CPS 758 Untersuchung des Mischungsgleichgewichts binärer Polymermischungen

Abstract

The phase diagram of a binary polymer blend can be derived from the glass temperaturesT _g of the demixed phases under the following conditions:

• 1. The T_g's of the pure components are sufficiently different from one another.

• 2. TheT _g 's of the one-phase homogeneous mixtures can be determined and vary monotonically with composition.

• 3. The equilibrium state of the mixture is attained after sufficient long annealing at temperatureT.

• 4. The equilibrium state at the temperatureT can be frozen by quenching.

These conditions are examined for mixtures of polystyrene (PS) and tetra methyl-bis-phenol A-polycarbonate (TMPC). The phase separation kinetics is investigated with respect to size and composition of the co-existing phases. The co-existance curves (binodal with lower critical point) are determined for mixtures with various molar masses of the PS component. The problems concerning the cloud point curves are shortly discussed.

BetweenT _g and the binodal the one-phase mixtures exist in a hindered thermodynamic state, because the crystallization of the TMPC component is a very slow process which requires very long annealing. With increasing amounts of PS in the mixture the crystallization half time of TMPC is lowered.