Critically evaluated rate coefficients for free-radical polymerization .2. Propagation rate coefficients for methyl methacrylate

Pulsed-laser polymerization (PLP) in conjunction with molar mass distribution (MMD) measurement is the method of choice for determining the propagation rate coefficient k(p) in free-radical polymerizations. The authors, members of the IUPAC Working Party on Modeling of kinetics and processes of polymerization, collate results from using PLP-MMD to determine k(p) as a function of temperature T for bulk free-radical polymerization of methyl methacrylate at low conversions and ambient pressure. Despite coming from several different laboratories, the values of k(p) are in excellent agreement and obey consistency checks. These values are therefore recommended as constituting a benchmark data set, one that is best fitted by k(p) = 10(6,427) L . mol(-1) . s(-1) exp(-22, 36 kJ . mol(-1)/R . T) The 95% joint confidence interval for these Arrhenius parameters is also given. In so doing, we describe the most appropriate statistical methods for fitting k(p)(T) data and then obtaining a joint confidence interval for the fitted Arrhenius parameters. As well, we outline factors which impose slight limitations on the accuracy of the PLP-MMD technique for determining k(p), factors which may apply even when this technique is functioning well. At the same lime we discuss how such systematic errors in k(p) can be minimized.