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Curing and thermal behavior of poly(allyl azide) and bismaleimides
I.K. Varma, V. Choudhary, B. Gaur, , S. Oberoi, R. Chauhan
Published in
Volume: 101
Issue: 1
Pages: 779 - 786
The reaction of poly(allyl azide) (PAA; number-average molecular weight = 1800 g/mol) with N-phenyl maleimide, 4,4′-bis(maleimidodiphenyl) ether, 4,4′-(bismaleimidodiphenyl) sulfone, and 1,6-bismaleimido hexane is described in this article. As indicated by Fourier transform infrared studies, the azido group reacted with the highly electron-deficient olefinic bond of N-phenyl maleimide or bismaleimides in a 3 + 2 cycloaddition reaction under mild reaction conditions. The curing of PAA with bismaleimides (10-30 phr) was monitored with differential scanning calorimetry. In freshly prepared samples of PAA and bismaleimides, a broad exothermic transition was observed in the temperature range of 150-280°C and could be attributed to the loss of N 2 from PAA and the curing of bismaleimides. The heat of the exothermic reaction (ΔH) depended on the structure and composition and was in the range of 800-1413 J/g. Isothermal heating in an air oven at 40°C (2 days) followed by 60°C (5-6 days) resulted in the conversion of a sticky, viscous liquid into an elastic, nonsticky material. No significant difference in the ΔH values of uncured and cured samples was observed, and this indicated the reaction of fewer azido groups with the bismaleimides (dipolarophiles). In the thermogravimetry traces, a mass loss was indicated in the temperature range of 130-280°C due to the loss of nitrogen from the azido group. © 2006 Wiley Periodicals, Inc.
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