Use the Q and e values listed in Table 7.4 for each of the comonomers to give five independent estimates of Q and e for acrylonitrile. Compare the average of these four with the values given for acrylonitrile in Table 7.4. [Pg.497]

Using the Q and e values in Table 6-7, calculate the monomer reactivity ratios for the comonomer pairs styrene-1,3-butadiene and styrene-methyl methacrylate. Compare the results with the r and rx values in Table 6.2. [Pg.543]

Regrettably, Q and e values are imprecise and tend to vary with the reactivity ratios used in their calculation (115). An attempt has been made to improve the Price-Alfrey equation by the assignment of different values of e to the monomer and to the radical derived from it (116). Schwan and Price (117) have reexamined the Price-Alfrey equation, and they write it in the form [Pg.122]

Greenley, R. Z., Q and e Values for Free Radical Copolymerizations of Vinyl Monomers and Telogens, pp. 267-274 in Chap. II in Polymer Elandbook, 3rd ed., J. Brandrup and E. H. Immergut, eds., Wiley-Interscience, New York, 1989b. [Pg.536]

These ethylene-based Q and e values may be used to calculate the reactivity ratios for the copolymerization of vinyl acetate with vinyl chloride. Agreement is good when these values are compared with experimental values. In Table IV reactivity ratios calculated from ethylene- and styrene-based Q and e values are shown. [Pg.57]

Using the tabulated Q and e values for any two monomers, one can calculate the and values from Eqs. (7.39) and (7.40) for this monomer pair whether or not they have ever been polymerized. [Pg.614]

On this basis, values of Q and e can be calculated for each monomer, so long as two arbitrary reference values are assumed. For this purpose Price took the values for styrene as Q = 1.0 and e = -0.8. Q and e values can then be obtained for all monomers that are copolymerizable with styrene. These monomers in their turn can serve as reference compounds for further determinations with other monomers that do not copolymerize with styrene. One of the main advantages of the so-called Q,e scheme is that the data can be presented in the form of a diagram instead of very complex tables of reactivity ratios. [Pg.235]

Table 7.4 Values of the Price-Alfrey Q and e Values for a Few Common Monomers |

Table III. Reactivity Ratios and Q and e Values for Ethylene-Vinyl Chloride and Ethylene-Vinyl Acetate Copolymerizations |

It appears that these ethylene-based Q and e values are capable of forming an internally consistent correlation scheme. It will be interesting to see whether this scheme is capable of yielding good results over the wide variety of monomers for which the styrene-based scheme has been so successful. [Pg.58]

The value of KgJKg can be determined also from Q and e values (36). The basic relationship (11) of the Q—e scheme (76) yields [Pg.46]

These are simply the equations of Alfrey and Price (1 j, which relate monomer reactivity ratios to Q and e values, and in which the reasonable values of 2 = and 2 = 1 re substituted, with the convention that the reference standard, ethylene, is monomer 2. In Equation 6 it is seen that the Qi value is simply a ratio of propagation rate constants unmodified by the presence of differences in e values, as is the case in the styrene-based scheme. This would seem to be a more desirable type of parameter to deal with, simply because its meaning is perfectly straightforward. [Pg.57]

VEs can also copolymerize by free-radical initiation with a variety of comonomers. According to the Q and e values of 0.023 and —1.77 (isobutyl vinyl ether), VEs are expected to form ideal copolymers with monomers of similar and e values or alternating copolymers with monomers such as maleic anhydride (MAN) that have high values of opposite sign (Q = 0.23 e = +2.25). [Pg.518]

Obviously the precision of this procedure is not very great, since the assumptions underlying the calculations of Q and e values can be regarded at best as semiquantitative. However, it has been shown that when the reactivity ratios are back-calculated from the Q,e values, quite good agreement is obtained with the experimental values, so that it is possible to make useful predictions of reactivity [Pg.235]

The application of NMR spectroscopy data to estimate the reactivity ratios is regarded to be very promising [272]. The Q and e values of the Alfrey-Price scheme may be immediately calculated analyzing the shifts of the corresponding bands in carbon-NMR spectra Such data obtained for more than fifty pairs of monomers are tabulated in Ref. [273]. A quite different method based on the application of the trivial expressions [Pg.63]

The most significant observation in the radical copolymerization of methyl methacrylate with vinylidene chloride in the presence of zinc chloride is the increase in the Q and e values of methyl methacrylate, the increase in the rx value of methyl methacrylate, and the decrease in the r2 value of vinylidene chloride (30). Although it has been proposed that these results arise from the increased reactivity of the complexed methyl methacrylate monomer, a more likely explanation is the homopolymerization of a methyl methacrylate-complexed methyl methacrylate complex accompanied by the copolymerization of methyl methacrylate with vinylidene chloride. [Pg.125]

These equations show the individual steps connected with the propagation reaction, i.e. the sums in the numerator or denominator are the sums of all possible propagation reactions in which a given monomer adds to the growing chains ending in every monomer unit. The Q and e values were obtained from binary copolymerization studies. The calculated and experimental results are compared in Table 4. [Pg.35]

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