A comparative study on the thermal behaviour and the flow characteristics of binary mixtures of Na(K)SCN and Na(K)I with polyoxyethylene (POE) within a broad temperature interval was conducted by means of a combined dynamic thermal analysis, gel permeating chromatography, dynamic viscometry, IR spectroscopy and an extrusion plastometer. The concentrations of the salts varied from 0.1 to 40 mass% and the mean viscosity molar mass ((M) over bar(v)) of POE was found within 7x10(3)-5.5x10(6) g mol(-1) range. The same optimum concentrations of the salts (2-5 mass%) were found to considerably improve the thermostability of POE in air and also its melt index. The thermostabilizing effect of the salts was achieved regardless of the molar mass of the POE and the way they were incorporated. The thermostability and the melt index of the POE increased in the order : KI, KSCN, NaSCN, NaI. By employing a novel and appropriate experiment, solid-phase alkali metal salt was found to ’trap’ the gaseous products of the primary decomposition of POE, thus forming the ionic complex and, also acting as an antioxidizing agent.