Chemistry Reference
In-Depth Information
1.04) matrix at 147
C. The analysis of the drop was
performed using 23 data points for the shape comparison. The correspondence of
the theoretical profile to these data points and to the original digitized drop profile is
excellent [
20
].
The experimental setup, the digital image processing routines, and the robust
shape analysis algorithm have been widely used to study the polymer polymer
interfacial tension [
20
], the effects of copolymeric additives on polymer polymer
interfacial tension [
45
,
48
] and the influence of copolymer molecular weight [
54
]
and architecture [
56
], the surface tension of homopolymers [
169
] and of miscible
polymer blends [
170
], the effects of end-groups on the polymer surface tension and
its molecular weight dependence [
171
], the effects of end groups on polymer
polymer interfacial tension [
172
], the work of adhesion of polymer wall interfaces
[
173
], etc. Moreover, the analysis algorithm was utilized by a different group in the
development of another pendant drop instrumentation [
164
] and their measure-
ments of polymer polymer interfacial tension [
21
].
(PBDH
M
n
¼
4,080;
M
w
/
M
n
¼
3
Interfacial Tension in Binary Polymer Blends
3.1 Experimental Studies of Polymer Interfacial Tension
Although knowledge of the interfacial tension in polymer/polymer systems can
provide important information on the interfacial structure between polymers and,
thus, can help the understanding of polymer compatibility and adhesion, reliable
measurements of surface and interfacial tension were not reported until 1965 for
surface tension [
135
,
138
] and 1969 for interfacial tension [
127
,
154
] because of the
experimental difficulties involved due to the high polymer viscosities. Chappelar
[
145
] obtained some preliminary values of the interfacial tension between molten
polymer pairs using a thread breakup technique. The systems examined included
nylon with polystyrene, nylon with polyethylene (PE), and poly(ethylene tere-
phthalate) with PE; the values are probably only qualitatively significant [
174
].
Determinations by Roe [
154
] and Wu [
127
,
152
,
153
] using the pendant drop
method and by Hata and coworkers [
128
,
175
] using the sessile bubble technique
have yielded values for a number of polymer pairs as a function of temperature.
Gaines [
174
] and Wu [
10
,
120
,
176
] provided extensive reviews of the early work in
the area of surface and interfacial tension of polymer liquids and melts.
In general, and for polymers that exhibit a miscibility gap at lower temperatures
(blends that show upper critical solution temperature, UCST, behavior), interfacial
tension is found to decrease linearly with increasing temperature, with temperature
coefficients of the order of 10
2
dyn/(cm
C) [
10
]. This is about one half of the values
observed for the temperature coefficients of polymer surface tension [
10
,
120
,
176
].
An increase in the molecular weight of either polymer leads, in general, to an
increase in interfacial tension [
10
,
19
,
20
,
120
,
176
]; however, there are few
