CPS 758 Untersuchung des Mischungsgleichgewichts bin�rer Polymermischungen

Abstract

The phase diagram of a binary polymer blend can be derived from the glass temperatures Tg of the demixed phases under the following conditions:1. The Tg's of the pure components are sufficiently different from one another. 2. The Tg'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 temperature T.4. The equilibrium state at the temperature T can be frozen by quenching. These conditions are examined for mixtures of polystyrene (PS) and tetra methyl-bisphenol 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.Between Ts 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.

A miscibility study of ternary blends of polystyrene, tetramethylbisphenol-A polycarbonate, and poly(2,6-dimethyl-1,4-phenylene oxide)

“…In addition, this blend displayed single-Tg behavior (cf. conclusions regarding miscibility of PS/TMPC blends, as summarized in Tables I and II, compare favorably with the phase diagrams reported by Illers et al [9]. The present DSC results for the PS/TMPC binary blends indicate that, for out purposes, the observation of a single glass transition with Tg well-predicted by Equation (2) serves well as the criterion for phase homogeneity.…”

“…Published studies [6][7][8] on PS/TMPC blends have shown that this pair is miscible at lower temperatures but exhibits a lower critical solution temperature (LCST) in the vicinity of 230 °C. More recently, Illers et al [9] reported phase diagrams of PS/TMPC blends in which the molecular weight of PS was systematically varied; the phase separation process was shown to be reversible, in support of the thermodynamic miscibility at lower temperatures. As for the TMPC/PPO pair, previous DSC and density measurements I I{}] indicated clear immiscibility in the accessible temperature range.…”

“…Values of the interaction parameter (Zi2) between PS (1) and TMPC (2) were not reported in the literature previously. However, this parameter can be estimated from a series of bimodal curves constructed by Illers et al [9] for PS/TMPC blends of different PS chain lengths. For binary mixtt, res of polydisperse polymers, the value of the interaction parameter at the critical temperature (To) can be expressed as [32].…”

“…The critical temperatures were taken as the minima of a series of binodal curves reported by lllers et al [9]. Although the critical point is not always located at the exact extremum of the binodal curve [32], the present procedure should result in only insignificant errors in T~.…”

Mutual diffusion and thermodynamics in the blends of polystyrene and tetramethylbisphenol‐A polycarbonate

“…where ri is obtained from (7) In the above relation, T f , P," , and p' are the equation of state parameters and Mi is the molecular weight of species i. The total mixing interaction energy 8 ; was also given as where el2 is the nonspecific mer-mer interaction between mer 1 and mer 2 and the additional energy attributed to the specific interaction fspecific was obtained…”