Aromatic polyureas

Example 5. Glycolysis of Polyurethanes with Propylene Oxide after Pretreatment with Ethanolamine.55 A rigid polyurethane foam (ca. 100 g) was dissolved in 30 g ethanolamine by heating. Excess ethanolamine was stripped, leaving a clear solution. Infrared and GPC analysis indicated that the clear solution obtained contained some residual polyurethane, aromatic polyurea, aliphatic polyols, aromatic amines, and N,N -bis(f -hydroxyethyljurea. Next the mixture was dissolved in 45 g propylene oxide and heated at 120°C in an autoclave for 2 h. The pressure increased to 40 psi and then fell to 30 psi at the end of the 2-h heating period. The product was a brown oil with a hydroxyl number of485. 

Perez, Jr., A. and Johnston, J. A., Performance and processing enhancements of aromatic polyurea elastomer systems prepared from high 2,4 -MDI isocyanates, presented at Polyurethanes... 

R.C. Schucker, Highly Aromatic Polyurea/Urethane Membranes and Their Use of the Separation of Aromatics from Non-aromatics, US Patent 5,063,186, 5,055,632 and 4,983,338 and many others. 

The first three, polyethers in the form of the soft segment of segmented polyurethanes, are described in detail in another chapter in this volume (6), as is the ninth of the list, identified as aromatic polyurea, an... 

FIGURE 5 Structure of aromatic polyurea with urea bond of dipole moment 4.9 debye. 

Takahashi, Y., Ukishima, S., lijima, M., and Fukada, E., Piezoelectric properties of thin films of aromatic polyurea prepared by vapour deposition polymerization, J. Appl. Phys., 70, 6983-6987 (1991). 

Besides P (MDA/MDl), different aromatic polyureas were synthesized by combining different diamine monomers with MDl monomer. The diamine monomers used were 4,4 -diamino diphenylmcthane (MeMDA), 4,4 -diamino diphenyl ether (ODA). and 4,4 -dia-mino diphrayl ihioether (SDA). 

X. S. VMug. M. fijima. Y. Ikkahashi, and E Fukada. Dependence piezoelectric activities of aromatic polyurea thin Alms on monomer composition ratio. Jpn. J. AppL Fkyt. ShZTtS (1993). 

Y. Ihkahashi. S. UUshima, M. lijima. and E Fukada, Piezoelectric properties of thin Alms of aromatic polyurea prepared by vapor deposition polymerization. J. AppL Pkys. 7)9 6983 (1991). 

S. Iksaka, K. Ohisbi. H. S. Nalwa, T. Watanabe, and S. Miyata. Ferroelectric polarization reversal stabilized by hydrogen bonding in N-phenylated aromatic polyurea. Polymer J.. 26 505 (1994V... 

H. S. Nalwa, T. IMitanabe, A. Kakuta, A. Mukoh. and S. Miyaia, N-Phcnylaied aromatic polyureas A new class of nonlinear optical materials exhibiting large second harmonic generation and u.v. transparency, Polymer 34 637 (1993)... 

R S. Nalwa. T. IMtanabe. A. Kakuta. and S. Miyata. (1993) Aromatic polyureas a new daas of chromophore main-chain polymers for second-order nonlinear optics. Nonlinear Optics. 8 137(1994)... 

The preparation of thin films of aromatic polyurea has been made possible by using the metlmd of vapor deposition pdymerizatioo. By the usual solution polymerization method, the product is in tite form of solid powders. Because of strong insolubility, it has not been possible to prepare very thin films of polyurea. 

Water On contact with water, aromatic polysubstituted ureas are formed, and carbon dioxide plus heat are evolved. In time, white aromatic polyurea crystals will precipitate. 

K a sample is taken through this valve, first flush out 1-5 gal of TDI (for proper disposal procedure, see Handling Spills and Leaks below). Flushing ensmes that a representative sample is being taken. This is particularly important in determining if aromatic polyurea or dimer (white precipitate) is present. 

Whether indoors or outdoors, bulk storage tanks should be blanketed with nitrogen. Without this dry atmosphere, water vapor will react with the TDI to form solid aromatic polyurea, which can plug lines and foam machine heads. 

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