The correlation between the value of α at the maximum reaction rate and the reaction mechanisms

Evaluation of Kinetic Parameters and Thermal Stability of Melt-Quenched BixSe100-xAlloys (x ≤7.5 at%) by Non-Isothermal Thermogravimetric Analysis

“…Among several other approaches (Criado et al, 1989;PerezMaqueda et al, 1996), the features of TG/DTG curves can be used to quest for probable kinetic reaction mechanisms responsible for the substance's thermal decomposition in a certain temperature range. Few tactics were proposed for choosing the reaction model that describes a thermal process in the sample upon non-isothermal heating on the basis of its asymmetry or shape of DTG curves via few characteristic parameters (Dollimore et al, 1992a(Dollimore et al, , 1992bGao et al, 1993;Haixiang et al, 2010;Lee & Dollimore, 1998). These parameters include the initial temperature T i , where mass loss commences and the final temperature T f , where no mass loss takes place, which on the DTG curves are often termed as diffuse (d) or sharp (s), depending on the decrease/ increase slanting of the conversion rate.…”

“…Some kinetic mechanisms lead to asymptotic or "diffuse" departure from base line of a DTG curve, while others produce "sharp" slant to the final TG/ DTG plateau (Dollimore et al, 1992a(Dollimore et al, , 1992bGao et al, 1993;Haixiang et al, 2010;Lee & Dollimore, 1998). The asymmetry of a DTG curve can be labeled by an asymmetry (shape) factor S=α/b, with α=T m −T 1 and b≡T 2 − T m (Dollimore et al, 1992a(Dollimore et al, , 1992bGao et al, 1993;Lee & Dollimore, 1998), so S≈1 for kinetic mechanisms of DTG curves with both T i and T f sharp (or diffuse) and S<1 for DTG curves with T i sharp and T f diffuse. But S>1 for DTG curves with "slow" departure from base line (T i diffuse) and with a "fast" return to the base line (T f sharp), for which we can disregard kinetic processes of first-order model functions; thus, visual inspection of the asymmetry of a DTG trace and its shaping features may help to limit kinetic mechanisms to favorite ones (Dollimore et al, 1992a(Dollimore et al, , 1992bGao et al, 1993;Haixiang et al, 2010;Lee & Dollimore, 1998 and half width ∆ 1/2 via constructing DTG curves for diverse sets of the reaction "kinetic triplet": E α , A and f[α (T)] that should characterize a unique solid state reaction, and then use a plausible shape method or flow chart (Haixiang et al, 2010) to further identify the more favored mechanism of thermal decomposition of a solid.…”

“…Some kinetic mechanisms lead to asymptotic or "diffuse" departure from base line of a DTG curve, while others produce "sharp" slant to the final TG/ DTG plateau (Dollimore et al, 1992a(Dollimore et al, , 1992bGao et al, 1993;Haixiang et al, 2010;Lee & Dollimore, 1998). The asymmetry of a DTG curve can be labeled by an asymmetry (shape) factor S=α/b, with α=T m −T 1 and b≡T 2 − T m (Dollimore et al, 1992a(Dollimore et al, , 1992bGao et al, 1993;Lee & Dollimore, 1998), so S≈1 for kinetic mechanisms of DTG curves with both T i and T f sharp (or diffuse) and S<1 for DTG curves with T i sharp and T f diffuse.…”

“…The asymmetry of a DTG curve can be labeled by an asymmetry (shape) factor S=α/b, with α=T m −T 1 and b≡T 2 − T m (Dollimore et al, 1992a(Dollimore et al, , 1992bGao et al, 1993;Lee & Dollimore, 1998), so S≈1 for kinetic mechanisms of DTG curves with both T i and T f sharp (or diffuse) and S<1 for DTG curves with T i sharp and T f diffuse. But S>1 for DTG curves with "slow" departure from base line (T i diffuse) and with a "fast" return to the base line (T f sharp), for which we can disregard kinetic processes of first-order model functions; thus, visual inspection of the asymmetry of a DTG trace and its shaping features may help to limit kinetic mechanisms to favorite ones (Dollimore et al, 1992a(Dollimore et al, , 1992bGao et al, 1993;Haixiang et al, 2010;Lee & Dollimore, 1998 and half width ∆ 1/2 via constructing DTG curves for diverse sets of the reaction "kinetic triplet": E α , A and f[α (T)] that should characterize a unique solid state reaction, and then use a plausible shape method or flow chart (Haixiang et al, 2010) to further identify the more favored mechanism of thermal decomposition of a solid. A shape method (flow chart) is recently proposed by Haixiang et al (2010) and simulated values of ∆ 1/2 for a non-isothermal dynamic curve (DTG or DSC curve with a constant heating rate β=dT/dt) for many kinetic model functions f[α(T)] (Criado et al, 1989;Dollimore et al, 1992aDollimore et al, , 1992bGao et al, 1993;Haixiang et al, 2010;Lee & Dollimore, 1998;PerezMaqueda et al, 1996), besides giving theoretical limits for theor m  in range 15 ≤x=E α /RT ≤70.…”

Copolymerization of acenaphthylene with methacrylic monomers

“…To avoid the approximations bearing the use of integral methods [41][42][43][44], we have applied the Dollimore [45][46][47][48] method which works with the differential equation. Taking into account the characteristics of the thermogravimetric curve, the initial and final temperatures and the α max reached at the maximum degradation rate temperature, a f(α) function can be obtained so that a plot of the left logarithmic term versus T -1 gives the Ea and A values.…”