Project Details:

Precise determination of molecular weight distributions of polyolefins by high temperature size exclusion chromatography and hyphenated techniques

The aim of this project is to unify the methods for establishing the molecular weight distribution (MWD) of polyolefins. The MWD is one parameter, which determines the processing or the final properties of the product. Only with a precise knowledge of the MWD it is possible to establish structure-properties relationships. At first, a round robin test with high temperature size exclusion chromatography (HT-SEC) of polyolefins will be considered: the new metallocene polyolefins are uniform, homogeneous polymers of narrow MWD. These products are of value to establish good calibration curves for SEC and will be considered as a part of the analysis. As a sensitive test of the calibration a polyethylene with a broad distribution will be included in the survey, because the determination of molecular averages of those samples is very sensitive to the strategy of data reduction (baseline evaluation, peak broadening). In a second attempt the MWD and long chain branching frequency of LDPE and the recently developed metallocene polyethylenes will be investigated. HT-SEC will be used in the analysis of these more complex polymers in conjunction with on-line detectors using viscometry and/or light scattering. IUPAC samples LDPE alpha and beta and a metallocene polyethylene with long chain branching will be measured.