Adsorption and Decomposition of Peroxides on the Surfaces of Dispersed Oxides Fe2O3, Cr2O3 and V2O5

The adsorption of peroxides on dispersed oxides Fe2O3, Cr2O3 and V2O5 was studied. It is shown that the adsorption of peroxides is described by the Langmuir equation. The adsorption of benzoyl peroxide grows within Fe2O3<Cr2O3<V2O5. Adsorption-desorption equilibrium constants (K) for Cr2O3 and V2O5 are the same, but for Fe2O3 this value is 6 times higher. The decomposition of peroxides is observed in the solution and on the surface of adsorbents. The effective activation energy (E) of the thermal decomposition of peroxides in the studied systems is in the range of 80–140 kJ/mol. The activation energy of degradation of peroxides on the surface (Es) of the dispersed oxides studied is lower. The degradation reaction of peroxides on the surface of Fe2O3 and V2O5 has an oxidation-reducing nature, during which free radicals are produced. On the surface of Cr2O3, there is a heterolytic decay of peroxides. The parameters of the reaction of peroxides decomposition are found. The decomposition of peroxides in the presence of Fe2O3, Cr2O3 and V2O5 in styrene is accompanied by the formation of polystyrene both in the solution and on the surface of the adsorbent.

Lifetime Prediction of Polymers: To Bet, or Not to Bet—Is This the Question?

Polymers are a great and very important category of organic compounds that have changed our lifestyle. In the last eighty years, we have used them for the most varied applications, and from the first structural ones we began to investigate their durability, which can be fatal in the successful completion of the application for which the material was designed. Over the last thirty years, the environmental problems related to the disposal of polymers that have completed their lifecycle have begun to arise, and the need to foresee their end of life has become increasingly urgent. In this manuscript, the reliability of the lifetime predictions of polymeric materials is faced with comparing measurements obtained at low temperature with those carried out at high temperatures, in the molten state. The obtained data were treated by a well-established kinetics model and discrepancies were observed in the two different conditions (high and low temperatures), which led to a mismatching between expected and real data. A correction of the data extrapolated from measurements obtained at high temperatures, by using a novel equation which takes into account the induction period (IP) of the degradation process, is proposed. Considerations about the useful parameters, namely initial decomposition temperature (Ti), activation energy of degradation (Ea), and glass-transition temperature (Tg), to be used for making predictions, are also carried out.

Influence of Irradiation on Fenton Degradation of Brilliant Red X-3B

Oxidative degradation of Brilliant Red X–3B has been carried out using Fenton’s reagent both in the dark and in the presence of visible light. The degradation rate was increased using Fenton’s process in the order of Dark < Visible < UV. At pH 3.3, the maximum Fenton and photo-Fenton effect were noticed. At [H2O2]/[Fe(III)] = 3.5, a steady Fenton effect was observed. Meanwhile, at [H2O2]/[Fe(III)] = 0.7, Fenton process in the dark minimized the photo effect. The degradation rate was positively influenced by the temperature where the activation energy of degradation was evaluated as 36.98 kJ mol-1.

Selective Depolymerization and Effects of Homolysis of Poly(L-lactic acid) in a Blend with Polypropylene

Blends of poly(L-lactic acid) (PLLA) and polypropylene (PP), which are candidates for the practical use of PLLA, were investigated for selective degradation of PLLA, resulting in quantitative conversion of PLLA components into cyclic monomers, lactides, using magnesium oxide (MgO) as a depolymerization catalyst. Obviously, the catalyst MgO selectively accelerated only the PLLA depolymerization in the blends, dominantly generating L,L-lactide as a volatile product and separating the PP component. Expected effects of homolysis in the blend system were also determined as slight changes in activation energy of degradation for both the components and through the suppression of degradation by an antioxidant.