Chemistry Reference
In-Depth Information
0,8
0,7
0,6
0,5
0,4
0,3
0,2
420
440
460
480
500
520
T
column
[K]
Fig. 33 The relationship of the amount of copolymer present in the sol phase and the temperature
in the column
in the case where the CPF is applied for cutting the short or the large molecular
weight parts from a synthetic polymer in order to tailor the material properties.
From the calculation results of the stepwise fractionation methods, it is known
that the amount of polymer should by equal in all fractions. In CPF, the amount of
polymer segments depends on the chosen working point (
n
FD
/
n
EA
) and the temper-
ature in the column. In Fig.
33
, the relationship between the temperature in the
column and the amount of polymer present in the sol phase is shown.
Using all this knowledge from the simulations above, the following so-called
optimized parameters for the CPF column:
X
FD
11
Z
FD
5
Z
EA
n
FD
n
EA
¼
0
:
¼
0
:
¼
0
:
15
=
¼
0
:
08
(74)
m
Max
¼
6
m
FD
¼
3
T
condenser
¼
430 K
were used to fractionate a copolymer into five fractions by four fractionation runs.
The temperature for each fractionation run was selected in such a way that in every
fraction there was nearly the same amount of polymer.
The results for this fractionation are presented in Table
2
, Fig.
34
, and Fig.
35
.
The differences between the original operating parameters (
73
) to the optimized
parameters (
74
) are, first, that the
n
FD
/
n
EA
ratio is changed slightly and, second, that
the temperature gradient is much more pronounced. The temperature at the con-
denser is changed from 520 to 430 K, whereby the temperature in the column is
raised, especially for the last fractionation run. Similar to the results found for
stepwise fractionation, the most important feature for an effective fractionation in
column is also that the polymer is equally distributed in the corresponding fractions.
The improvement can be recognized clearly if the fractionation with respect to
the chemical composition is analyzed (Table
2
and Fig.
35
). The fractionation
