Kinetics for the Degradation of Nylon and Kevlar Parachute Materials

摘要

The degradation of nylon 66 and Kevlar 29 yarns at elevated temperatures and over a broad range of humidities was studied and a rate relationship developed which models the degradation and permits computation of rate constants. The degradation rates are slow initially due to the presence of an inhibitor but increase rapidly as the inhibitor is depleted. The effect of relative humidity (RH) can be very large especially at values in the 100% range. An exponential relationship exists for nylon between the rate constant and RH. Kinetic parameters were evaluated and the rate constants at 25 sup 0 C calculated. These values showed that the tensile strength of nylon 66 will remain at a safe level over a 25-year period if the humidity is maintained at the 10% range or less. Kevlar 29 is more resistant and can tolerate humidity levels in the range of 90% or less. Degradation is governed by thermal-oxidative and moisture induced mechanisms. At the very high humidities the moisture induced degradation predominates. A relationship is developed which predicts the degradation rate over a very broad range of temperatures and humidities. (ERA citation 11:051367)