Morphological changes in nylon 6 and effect on mechanical properties. II. Dynamic mechanical properties

Abstract

AbstractDynamic mechanical measurements were carried out on nylon 6 film treated with heat and swelling agents to produce changes in the crystalline morphology. The original smectic hexagonal crystal form was changed by heat treatment and phenol treatment to an unoriented and oriented α‐crystalline form, respectively, and by I2/KI treatment to a preferentially oriented γ‐crystalline form. The behavior of the αa mechanical loss peak located at about +70°C was investigated in most detail. This peak was independent of frequency on the low‐temperature side of the peak but markedly frequency‐dependent on the high‐temperature side. The low‐temperature side of the peak probably represents a thermodynamically controlled “melting” or bond‐breaking process which frees molecular units to participate in a viscoelastic relaxation process which is the controlling factor in the high‐temperature side of the peak. Frequency‐temperature superposition of data from the high‐temperature side of the peak gave shift factor values which showed two straight‐line regions in the Arrhenius plot for the specimens containing some smectic hexagonal form, and a single straight line in the other cases. Activation energy values obtained were 30–50 kcal. The αa peak split into two components with an increase in absorbed phenol, indicating that two loss mechanisms corresponding to two noncrystalline phases (one amorphous and one more highly ordered or hindered) are involved.