New segmented polyurethane ureas based on 4,4′-dicyclohexylmethane diisocyanate and on various soft segments

✍ Scribed by Nathalie Samson; Françoise Mechin; Jean-Pierre Pascault

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 222 KB
• Volume: 70
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19981219)70:12<2331::aid-app4>3.0.co;2-n

✦ Synopsis

Linear segmented polyurethane ureas were prepared from 4,4Ј-dicyclohexylmethane diisocyanate (H 12 MDI), 4,4Ј-diamino-3,3Ј-dicyclohexyl methane (3DCM), and various hydrophilic and hydrophobic soft segments. Kinetic studies of the synthesis of the diisocyanate-terminated prepolymers revealed that the use of too little reactive polyols (that is, polyoxypropylene that bears secondary hydroxyls) could be rather tricky; the noncatalyzed reaction is very slow, but the use of a catalyst soon triggers the formation of side products, and the processing window consequently becomes quite short. Microcalorimetric and dynamic mechanical measurements showed that all the materials were highly phase-segregated elastomers and displayed good mechanical properties up to high temperature (typically 180°C), provided that they had been postcured properly; in this respect, the dramatic effects of isolated (nonchemically linked) hard segments, as well as of too low postcuring temperatures, were demonstrated. Polyurethane ureas compare well with polyureas, and their synthesis can be a good way to cope with the lack of well-adapted commercial diamino-terminated prepolymers.