Oxidative aging polyurethane foam

Three methods that were used to measure the chemical changes associated with oxidative degradation of polymeric materials are presented. The first method is based on the nuclear activation of lsO in an elastomer that was thermally aged in an, 802 atmosphere. Second, the alcohol groups in a thermally aged elastomer were derivatized with trifluoroacetic anhydride and their concentration measured via 19F NMR spectroscopy. Finally, a respirometer was used to directly measure the oxidative rates of a polyurethane foam as a function of aging temperature. The measurement of the oxidation rates enabled acceleration factors for oxidative degradation of these materials to be calculated. 

The oxidation rates measured by the respirometer were used to calculate acceleration factors for the oxidative aging of the polyurethane foam. The oxidation rates at each temperature were averaged and used to calculate acceleration factors that were normalized to 1.0 at 95°C. The results versus inverse temperature are shown in Figure 7. The acceleration factor plot exhibits some curvature in the lower temperature region of the curve. The activation energy of the relatively linear region between 50 and 110°C is 92 kJ/mol. 

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