Polymer morphology and random chain scission of nylon 66

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Abstract
Nylon 66 films with varying spherulite size but almost constant percentages of crystallinity were prepared (melt method). These films were degraded by NO2 over a range of temperatures from 35 to 65°C. Random chain scission took place except in the initial stages at low temperatures at which some crosslinking occurred. Observation of the films with the extent of degradation under polarized light revealed that dark bands developed around and also inside spherulite boundaries that became wider with the extent of degradation. This indicates that amorphous material is formed during random chain scission; the spherulites remained practically intact, however. The experimental chain scission rate constants did not change essentially with spherulite diameter until small diameters were reached, at which time the rate constants increased noticeably. Degradation can be accounted for by chain scission in amorphous and interfacial regions; in the latter the rate constants increased with this area and in addition main chain links were weaker in fold regions, due to strain energy, than normal ones in amorphous regions. The energy of activation for chain scission was compatible with a predominantly diffusion‐controlled process.

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