Spherulites in nylon 610 and nylon 66

The two types of spherulites in nylon 610 differ in birefringence, melting point, and rate of growth. The rates of growth depend strongly upon the degree of supercooling, and—at least for the positive spherulites—to a small extent on the molecular weight.

The rate curve for the positive spherulites has a singular point at 188°C. and appears to have a maximum in the neighborhood of 120°C. Concentric rings were observed in positive spherulites only after crystallization in the temperature range between 188° and 195°C. Positive spherulites formed near 180°C. have maximum birefringence.

Negative spherulites were observed only in specimens allowed to crystallize between 205° and 225°C. Three types of spherulites were observed in nylon 66. The large, positive, and highly birefringent spherulites have the same melting point, 273—274°C., as the negative spherulites.

The small positive spherulite with normal birefringence melt at 269.5—270°C. Simultaneous growth of all three types of spherulites was observed only between 250 and 255°C.