Chemistry and Properties of Crosslinked Polymers by S. S. Labana (Auth.)

By S. S. Labana (Auth.)

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SUMMARY A series of novel AB-type polyurethanes, each containing an in-chain phenylene unit, have been prepared by the intermolecular reaction of the intermediate hydroxy isocyanates generated from the Curtius reaction. When a 5-membered ring (benzoxazolinone) could be formed, intramolecular reaction occurred exclusively. When 6-membered rings (benzoxazinones) could be formed, both intramolecular and intermolecular reactions occurred, with the former predominating. If only 7-membered rings (benzoxazepinones) could be formed, or if ring formation was precluded by using p-phenylene substituted precursors, intermolecular reaction occurred exclusively.

8. K. Soga, S. Hosada, and S. Ikeda, Makromol. , 175, 3309 (1974). 9. Y. Iwakura, K. Hayashi, and K. Iwata, Makromol. , 89. 214 (1965). LINEAR AND CROSSLINKED AB-TYPE POLYURETHANES 47 10. Reference 1, Chapters 4 and 5. 11. H. Lindemann and W. , 451, 241 (1926). 12. W. G. Bywater, W. R. Coleman, 0. Kamm, and H. H. Merrit, J_. Amer. Chem. , 67, 905 (1945). 13. H. K. Hall and A. K. Schneider, J_. Amer. Chem. Soc. , 80, 6409 (1958). 14. G. Barger, J_. Chem. S o c , 85, 286 (1904). 15. H. Lindemann and W.

The polyamines and polyamides are most reactive toward glycidyl ether epoxy resins, most amines can cause dermatitis and many are toxic; the cured products have poor electrical properties. Epoxy resins crosslinked with carboxylic acid anhydrided have good electrical and heat aging properties, but very long cure times and high cure temperatures are required to obtain these properties. The working life stability of epoxy-anhydride resins is usually less than one month at room 49 50 MARK MARKOVITZ temperature.

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