M00001467
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ISO 16014-2 2nd Edition, July 1, 2012 Plastics - Determination of average molecular mass and molecular mass distribution of polymers using size-exclusion chromatography - Part 2: Universal calibration method
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Availability date: 07/13/2021
Description / Abstract:
This part of ISO 16014 specifies a method for determining the
average molecular mass and the molecular mass distribution of
polymers using size-exclusion chromatography (SEC). The average
molecular mass and the molecular mass distribution are calculated
using a universal calibration curve instead of the conventional
calibration curve.
A list of documents related to this part of ISO 16014 is given
in the Bibliography.
NOTE The concept of the universal calibration method is based on
a relationship by which the retention time in SEC depends on the
size of the polymer molecule (the hydrodynamic volume) or on the
product of the intrinsic viscosity [η] and the molecular
mass M. Many polymers classified as random-coil polymers
(regardless of their chemical structure, degree of branching,
composition or tacticity) have been experimentally confirmed as
following this relationship. The universal calibration curve is
prepared by plotting the logarithm of [η]M
against the elution time t or elution volume V using
polymer standards such as polystyrene with narrow molecular mass
distributions. The molecular mass Mi of an
unknown polymer sample can then be calculated from the value of
[η]M at each retention time using the universal
calibration curve and [η] or K and a in
the Mark-Houwink-Sakurada equation ([η] =
KMa → [η]M =
KMa+1), where K is a constant
and a is an exponent depending on the experimental conditions.
Therefore this test method is classified as a relative method as
described in ISO 16014-1, but the average molecular masses and
molecular mass distributions calculated by the method are equal to,
or nearly equal to, the absolute values.