Polyurethanes, dielectric analysis

It is important to note that values of tan 6 at 4 to 10 K for the OU sample coincide closely to those of the annealed PP-F. In both cases, the dielectric loss is lower than that for the unannealed PP-F. This may be attributed to a suppression of the 30 K peak in the former two samples. In short, this illustrates that the polypropylene layers in the laminates undergo changes during the lamination process that must be taken into account in an analysis of the relative contributions of the polypropylene and polyurethane to tan 6. 

Jonscher A K (1983) Dielectric Relaxation in Solids, Chelsea Dielectrics, London. 24. Vatahs A S, Kanapitsas A, Delides C G and Pissis P (2001) Relaxation phenomena and morphology in poljrmer blends based on polyurethanes investigated by various thermal analysis techniques, Thermochim Acta 372 33-38. 

The molecular mobility and microphase separation in blends of crosslinked polyurethane (PUR) and styrene-acrylonitrile (SAN) copolymer were investigated. The PUR and SAN copolymer were prepared by reactive blending with polymer polyols. DSC, thermally stimulated depolarisation currents (TSDC) techniques, dielectric relaxation spectroscopy (DRS) and dynamic mechanical thermal analysis over a wide range of... 

For the identification of space effects on polymers, numerous standard tests must be used, namely spectroscopy, thermal analysis, dielectric and conductivity measurements, mechanical and viscoelastic property determination, etc. In the late 1990s NASA decided to substitute polyurethane coatings (having carcinogenic) with another one. The 18 alternative candidates were subjected to 34 standard test procedures (Table 3.7). In the following report the number of candidates fell to eight, from which the best with the lowest cost-to-performance ratio will have to be selected. This procedure illustrates how involved the polymeric testing for space application is, even if the test procedures are quite standard. 

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