Sub-Tg thermal properties of amorphous waxy starch and its derivatives
1994
Yuan, R.C. | Thompson, D.B.
The sub-Tg thermal properties of aged amorphous waxy starch, beta-limit dextrin, and amylopectin triacetate at low moisture contents were studied by differential scanning calorimetry (DSC). When Tg was above 50 degrees C (approximately 5-14% moisture), a 50 degrees C endothermic peak was observed in waxy starch and beta-limit dextrin samples. The delta H of the 50 degrees C peak was proportional to the moisture content. At a similar moisture content the delta H of beta-limit dextrin was greater than that of waxy starch. No 50 degrees C peak was observed in the amylopectin triacetate samples at the moisture contents studied (approximately 0.5-5% moisture), All amylopectin triacetate samples showed an endothermic overshoot associated with the glass transition. It is suggested that water-hydroxyl group interactions may be required for the formation of the sub-Tg peak. The 50 degrees C endotherm is a separate event different from the aging peak associated with the glass transition seen in many polymers.
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