Chemistry Reference
In-Depth Information
Fig. 9 Experimental
interfacial tension as a
function of temperature for
PE/PS pairs.
Filled triangles
PE 82,300 (
M
w
/
M
n
= 4.00)/
PS 200,600 (
M
w
/
M
n
= 1.11);
open diamonds
PE 82,300
(
M
w
/
M
n
= 4.00)/PS 18,100
(
M
w
/
M
n
= 1.07);
open
triangles
PE 82,300
(
M
w
/
M
n
8
7
6
5
PE
2
/PS Mn 200,600
PE
2
/PS 18,100 mono
PE
2
/PS 18,100 poli7
4
4.00)/PS 18,100
(
M
w
/
M
n
2.68) [
23
]
180
200
220
240
Temperature (
°
C)
8
Fig. 10 Experimental
interfacial tension as a
function of molecular weight
polydispersity,
M
w
/
M
n
.
Open triangles
PE 82,300
(
M
w
/
M
n
4.00)/PS 18,100;
open circles
PE 82,300 (
M
w
/
M
n
PE2/PS Mn 18.100 g/mol
PE2/PS Mn 107.200 g/mol
7
6
4.00)/PS 107,200 [
23
]
5
4
1,0
1,5
2,0
Polidispersity
2,5
3,0
due to the migration of the short chains of the polydisperse systems to the interface
(see Sect.
3.2.3
). Thus, the short chains act similarly to a surfactant in that they
lower the interfacial tension and broaden the thickness of the interface. Similar
results have been shown by Nam and Jo [
26
] for PBD (
M
n
¼
4100,
M
w
/
M
n
¼
1.4)
and PS (average
M
n
5500). Nam and Jo [
26
] also showed that the temperature
coefficients increased linearly with increasing polydispersity in the range 1.1 1.5.
The interfacial tension between PE and PS increased with increasing PS molec-
ular weight, whereas the influence of molecular weight decreased significantly
when the PS molecular weight exceeded a certain value of the order of 45,000
[
23
]. The experimental data of interfacial tension as a function of molecular weight
could be fitted to a type of power law if two molecular weight ranges were
considered: one below and the other above this characteristic molecular weight.
Moreover, the influence of PS molecular weight on the interfacial tension between
PE and PS was shown to be smaller for lower molecular weights than for higher
molecular weights of PE [
23
]. These are clearly shown in Fig.
11.
