Blends PMMA/SAN

EOS models were derived for polymer blends that gave the first evidence of the severe pressure - dependence of the phase behaviour of such blends [41,42], First, experimental data under pressure were presented for the mixture of poly(ethyl acetate) and polyfvinylidene fluoride) [9], and later for in several other systems [27,43,44,45], However, the direction of the shift in cloud-point temperature with pressure proved to be system-dependent. In addition, the phase behaviour of mixtures containing random copolymers strongly depends on the exact chemical composition of both copolymers. In the production of reactor blends or copolymers a small variation of the reactor feed or process variables, such as temperature and pressure, may lead to demixing of the copolymer solution (or the blend) in the reactor. Fig. 9.7-1 shows some data collected in a laser-light-scattering autoclave on the blend PMMA/SAN [46],... 

For the blend PMMA/SAN-31.5 (code 31.5 wt% of AN in SAN) a phase separation temperature of 184 C has been observed for the quiescent 60/40 blend which shifted by about 10 K at a shear rate of 2 s 1 [118]. All the parameters occurring in Eq. (63) are known for the system under discussion except the quantity AN,. Thus, AN, can be estimated. Employing the individual segmental interaction parameters submitted in Ref. [6] one easily arrives at... 

Table 14.14. Aging parameters calculated from the C-F and P-M analysis of data obtained from PMMA, SAN (26.6 wt% AN) and their (50/50) blend PMMA/SAN at T = (T - 10 K)...

Fig. 12. Arrhenius plot of the apparent diffusion coefficient for PMMA/SAN-31.5(50/50)(31.5 wt% AN in SAN). The apparent diffusion coefficients results after temperature jumps from 210°C to different annealing temperatures below the LOST (cf. Fig. 1 la). Phase separation of the blend starts at 200 JC...

The influence of different capillary diameters and filling length were studied as were different kinds of optical observation methods. We found a pronounced decrease of the LCST cloud point temperature of this blend of PMMA/SAN with increasing pressure (3). 

These parameters have been found useful to predict miscibility of blends containing one component whose structure systematically varied, e.g., polyesters with either halogenated polymers or Phenoxy [Prud homme, 1982 Harris et al, 1983 Woo ei al, 1985 Woo et al, 1986], polyamide blends [Ellis, 1989], ternary blends [Shah et al, 1986] and other systems, viz. SAN/ PMMA, SAN/PC, polyethyloxazoline/polyester, PPE with a mixture of P(oClS) and P(pClS), PC/PCL/Phenoxy, and many more. 

There are fewer methods available to measure the interphase thickness, e.g., ellipsometry, microscopy, and scattering. A summary of the measured Al is given in Table 7.3. The temperature dependence of Al in PMMA/SAN and PMMA/PS blends is presented in Figure 7.6. More information on the fundamentals, methods of measurements, and numerical values of the interfacial ten-... 

Mechanical tests, molecular weight, and solubility measurements on irradiated PMMA/SAN blends showed that phenyl substitution in one of the polymers can offer partial radiation protection to the other component. Protective effects of the phenyl group are short range and occur only in miscible blends where mixing at the molecular level exists. However, the protection is not complete since some 15% of the yield for main chain scission in PMMA could not be suppressed, even at high styrene (in SAN) concentrations. 

Non-irradiated blends of PMMA/SAN showed composition dependence of the flexural strength. It was found that adding as litfle as 20 wt% of SAN to PMMA reduced the degradation effect of irradiation by a factor of 4. Irradiated PMMA showed random chain scission without cross-linking — G(scission) in /unolT for PMMA decreases from 0.12 at 100% PMMA, to 0.24... 

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... 

Figure 14.6. Comparison of the experimental enthalpy change on aging for t minutes, PMMA, SAN containing 26.6 wt% AN, and a 50/50 blend of these two polymers, with the theoretical curves derived from the Petrie-Marshall (PM) and Cowie-Ferguson (CF) models.

As long as the measuring time is short compared with the relaxation or retardation times the aging process can be studied effectively, and short-term stress-relaxation measurements have been carried out on blends of SAN/PMMA and PS/PPE [Ho et al., 1991]. Eq 14.13 was used to fit the data and the authors found that x could be expressed by ... 

CAR Cardelli, C., Conti, G., Gianni, P., and Porta, R., Blend formation between homo-and copolymers at 298.15 K. PMMA-SAN blends, J. Therm. Anal. Calorim., 71, 353,2003. 

Figure 1 shows the interfacial thickness X, measured by ellipsometry for the blend systems PS/PMMA, PMMA/SAN-5.7 and PMMA/SAN-38.7. The systems containing random copolymers show a relatively thick interface. This is caused by their small polymer-polymer interaction parameter Xab and will be discussed below. The interfacial thickness in the system PS/PMMA increases slightly with temperature. The value at 120 °C was obtained by neutron reflectivity and was taken from ref. 4. 

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... 

Figure 1 showed the temperature dependence of the interfacial thickness for PS/PMMA and two PMMA/SAN blends. Using equation (7) it is then possible to calculate the polymer-polymer interaction parameter Xab as a function of the temperature. The interaction parameter Xab between PMMA(A) and SAN(B) is then given by ... 

Cowie, J. M. G., and Ferguson, R., Physical ageing studies in a series of SAN copolymers and a blend of PMMA/SAN, presented at lUPAC, Montreal, 1991. 

PMMA/ABS In blends of PMMA and styrene-acrylonitrile (SAN) copolymers, there is a critical composition of the SAN, at approximately 28 wt % acrylonitrile, that marks the transformation fix>m miscibility to immiscibility with PMMA. Confirmation of this behavior is provided by the curves presented in Figure la for blends involving SAN containing 25 wt % and 30 wt % AN, respectively, obtained by conventional d.s.c. The matrix of ABS would be expected to behave in a similar manner. However, the presence of the strongly scattering polybutadiene dispersed phase in the ABS excludes optical scattering methods for the determination of phase... 

Figure 3.2. Comparison of the dCp/dr versus temperature data for a PMMA/SAN(50 50) blend from experiment (square points), theory (solid line) and from the Gaussian function...

Figure 3.12. Heat flow versus temperature data for (a) the miscible blend and (b) the physical mixture (PMMA/SAN, 50/50 (wt/wt)).

Figure 3.15 shows the glass transition temperatures plotted versus composition for these PMMA/SAN blends. This shows a positive deviation from linearity often observed for miscible blends and ascribed to specific interactions between segments [6,38]. 

Given the small positive values of A2, blends of PMMA/SAN, PVC/PMMA, PPE/PS, and PVME/PS are miscible. However, in each system, the value of A2... 

PMMA/SAN/SMA PEM/SAN/SMA MAN/SAN/SMA Samples were either cast from MEK or melt blended DSC at 20 °C/min Tg from the onset during the second heating cycle 5... 

Fig. 8.5 Shear rate dependence of cloud points in PMMA/SAN blends...

Fig. 8.6 Phase diagrams at various shear rates of PMMA/SAN blend. Phase diagram does not change more than y = 12 s ...

Fig. 8.7 Normalized shift in the cloud point curve Ar(y) / T(0) as a function of y for different compositions of the PMMA/SAN blends...

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