The structural interpretation of DSC curve specificity of poly(caprolactam) fibers. I. The specificity of the element of the curve observed in the temperature range ∼40-65°C

The index τ determined from the thermogram was correlated with the selected parameters of the amorphous material structure of polycaprolactam fibers. The investigated structural parameters were as follows: (a) the orientation factor determined by infrared absorption spectroscopy, based on the absorption band at 1130 cm−1; (b) the fraction of taut tie molecules calculated on the basis of the determined axial elastic modulus and volume crystallinity of the fiber. The occurrence of straight‐line relations between the values of the index τ and the values of the investigated structural parameters was found out. The conclusion was formulated that the specificity of the investigated element of the DSC curve reflects the entropy transition rate. That transition, stimulated by fiber heating during the DSC experiment, consists of the increase of the disorder of taut tie molecules. Probably, the rate of that transition changes relatively to the magnitude of the stress affecting taut tie molecules.