GLASS-RUBBER TRANSITION IN STARCH-SORBITOL FILM

A b s t r a c t . Rheological behaviour of wheat starch-sor bitol films, obtained by the casting/ evaporation method from solution has been studied b y the dynamic mechanical-thermal analysis (DMTA). The dispersion curves of the storage and lo ss moduli have revealed characteristic sharply outlined glass transition in the temperature range of 270-300 K, with transition point Tg changing depending on the drying conditions and frequency of the tensile stress applied. The method of data transformation based on the theory of Williams-Landel-Ferry involving the frequency shift to superimpose the time-temperature dependence of viscoelastic properties has been used to produce a master curve for the starch-sorbitol film. K e y w o r d s : starch film, sorbitol, DMTA, glass transi tion, WLF equation