No abstract

The kinetics of poly(ethylene terephthalate) melting are studied by DSC and treated in the framework of a nucleation kinetic model. The study focuses on the temperature dependence of the effective activation energy of melting. A theoretical dependence is derived from the model and an experimental one from the Kissinger plot. It is demonstrated that the theoretical dependence satisfactorily predicts the experimental one and fi tting the former to the latter can be used for estimating the surface free energy of a nucleus.

A recently proposed method is used to parameterize the nucleation‐driven kinetics of poly(ε‐caprolactone) melting. The method is based on fitting a theoretically derived temperature dependence of the effective activation energy to the experimental dependence obtained from the Kissinger plot. Although the theoretical dependence fits the experimental one accurately, the fit gives rise to a surface free energy that is significantly smaller than the one obtained from crystallization data. A similar result is reported in other publications that make use of a homogeneous nucleation model for poly­mer melting. It is argued that a heterogeneous nucleation model is a more appropriate representation of the melting process and that its use resolves the problem of estimating the unusually small surface free energies.

No abstract

Data relative to methane trapping of SiCl 2 and a rate constant for the SiCl 2 into C9 H bond insertion process of at 921 K are reported. Results on thedecomposition of the trapping product, methyldichlorosilane, are also reported. This decomposition follows first-order kinetics with a rate constant of at 905 K Ϫ3 Ϫ1k ϭ 1.5 Ϯ 0.2 ϫ 10 s and produces methane, trichlorosilane, methyltrichlorosilane, and tetrachlorosilane. It is argued that the decomposition involves silylene intermediates, is nonchain, and is initiated primarily by the molecular methane elimination process MeSiHCl 2 91 : Free CH ϩ SiCl .4 2 radicals and Si9 C bond fission may also contribute to the decomposition but are not dominant. The kinetics of MeSiHCl 2 decomposition are shown to be consistent with the kinetics of the reverse SiCl 2 /CH 4 trapping reaction and with the overall reaction thermochemistry. Reaction modeling gives product yields, reactant conversions, and rates in reasonable agreement with the data.