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Kinetics of degradation of perchloroethylene under ultrasonic irradiation and photooxidation in aqueous solution

Kargar M., Nabizadeh R., Naddafi K., Nasseri S., Mesdaghinia A., Mahvi A. H., Alimohammadi M., Nazmara S.

Environment Protection Engineering

2013

Vol. 39, nr 4

29--38

Sonolysis and photodegradation of various compounds such as chlorinated aliphatic hydrocarbons are the recent advanced oxidation processes. Perchloroethylene PCE is one of these compounds mainly used as a solvent and degreaser. In this work, elimination of perchloroethylene in aqueous solution by ultrasonic irradiation and photooxidation by UVC were investigated. Head space gas chromatography with FID detector was used for analyses of PCE. Results showed that PCE could be effectively and rapidly degraded by ultrasonic irradiation, photooxidation by UVC and combination of these methods. The order of studied reactions for degradation PCE has been determined.

The Applicability of Chromatographic Methods in the Investigation of Ageing Processes in Double Base Rocket Propellants

Matečić-Muśanić S., Sućeska M., Čuljak R.

Central European Journal of Energetic Materials

2013

Vol. 10, no. 2

245--262

The ageing of double base (DB) rocket propellants is the result of chemical decomposition reactions and physical processes, causing degradation of a number of relevant propellant properties (such as reduction in stabilizer and nitroglycerine (NG) content, reduction of the mean molecular mass of nitrocellulose (NC) etc.), which is refected in a decrease in the reliable service life time of DB propellants. This is the reason why the study of processes of ageing and their consequences (effects) is so important. In this paper we have studied the kinetics of DB rocket propellant decomposition during their artifcial ageing, i.e. at elevated temperatures. The kinetic parameters were obtained by measurements of the stabilizer/Ethyl Centralite (EC) content and the mean molecular mass reduction of NC, during artifcial ageing at temperatures of 80, 85 and 90 °C. Consumption of the EC was observed using High Performance Liquid Chromatography (HPLC), whilst the reduction in the mean molecular mass of NC was monitored using Gel Permeation Chromatography (GPC). It has been shown that artifcial ageing of DB propellant causes signifcant EC consumption and a reduction in the mean molecular mass of NC, from the very beginning of ageing. EC is entirely consumed after 120 days at 80 °C, and is followed by the intensive reactions of NC decomposition. Signifcant changes in the mean molecular mass of NC starts after 60 days of ageing at 90 °C (or ~250 days at 80 °C). The results obtained from the kinetic data have shown that the activation energy of DB propellant decomposition, determined on the basis of changes in the mean molecular mass of NC is 145.09 kJ•mol-1 , whilst the activation energy of decomposition obtained on the basis of EC consumption is 142.98 kJ•mol-1 , which is consistent with available literature values [1, 2].

Kinetics of decomposition of poly(vinyl chloride)/low-migration polyesterurethane plasticizer blend - a thermogravimetric study

Świerz-Motysia B., Pielichowski K.

Polimery

2005

T. 50, nr 7-8

601-604

Kinetics of decomposition of poly(vinyl chloride) (PVC), plasticized either by di(2-ethylhexyl)phthalate (DEHP) or medium molecular weight polyesterurethane (PESTUR) or by both plasticizers, was studied by isoconversional methods on the basis of thermogravimetric data under dynamic heating conditions. It has been found that the initial decomposition temperature is higher for PVC plasticized with PESTUR in comparison with PVC plasticized with DEHP or with PESTUR/DEHP, and thermal degradation shows features of multistep complex process. Application of polymeric plasticizer leads to the increase in values and a "smoothing" effect in the course of energy of activation and pre-exponential factor at initial stage of decomposition indicating thus the hindered migration of medium molecular weight compound from PVC matrix (in comparison with PVC containing monomeric DEHP) due to steric hindrances as well as due to specific interactions between C=O and Cl groups along the macrochains.

Badano kinetykę rozkładu poli(chlorku winylu) (PVC), plastyfikowanego za pomocą ftalanu 2-dietyloheksylu (DEHP), poliestrouretanu o średnim ciężarze cząsteczkowym (PESTUR) lub za pomocą obu zmiękczaczy, przy użyciu metod izokonwersyjnych na podstawie danych analizy termograwimetrycznej prowadzonej w warunkach dynamicznych. Stwierdzono, że początkowa temperatura rozkładu jest wyższa w przypadku PVC plastyfikowanego za pomocą PESTUR w porównaniu do PVC plastyfikowanego z zastosowaniem DEHP lub PESTUR/DEHP, a degradacja termiczna charakteryzuje się złożonym wieloetapowym przebiegiem. Zastosowanie plastyfikatora polimerycznego spowodowało zwiększenie wartości i "wygładzenie" przebiegu zmian energii aktywacji i czynnika przedwykładniczego w początkowym etapie rozkładu, wskazując na utrudnioną migrację związku średniocząsteczkowego z matrycy PVC (w porównaniu do PVC zawierającego monomeryczny DEHP) z powodu utrudnień sterycznych oraz oddziaływań pomiędzy grupami C=O i Cl wzdłuż makrołańcuchów.