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What does TPU stands for?

Complete Guide on Thermoplastic Polyurethanes (TPU)

Learn more about Thermoplastic Polyurethane, a versatile thermoplastic elastomer with high durability and flexibility. Understand how it is produced, its main properties and benefits which enable various industries to produce advance products. Also, get detailed information on popular applications of thermoplastics polyurethanes ranging from automotive to agriculture and many more.

Overview

What Does TPU Stands For?

What Does TPU Stands For?

Thermoplastic polyurethane (TPU) is a melt-processable thermoplastic elastomer with high durability and flexibility.

TPU provides a large number of physical and chemical property combinations for the most demanding applications such as automotive, wires and cables, breathable films for leisure, sports and textile coatings, weatherable, non-yellowing films etc.

It has properties between the characteristics of plastic and rubber. Thanks to its thermoplastic nature, it has several benefits over other elastomers are unable to match, such as:

  • Excellent tensile strength,
  • High elongation at break, and
  • Good load bearing capacity

Properties of Thermoplastic Polyurethanes

Thermoplastic polyurethane (TPU) was discovered in 1937 by Otto Bayer and his coworkers at the laboratories of I.G. Farben in Leverkusen, Germany.


How TPU is Produced?

How TPU is Produced?

It is produced when a polyaddition reaction occurs between a diisocyanate and one or more diols in a specific way. The three basic raw materials required to produce a TPU are:

  • A polyol or long-chain diol
  • A chain extender or short-chain diol
  • A diisocyanate

It is a linear segmented block copolymer composed of hard and soft segments.

  • Soft Segment (polyether or polyester): It is built out of a polyol and an isocyanate which provides flexibility and elastomeric character of a TPU. 
  • Hard Segment (aromatic or aliphatic): It is constructed from a chain extender and isocyanate giving TPU its toughness and physical performance properties
    • Aromatic TPUs - based on isocyanates such as MDI
    • Aliphatic TPUs - based on isocyanates like H12 MDI, HDI and IPDI

Molecular Structure of Thermoplastic Polyurethanes
Molecular Structure of Thermoplastic Polyurethanes


Key Properties of Thermoplastic Polyurethane

Key Properties of Thermoplastic Polyurethane

TPUs allow industries to mainly benefit from the following combination of properties :

Abrasion/Scratch Resistance


High abrasion and scratch resistance ensure durability and aesthetic value

When abrasion and scratch resistance are critical for an application like automotive interior parts, sports and leisure applications or technical parts, as well as specialty cables, TPUs give excellent results compare to other thermoplastic materials.

The abrasion resistance of materials is usually determined by measuring the weight loss of a specimen in a standardized wear test as shown in the chart below:

TPU abrasion resistance in comparison to other materials

Comparative results of such a test as depicted in the figure above, clearly show the superior abrasion resistance of TPU when compared to other materials, such as PVC and rubbers.


Soft Touch/High Comfort of Use for Ergonomic Applications


Recent developments have made it possible to produce plasticizer-free TPU in the hardness range of 55 to 80 Shore A.

These solutions offer a high quality surface finish, excellent adhesion to engineering plastics such as ABS and Nylon, as well as unequalled scratch and abrasion resistance.


UV Resistance


Aliphatic TPUs ensure color fastness to your aesthetic parts. They show a superior stability to ultraviolet radiation and thus superior color stability, while maintaining good mechanical properties.

Aliphatic TPU have exactly the right property profile and versatility to make it the material of choice for electronic applications. For both light & dark color parts, OEMs can rely on TPU's high scratch resistance & UV performance.

» Check Out Commercial TPU Grades for Electronic Components


Highly Breathable TPU Ensures Optimum Comfort


Highly Breathable TPU Ensures Optimum Comfort Whether your design is in sportswear, footwear or building and construction products, highly breathable TPU are available to ensure optimum comfort.

Unlike traditional TPU which typically have a vapor transmission below 1 500 g./m2/day,highly breathable grades have values as high as 10 000 g./m2/day (+560%). Traditional TPU can be blended with breathable ones to fine-tune the breathability according to your application requirements.


Combination of High Transparency with Abrasion Resistance


Crystal-clear TPU are available with very good hardness. This characteristic allow the use of TPU in the extrusion of transparent films & tubes and hoses, or in the injection molding of technical, aesthetic parts, where transparency at a thickness as high as 6mm can be achieved.


Other Benefits of TPU


  • High elasticity across the entire hardness range
  • Excellent low-temperature and impact strength
  • Resilience to oils, greases and numerous solvents
  • Good flexibility over a wide temperature range
  • Robust weather and high-energy radiation resistance

Thermoplastic polyurethanes are elastic and melt-processable. Additives can improve dimensional stability and heat resistance, reduce friction, and increase flame retardancy, fungus resistance, and weatherability.

Aromatic TPUs are strong, general-purpose resins that resist attack by microbes, stand up well to chemicals. An aesthetic drawback, however, is the tendency of aromatics degrade by free radical pathways induced by exposure to heat or ultraviolet light. This degradation leads to product discoloration and loss of physical properties.

Additives such as antioxidants, UV absorbers, hindered amine stabilizers are used to protect polyurethanes from UV light-induced oxidation and hence make thermoplastic polyurethanes suitable for wide range of applications that may require both thermal and/or light stability.

Aliphatic TPU, on the other hand, are inherently light stable and resist discoloration from UV exposure. They are also optically clear, which makes them suitable laminates for encapsulating glass and security glazings.

Other specialty grades include:
  • Reinforced TPU – When mixed with glass or mineral fillers/fibers, it becomes a structural engineering polymer with desirable properties of abrasion resistance, high impact strength, good fuel resistance, and high flow characteristics
  • Flame Retardancy – Flame retardant TPU grades are widely used to provide tear resistance and toughness for cable jacketing


Main Types of TPU Films

Main Types of TPU Films

Polyester, Polyether and Polycaprolactone are the three main chemical classes of TPU films.

Types of Thermoplastic Polyurethane (TPU)
Credit: Huntsman


Polycarbonate Diols (PCDs)


Another interesting class of polyols used for thermoplastic polyurethane production is Polycarbonate diols generally used to produce polyurethanes that incorporate the carbonate linkages for superior performance. Polycarbonate-polyurethanes can also be produced through the use of polycarbonate-based polyurethane prepolymers.

A polycarbonate-based polyurethane prepolymer is a derivative of the corresponding polycarbonate diol in which all the polyol hydroxyl (OH) end groups have been reacted with an isocyanate leaving isocyanate groups (NCO) at the termini instead of hydroxyls.

When compared to polycaprolactone and PTMEG based polyurethanes, PU elastomers based on PC-PU prepolymers exhibit:

  • Extreme durability
  • Higher chemical resistance
  • Improved hydrolytic stability
  • Greater thermal resistance
  • Better abrasion resistance, and
  • Superior mechanical properties

Achieve best in class durability of your PU based Materials thanks to breakthrough PCD


Limitations of Thermoplastics Polyurethanes

Limitations of Thermoplastics Polyurethanes

  • Some grades of TPU have relatively short shelf life
  • Drying time is required before processing can begin
  • Not as cost-effective as other alternatives
  • Narrower hardness range than other thermoplastic elastomers
  • Narrow temperature range for processing
  • Tendency to be hydrolyzed especially in case of polyester-based TPU


Popular Processing Methods for TPU

Popular Processing Methods for TPU

Thermoplastic Polyurethane can be processed easily via conventional processing methods like injection molding, extrusion, blow and compression molding etc. They are easily molded into shapes to produce grips, gaskets, caps, prosthetics and several other applications as discussed above.

It can also be compounded to create robust plastic moldings or processed using organic solvents to form laminated textiles, protective coatings or functional adhesives.

Drying is a critical step in ensuring TPU’s process effectively and that a good part is obtained upon molding. If moisture is not removed from the polymer effectively before processing, drying of molded parts would not take effectively leading to loss in properties and brittleness.

Recommended residual moisture content

  • For injection molding ≤ 0.05%
  • For extrusion 0.02%


TPU Safety Environmental Benefits

TPU Safety Environmental Benefits

TPU Safety TPU is biodegradable & can be recycled. Other benefits offered by TPU over PVC include:

  • Environmental protection
  • TPU is abrasion resistant while PVC can crack over time
  • More elastic and lighter than PVC
  • In medical devices it is accepted as a safe alternative to PVC because TPU healthcare grades do not use rubber accelerators and plasticizers that can cause skin irritation or dermatitis

Polyurethanes used as insulator effectively improve the energy efficiency of buildings, transportation and appliances & hence lower carbon emissions. In vehicles, TPU products enhance fuel efficiency, because they are lighter than alternative metals.


Find Suitable Thermoplastic Polyurethane Grade


View a wide range of thermoplastic polyurethane grades available today, analyze technical data of each product, get technical assistance or request samples.

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