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Polimero definicion yahoo dating

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Thermoplastic polyurethane TPU is any of a class of polyurethane plastics with many properties, including elasticitytransparencyand resistance to oil, grease and abrasion. Technically, they are thermoplastic elastomers consisting of linear segmented block copolymers composed of hard and soft segments.

TPU is a block copolymer consisting of alternating sequences of hard and soft segments or domains formed by the reaction of: For example, a greater ratio of hard to soft segments will result in a more rigid TPU, while the reverse is also true. The final resin "Polimero definicion yahoo dating" of linear polymeric chains in block-structures.

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Such chains contain low polarity segments which are rather long Polimero definicion yahoo dating soft segmentsalternating with shorter, high polarity segments called hard segments.

Both types of segments are linked together by covalent links, so that they actually form block-copolymers. 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 crystalline or pseudo crystalline areas located in a soft and flexible matrix.

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This so-called phase separation between both blocks can be more or less important, depending on the polarity and the molecular weight of the flexible chain, the production conditions, etc. The crystalline or pseudo crystalline areas act as physical cross-linkswhich account for the high elasticity level of TPU, whereas the flexible chains will impart the elongation characteristics to the polymer.

These "pseudo crosslinks", "Polimero definicion yahoo dating," disappear under the effect of heat, and thus the classical extrusioninjection moulding and calendering processing methods are applicable to these materials. Consequently, TPU scrap can be reprocessed.

TPU has many applications including automotive instrument panels, caster wheels, power tools, sporting goods, medical devices, drive belts, footwear, inflatable rafts, and a variety of extruded film, sheet and profile applications. It is also used to make keyboard protectors for laptops.

TPU is well known for its applications in performance films, wire and cable jacketing, hose and tube, in adhesive and textile coating applications and as an impact modifier of other polymers. Several thousands of TPU Polimero definicion yahoo dating are bound together to create a comfortable sole for the shoe.

The currently available TPUs can be divided mainly in two groups, based on soft segment chemistry:. Main differences between polyester- and polyether-based TPU. In other words, polyether-based TPU is used only in cases where excellent hydrolysis and microbial resistance is required, as well as in cases where extreme low temperature flexibility is important.

When stable light colour and non-yellowing performance are required, aliphatic TPU based on aliphatic isocyanates is used. From Wikipedia, the free encyclopedia.

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