Effect of gamma irradiation on thermophysical properties of plasticized starch and starch surfactant films

• The films were prepared basing starch, surfactant and glycerol.
• Two glass transitions were observed showing an existence of two phase system.
• The first Tg of the starch–CTAB films shifts after irradiation to lower temperature.
• In all the other cases it shifts after irradiation to higher temperature.
• Differences in volatile fractions content are not important for the temperature shift.

In this work the influence of gamma irradiation on the thermomechanical properties of the films formed in potato starch–glycerol and potato starch–glycerol–surfactant systems were examined by Dynamic Mechanical Analysis, DMA, and Differential Scanning Calorimetry, DSC, and the results were correlated to the amount of the volatile fraction in the films.The starch was irradiated with a dose of 30 kGy. The films were prepared by casting from solutions with addition of 0, 20 and 30 wt% of glycerol. Two endotherms attributed to glass transitions were observed in water or glycerol plasticised samples, the first one shifting to higher temperature after irradiation. A similar shift was observed after irradiation of films prepared from starch–sodium laurate and starch–sodium palmitate systems, while a decrease in glass transition temperature was observed in the case of starch–cetyltrimethylammonium bromide films. Small differences in the content of the volatile fraction reached after the appropriate conditioning had no impact on the direction of temperature shift of Tg observed after irradiation.