Some aspects of the crystallization of nylon 66 (polyhexamethylene adipamide)

A study has been made of crystallization phenomena in nylon 66 occurring after fusion at temperatures just above the melting point. It appeared to be possible to obtain optically negative spherulites in nylon 66 by crystallizing at temperatures between 250 and 258°C., after fusion at temperatures above 258 but below 265°C. The radial growth rate of the negative spherulites has been determined and has been found to depend on the crystallization temperature. The optically negative spherulites have a higher optical melting point than the optically positive spherulites hitherto observed in nylon 66. Another type of spherulitic structure with spherulites of a fibrous appearance, of which the optical sign cannot be determined, is reported. An attempt is made to explain the data obtained on the basis of the generally accepted crystallization mechanism, valid for linear high polymers.