In the big family of industrial materials, TPU (Thermoplastic Polyurethane Elastomer) and PU (Polyurethane) are often mentioned. They have similar names and both belong to the polyurethane family, so many people get them confused. In fact, they are like two brothers in the same family with very different personalities, each having their own characteristics and strengths. Today, let's take a good look at the differences between TPU and PU to make it clear for you.
Essence: Same Origin, Different Formulas
TPU and PU are essentially composed of the same type of material and both belong to the polyurethane family. It's like bread and cake; the main ingredient is flour, but with different formulas, the end products are quite different.
PU is a general term for high molecular compounds formed by the reaction of diisocyanates or polyisocyanates with compounds containing more than 2 hydroxyl groups. Its main chain contains many repeated NHCOO groups. Common diisocyanates include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), etc. According to the different hydroxyl components used, it can be divided into polyester type and polyether type.
TPU, on the other hand, is a thermoplastic polyurethane elastomer, also known as thermoplastic polyurethane rubber, which is an (AB)n type block linear polymer. A is a high molecular weight (1000-6000) polyester or polyether, B is a diol containing 2-12 straight-chain carbon atoms, and the chemical structure between the AB segments is connected by diisocyanates (usually MDI).
Simply put, their "genes" are similar, but the formulas used in the production process are different, which leads to differences in their properties and applications.
Characteristics: Each Has Its Own Merits, Different Uses
Differences in Physical Properties
In terms of appearance, TPU is usually white irregular spherical or columnar particles with a relative density of 1.10-1.25. The relative density of the polyether type is smaller than that of the polyester type. PU has a more varied form and can be in the form of foam, elastomer, etc.
In terms of temperature adaptation, the glass transition temperature of polyether-type TPU is 100.6-106.1°C, and that of polyester-type TPU is 108.9-122.8°C. The brittle temperature of both polyether and polyester types is lower than -62°C, and the low-temperature resistance of the hard ether type is better than that of the polyester type. The temperature adaptation range of PU varies greatly depending on the type. For example, flexible PU foam may become hard at low temperatures, affecting its elasticity.
Differences in Mechanical Properties
TPU is characterized by excellent wear resistance, excellent ozone resistance, high hardness, high strength, good elasticity, low-temperature resistance, as well as good oil resistance, chemical resistance, and environmental resistance. In a humid environment, the hydrolysis stability of polyether-type TPU is far better than that of polyester-type TPU.
The performance of PU varies greatly depending on the type. For example, rigid PU foam has good thermal insulation and structural strength and is often used as insulation material; flexible PU foam has good elasticity and a comfortable feel and is often used in sofas, mattresses, etc.
Case 1: Sports Shoe Soles
The soles of sports shoes have high requirements for wear resistance and elasticity. A well-known sports brand, when designing a professional running shoe, found through tests that the sole made of TPU had significantly less wear than the PU sole after tens of thousands of friction tests, and the elasticity was better maintained, which could provide more lasting support and cushioning for athletes. Therefore, this professional running shoe finally chose TPU as the sole material.
Case 2: Oil Pipelines
In some industrial scenarios, it is necessary to transport oily substances with certain corrosiveness. A chemical plant, when choosing materials for oil pipelines, compared TPU and PU pipelines. Thanks to its good oil resistance and chemical resistance, the TPU pipeline had almost no corrosion on the inner wall during long-term use and no leakage; while the inner wall of the PU pipeline was corroded to a certain extent after being used for a period of time, affecting the transportation efficiency and safety. Therefore, the chemical plant finally chose TPU pipelines.
Applications: Segmented Scenarios, Each Showing Its Strengths
Applications of TPU
Due to its good processability, weather resistance, and environmental protection, TPU is widely used in shoe materials, pipes, films, rollers, cables, and other related industries.
In terms of shoe materials, in addition to the aforementioned running shoe soles, many sports shoe air cushions also use TPU materials because they can provide good elasticity while withstanding large pressure. In the cable industry, TPU is often used as a sheath material for cables due to its good environmental resistance and insulation, protecting the internal wires from the external environment.
Applications of PU
PU also has a very wide range of applications and can be used to manufacture plastic products, wear-resistant synthetic rubber products, synthetic fibers, rigid and flexible foam plastic products, adhesives, and coatings, etc.
Many of the sofas we sit on and mattresses we sleep on in daily life use flexible PU foam, which can provide a comfortable touch and good support. In the construction field, rigid PU foam is often used as wall insulation material because of its excellent thermal insulation performance. In the automotive industry, PU can be used to manufacture car seats, instrument panels, and other components, which are both lightweight and durable.
Case 3: Car Seats
When a car manufacturer designed the seats for a high-end car, the filling part of the seat used flexible PU foam because it can provide comfortable support according to the human body curve and is light in weight, which is beneficial to the energy saving of the car. The edge part of the seat is wrapped with TPU material because TPU has good wear resistance and can withstand long-term friction, keeping the seat looking good.
Choosing TPU and PU, Elite Mold Tech Provides One-Stop Service
Understanding the differences between TPU and PU is crucial in actual production when choosing the right materials. Whether you need to make wear-resistant parts with TPU or produce comfortable foam products with PU, Elite Mold Tech can provide you with one-stop services from design to post-processing, including CNC parts processing, 3D printing, die casting, and plastic injection molding.
If you have relevant needs, please feel free to contact us via email at contact@elitemoldtech.com or WhatsApp at +86 19860504405, and we will provide you with professional solutions.
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