Reaction of nitrogen dioxide with linear polyurethane

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Abstract
Linear polyurethane has been exposed to nitrogen dioxide over a temperature range from 15 to 60°C at pressures of 20 and 2 mm Hg, respectively. Normal random‐chain scission of urethane links takes place accompanied by a limited amount of random crosslinking. These crosslinks are eventually irreversibly scissioned again. At the same time, carbon dioxide is evolved, and the infrared spectra of the polymer films change during exposure, indicating disappearance of urethane linkages and formation and decay of nitro and nitroso groups along the polymer backbone. The overall reaction is diffusion‐controlled at least down to a film thickness of 10 μ. All energies of activation of the various processes are relatively small as expected for a diffusion controlled process. Tentative mechanisms have been proposed agreeing well with experimental results.

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