Thermoplastic polyurethane
![]() | This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)
|
Thermoplastic polyurethane (TPU) is any of a class of
Chemistry
TPU is a block copolymer consisting of alternating sequences of hard and soft segments or domains formed by the reaction of (1)
Morphology
A TPU resin consists of linear polymeric chains in block-structures. Such chains contain low polarity segments which are rather long (called soft segments), alternating with shorter, high polarity segments (called hard segments). Both types of segments are linked by covalent links so that they actually form block-copolymers. The miscibility of the hard and soft segments in TPU depends on the differences in their glass transition temperature (Tg)[1] which occurs at the onset of micro-Brownian segmental motion, identifiable by dynamic mechanical spectra. For an immiscible TPU, the loss modulus spectrum typically shows double peaks, each of which is assigned to the Tg of one component. If the two components are miscible, the TPU will be characterized by a single broad peak whose position lies between that of the two original Tg peaks of the pure components.
The polarity of the hard pieces creates a strong attraction between them, which causes a high degree of aggregation and order in this phase, forming
These "pseudo crosslinks", however, disappear under the effect of heat, and thus the classical
Uses
TPU has many applications, including automotive instrument panels, caster wheels, power tools, sporting goods, medical devices, drive belts, footwear, inflatable rafts, fire hoses, buffer weight tips and a variety of extruded film, sheet and profile uses.[2][3] TPU is also a popular material found in flexible outer cases of devices like mobile phones and keyboard protectors.[4]
TPU is well known for its applications in wire and cable jacketing, hose and tube, in adhesive and textile coating applications, and as an impact modifier of other polymers.[5] It is also used in high-performance films, such as high impact resistant glass structures.
TPU is the thermoplastic elastomer used in
Overview of TPU on the market
Properties of commercially available TPU include:
- high abrasion resistance
- low-temperature performance
- high shear strength
- high elasticity
- transparency
- oil and grease resistance
The currently available TPUs can be divided mainly into two groups, based on soft segment chemistry:
- polyester-based TPUs (mainly derived from adipic acid esters)
- polyether-based TPUs (mainly based on tetrahydrofuran (THF) ethers).
The differences between these two groups are outlined in the table below.
Table of properties
Table 1: Main differences between polyester- and polyether-based TPU.[6]
(A = excellent; B = good; C = acceptable; D = poor; F = very poor)
Property | Polyester-based TPU | Polyether-based TPU |
---|---|---|
Abrasion resistance | A | A |
Mechanical properties | A | B |
Low temperature flexibility | B | A |
Heat aging | B | D |
Hydrolysis resistance | D | A |
Chemical resistance | A | C |
Microbial resistance | D | A |
Adhesion strength | B | D |
Injectability | B | B |
TPU is the right choice when a flexible at low temperatures and/or abrasion resistance
When stable light colour and non-yellowing performance are required, aliphatic TPU based on aliphatic isocyanates is used.
BASF has pioneered crosslinking during TPU transformation, made possible by adding liquid crosslinkers or using a solid granulated additive masterbatch. Plant-based bio TPU has been developed for green thermoplastic elastomer applications by BASF, Merquinsa-Lubrizol and GRECO, marketed as Elastollan N, Pearlthane ECO and Isothane respectively.
Safety
TPU may contain siloxanes, some of which are considered substances of very high concern by the European Union.[7][8]
See also
- Fracking hose
- Mobile phone cover
- Polycarbonate
- Silicone
References
- ISBN 978-0-12-525050-4.[page needed]
- ^ "Texin® thermoplastic polyurethane (TPU) resin". Bayer Material Science. Archived from the original on 2011-07-26. Retrieved 2012-02-26.
- ^ "Thermoplastic Polyurethane". American Chemical Council. Retrieved 2012-02-26.
- ^ Michael, John. "TPU Cases". Cellz. Archived from the original on 13 November 2014. Retrieved 13 November 2014.
- ^ http://pub.lubrizol.com/Engineered-Polymers/Markets/Industrial-Solutions [dead link]
- ^ "Pearlthane". Merquinsa, A Lubrizol Company. Retrieved 2013-01-31.
- ISBN 978-87-92903-02-0.
- ECHA. Retrieved 2019-12-18.