| Popis: |
Results of investigations using DTA, TGA and dilatometry show that thermal decomposition of gelatine begins directly after supercontraction (≈210°), i.e. after transition of gelatine into the high-elastic state. Thermal oxidation in gelatine is most rapid on transition to the plastic state (>230°). The effect of low molecular weight substances on the thermal resistance of gelatine is observed first of all as a reduction of the transition temperature to the high elastic and plastic state. However, the initial weight loss sustained by gelatine films, independent of the temperature of super-contraction, corresponds to practically one temperature range (150–160°) which should, apparently, be considered the lower limit of thermal resistance of plasticized gelatine in the high elastic or plastic state. Thermal oxidation in gelatine in this temperature range is obviously promoted by functional groups of dehydrated gelatine. If in the temperature range of 150–160° gelatine continues to remain in the glassy state, on heating above this temperature processes of macromolecular crosslinking prevail and thermal oxidation is only suddenly accelerated when the gelatine changes into the high elastic state (above the temperature of supercontraction). |
