Measuring the Glass Transition of Latex-Based Polymers in the Hydroplasticized State via Differential Scanning Calorimetry

Polymers produced as aqueous-based latices arc always saturated with water, and the "wet" T(g) of these polymers can be significantly lower than the equivalent "dry" T(g) of the same polymers. The differential scanning calorimeter is a simple and effective tool to determine the wet T(g), and raw latex can be used without any special sample preparation. It is necessary, as always, to include a preheat step in the DSC procedure in order that the thermal scan produces quality data. We show that this technique can be performed in many temperature ranges, including temperatures well below the freezing point of water. Extension to the measurement of both thermal transitions for composite latex particles shows that the wet latex data, and information contained in them, can be quite different from the dried polymer data obtained from the same instrument. Special considerations are necessary for polymers with wet T(g)'s near the freezing point of water.