Biomedical Engineering Reference
In-Depth Information
Fig. 2
Viscosity ratio
λ
versus PDMS drop size (
D
) for PS/PDMS blends [8]
Chuai et al. [9] studied the influence of the viscosity ratio on the morph-
ology of a PS/PDMS blend in order to determine the composition range
where a co-continuous structure is obtained. Since a good synergy of the ho-
mopolymer properties arises from co-continuous blends, they are of great
interest. For more information, the reader is referred to the excellent review
by Pötschke and Paul [10]. Chuai et al. compared three different PS/PDMS
systems with varying PS viscosities and fixing the PDMS one. Using a typical
extraction method, they measured the degree of continuity (Eq. 2) for each
pair of homopolymers for various polymer compositions.
mass of polymer 1 (residual or extracted)
mass of polymer 1 in the sample before extraction
.
Φ
i
,1
=
(2)
They observed that the range of compositions was broader for the PS/PDMS
pair having the smaller viscosity ratio. This tendency is in good agreement
with the predicted relationship [11-14]:
η
1
(
.
γ
)
η
2
(
.
γ
)
≈
Φ
1,PI
(3)
Φ
2,PI
1
(1 +
Φ
2,PI
=
)
.
(4)
λ
the viscosity and
.
γ
the
shear rate applied for mixing the blend. Equation 4 is obtained from Eq. 3
with
In Eq. 3, 1 and 2 are the blend components,
η
λ
=
η
1
/η
2
and
Φ
2,PI
=1-
Φ
1,PI
. However, accurate calculated theoretical
