The objective of this study is determining the kinetic parameters of thermal degradation of polyurethane elastomers before and after UV irradiation. To determine the kinetic parameters of elastomeric polyurethane (PUR) decomposition the Freeman-Carroll method of calculation is applied. The effect of soft segment and hard segment type, soft segment molecular weight and hard segment content on the kinetic parameters of the degradation process were measured. Polyurethane elastomers were obtained from poly(oxytetramethylene) glycol, PTMO, of 1000 and 2000 molecular weight and polycaprolactone glycol of 1250 molecular weight (PCL), 4,4 0 diphenylmethan diisocyanate (MDI) and 4,4 0 -dicyclohexylmethane diisocyanate (H 12 MDI) and 1,4-butanediol as chain extender. The activation energy values obtained for PUR elastomers based on polyester soft segment were higher than those based on polyether soft segment.The PUR elastomers based on aromatic type of diisocyanate have lower activation energy values than those based on cycloaliphatic type of diisocyanate.

The kinetics of the thermal degradation of polyurethane (PU) elastomers based on poly(ether polyol) soft segments and an aromatic type of diisocyanate were investigated by thermogravimetric analysis (TGA) under a nitrogen atmosphere employing four heating rates. The corresponding kinetic parameters of the two degradation stages were estimated by minimizing the output error functional and by the Kissinger method. In evaluating the kinetic parameters of the two-step PU thermal decomposition, a differential thermogravimetry curve was applied as an objective functional in a regression procedure. Parameter estimation was obtained by minimizing the weighted quadratic output error functional with the modified Nelder-Mead simplex search algorithm. The confidence regions in the preexponential factor-activation energy space were established for both the first and second stages of degradation. The effect of the molecular weight of the soft segment and the content of the hard segment on the activation energy of the degradation process was constructed by response surface methodology.

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In this work, thermogravimetric analysis is used to determine the kinetic parameters of thermal degradation of polyurethane (PU) elastomers, based on poly(ether polyol) soft segment and aromatic-type diisocyanates. To determine the kinetic parameters of PU thermal decomposition, a nonlinear regression procedure is applied. Parameter estimation is obtained by minimizing the weighted quadratic output error functional with the modified Nelder-Mead simplex search algorithm. The confidence region of pre-exponential factoractivation energy are established both for the first and second steps of degradation. The effect of the soft segment molecular weight and hard segment content on the activation energy of the degradation process has been studied.

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