Glass Transition Temperature of Nylon 6

Studies of nylon 6 of various relative lengths have been made by measuring the sonic modulus and length as functions of temperature from -50°C to 180°C. Conclusions based on these data indicate that the transition of dry nylon 6 yarn from a glass to rubberlike material takes place in two discrete steps, one centering about -50°C and the other starting at 70°C. Between these two steps, nylon 6 behaves like a ductile material, neither glassy nor rubberlike. The lower step in this transition is a result of attainment of sufficient thermal kinetic energy to permit rotational and translational motion of short-chain segments between completed hydrogen bonds in the amorphous regions. The upper step at 70°C is postulated to be the temperature at which the completed hydrogen bonds become sufficiently weak to allow motion of greater segmental lengths.

Moisture in nylon 6 yarn is an effective plasticizer between 25°C and 100°C. However, it raises the temperature of the first step in the glass transition by interfering with segmental motion.