Number: 422/4/98
Title: Precise determination of
molecular weight distributions of polyolefins by high temperature
size exclusion chromatography and hyphenated techniques
Coordinator(s): D.
Lilge
Remarks: A meeting of participants
interested in this topic was arranged at Ludwigshafen in June 1997.
The participants will work out the final details of the round robin
tests and the analysis of long chain branched polyethylenes.
Completion Date: 2001
Objective:
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.
Last update: 5 August 2001
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