A study of evaluation method of the laminated film in low temperature aging process

Abstract

In this study, the aging process of a laminated film at low temperature below －100°C was examined on the basis of the accelerated test by the heat-shock cycle as well as the master curve of dynamic storage modulus. The component materials of the laminated film were nylon, polyethylene, aluminum foil and adhesive. When the laminated film was alternately exposed to the environmental temperature between －130°C to 25°C and vice versa for 1 cycle, the dynamic storage modulus of the film decreased with the number of heat-shock cycles. On the other hand, static mechanical properties such as static tensile modulus and strength as well as the coefficient of thermal expansion of the laminated film were not changed on the heat-shock cycle. The reason has not been cleared yet, though, it was deduced that degradation for the laminated film on heat-shock cycle can only be detected on the small deformation measured, not for large deformation process. Therefore, the dynamic storage modulus of the laminated film was employed to estimate the degradation process of the laminated film. Moreover, the dynamic storage moduli of each component of the laminated film were measured to calculate the master curves of the laminated film based on the rule of mixture. Then, the master curve measured for the laminated film was compared with the calculated master curve above mentioned. As a result, the master curve derived from the dynamic storage modulus was similar to that derived from the heat-shock cycle measurement. When comparing these master curves, degradation of laminated film for “one year” corresponded to the number of heat-shock cycles “70 cycles”. Finally, when compared the measured master curve obtained from the laminated film with the calculated master curve derived from each component, it was found that these master curves showed a good match within the range of the accuracy of a measuring apparatus (~10%).