhibit improved resistance to hydrolysis. Among them, polyether-ester-based and polyether-based thermoplastic polyurethanes demonstrate the best hydrolysis resistance at high temperatures.
Polyesters are susceptible to hydrolytic degradation upon exposure to water molecules, and the acids generated during hydrolysis can further catalyze the hydrolysis of the polyester itself. The type of polyester used has a certain impact on the physical properties and water resistance of elastomers. As the number of methylene groups in the polyester diol raw material increases, the water resistance of the resulting polyester-based polyurethane elastomers improves. Polymers with lower ester group content also exhibit better water resistance. Similarly, polyurethane elastomers synthesized from long-chain dicarboxylic acids demonstrate superior water resistance compared to those made from short-chain dicarboxylic acids.
 

V. Differences in Antimicrobial Properties Between Polyester-Based TPU and Polyether-Based TPU
Polyester-based flexible thermoplastic polyurethanes, when in prolonged contact with moist soil, can be eroded by microorganisms; in contrast, polyether-based flexible or rigid thermoplastic polyurethanes, as well as polyether-based thermoplastic polyurethanes or rigid thermoplastic polyurethanes, generally are not subject to microbial erosion.
 

6. Price Differences Between Polyester-Based TPU and Polyether-Based TPU
Polyether-based polyurethane elastomers are significantly more expensive than polyester-based polyurethane elastomers, primarily because:
(1) Polyether-based polyurethanes exhibit excellent hydrolysis resistance, low-temperature resistance, and flexural resistance.

(2) Compared to polyester polyols, polyether polyols—used as the soft segments in polyurethane TPU—have higher raw material costs.

(3) The production process for polyether polyols is significantly more complex than that for polyester polyols.

(4) It is relatively difficult to control the various process conditions during the reaction of polyether polyols.

(5) When producing polyether polyols, the equipment used for production must meet high standards. Additionally, during the production process, it is important to take appropriate protective measures.