blends is further complicated by the large differences in undercooling of both
resins, as will be discussed in sect. 4.1.3.
3 Molar Mass Distribution Characterization Techniques
The molar mass distribution (MMD) is the most fundamental structural parameter
for all homopolymers and, together with the CCD and their interdependence
(bivariate distribution), defines the microstructure of most polyolefin copolymers.
Until the late 1960s, only molar mass averages could be obtained by light scattering, osmometry or viscosity measurements. It requires a separation process to
measure the full MMD, and this only became available with the development of
gel permeation chromatography (GPC) by Moore in 1964 [10], which represented a
significant contribution in the polymer chemistry field. Today most MMD data for
synthetic polymers are obtained by this chromatographic technique.
In recent years, field flow fractionation (FFF) [11], which has been used with
success in biological macromolecule separation, has become available for the
measurement of the MMD of very high molar mass resins.
3.1 GPC/SEC
Gel permeation chromatography (GPC) is also known as size-exclusion chromatography (SEC) and both names are used today in the literature. The GPC technique
has been extensively used in the last 50 years and has contributed to the development of polyolefin catalysts, processes, and the improvement of resin performance.
There exist good references that deal with the fundamentals of the technique
[12, 13], calibration procedures [14–16], and the analysis of LCB [17–23], which
still demands significant attention.
In this review, we will focus on the new and most recent technological developments in automation, infrared detection, and its applications in polyolefin analysis.
GPC instrumentation for high temperature analysis, being a niche market, has
remained unchanged for a long time. In recent years, new instrumentation has
been introduced with significant engineering advances [24] like modular design to
facilitate maintenance tasks, larger volume vials to reduce sample non-homogeneity,
automated sample preparation (filtration included), and having a separate column
oven compartment to prevent column damage during maintenance tasks.
A large amount of attention has been put into minimizing polymer degradation
during the sample preparation because of the high temperature and large time
required for polyolefins dissolution (including the waiting time for injection in
autosamplers) and to reduce the potential shear degradation during stirring and
filtration. The dual temperature zone autosamplers developed in the 1990s and the
incorporation of antioxidant in the dissolution process provided an improvement,
but not enough for the very labile polypropylene resins that may suffer chain
Polyolefin Characterization: Recent Advances in Separation Techniques
211
resins, as will be discussed in sect. 4.1.3.
3 Molar Mass Distribution Characterization Techniques
The molar mass distribution (MMD) is the most fundamental structural parameter
for all homopolymers and, together with the CCD and their interdependence
(bivariate distribution), defines the microstructure of most polyolefin copolymers.
Until the late 1960s, only molar mass averages could be obtained by light scattering, osmometry or viscosity measurements. It requires a separation process to
measure the full MMD, and this only became available with the development of
gel permeation chromatography (GPC) by Moore in 1964 [10], which represented a
significant contribution in the polymer chemistry field. Today most MMD data for
synthetic polymers are obtained by this chromatographic technique.
In recent years, field flow fractionation (FFF) [11], which has been used with
success in biological macromolecule separation, has become available for the
measurement of the MMD of very high molar mass resins.
3.1 GPC/SEC
Gel permeation chromatography (GPC) is also known as size-exclusion chromatography (SEC) and both names are used today in the literature. The GPC technique
has been extensively used in the last 50 years and has contributed to the development of polyolefin catalysts, processes, and the improvement of resin performance.
There exist good references that deal with the fundamentals of the technique
[12, 13], calibration procedures [14–16], and the analysis of LCB [17–23], which
still demands significant attention.
In this review, we will focus on the new and most recent technological developments in automation, infrared detection, and its applications in polyolefin analysis.
GPC instrumentation for high temperature analysis, being a niche market, has
remained unchanged for a long time. In recent years, new instrumentation has
been introduced with significant engineering advances [24] like modular design to
facilitate maintenance tasks, larger volume vials to reduce sample non-homogeneity,
automated sample preparation (filtration included), and having a separate column
oven compartment to prevent column damage during maintenance tasks.
A large amount of attention has been put into minimizing polymer degradation
during the sample preparation because of the high temperature and large time
required for polyolefins dissolution (including the waiting time for injection in
autosamplers) and to reduce the potential shear degradation during stirring and
filtration. The dual temperature zone autosamplers developed in the 1990s and the
incorporation of antioxidant in the dissolution process provided an improvement,
but not enough for the very labile polypropylene resins that may suffer chain
Polyolefin Characterization: Recent Advances in Separation Techniques
211