Chemistry Reference
In-Depth Information
Figure 8.
CEF analysis of a linear low density polyethylene. A - Concentration (CH
2
), B - Composition (CH
3
) and C -
Viscometer output.
que with extended separation. The new
technique has been named crystallization
elution fractionation, CEF, as it combines
the separation power obtained in the
crystallization cycle (equivalent to CRYS-
TAF), with the one obtained in the elution-
melting cycle (equivalent to TREF).
CEF is performed in a simplified TREF
instrument and can easily adapt viscometry,
light scattering, composition, or other detec-
tors to determine molar-mass composition
dependence or to obtain further information
of polymer microstructure. The same CEF
apparatus can perform TREF and dynamic
crystallization.
The analysis time of the CCD has been
dramatically reduced with improvements in
TREF column and hardware design, and
with newer techniques becoming available.
The analysis by classical TREF of one
sample took 100 hours in the eighties
(around five samples could be analyzed
per week). The development of CRYSTAF
in the nineties allowed analyzing five
samples in 8 hours (15 samples per day).
In the last years, improvements in TREF
allowed the analysis of five to ten samples
per day. Today, CEF can analyze one
sample in less than 30 minutes, enough for
the demanded high throughput screening of
50 samples per day.
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