Critically evaluated rate coefficients
for free-radical polymerization - 2. Propagation rate coefficients for
methyl methacrylate
S. Beuermann, M. Buback, T.P. Davis, R.G. Gilbert, R.A. Hutchinson,
O.F. Olaj, G.T. Russell, J. Schweer, and A.M. vanHerk
Synopsis: 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.
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