Degradation and crosslinking in irradiated polyamides and the effect of oxygen diffusion

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Abstract
The changes in relative viscosity which occur when nylon 66 is irradiated with 2 m.e.v. electrons under an oxygen‐free atmosphere under various conditions have been observed. A mechanism is proposed which reconciles all of these observations, and on the basis of this postulated mechanism yields of chain breaks and crosslinks are calculated. The effect of the presence of a small concentration of a vinyl monomer (acrylic acid) in the polymer during irradiation on degradation and crosslinking is also considered. The rate of penetration of oxygen into irradiated polyamides has been measured. There is a marked reduction in penetration rate which results from the presence of free radicals in the fiber and the irreversible reaction which results. The data are treated by an approximate diffusion equation and estimates of true diffusion coefficients are given. The effect of filament diameter on the extent of degradation which occurs when fibers of nylon 66 are irradiated and then exposed to air has been investigated. The marked dependence of degradation on fiber thickness is related qualitatively to the data on rate of oxygen penetration.

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