Many different materials are used for printing on polymer substrates. Often their performance depends on the glass transition of the printing material as this will influence the rate of drying, smudge resistance, colour-fastness etc. Performance may also depend on the properties of the substrate and, crucially, these properties after the print has been applied, i.e. beneath the print. The image below shows a topographic map of a polymer film that has some printing on it.

The results of the local thermal analysis at the selected points are show below. The smooth areas show the melting of the polyester. The strong DTA signal shows this to be a melting. The printed area, point 2, shows a softening at approximately 100°C. This is not a melting transition as the DTA signal is weak thus it is probably a glass transition. We then see the melting of the substrate beneath the coating and it is very similar to the uncoated areas. This demonstrates that the printing process has not affected its properties significantly.