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What is thermoplastic polyurethane?

Views: 286     Author: Vickey     Publish Time: 2023-08-28      Origin: Site

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What is thermoplastic polyurethane?

Thermoplastic polyurethane (TPU) is a type of polyurethane polymer with a variety of characteristics, such as transparency, flexibility, and resistance to abrasion, grease, and oils. Technically speaking, they are linearly segmented block copolymers with hard and soft segments that are thermoplastic elastomers.

Chemistry

As a result of the reaction between diisocyanates and short-chain diols (also known as "chain extenders") and diisocyanates and long-chain diols, TPU is a block copolymer made up of alternating sequences of hard and soft segments or domains. A vast range of distinct TPUs may be generated by altering the ratio, structure, and/or molecular weight of the reaction molecules. This enables urethane chemists to precisely adjust the polymer's structure to the material's desired final qualities.

Uses

TPU is used in a wide range of products, including drive belts, footwear, inflatable rafts, fire hoses, power tools, sporting goods, medical equipment, instrument panels for cars, caster wheels, and extruded film, sheet, and profile. TPU is a common material that is also used to make the flexible outer casings of gadgets like keyboard protectors and cell phone cases.

TPU is well recognized for its uses in the coating of textiles and adhesives, hose and tube construction, wire and cable jacketing, and as an impact modifier for other polymers. Great-performance films and glass constructions with great impact resistance also employ it.

The thermoplastic elastomer TPU is utilized in 3D printing using fused filament deposition (FFD).It is an excellent filament for 3D printers when items need to be flexible and elastic since it does not warp and requires no priming. TPU is a thermoplastic, so it can be melted by the heat of a 3D printer, printed on, and then cooled back into a solid that is elastic. TPU powders are also utilized in 3D inkjet printing and selective laser sintering (SLS), two other 3D printing techniques. Large vertical injection or extrusion molding machines may also utilize it to print directly without first preparing the powder or extruding the filament.

Morphology

A TPU resin consists of linear polymeric chains in block-structures.These chains alternate between longer, low-polarity segments (known as soft segments) and shorter, high-polarity parts (known as hard segments). Covalent bonds are used to bind the two different types of segments together, resulting in block-copolymers.

The difference in glass transition temperature (Tg), which happens at the start of micro-Brownian segmental motion and is discernible by dynamic mechanical spectra, determines the miscibility of the hard and soft segments in TPU. The loss modulus spectrum of an immiscible TPU often exhibits two peaks, each of which is attributed to the Tg of a different component. A single wide peak that is located between the two original Tg peaks of the pure components will define the TPU if two components are miscible.

In this phase, there is a high degree of organization and aggregation due to the polarity of the hard parts, which leads to strong attraction between them and the formation of crystalline or pseudocrystalline zones within a soft and flexible matrix. Depending on the polarity and molecular weight of the flexible chain, the production circumstances, etc., this so-called phase separation between the two blocks may be more or less significant. The crystalline or pseudocrystalline regions serve as physical cross-links, which contribute to the high level of elasticity of TPU, while the flexible chains will provide the polymer with its elongation properties.

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