Styrene-acrylonitrile copolymer constants

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.)...

From TGA curves for a series of copolymers of varying molecular weights it was shown that at about 270 °C, a marked weight loss begins for each copolymer and the temperature corresponding to the maximum rate is almost identical for each sample. The weight loss of each copolymer is completed at about 390 °C. Thus, it appears that molecular weight has little effect on the thermal stability of the styrene-acrylonitrile copolymers studied when the acrylonitrile content is maintained constant for each sample. 

The tendency for alternation of monomers in a styrene-maleic anhydride and styrene-acrylonitrile copolymers at moderate temperatures has been attributed to the formation of a charge transfer complex (CTC) between a donor (D) and an acceptor (A). This CTC is readily detectable by UV or nmR spectroscopy. More important, the equilibrium constant decreases as the temperature is increased and this effect can be followed by instrumental analysis. Thus it is possible to extrapolate to a higher temperature at which the CTC does not exist (16). Thus, by proper temperature control, it is possible to produce SMA alternating copolymers, block copolymers of vinyl monomers with both alternating and random SMA (17) and completely random copolymers of SMA (18). Half esters of SMA have been used as viscosity control agents in petroleum crudes (19). 

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 Periodically the flask was removed from the bath, cooled and a sample withdrawn for GPC analysis.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. 

Indirect fluid beds have already proved efficient in drying very heat-sensitive polymers with large constant-rate drying periods, as in drying PVC, polyethylene, acrylonitrile-butadiene-styrene (ABS) copolymers, and polycarbonates (PC). 

Monomer compositional drifts may also occur due to preferential solution of the styrene in the mbber phase or solution of the acrylonitrile in the aqueous phase (72). In emulsion systems, mbber particle size may also influence graft stmcture so that the number of graft chains per unit of mbber particle surface area tends to remain constant (73). Factors affecting the distribution (eg, core-sheU vs "wart-like" morphologies) of the grafted copolymer on the mbber particle surface have been studied in emulsion systems (74). Effects due to preferential solvation of the initiator by the polybutadiene have been described (75,76). 

Compositionally uniform copolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) are produced in a free running batch process by virtue of the monomer reactivity ratios for this combination of monomers (r (TBTM) = 0.96, r (MMA) = 1.0 at 80°C). Compositional ly homogeneous terpolymers were synthesised by keeping constant the instantaneous ratio of the three monomers in the reactor through the addition of the more reactive monomer (or monomers) at an appropriate rate. This procedure has been used by Guyot et al 6 in the preparation of butadiene-acrylonitrile emulsion copolymers and by Johnson et al (7) in the solution copolymerisation of styrene with methyl acrylate. 

Similar results have been submitted on solutions of PMMA and poly(styrene-co-acrylonitrile) (SAN) in toluene [96], The components are miscible when the AN content in SAN ranges from 9.4 up to 34.4 wt% (window of miscibility). Only immiscible pairs were studied. An example of structure evolution in blend solutions, comprising copolymers of different AN content, in the course of annealing time at constant annealing temperature is shown in Fig. 15. The results can be summarized as follows ... 

MABS polymers (methyl methacrylate-acrylonitrile-butadiene-styrene) together with blends composed of polyphenylene ether and impact-resistant polystyrene (PPE/PS-I) also form part of the styrenic copolymer product range. Figure 2.1 provides an overview of the different classes of products and trade names. A characteristic property is their amorphous nature, i.e. high dimensional stability and largely constant mechanical properties to just below the glass transition temperature, Tg. 

After the formulas for rate constants are known, any diad sequence distribution can be calculated in the copolymer with an unknown composition from the dimer yields. The procedure has been studied for several copolymers including poly(acrylonitrile-co-m-chlorostyrene) [17], poly(styrene-co-glycidyl methacrylate) [19], poly(acrylonitrile-co-p-chlorostyrene) [17], poly(styrene-co-methacrylate) [20], poly(styrene-co-p-chlorostyrene) [18], and for other copolymers [14, 21-29]. 

Fig. 7. Plots of oxygen uptake against time [333] (a) linear, polymers that show no induction period but absorb oxygen at a relatively constant rate (polymethylmethacrylate, polystyrene, polycarbonate) (b) autoretardant, polymers that exhibit no induction period but initially absorb oxygen at a relatively rapid rate, followed by a slower steady rate (polyethylene, polypropylene, nylons) (c) polymers that display autocatalytic behaviour (the modified acrylics, acrylonitrile—butadiene—styrene copolymer) (d) polymers that can be considered a combination of autocatalytic and autoretardant, (c) and (d) can be considered as autocatalytic, since the processes usually become autoretardant in the later stages of oxidation.

Acrylonitrile/Butadiene/Styrene (ABS) Acry-lonitrile/butadiene/styrene (ABS) polymers are not true terpolymers. As HIPS they are multipolymer composite materials, also called polyblends. Continuous ABS is made by the copolymerization of styrene and acrylonitrile (SAN) in the presence of dissolved PB rubber. It is common to make further physical blends of ABS with different amounts of SAN copolymers to tailor product properties. Similar to the bulk continuous HIPS process, in the ABS process, high di-PB (>50%, >85% 1,4-addition) is dissolved in styrene monomer, or in the process solvent, and fed continuously to a CSTR where streams of AN monomer, recycled S/AN blends from the evaporator and separation stages, peroxide or azo initiators, antioxidants and additives are continuously metered according to the required mass balance to keep the copolymer composition constant over time at steady state. 

In this paper we will discuss evidence for the existence of CTC s of styrene and acrylonitrile and the resultant differences in the copolymer produced from them. We will also report the preparation of copolymers with block copolymer characteristics from poly(styrene-co-acrylonitrile) macroradicals prepared in tert-butyl alcohol. This solvent is a poor solvent for the macroradical and exhibits a very low chain transfer constant (28). The copolymers reported in this paper were prepared in the absence and presence of zinc chloride (ZnCU), and the effect of ZnClz on the reactivity of the macroradical will be discussed. 

Even random copolymers of ethylene and vinyl alcohol as well as of styrene and acrylonitrile follow Equation (21) see next paragraph (Kammer and Kressler, 2010). In reference Pefferkom et al., 2010, PVT data of the blend were determined that allowed for calculation of the left-hand side of Equation (21). Results for the blend under discussion are presented in Figure 9 as a function of blend composition. The data obey Equation (21) in fair approximation as long as PMA is in excess. But, the calculated value ofA 2.210 (J m kg ) is considerably lower than the value found by Sanchez. When PEO is in excess, quantity y Klpy is no longer constant, but becomes a function of composition and eventually approaches A = 2.78 10 (J m kg ). ... 

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