Crystallinity changes evidence in modified and dyed Poly(ethylene terephthalate) films monitored by photothermal method.

The thermal properties of some modified poly (ethylene terephthalate)-PET f ilms were measured for a set of samples by changing preparation conditions such as temperature and time of surface modification (first step), and also time and temperature of dyeing (second step). Samples were modified with N ,N-dimethylacrylamide for incorporating the dye Blue Samaron HGS. From the results of thermal diffusivity and specific heat we were able to point that the PET film improved their heat conduction after dyed at temperature belo w 70 degreesC (glass transition) for a time of dyeing of 30 min. While for the set dyed above T-g the thermal diffusivity decreases drastically for a 6 hour swelling time. This behavior indicates microstructural variation fol lowed by cristallinity changes in the polyester chains, sensed by the therm al diffusivity. This crystallinity changes evidence was confirmed from x-ra y analysis.