Bulk copolymerization of styrene

To study the bulk copolymerization of styrene n-butyl methacrylate both conventional and unconventional GPC analyses were used. The normally obtained chromatograms, (from dual U.V. detectors) primarily provided area ratios intficative of composition as a function of retention volume. However, even this information was only obtainable after average compositions had been otherwise determined. Furthermore, in general, since the GPC normally separates on the basis of hydrodynamic volume, the polydispersity of aU polymer molecular properties at e h retention time is of serious concern. 

Figure 1. Free radical bulk copolymerization of styrene...

Table 6.3 Summary of reactivity ratios determined by various methods for the bulk copolymerization of styrene with methyl a-hydroxymethyl acrylate at T = 80 °C [226]...

Table 6.5 Experimental dependences of fractions of triads centered by methyl methacrylate unit and MMA characteristic coefficient (6.15) on monomer feed composition for bulk copolymerization of styrene with methyl methacrylate at T = 60 °C [80]...

Unfortunately, as far as the author knows, there are only a few publications where the problem of the validity of this or that model over a wide range of conversions and initial monomer feed compositions was discussed carefully enough. Here one might mention the works listed as Refs. [310,201] on the bulk copolymerization of styrene and heptyl acrylate, where the adequacy of the terminal model was undoubtedly proved, and its parameters rj = 0.87 and r2 = 0.27 were estimated. Really, the calculated copolymer composition and monomer feed composition drift with conversion are in full agreement with both NMR (Table 6.9) and UV (Fig. 18) data. 

The measurement of bulk copolymerization of styrene (Mi) and methyl methaciylate (M2) at 30°C in a feed of 0.031 mole fraction styrene with initiation by photosensitized decomposition of benzoyl peroxide gave a value... 

A number of studies have attempted to model this process stage by stage and to determine the values of some kinetic constants. Thus, in112 the researchers investigated the initial stage of isothermal bulk copolymerization of styrene with polybutadiene in the presence of di-tert-butyl peroxide. 

In the study113) an attempt was made to model the whole process of thermal bulk copolymerization of styrene with polybutadiene up to high degrees of conversion. The calculations were based on the previously developed model of thermal bulk polymerization of styrene and supplemented with the reactions of chain transfer to rubber. 

To give an example of reduced activity of PVGs, papers [45, 46] can be mentioned where hydrodynamic properties of the products of bulk copolymerization of styrene with 0.4% DVB (without removing the inhibitor ieri-butylcatechol) have been examined. If the copolymerization was ideal, one DVB molecule, surrounded by 250 styrene units, would form a tetrafunctional branching point in the macromolecule and the molecular weight of a chain between two branching points should be as high as... 

Jaisinghani and Ray (40) also predicted the existence of three steady states for the free-radical polymerization of methyl methacrylate under autothermal operation. As their analysis could only locate unstable limit cycles, they concluded that stable oscillations for this system were unlikely. However, they speculated that other monomer-initiator combinations could exhibit more interesting dynamic phenomena. Since at that time there had been no evidence of experimental work for this class of problems, their theoretical analysis provided the foundation for future experimental work aimed at validating the predicted phenomena. Later studies include the investigations of Balaraman et al. (43) for the continuous bulk copolymerization of styrene and acrylonitrile, and Kuchanov et al. (44) who demonstrated the existence of sustained oscillations for bulk copolymerization under non-isothermal conditions. Hamer, Akramov and Ray (45) were first to predict stable limit cycles for non-isothermal solution homopolymerization and copolymerization in a CSTR. Parameter space plots and dynamic simulations were presented for methyl methacrylate and vinyl acetate homopolymerization, as well as for their copolymerization. The copolymerization system exhibited a new bifurcation diagram observed for the first time where three Hopf bifurcations were located, leading to stable and unstable periodic branches over a small parameter range. Schmidt, Clinch and Ray (46) provided the first experimental evidence of multiple steady states for non-isothermal solution polymerization. Their... 

Figure 4 Triad fractions for bulk copolymerization of styrene and acrylonitrile at 60 C. Xs = mole fraction S in the monomer A = styrene centred triads, B = acrylonitrile centred triads penultimate model----. ...

Some effect of viscosity on r has been observed [Kelen and Tudos, 1974 Rao et al., 1976]. Copolymerization of styrene (Mil-methyl methacrylate (M2) in bulk leads to a copolymer containing less styrene than when reaction is carried out in benzene solution [Johnson et al., 1978]. The gel effect in bulk polymerization decreases the mobility of styrene resulting in a decrease in r and an increase in r%. 

Example 13.6 The following data were obtained using low-conversion batch experiments on the bulk (solvent-free), free-radical copolymerization of styrene (X) and acrylonitrile (Y). Determine the copolymer reactivity ratios for this polymerization. 

Although the criterion for an anionic initiator given above is very useful, it is now known that other complicating factors can arise. O Driscoll and Tobolsky (79,80) have investigated the copolymerization of styrene and methyl methacrylate using lithium in bulk and in various ratios of tetrahydrofuran and heptane. In all of these systems the authors found considerably more than the less than 1% styrene reported for sodium and potassium. In fact as much as 33% styrene is... 

An analogous analysis of the solution copolymerization of styrene with acrylonitrile in toluene leads [283] to the same conclusion concerning the choice of the kinetic model as for the bulk copolymerization of these monomers. The applicability of the penultimate model (2.3) was also convincingly proved [283] for the given system, and the estimated values of its four parameters (2.4) (see Table 6.8) were found to be slightly different from the ones obtained in the bulk copolymerization [283], The experimental values of the fractions of all six triads, determined by means of NMR, in the solution copolymerization products, practically do fit the theoretical plots of the triad fractions vs conversion, which were calculated on the basis of the kinetic parameters presented in Table 6.8. 

Problem 7.16 Bulk polymerization of styrene in the presence of 1 g/L of AIBN initiator at 60°C gave a measured polymerization rate of 5.92 mol/L-s. Predict the rate of copolymerization at 60°C of a mixture of styrene (Mi) and methyl methacrylate (M2) with 0.579 mole fraction styrene and the same initial concentration of the initiator as in the homopolymerization case. Compare the rates predicted from chemical control, diffusion control, and combined models with the experimental value of 4.8x10 mol/L-s [25]. Use relevant kp and kt values for homopolymerization from Table 6.7 and assume 0 = 15. [Other data ri = 0.52, T2 = 0.46 monomer density = 0.90 g/cm .]... 

Spontaneous copolymerization of styrene and maleic anhydride in the presence of a molten polymer or a bulk polymer undergoing deformation at elevated temperatures is a rapid and convenient route for carboxylating polymers. The reaction is carried out on the bulk polymer at 120° to 200°C. (depending upon the softening or melting point of the polymer) by injecting an equimolar solution of maleic anhydride in styrene into the molten polymer (II, 12). 

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. 

Webb S. Bulk thermal copolymerization of styrene and acrylic acid in continuous flow reactors [dissertation]. Hamilton McMaster University 1985. 

Figure 22-4. Graphical evaluation of linear copolymerization equations after Fineman-Ross [Equation (22-25)] and Kelen-Tiidos [Equation (22-28)], for the free radical copolymerization of styrene with methyl methacrylate in bulk at 6(f C.

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