Thermal Creep Phenomena of PET Base Film by Thermal Pulse

Abstract

It has been recently attempted to improve the printing speed of Dye Diffusion Thermal Transfer (D2T2). However, it has been pointed out that the crease of printing film is caused in high speed printing. Therefore, it is necessary to investigate thermal creep properties of film heated by thermal pulse under weighting.
The thermal creep properties of four kinds of PET base films (A-D) was measured by the new method developed in our laboratory. Two types dependence of thermal creep on temperature were obtained in the measurement. All of four kinds of films indicate the thermal creep of type I i.e. elongation at low temperature and of type II i.e. shrinkage at high temperature. These thermal creep properties suggest that the crystal structure of PET base film changes from fringed micelle state to folding state at high temperature.
A and B strongly shrunk by thermal pulse when it was weighted to MD direction at high temperature. Otherwise C and D strongly shrunk by thermal pulse when it was weighted to TD direction at high temperature. There is the linear relation between dynamic data of shrinkage ratio (ΔFMD/ΔFTD) and static ratio (MD/TD) data measured by conventional method.
Hence, the dynamic thermal creep properties of the high polymer can be measured by our newly developed method.