Styrene - acrylonitrile copolymers Fractionation

Glockner, G., van den Berg, J. H. M., Meijerink, N. L., Scholte, T. G. Characterization of copolymers chromatographic cross-fractionation analysis of styrene-acrylonitrile copolymers , in Kleintjens, L., Lemstra, P. (ed) Integration of Fundamental Polymer Science and Technology , Elsevier Applied Science Publ., Barking, UK (1986), p. 85... 

Figure 12.8 Microcolumn size exclusion chromatogram of a styrene-acrylonitrile copolymer sample fractions transferred to the pyrolysis system are indicated 1-6. Conditions fused-silica column (50 cm X 250 xm i.d.) packed with Zorbax PSM-1000 (7 j.m dty, eluent, THF flow rate, 2.0 xL/min detector, Jasco Uvidec V at 220 nm injection size, 20 nL. Reprinted from Analytical Chemistry, 61, H. J. Cortes et al., Multidimensional chromatography using on-line microcolumn liquid chromatography and pyrolysis gas chromatography for polymer characterization , pp. 961 -965, copyright 1989, with permission from the American Chemical Society.

Of the styrene copolymers used for food packaging the styrene-acrylonitrile copolymer known as SAN still needs to be mentioned. SAN copolymers possess better mechanical properties and better resistance to oils and aroma compounds than PS. Copolymers with acrylonitrile fractions of 20-35 % find uses as household and camping dishes. Copolymers with a higher acrylonitrile content (> 60%) have earned particular importance as barrier plastics. With an increasing acrylonitrile fraction, the gas permeability decreases sharply. 

Lovric L and Res INA (1969) Fractionation of styrene-acrylonitrile copolymers. J Polym Sci, Part A-2 7 1357-66. 

Teramachi S and Fukao T (1974) Cross fractionation of styrene-acrylonitrile copolymer. Polym J 6 532-6. 

Good agreement with equation (12.5) was also obtained by Narkis and Nicolais (1971), who studied the effect of glass bead concentration on styrene-acrylonitrile copolymers at 110°C, a temperature close to the glass temperature, the best lit being obtained with equation (12.6d) to represent ij/Vf. As expected, the filler shifted the relaxation curves to longer times, in proportion to the volume fraction of filler—an observation consistent with reported increases in 7 (see below). 

Superposition techniques may also be used to correlate stress-strain behavior in the rubbery state. In their study of styrene-acrylonitrile copolymers filled with glass beads, Narkis and Nicolais (1971) obtained stress-strain curves at temperatures above 7. Stress-strain curves were plotted for different fractions of filler, and in terms of both the polymer and composite strain. At a given strain, the stress increased with increasing filler concentration, as expected. It was possible to shift curves of stress vs. polymer strain along the stress axis to produce a master curve (Figure 12.12). In addition to the empirical measurements, an attempt was made to calculate stress-strain curves from the strain-independent relaxation moduli (see Section 1.16 and Chapter 10) by integrating the following equation ... 

Figure 12.11. Yield stress vs. a-rB for styrene-acrylonitrile copolymers containing diiferent concentrations of glass beads (T r = 24°C the numbers on the curves give Vf, the volume fraction of filler). The upper curve corresponds to equation (12.25) with constants A and B equal to 1.0 x 10 and 3 x 10, respectively it also corresponds closely to estimated values of a,., the yield stress of unfilled polymer. (Nicolais and Narkis, 1971.)...

The styrene-acrylonitrile copolymers and block copolymers were characterized by selective solvent fractionation, NMR, pyrolysis gas chromatography, and differential scanning calorimetry. 

Ternary blend using binary interaction model Gan et al. [18] found for certain copolymer compositions and volume fractions the ternary blend system of styrene acrylonitrile copolymer (SAN), polycarbonate (PC) homopolymer and polycaprolactone (PCL) was completely miscible. Develop the expression for binary interaction energy B for the ternary blend using binary interaction model. Is the intramolecular repulsion in the copolymer sufficient to drive miscibility with two other homopolymers without any common monomers ... 

TEC is a useful technique for separating polymers into molecular weight fractions on a fairly small scale. It has been used to fractionate PET [135, 136], styrene-butadiene copolymers [137], styrene acrylonitrile copolymers [138], polyoxypropylene glycols [136], Nylon-styrene graft copolymers and PMMA [139-141], styrene-methacrylate copolymers [142], poly-a-methylstyrene [143], polyvinyl acetate-styrene copolymers, and polyvinyl alcohol-styrene copolymers [144]. 

Laser Raman spectroscopy has been proposed as a useful technique for probing the microstructure of copolymers. Good correlations were found between the concentrations of some isolated, dyad, triad and tetrad comonomer sequences in vinyl chloride/vinylidene chloride copolymers and certain scattering intensities [99]. The positions and intensities of particular absorption bands have also been correlated with chain microstructure in an infrared study of ethylene/vinyl chloride copolymers, previously characterised by C-NMR analysis [100]. More recently, FTIR spectra have been analysed for monad, dyad and triad monomer sequence-distribution dependencies in random styrene/acrylonitrile copolymers [101]. Changes in peak intensities from normalised spectra were correlated with microstructure probabilities assignments were given if there existed a linear relationship between peak intensity and the number fraction of a microstructure. 

For example, SSF and SPF were applied to styrene-acrylonitrile copolymer in either toluene [62] or a mixture of methyl ethyl ketone and cyclohexane [63] as solvent. These types of fractionation are also called one-direction fractionatiOTis. 

Styrene acrylonitrile copolymers have been fractionated by high performance... 

The CN bond stretching frequency was shifted to a higher value with an increase in the methacrylonitrile (MAN) content in the copolymers. There was no linear relationship between the CN frequency and the diad fraction of MAN-MAN linkages in the copolymer chain, as reported previously for styrene-acrylonitrile copolymers. Different methods for the copolymer sample preparation can cause differences in the shifts in the CN frequency. This suggests that the polymer morphology plays an important role. A study of blends of polymethacrylonitrile (PMAN) with polystyrene has shown that the CN frequency is shifted to a higher value with an increase of the PMAN composition of the blends. 

A commercially important example of the special case where one monomer is the same in both copolymers is blends of styrene—acrylonitrile, 1 + 2, or SAN copolymers with styrene—maleic anhydride, 1 + 3, or SMA copolymers. The SAN and SMA copolymers are miscible (128,133,144) so long as the fractions of AN and MA are neatly matched, as shown in Figure 4. This suggests that miscibility is caused by a weak exothermic interaction between AN and MA units (128,133) since miscibility by intramolecular repulsion occurs in regions where 02 7 can be shown (143) by equation 11. 

Ogawa T and Sakai M (1981) Column fractionation of acrylonitrile-styrene copolymers. J Polym Sci, Polym Phys Ed 19 1377-83. 

To demonstrate the livingness of styrene-acrylonitrile random copolymerizations, TEMPO (0.084 g) and BPO (0.101 g) were dissolved in 30 mL of styrene and 10 mL of acrylonitrile. The reaction mixture was stirred and purged with argon. The flask was sealed, lowered into a oil bath at 125 C and the mixture allowed to reflux. Periodically the flask was removed from the bath, cooled and a sample withdrawn for GPC analysis. To measure the composition of the copolymers, a series of polymerizations taken to low conversion were done in a Parr pressure reactor. The total moles of monomer were kept constant at 0.55, and the relative amounts of the two monomers were adjusted to vary the mole fraction of acrylonitrile from 0.1-0.9. 

Random copolymers of styrene/isoprene and styrene/acrylonitrile have been prepared by stable free radical polymerization. By varying the comonomer mole fractions over the range 0.1-0.9 in low conversion SFRP reactions it has been demonstrated that the incorporation of the two monomers in the copolymer is analogous to that found in conventional free radical copolymerizations. The composition and microstructure of random copolymers prepared by SFRP are not significantly different from those of copolymers synthesized conventionally. These two observations support the conclusion that the presence of nitroxide in the SFR process does not influence the monomer reactivity ratios or the stereoselectivity of the propagating radical chain. Rather, the SFR propagation mechanism is essentially the same as that of the conventional free radical copolymerization process. 

In experiments on immiscible blends, as noted by Dlubek et al. [2002], it is to be anticipated that the PALS parameters h and T3 will depend on the volume fractions and compositions of the three phases, as well as the effect of any interaction between the blend components. Such interactions have been identified in the studies of Wastlund et al. [1998] and Dlubek et al. [1999]. Thus, as pointed out above, the decrease in T3 observed by Wastlund et al. [1998] in 50 50 SMA24/SANx blends when the acrylonitrile content of the SANx increases from x=22% to x=33%, is interpreted as being due to increased interaction between the maleic anhydride and acrylonitrile groups. On the other hand, Dlubek et al. [1999] studied blends of an acrylonitrile-butadiene-styrene (ABS) copolymer and polyamide-6 (PA-6). This blend may be assumed to be quite heterogeneous, consisting of a two-phase structure having PA-6 crystals embedded in an amorphous ABS matrix and elastomeric... 

A range of polymer blends were investigated by Kirste et al. who found that most of the systems under investigation had positive Ai values. Only blends of polystyrene-acrylonitrile copolymer with differing styrene weight fractions were found to have. >4 2 less than zero. This would lead to phase separation at a sufficiently high molecular weight in these blends. 

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