Cloud point curves polymer blends

Lee MH et al. (2001) The effect of end groups on thermodynamics of immiscible polymer blends. 2. Cloud point curves. Polymer 42(21) 9163-9172... 

Fig. 5 Cloud point curves for blends of styrenic polymers with tetramethyl bisphenol-A polycarbonate.

Figure 9.7-1 Experimental cloud-point curve of the polymer blend Poly(methyl methacrylate)/Poly(styrene-co-acrylonitrile (28%AN)) as a function of pressure.

All the PCL/PC blends with 20-80 wt % PCL were crystalline and cloudy at room temperature. The blends became optically clear when heated (to about 60 °C) and the PCL melted. They then became cloudy again at temperatures of about 260 °C with the onset of liquid-liquid phase separation occurring as a result of LCST behaviour. For PCL-700 (Table 1) the cloud-point curve was fairly flat over much of the composition range but rose slightly (about 5 °C) in blends containing 80 wt % PCL [21]. In comparable experiments with PCL-300 (Table 1) the cloud point curve varied more strongly with composition and was raised with a critical point at about 272 °C. These observations were consistent with the normal enhanced miscibility of lower-molecular-weight polymers. 

Interaction parameters can also be calculated from values of the expansion coefficients of polymer blends 66) using Equation-of-state theories, or from values of the isothermal compressibility of the mixture B9>. They can also be obtained from measures of volume changes on mixing. The measure of a cloud point diagram itself can in principle be used to calculate an interaction parameter though the converse is usually done in that spinodal curves are simulated using interaction parameters. This will be discussed in a later section of this review. 

Fig. 10.38 Qualitative comparison between the theory and the experimental phase diagram (cloud points) for the PVA/PMMA polymer blend without fillers (filled diamonds) and with 10 wt% fumed silica (open squares). The two curves correspond to the spinodals calculated using equations. It is assumed that both PVA and PMMA had degrees of polymerization (N) 1,000 and that (pN) a + bT, with (a)-lO.O, (b) 0.026374. Finally, assumed that (F) 0.65. For the filled system, we took nanoparticle loading of 14 vol%, with the dimensionless particle radius (R) 20 (corresponding to the real- particle radius of 10 run) (Ginzburg 2005)...

In an amorphous polymer blend system, we can determine the phase boundary curve, i.e. a temperature versus composition phase diagram, by using DSC to follow the appearance of two separate T s at a certain annealing temperature. The phase diagram can also be obtained simply by optical observation. The temperature at which the first faint opalescence appears on heating is designated the cloud point. 

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