Thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide)

Abstract

ABSTRACT:The kinetics of the thermal and microwaveassisted oxidative degradation of poly(ethylene oxide) were determined with potassium persulfate as the oxidizing agent. Gel permeation chromatography was used to determine the variation of the molecular weight with time. The degradation was studied as a function of the temperature and persulfate concentration, and it was found that the degradation rate increased with the temperature and concentration of persulfate. Continuous distribution kinetics were used to determine the rate coefficients for the degradation process, and the activation energies were obtained. The results indicated that the microwave-assisted process had a lower activation energy of 10.3 kcal/mol, whereas that of the thermal degradation was 25.2 kcal/mol.

Microwave material processing—a review

“…212 Similarly, studies on thermal and microwave-assisted oxidative degradation of poly(ethylene oxide) with potassium persulfate as oxidizing agent indicated that lower activation energy was achieved with microwave-assisted heating (43.1 kJ/mol) compared to that of thermal degradation (105.5 kJ/mol). 213 Temperature profile measurement during dehydrochlorination of poly(vinyl chloride) using microwave irradiation showed that the thermal runaway was influenced mainly by the strength of incident microwave power by the preheating temperature of polyvinyl chloride (PVC) before irradiation. 214 Pyrolysis of waste polystyrene by microwave irradiation was carried out in the range of 1100-1200 C and it was found that polystyrene was converted into 80% liquid, 15% gas and 5% char residue.…”

Intensification of degradation of guar gum: Comparison of approaches based on ozone, ultraviolet and ultrasonic irradiations

“…The observed trends can be explained by the fact that SO 4 À species has been known to be more selective for electron transfer reactions, while HO radicals can rapidly take part in hydrogen addition or abstraction reactions [25]. Also the dissociation of KPS into radicals is not significant at lower temperature, and hence no significant effect may be observed on the kinetic rate constants [8,26] Experiments were performed to study the efficacy of ozone for the viscosity reduction of guar gum solution. Ozone was introduced into the solution at different flow rates such as 100, 200, 300 and 400 mg/h and the obtained results for the effect of varying ozone flow rate on the extent of degradation of GG has been depicted in Fig.…”

Polymer Degradation Under Microwave Irradiation

“…Potassium persulfate, K 2 S 2 O 8 , is such a free radical initiator and is widely used to produce the initial radicals needed in conventional emulsion polymerizations. This compound was also used as an oxidizing agent for the thermal and microwave-assisted oxidative degradation of poly(ethylene oxide) by Vijayalakshmi et al [63]. Parameters that were found to increase the degradation rate included temperature, concentration of persulfate and heating cycle time.…”

“…The degradation kinetics was also studied and the rate coefficients were obtained from a theoretical simulation model using the principles of continuous distribution kinetics. It was found that microwave-assisted degradation was far more effective than conventional heating in solution, in terms of reducing reaction time, lowering the activation energies and obtaining higher rates [63].…”