Attributes SCP formation Activation energy 37.5 [+ or -] 2 (b) Activation enthalpy
(kJ/mol) 73.2 [+ or -] 3 (b) Activation entropy (J/mol x K) -16.88 [+ or -] 4 (a) Attributes Thermal inactivation P Activation energy 42.57 [+ or -] 1.5 (a) 0.025 Activation enthalpy
(kJ/mol) 82.47 [+ or -] 2 (a) 0.011 Activation entropy (J/mol x K) -535 [+ or -] 14 (b) 0.0001 Each value is a mean of three replicates.
4, we see that the values of the activation enthalpy
display a strong deviation from the zero entropy line, meaning that the distribution of relaxation times is now very wide in enthalpy (or energy), as well as in entropy (or in prefactor).
A third thermal degradation parameter, the activation enthalpy
, was obtained from the following equation: E = [DELTA][H.sup.#] - R[T.sub.S].
Table 3: Activation parameters for the corrosion of 6061 Al alloy in 0.5 M sodium hydroxide solution in the presence of MAMT Inhibitor [E.sub.a] [DELTA] [H.sun.a] - [DELTA] [S.sub.a] concentration (kJ mo[l.sup.-1]) (kJ mo[l.sup.-1]) (J mo[l.sup.-1] (ppm) [k.sup.-1]) 0 17.79 15.19 160.98 5 24.70 22.10 143.12 10 24.85 22.25 143.37 25 27.65 25.05 135.06 50 30.83 28.23 125.83 The effect of chemically stable surface active inhibitors is to increase the energy of activation and to decrease the surface area available for corrosion.30 The results in Table 3 indicate that the value of activation energy [E.sub.a], activation enthalpy
[DELTA] [H.sub.a], and activation entropy [DELTA] [S.sub.a] are given in Table 3.
Figure 4 presents the OIT activation enthalpy
plot of two of the films.
The energy of activated molecules is a kind of triplet consisting mostly of three components: activation enthalpy
, activation entropy and free energy of activation [8, 22].
where [DELTA][H.sub.eq.sup.0] is the enthalpy of the equilibrium, [DELTA][H.sub.app] is the apparent enthalpy of activation, and [DELTA][H.sub.prop] is the activation enthalpy
This suggests that the activation volume [V.sup.*] and the activation enthalpy
[DELTA]H expressed in Eq 6 seem to be the material characteristics of the blend.
We have also extracted from TSC the distribution of the activation enthalpy
. Those values have allowed us to identify localized and delocalized movements.
From Eq 2, the activation enthalpy
is then given by:
It is shown that activation parameters, like the activation enthalpy
and volumes, depend on these stress components only through a linear combination, or "reduced mixed stress," s = u/[Mu] = ([[Sigma].sub.c] + m[[Sigma].sub.n])/[Mu], with [Mu] the shear modulus.
Indeed, if [V.sub.a] is independent of the stress and the temperature, it is possible to relate the activation volume and the activation enthalpy
to parameters measured by experiment (10):