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

Abstract

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.

Investigation of the curing process of spray polyurea elastomer by FTIR, DSC, and DMA

“…In Figure 5(a), the DMA spectra have two tan delta peaks, T gs at −40°C and T gh at 170°C. T gs and T gh refer to soft segment glass transition and hard segment glass transition, respectively,19, 22, 27 and the T gh peak is apparently wider. Based on the discussion of DSC results in the former section, it is easy to deduce that, as temperature rises, the frozen hard segments in interphase relax gradually, which make the T gh peak wide.…”

Nanostructured poly(urethane)s and poly(urethane-urea)s from reactive solutions of poly[styrene-b-butadiene-b-(methyl methacrylate)]-triblock copolymers

“…The process used is equivalent to a onestage synthesis for the polyurethane-urea, and the reaction between IPDI and MCDEA must be much faster than that with the oligodiol that bears secondary hydroxyl groups, resulting in isolated polyurea hard segments that rapidly phase-separate. After this point the stoichiometry is no longer balanced and the oligodiol is unable to react [34]. These separated hard segments can presumably be related with the clear areas in the TEM micrographs.…”

Multimodal polymer networks: design and characterisation of nanoheterogeneous PU elastomers

“…Because of the incompatibility of the components of segmented polyurethanes (PU), localised nanophase separation occurs, leading to the well recognised domain structure. The morphological complexity results in the domain formation due to the segregation phenomena on different levels 7,8) . By incorporation of multifunctional molecules the phase separation is hindered due to the branching and crosslinking during the polyaddition.…”