تغييرات انتالپي ژلاتين در زمان نگهداري در حالت شيشه اي

Enthalpy Relaxation of Gelatin in the Glassy State.

The glass transition temperature (Tg) and the melting temperature (Tm) of gelatin at water contents between 7 and 14% were measured using differential scanning calorimetry. The plasticisation of the polymer by water led to a decrease in Tg and Tm. The Tg of partially crystalline gelatin was higher than that of the amorphous one obtained by quenching from the melt. The enthalpy relaxation occuring during the ageing of gelatin in the glassy state was studied for different structures (partially crystalline or amorphous), water contents and ageing temperature (Ta). The extent and rate of this relaxation associated with physical ageing were found to increase when the shifted temperature parameter (Ta-Tg) increased. This parameter was able to account for the effects of structure, water content and ageing temperature.