Thermoplastic polyurethane elastomer composition

The foregoing mastication pattern is characteristic of the several fully formed thermoplastic polyurethane elastomer compositions we have examined. An obvious question the pattern raises is why mastication reduces already formed polymer to such essentially constant low viscosity level under a given set of shear/temperature/time conditions while the same conditions raise the viscosity of the same composition of forming polymer to a much higher and growing or constant viscosity level, (e.g., Polymer 5, Figure 3). 

Soft blocks are composed of linear, dihydroxy poly ethers or polyesters with molecular weights between 600 and 3000. In a typical polymerization of a thermoplastic polyurethane elastomer, the macroglycol is end capped with the full amount of aromatic diisocyanate required in the final composition. Subsequently, the end-capped prepolymer and excess diisocyanate mixture reacts further with the required stoichiometric amount of monomeric diol to complete the reaction. The diol links the prepolymer segments together while excess diol and diisocyanate form short hard-block sements, leading to the (AB)n structure illustrated in Figure 1. Block lengths in (AB)n polymers are frequently much shorter than those in anionically synthesized ABA block copolymers. 

Published information on urethane polymerization detail largely concerns thermoset urethane elastomers systems.4 13 In particular, the work of Macosko et. al. is called to attention. The present paper supplements this literature with information on the full course of linear thermoplastic urethane elastomer formation conducted under random melt polymerization conditions in a slightly modified Brabender PlastiCorder reactor. Viscosity and temperature variations with time were continuously recorded and the effects of several relevant polymerization variables - temperature, composition, catalyst, stabilizer, macroglycol acid number, shortstop - are reported. The paper will also be seen to provide additional insight into the nature and behavior of thermoplastic polyurethane elastomers. 

Polyurethane, PUR thermoplastic polyurethane elastomer, TPU. Applications blocks, plates, formed pieces, cavity forming, composites, coatings, impregnations. 

Method D appears to be possibly the most important type of isocyanate-based adhesive system. It is similar to Method B in that a preformed, fully reacted, high molecular weight polymer is employed as a vehicle in the adhesive formulation. The strength of the vehicle holds adherend members in exact position after assembly until the full bond has formed. Method D differs from Method B in that its vehicle polymer is a polyurethane. A further difference is that the inherent adhesive character and strength of the polyurethane vehicle frequently enables its use without added di- or poiyisocyanate. This strength may be realized in essentially amorphous compositions such as the thermoplastic polyurethane elastomers or millable gums. Or it may be achieved with crystallizing urethane adhesive polymers. 

Polyurethane elastomer, thermoplastic gas-liberating compositions Sulfamic acid gasoline... 

J. E. Brarm and S.H. Cree, Compatible thermoplastic polyurethane-polyolefin blend compositions, US Patent 6632879, assigned to DuPont Dow Elastomers L.L.C. (Wilmington, DE), October 14,2003. 

Polyurethanes are obtained by the reaction between polyols and isocyanates. They are of diverse chemical natures and applications. Most are thermosets (see Thermosets and Composites, M. Biron, Elsevier Ltd (2004) ISBN 1856174115) but others are thermoplastics (TPU), ranging from elastomer flexibility to polyethylene rigidity. 

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