Chemistry Reference
In-Depth Information
0,8
0,6
feed
0,4
sol
0,2
gel
0,0
0
500
1000
1500
2000
2500
3000
r
Fig. 11 Comparison of experimental [
90
](
solid line
) and calculated (
broken line
) fractionation for
EVA in methyl acetate
using elementary analysis. The broadness of the distribution, e, was estimated using
the Stockmayer theory [
56
], yielding e
0.25. The parameters occurring in the
G
E
¼
model (
5
) were chosen as:
r
A
¼
:
w
AP
¼
:
75 K
p
A
¼
:
g
A
¼
:
:
2
08
80
0
1
0
3
(60)
Unfortunately, Schirutschke [
90
] did not give any information about the chemi-
cal polydispersity in the experimentally obtained fraction. For this reason, the
comparison between the experiment and the modeling results is limited to the
fractionation according to the molecular weight. In Fig.
11
, the function
F
(
r
),
which is defined as:
ð
1
F
ð
r
Þ¼
Wr
ðÞ
;
y
d
y
(61)
0
is compared with the experimental data [
90
], where the experiment was performed
at 303.15 K. From Fig.
11
, it can be concluded that the proposed theoretical
framework is able to describe the polymer distribution in the coexisting phases.
Moreover, this comparison also shows the large impact on the LLE of the chemical
heterogeneity, even if the broadness of this function is only small.
3.2 Stepwise Fractionation Procedure
Cross-fractionation as a mean of evaluating the molecular weight and chemical-
composition distribution of heterogeneous copolymer is composed of two steps.
