hrvatski

Određivanje kinetičkih parametara neizotermne razgradnje PHB-a IKP metodom

The thermal degradation of biodegradable poly(3-hydroxybutyrate) (PHB) at processing temperatures is one of the main obstacles for its broad application. From the data obtained from non-isothermal thermogravimetric analysis, information about the kinetics of thermal degradation can be obtained. Therefore, the non-isothermal degradation of PHB was investigated in the temperature range 50-650&ordm ; C at four heating rates (2.5, 5, 10 and 20&ordm ; C/min). The present work uses invariant kinetic parameters method (IKP method) to calculate the invariant kinetic parameters, i.e. activation energy (Einv) and pre-exponential factor (Ainv). The IKP method is applied on the conversion range 0, 10≤ alpha≥ 0, 90. The calculated value of Einv is compared and practically equals the values obtained by isoconversional Flynn-Wall-Ozawa method. In order to explain the thermal degradation of the investigated material, it is necessary to know the kinetic triplet (E, A and conversion function, f(alpha)). The IKP method allows evaluating numerically f(alpha). The values of invariant kinetic parameters were used for numerical evaluation of f(alpha). The plot f(alpha) vs. alpha exhibits a maximum what suggests that the non-isothermal degradation of PHB occurs through a mechanism like those represented by the Avrami-Erofeev equations (with m>1). However, the values of f(alpha) can not be fitted exactly by any of the ideal Avrami-Erofeev kinetic model. The exact analytical form of f(alpha) is difficult to be find.

metoda invariantnih kinetičkih parametara (IKP metoda); neizotermna kinetika; toplinska razgradnja PHB-a

nije evidentirano