HIGH-TEMPERATURE THERMAL FIELD-FLOW FRACTIONATION OF POLYETHYLENE ANDPOLYSTYRENE

In this paper the high-temperature thermal field flow fractionation me thod is exploited for the analysis of polyethylene (PE). The experimen tal apparatus set-up, obtained by simply modifying a commercial instru ment, is presented. The numerical procedure for deriving retention cal ibration plot versus molecular weight is discussed with reference to t he specific polymer-solvent pair, PE-o-dichlorobenzene (ODCB), here em ployed. Different methods for computing the physicochemical data set o f the solvent, necessary for calibration, are compared. The selectivit y of the checked PE-ODCB system proves comparable with respect to the values currently found in thermal field-flow fractionation (ThFFF) ana lysis. Differences are found between PE and polystyrene (PS) analysis in the same solvent. The conditions for high temperature ThFFF operati on in PE analysis and their advantages are discussed with respect to t he standard SEC technique for PE, PS, and PE-PS copolymer analysis. Mo lecular weight distributions obtained by ThFFF of two PE commercial sa mples agree with those obtained by SEC. (C) 1995 John Wiley and Sons, Inc.