Effect of Solvent on the Rate Constants in Solution Polymerization III. Butyl Acrylate/Vinyl Acetate

Abstract

ABSTRACT:An experimental and modelling study has been carried out to explore the kinetics of the copolymerization of butyl acrylate and vinyl acetate (BuA-V Ac) in solution. A series of batch free radical copolymerization experiments has been carried out using the system BuA-VAc in an ethyl acetate (EAc) solvent. Experimental data were obtained from gravimetric and NMR measurements. The pseudo-homopolymerization constants identified in Parts I and II of this work (McKenna et a/., J. Polym. Sci., Polym. chem., in press) were used along with literature values for the propagation rate constants and reactivity ratios to model the different reactions presented here. It was found that the reactivity ratios of Dube and Penlidis [Polymer, 36, 587 (1995) With the exception of Parts 1 and 2 1 • 2 of this work, and the study published by Dube and Penlidis, 3 recent studies on the solution copolymerization of butyl acrylate (BuA) and vinyl acetate (V Ac) are scarce. And, as we have pointed out in the previous articles, even when data are available there seems to be a rather wide dispersion in reported values of the homopolymerization kinetic constants for propagation and termination, kP and k 1 • This dispersion might in part be attributable to a lack of correlation of data with reaction conditions.In a batch reactor, and in the absence of any gel effect, monomer conversion in a homopolymerization as a function of time is given by:Iff, kd and t are known, then it is possible to estimate the value of kp/k(l_: 5 by regressing the ln(l-x) as a function ofj(t) = -kdt/2)). As can be seen in Figure 1, the lumped rate constant kP/k 1°· 5 of BuA is a function of the initial monomer concentration, even though this quantity does not appear in eq I. Very similar results were observed for VAc.Note that as shown in ref 1 and 2, the values of kp/ kt 5 varied by approximately a factor of 2 over the range of concentrations studied. This means that regardless of the cause of this variation (it was proposed that chain transfer reactions were in part responsible), the radical concentration in the systems studied changed very little, and when they did change, it was not particularly rapid. Furthermore, it can also be seen from Figure 1, and from all of the curves presented in the first 2 parts of this series that the ln(1-x) is a strongly linear function of fit). This clearly demonstrates that it is reasonable to invoke the quasi-steady state assumption (QSSA) in the derivation of the equations used to analyse kp/k1°· 5 • t To whom correspondence should be addressed.Recent works have discussed the possibility that diffusion of macroradicals (i.e., chain length) might indeed be important even at low conversions in some case. 4 • 5 And since overall chain length is controlled to a large extent by monomer concentration, it is not surprising that in such a case the observed value of the rate constants should vary with the initial monomer concentration. This variation was therefore attributed, at least in part, to the fact there is a great deal of...

Off‐line monitoring of butyl acrylate and vinyl acetate homopolymerization and copolymerization in toluene

“…Therefore, it is expected that the solution copolymerization of these two monomers would show similar behavior. Recent work on BA/VAc copolymerization in solution is scarce, apart from that of McKenna and Heredia 38 where ethyl acetate was used as a solvent. They concluded that, similar to the homopolymerization reactions of VAc and BA, the lumped constant was dependent on the solvent concentration.…”

Sol MWD During Styrene, Vinyl Acetate, Methyl Methacrylate, and Butyl Acrylate Homopolymerization: A Numerical Study Using the NFT Approach

“…f 0.6 and 0.63 [49,50] This faster increase in X w can be explained by the complete depletion of initiator. It is observed in Figure 5c that X n slightly decreases from a higher value at 60 8C, and slowly increases from a lower value at 120 8C.…”

Applications of Nonlinear Observers and Control: Improving Productivity and Control of Free Radical Solution Copolymerization

“…Also, despite the very high value for k t supplied to the observer at time zero, it can be seen that the estimated value of the overall termination rate constant shown in Figure 6 also converges toward the theoretical value calculated from estimator input concentrations and a previously presented model. 28 Note that the speed of convergence would be improved if we had supplied the estimator with an initial value of the overall rate constant that was much closer to the "true" value. As can be seen in Figure 6, the initial guess for k t was in fact 2 orders of magnitude greater than the "real" value.…”