DETERMINATION AND CORRECTION OF PEAK BROADENING IN SIZE-EXCLUSION CHROMATOGRAPHY OF CONTROLLED RHEOLOGY POLYPROPYLENE

The peak broadening in size exclusion chromatography of seven commerci al polystyrene (PS) standards with narrow molar mass distribution (MMD ) and of 6-9 polypropylene (PP) fractions (MBAR(w)/MBAR(n) = 1.34-2.10 ) obtained by direct extraction was determined in four different colum n sets. The dependence of the Gaussian peak broadening parameter, sigm a2, on the peak elution volume was different for PS and PP. For a comm ercial grade of controlled rheology PP (CR-PP) (Daplen PT55) with MBAR (w)/MBAR(n) < 3 it was shown that disregard of the peak broadening eff ect leads to considerable errors in the MMD at low and high molar mass and in the polydispersity parameter MBAR(w)/MBAR(n). The same lot was studied in an Austrian National Research program for its physical pro perties in processing and application and in a round-robin test of IUP AC working party IV.2.2. on molecular characterization of commercial p olymers. (C) 1994 John Wiley & Sons, Inc.