temperatures. To elute all different fractions, the solvent flow is started again at an
appropriate rate.
The advantages of the two processes explained in Fig. 2.44a, b are combined in
CEF. The sample loading step is the first step. It is the same for all three methods.
The crystallization with a continuous flow through the column enhances the
physical separation according to crystallinity during this step and this dynamic
crystallization is combined with the typical TREF elution cycle as a next step; see
Fig. 2.44c. The set-up resulted in enhanced resolution in a shorter time frame.
CEF has been shown to provide reproducible and very fast analyses of the
compositional distribution of complex polyolefins, one application being in highthroughput experimentation [114]. Analysis times of less than 30 min could be
achieved. The gain in separation from TREF to CEF is presented in Fig. 2.45 for a
blend of two metallocene-type resins [9]. The crystallization peaks of the two
components are separated by 20.7
C for CEF compared to only 12.7
C for TREF.
2.3.1 Analysis of Complex Polyolefins by CEF [113]
As mentioned earlier, CEF is faster than TREF and CRYSTAF, and significantly
improved fractionations are obtained. This makes CEF an interesting alternative to
the more conventional polyolefin fractionation techniques. CEF experiments can be
conducted in a standard TREF instrument as they only require a typical tunable
column oven and a HPLC pump to deliver the solvent flow. Similar to TREF, a
range of different detectors can be used to monitor concentration, chemical composition and molar mass.
2.3.1.1 Aim
In the present application, a range of different complex polyolefins shall be
fractionated. The experimental approach of CEF shall be described and the quality
of fractionations obtained shall be discussed.
2.3.1.2 Materials
• Polymers. Metallocene-type resins with densities of 0.902 g/mL and 0.937 g/
mL, Elite
TM resin of Dow Chemical, LLDPE
2.3.1.3 Equipment
• CEF. CEF Instrument (Polymer Char, Valencia, Spain); see Fig. 2.46.
• Detectors. Dual wavelength IR detector, dual capillary viscometer.
• Solvent. ODCB.
• Crystallization and elution protocol. As described in the text.
2.3.1.4 CEF Measurements and Discussion
The fractionation of a typical complex polyolefin, Elite
TM from Dow Chemical, is
shown in Fig. 2.47. This fractionation was accomplished in only 23 min using very
fast crystallization and heating rates (10
C/min for both). Nevertheless, excellent
2.3 Crystallization Elution Fractionation
67
appropriate rate.
The advantages of the two processes explained in Fig. 2.44a, b are combined in
CEF. The sample loading step is the first step. It is the same for all three methods.
The crystallization with a continuous flow through the column enhances the
physical separation according to crystallinity during this step and this dynamic
crystallization is combined with the typical TREF elution cycle as a next step; see
Fig. 2.44c. The set-up resulted in enhanced resolution in a shorter time frame.
CEF has been shown to provide reproducible and very fast analyses of the
compositional distribution of complex polyolefins, one application being in highthroughput experimentation [114]. Analysis times of less than 30 min could be
achieved. The gain in separation from TREF to CEF is presented in Fig. 2.45 for a
blend of two metallocene-type resins [9]. The crystallization peaks of the two
components are separated by 20.7
C for CEF compared to only 12.7
C for TREF.
2.3.1 Analysis of Complex Polyolefins by CEF [113]
As mentioned earlier, CEF is faster than TREF and CRYSTAF, and significantly
improved fractionations are obtained. This makes CEF an interesting alternative to
the more conventional polyolefin fractionation techniques. CEF experiments can be
conducted in a standard TREF instrument as they only require a typical tunable
column oven and a HPLC pump to deliver the solvent flow. Similar to TREF, a
range of different detectors can be used to monitor concentration, chemical composition and molar mass.
2.3.1.1 Aim
In the present application, a range of different complex polyolefins shall be
fractionated. The experimental approach of CEF shall be described and the quality
of fractionations obtained shall be discussed.
2.3.1.2 Materials
• Polymers. Metallocene-type resins with densities of 0.902 g/mL and 0.937 g/
mL, Elite
TM resin of Dow Chemical, LLDPE
2.3.1.3 Equipment
• CEF. CEF Instrument (Polymer Char, Valencia, Spain); see Fig. 2.46.
• Detectors. Dual wavelength IR detector, dual capillary viscometer.
• Solvent. ODCB.
• Crystallization and elution protocol. As described in the text.
2.3.1.4 CEF Measurements and Discussion
The fractionation of a typical complex polyolefin, Elite
TM from Dow Chemical, is
shown in Fig. 2.47. This fractionation was accomplished in only 23 min using very
fast crystallization and heating rates (10
C/min for both). Nevertheless, excellent
2.3 Crystallization Elution Fractionation
67