Chemistry Reference
In-Depth Information
Table 3.2
Hoffman-Lauritzen parameters for crystallization of PET
K
g
ￗ 10
−5
(K
2
)
U
*
(kJ mol
−1
)
Ref.
Regime I/III
Regime II
5.0
2.5
6.3
[
110
]
8.7
6.1
6.3
[
111
]
12.80
a
12.75
[
114
]
2.8
6.3
[
115
]
3.0
6.3
[
116
]
3.7
b
6.3
[
117
]
2.3
6.3
[
118
]
3.2
1.9
4.3/2.3
Equation 3.60
a
Identified as
regime III
b
Regime is not identified
larger value of
K
g
. Therefore, fitting both
K
g
and
U
*
seems like a better approach
that should result in more reliable estimates of these values.
The use of Eq. 3.60 yields the
K
g
values 3.2 and 1.9 10
5
K
2
for respectively
higher and lower temperature portions of
E
ʱ
versus
T
dependence. It is noteworthy
that the higher temperature portion gives the
K
g
value that is 1.7 times larger than
the value related to the lower temperature portion. The ratio is very close to the
theoretical ratio 2 that represents a change in the crystallization mechanism from
regime I to regime II [
103
]. This is an important clue regarding the mechanism of
crystallization.
It was mentioned earlier that the Hoffman-Lauritzen equation holds for super-
coolings as large as 100 ﾰC that makes it potentially possible to fit both melt and
glass crystallization kinetics with one set of the
K
g
and
U
*
parameters. Figure
3.40
presents the
E
ʱ
versus
T
dependencies for crystallization of PET glass and melt. The
Fig. 3.40
Experimental
E
ʱ
versus
T
data for melt
(
circles
) and glass (
squares
)
crystallization of PET.
Solid
line
represents a fit for the
melt data.
Dashed line
has
been obtained by fitting
combined (
melt and glass
)
crystallization data. (Repro-
duced from Vyazovkin and
Dranca [
108
] with permission
of Wiley)
200
100
0
-100
Melt crystallization
Cold crystallization
K
g
=3.2, U
*
=4.3
K
g
=3.6, U
*
=7.5
-200
-300
-400
400
420
440
460
480
500
T / K
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