Oxygen absorption kinetics

J. Kiraly (Surface Oxidation Phenomena on a Germanium Single-Crystal Surface. II. Oxygen Absorption Kinetics) ibid. 74 (11), p. 553 (1968). 

Fig. 21. Kinetic curves of photosensitized oxygen absorption by thermally treated PAN samples during irradiation with white light. ( ) PAN (450 °C,...

Fig. 22. Kinetic curves of oxygen absorption by ascorbic acid in the presence of polytpro-pionitrile). (1) in the dark (2) in red light (3), (4) in white light...

Because the Adler model is time dependent, it allows prediction of the impedance as well as the corresponding gaseous and solid-state concentration profiles within the electrode as a function of time. Under zero-bias conditions, the model predicts that the measured impedance can be expressed as a sum of electrolyte resistance (Aeiectroiyte), electrochemical kinetic impedances at the current collector and electrolyte interfaces (Zinterfaces), and a chemical impedance (Zchem) which is a convolution of contributions from chemical processes including oxygen absorption. solid-state diffusion, and gas-phase diffusion inside and outside the electrode. 

Figure 1.8. Kinetic curves of oxygen absorption by PCA samples, containing derivatives of aroilenbenzimidazole 1 mass % of XLl-(l), XL-(2), XLll-(3).

Table 9. Kinetics of oxygen absorption by dyed and nndyed PCA fibres-derivatives of bis-aroilenbenzimidazole...

Figure 2.6. Kinetic curves of oxygen absorption at irradiation (1) and after irradiation (2) of CDA by the light with wave length of 253,7 nm and intensity 1-0,510 quant/cm s at 298°K and pxygen pressure 150 T. 2-theoretical curve of photochemical aftereffect, calculated according to the equation 3.1 at Kn[RH]/Kr=o,9-10 5 mole/kg, y=5,3 T=300s WTeM=l,69-10 8 mole/kg s.

A.E. Neverov, G. A. Nikolaev, Study of kinetics of oxygen absorption in the process of polycaproamide thermooxidation and prediction of its storage life/IHighmolecjilar compounds (1982), A-24, No 4, 272-275 (in Russian). 

Judging by kinetics of oxygen absorption at 350 °C (processing temperature) and data of dynamic TGA/DTA, thermo-oxidative stability of TCP with various concentrations of TPA/IPA decreases in the sequence IPA-0 > IPA-25 > IPA-50 > IPA-75 > IPA-100. 

Thermo-oxidation of polyphthalamides (PPA-1 and PPA-2) display the same regularities (kinetics of mass losses, oxygen absorption and release of the main volatile products, composition of volatile and heavy products relative to the polymer structure, oxidation inhibiting by adding PCA and transition metal compounds, etc.), which are described in detail for PAI, PPQ, polybenzoxazole (PBO), PEI, PI, PAIM, polyphenyl sulfide (PSP), PES and LCP. The degradation mechanism will now be discussed in more detail using PPA-1 and PPA-2 as examples (see Figure 7.5 and 7.6). 

Oxidation of polypropylene describes the kinetic curve of oxygen absorption, which has an S-shape (fig.l). This curve is characterized by an induction period of self-acceleration and deceleration of oxidation in a deep stage of the process. A typical kinetic curve of oxygen uptake for isotactic PP is shown in Figure 1. For comparison, the kinetic curve for polyethylene (PEHD). The kinetic equation represents the dependence of the amount of... 

Kinetic equations for determining the rate of oxygen absorption can be obtained from the kinetic equations for the intermediate concentrations of particulate matter ... 

The direct correlation between initial structure of polymer and kinetics of oxygen absorption is consequent from our scheme (Shibryaeva L.S.and al.,2003 2006 2010.)... 

As an example, the figure shows the kinetic dependences of oxygen absorption in a model reaction of initiated cumene oxidation in the absence of antioxidant (straight line 1) and in the presence of Urotractin (curve 2), Spasmex (curve 3), Promena (ciuve 4), Contrinol (curve 5), Cyston (curve 6), Urolyzin (curve 7). 

FIGURE 1 Kinetic Dependences of Oxygen Absorption 1 ml of hydrocarbon, 1 mg of initiator, t = 60°C. 

Figure 7.12. Kinetic curves of oxygen absorption for ethylbenzene oxidation in the absence (1) and presence (2 and 3) of BHT. [BHT]o=6.5 10 M (2) and I TO " M (3), respectively, T= 120 °C. The initial concentration of ethylbenzene hydroperoxide was I TO M (points - experimental curves -calculation).

Experimental results and their numerical description. It follows from results shown in Figures 7.11 and 7.12 that calculated kinetic curves for oxygen absorption describe with reasonable accuracy the experimental data for the oxidation of ethylbenzene at 60 °C and 120 °C, inhibited by butylated hydroxytoluene and without it. 

The relative rates of autoxidation of different unsaturated fatty acids and esters were compared on the basis of oxygen absorption measurements (Table 1.1). In neat systems without added initiator, linoleate was 40 times more reactive than oleate, linolenate was 2.4 times more reactive than linoleate, and arachidonate was 2 times more reactive than linolenate. The oxidizability of polyunsaturated fatty acid (PUFA) esters was also compared on the basis of oxygen uptake measured kinetically by the induction period method described above, in solution in the presence of azo initiators. The oxidizability of 18 2,18 3,20 4, and 22 6 was linearly related to the number of bis-aUyUc positions present in the fatty esters. From this relationship, the oxidizability of each PUFA was increased approximately two fold for each active bis-allylic methylene group. Thus, the oxidizability of 22 6 was 5 times greater than that of 18 2. 

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