Conference Report

244

The First International Conference onPolyolefin Characterization

Joao B. P. Soares

The First International Conference on Polyolefin Charac-

terization (1st ICPC) took place in Houston, TX, from

October 16 to 18, 2006. 107 participants from 18 different

countries attended the conference: 65 from the industry,

18 from vendor companies, and 24 from academia. The

strong participation from the polymer manufacturing

industry from North America, Europe and Asia shows the

industrial relevance and need of such a conference.

Sections were divided according tomain topic areas into

Separation and Fractionation, High Throughput, Thermal

and Crystallinity Analysis, Spectroscopy, and Rheology. In

addition to the oral presentations, 29 posters were dis-

played. Some of these oral and poster presentations were

published in volume 257 of Macromolecular Symposia.

The International Conference on Polyolefin Character-

ization will be held biannually, alternating between North

American and European locations. The 2nd ICPC will take

place from September 14 to 17, 2008, in Valencia, Spain

(http://www.icpc-conference.org/information.html).

A clear message came out of the conference: the

development of polyolefin resins with complex molecular

architectures will require the use of more powerful charac-

terization techniques and stimulate the development of

new analytical methods. The use of hyphenated fractiona-

tion methods is already common in industry and acade-

mia, and we expect that automated cross-fractionation

instruments will be applied routinely in the near future.

The use of high-throughput methods is also changing the

way polyolefin analysis is being approached, with

emphasis on high-definition and low-analysis-time tech-

niques. Finally, some new techniques, such as molecular

topology fractionation, high-temperature gradient HPLC,

and dilute solution differential scanning calorimetry (DSC)

have the potential to reveal polyolefin microstructural

details that so far have been difficult, if not impossible, to

measure by conventional characterization techniques.

A few highlights from the 1st ICPC are briefly reviewed

below.

J. B. P. SoaresDepartment of Chemical Engineering, University of Waterloo,Waterloo, ON, Canada N2L 3G1E-mail: jsoares@uwaterloo.ca

Macromol. Mater. Eng. 2008, 293, 244–245

� 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Cross-Fractionation Techniques

Cross-fractionation techniques combine TREF (tempera-

ture rising elution fractionation) and GPC (gel permeation

chromatography) to generate the joint distribution of

molecular weight (MWD) and chemical composition (CCD)

of polyolefins. Figure 1, showing the joint MWD-CCD of a

polyolefin made with two single-site catalysts, illustrates

nicely the power of cross-fractionation techniques.

There are two strategies for cross-fractionation of

polyolefins: TREF-GPC and GPC-TREF. In TREF-GPC, the

polymer sample is first fractionated according to its

chemical composition (or stereo- and regioregularity, for

the case poly(propylene), by TREF and then its narrow-CCD

fractions are injected into a GPC instrument for MWD

determination. In GPC-TREF, the reverse procedure is

adopted. The proponents of GPC-TREF claim that doing

the fractionation first by molecular weight eliminates the

molecular weight effects on the subsequent TREF fractio-

nation, leading to better resolved distributions. David

Gillespie (Dow Chemical) showed that GPC-TREF can be

used to obtain the joint MWD-CCD of copolymers with

very low comonomer content. On the other hand, for

samples with broad CCD and narrow MWD, Alberto Ortin

(Polymer Char) demonstrated that TREF-GPC is very

effective. Tetsuya Morioka (Japan Polychem Corporation)

also showed how a TREF-GPC apparatus could be used to

characterize poly(propylene) impact resins.

Hyphenated (Multiple Detector) Techniques

Hyphenated analytical techniques are becoming the

standard choice in the polyolefin industry because they

are very powerful and relatively easy to use. There are two

main analytical approaches: 1) Fractionation of the resin

according to the molecular weight with a GPC equipped

with a chemical-composition-sensitive detector such as an

infrared (IR) spectrometer to measure the average

comonomer content as a function of molecular weight

(GPC-IR), or 2) Fractionation of the copolymer according to

chemical composition with a TREF system having a

molecular-weight-sensitive detector, such as light scatter-

ing (LS) or differential viscosity (DV) detectors, to measure

DOI: 10.1002/mame.200800024

Conference Report

Figure 1. JointMWD-CCDof a polyolefinmadewith two single-site catalysts (Courtesy ofPolymer Char). The temperature coordinate can be converted into a comonomer fractionaxis through a calibration curve.

the average molecular weight as a function of chemical

composition (TREF-LS).

Wallace Yau (Equistar Chemical, currently at Dow Che-

mical) showed many applications of hybrid 3D-GPC-TREF

system equipped with DV, IR, and LS detectors. This

analytical system permits the fractionation of polyolefins

by GPC or TREF and shares the same powerful triple

detector system. Edwin Mes (Dow Benelux) demonstrated

how high-temperature asymmetric flow field flow frac-

tionation (HTAF4) could be coupled with IR, LS and DV

detectors for the analysis of polyolefins with ultra-high

molecular weights. For ultra-high molecular weight

samples, GPC systematically underestimates Mw likely

because of chain degradation in the GPC columns. This

problem is absent in HTAF4 since the fractionation occurs

in a channel without a stationary phase, reducing the

internal shear stress and chain scission of the polymer

molecules.

New Fractionation Techniques

Benjamin Monrabal (Polymer Char) introduced crystal-

lization elution fractionation (CEF), a new technique that

combines the mechanisms of TREF and Crystaf (crystal-

lization analysis fractionation) in a single instrument. The

major innovation in CEF is that the crystallization process

takes place inside a TREF column under constant solvent

flow. This modification in the TREF crystallization proce-

dure surprisingly achieves a much higher separation effi-

ciency which, in turn, allows for much faster CCD analysis.

This makes CEF ideally suited for high-throughput

experiments.

Another very interesting new fractionation technique

was introduced by David Meunier (Dow Chemical).

Meunier and co-workers developed a method called

Macromol. Mater. Eng. 2008, 293, 244–245

� 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

molecular topology fractionation (MTF)

that can separate polymer chains

according to their long chain branch

(LCB) topology. MTF uses a column

packed with spherical polystyrene-

functionalized silica particles with chan-

nels having dimensions similar in size to

the dimensions of the polymer chains

being analyzed. The fractionation is not

regulated by size exclusion, but seems to

be influenced by chain entanglements

with the column packing. Therefore,

linear chains are eluted first, followed

by LCB chains of different branching

topologies.

Harald Pasch (German Institute for

Polymers, Darmstadt) showed how high-temperature

gradient HPLC can be used to fractionate ethylene/

propylene copolymers of low crystallinity that cannot

be separated by TREF or Crystaf. Using a mobile phase of

ethylene glycol monobutylether (EGMBE) and

1,2,4-trichlorobenzene (TCB), and silica gel as the sta-

tionary phase, copolymers with different ethylene con-

tents were separated according to their chemical composi-

tions.

Joao Soares (University of Waterloo) showed how

solution differential scanning calorimetry (DSC) could be

used to complement the results obtained by Crystaf or

TREF. The crystallization in Crystaf and TREF is assumed to

be regulated by the length of the longest crystallizable

sequence in the polymer chain. As the longest sequence

crystallizes, the polymer chain precipitates from solution

and, as a consequence, TREF and Crystaf are ‘‘blind’’ to the

crystallization of any other sequences in that chain.

Solution DSC, on the other hand, can detect the crystal-

lization of all crystallizable sequences in the polymer

chain. Therefore, TREF and Crystaf are able tomeasure only

intermolecular crystallizability differences, whereas solu-

tion DSC can detect both inter- and intramolecular

crystallizability differences. The difference between these

profiles is a measurement of the intramolecular variation

in crystallizability of the chains.

All of these techniques have their strong and weak

points, and several are complementary to each other, as

demonstrated in the 1st ICPC. In our opinion, a clear

knowledge of what these techniques can offer is essential

for the development of new resins and optimization of

existing ones, as well as for the development of new

polymerization catalysts and processes. We hope the 2nd

ICPC will continue to provide a venue for the dissemina-

tion of these essential characterization techniques in 2008.

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