Dimensional Stability of Thermoplastic Starch Oriented Films

ABSTRACT Dimensional stability at different temperatures of oriented films of thermoplastic starch (TPS) obtained by blown extrusion and the structural changes that they undergo after heating were evaluated by means of X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The degree of orientation of the TPS and the shrinkage temperature were found to influence this property. However, the moisture absorption of TPS prevents the films from holding their shape at ambient conditions after orientation. Also, structural changes of the TPS could be seen when subjected to heat. These were associated with the increase in the relative crystallinity indices calculated by XRD and FTIR, and the increase in the fusion enthalpy. It was concluded that the dimensional stability of TPS films is affected by moisture absorption, which would limit the application as a shrink film.