Miscibility windows

Poly(ethyl methacrylate) (PEMA) yields truly compatible blends with poly(vinyl acetate) up to 20% PEMA concentration (133). Synergistic improvement in material properties was observed. Poly(ethylene oxide) forms compatible homogeneous blends with poly(vinyl acetate) (134). The T of the blends and the crystaUizabiUty of the PEO depend on the composition. The miscibility window of poly(vinyl acetate) and its copolymers with alkyl acrylates can be broadened through the incorporation of acryUc acid as a third component (135). A description of compatible and incompatible blends of poly(vinyl acetate) and other copolymers has been compiled (136). Blends of poly(vinyl acetate) copolymers with urethanes can provide improved heat resistance to the product providing reduced creep rates in adhesives used for vinyl laminating (137). 

Range of copolymer compositions in a polymer mixture, at least one component substance of which is a copolymer, that gives miscibility over a range of temperatures and pressures. Note 1 Outside the miscibility window immiscible mixtures are formed. 

Note 2 The compositions of the copolymers within the miscibility window usually exclude the homopolymer compositions of the monomers from which the copolymers are prepared. 

Note 3 The miscibility window is affected by the molecular weights of the component... 

Note 4 The existence of miscibility windows has been attributed to an average force between the monomer units of the copolymer that leads to those units associating preferentially with the monomer units of the other polymers. 

This dependence of the strength of the silanol self-association on the substituents provided an approach for tailor-made miscibility in their binary hydrogen bonded polymer blends.10 A miscibility window was formed for ST-VPDMS/PBMA blends when the copolymers contained 4 to 34 mol % silanol groups." As a direct result of reduced silanol self-association in ST-VPMPS copolymers, a extended miscibility window was formed when ST-VPMPS copolymers contained 9 to 56 mol % silanol groups.12... 

The miscibility gap will be described more accurately when a meanfield lattice gas approach is choosen [30], The mathematical form of the interaction function in all the above models may bring about a negative value for the effective interaction parameter, g, while all binary interactions by themselves are positive. The complexity of copolymer phase behaviour can be attributed to this peculiarity, like the miscibility-windows in mixtures of a copolymer with another homopolymer [37], or with a second copolymer [38,39]. 

Blends of poly(vinyl chloride) (PVC) and a-methylstyrene—acrylonitrile copolymers (a-MSAN) exhibit a miscibility window that stems from an LCST-type phase diagram. Figure 3 shows how the phase-separation temperature of 50% PVC blends varies with the AN content of the copolymer (96). This behavior can be described by an appropriate equation-of-state theory and interaction energy of the form given by equation 9. 

The interaction parameter / can also be estimated by the use of solubility parameters (8) / is proportional to (8M — 8TS)2. But this approach has a considerable error (A8 in the range of 0.4 MPa1/2), and considers only the excess free enthalpy. For these reasons it is better to determine the miscibility window experimentally. 

Suess M, Kressler J, Kammer HW (1987) The miscibility window of poly(methyl methacrylate) poly(styrene-co-acrylonitrile) blends. Polymer 28 957-960... 

Miscibility windows originate from a delicate balance of inter- and intramolecular repulsions. Figure 8 gives an example. The corresponding homopolymers are immiscible, but, not so PPO and the random copolymers in a certain range of copolymer composition. Experimentally determined miscibility windows are listed in Table 3. 

Fig. 8. Miscibility window of 40/60 blends of poly(o-chlorostyrene-rcm-p-chlorostyrene) and PPG O miscible, immiscible [40]...

In addition to blending with SPMI copolymers, PMI can be incorporated into ABS using mass, emulsion [46-50] or suspension [42] free radical polymerization techniques. The high heat ABS resin can be completely produced by mass polymerization, or mass polymerized PMI-SAN can be blended with (emulsion polymerized) SAN-grafted rubber concentrates and/or conventional mass ABS. Sumitomo Naugatuck determined an empirical relation for the compatibility of SAN/SAN-PMI blends based on the polar monomers in each component [51]. Figure 15.4 shows that the miscibility window with SANs becomes wider with increasing PMI level in the terpolymer [52]. 

We have demonstrated miscible blends of PET-PHB/PEI can be formed by rapid solvent casting from the mixed solvent of phenol and tetrachloroethane. The miscibility was confirmed by the systematic movement of Tg in the DSC studies. However, the blend is unstable and undergoes thermally induced phase separation with a miscibility window reminiscent of LCST. The dynamics of spinodal decomposition is non-linear in character and obeys the power law with kinetic exponents of -1/3 and 1 in accordance with the cluster dynamics of Binder and Stauffer as well as of Furukawa. In the temporal scaling analysis, the structure function exhibits universality with time, suggesting temporal self-similarity of the system. 

Scheidgen, A.L. Schneider, G.M. Fluid phase equilibria of (carbon dioxide plus a 1-alkanol plus an alkane) up to 100 MPa and T = 393 K cosolvency effect, miscibility windows, and holes in the critical surface. J. Chem. Thermo. 2000, 32, 1183-1201. 

After experimentally confirming validity of this idea, the principal authors attempted to use this approach for explanation of the so call miscibility windows [Paul and Barlow, 1984]. The latter term refers to either polymer/copolymer blends that show miscibility only within a limited rage of the copolymer composition [viz. Balazs et al., 1985 Fernandes et ah, 1986 Goh and Lee,... 

The segmental interaction parameters have been also used to explain the miscibility window or miscibility chimney in polymer/copolymer or copolymer/copolymer blends [Lath and Cowie,... 

The phenomenon appears to be similar to the so-called miscibility window in some blends with random copolymers [ten Brinke et al., 1983]. Microphase separation and the evolution of the multiblock copolymer phase in the form of smallsized particles (up to 100 nm in diameter) is the physical basis of their transparency. Thus, these transparent blends are considered micro-heterogeneous systems [Papkov et al., 1998]. Detailed theoretical and experimental investigations are required to understand details of this phenomenon [Sikora and Karasz, 1993]. 

A more comprehensive study of this system has been carried out by Cowie and Ferguson [1991]. These authors followed the enthalpy and stress relaxation of a series of PMMA/SAN blends with SAN compositions spanning the miscibility window, i.e., from 13.3 to 30 wt% AN. It was found that the blends relaxed faster than either of the components, when aging temperatures were (Tg - T ) = 10°C, but that this was no longer the case at (Tg - T ) = 20°C where blend aging was intermediate to both components. The data were analyzed using both the P-M and C-F approaches and examples of AH(t, T ) vs. log t plots are shown in Figure 14.6. The C-F model... 

MiscihUity detection Miscibility vs. flow Miscibility window Miscibility... 

Furthermore, it is interesting to study also the interfacial thickness in the system PMMA/SAN-38.7 by ERD. As already discussed, using a copolymer composition just outside the miscibility window generates an extremely small interaction parameter Xab in blends with PMMA. Because of the relation X Xab it can be seen that a small X parameter yields a large interfacial thickness X. Figure 7 shows an example of a contour plot for the system SAN-38.7/PMMA. In this configuration a thin PMMA film is on top of... 

M. Suess, J. Kressler, and H.W. Kammer, The miscibility window of polyfmethyl methacrylate) /... 

EFFECT OF SPECIFIC INTERACTION ON MISCIBILITY WINDOWS OF PVC/SAN S COPOLYMER BLENDS... 

The change of miscibility window in the blends of PVC with the serise of SAN s copolymer was studied by DSC. In the case of the blend of PVC with SAN had been already reported by other resercher (2). As shown in the Table 1 and 2, the blend of PVC with a SAN is found to have the broadest miscibility window, in which the AN composition of a SAN is from 18 wt% to 51 wt /o. The blend of PVC with MSMAN show the miscibility in which MSMAN copolymer had AN composition from 27 wt% to 46 wt%. 

PVC/aSAN system has shown the broadest miscibility window among the series of SAN s copolymer for FVC/SANs blends. It seemes to be caused by specific interaction between the nitrile group of acrylonitrile and othydrogen of PVC. 

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