Chemistry Reference
In-Depth Information
determinations for new polymer
solvent combinations or new ranges of polymer
molecular weights.
The equation of Solomon and coworkers
[12]
,
p
2
1
2
η
η
0
2
ln
η
η
0
½
5
1
2
(3-93)
c
is easy to calculate and applies to many common polymer solutions. Reference
[13]
cites other manual calculation procedures for single-point [
η
]'s.
3.3.5
Solution Viscosity Terminology
There are two terminologies in this field. The trivial nomenclature is vague and
misleading but it is widely used. The IUPAC nomenclature
[14]
is clear, concise,
and rarely used.
Table 3.2
lists the common names and usual symbols.
The intrinsic viscosity is also called the limiting viscosity number. Many of
these so-called viscosity terms are not viscosities at all. Thus,
η
r
and
η
sp
are actu-
ally unitless ratios of viscosities; [
η
] is a ratio of viscosities divided by a concen-
tration. The units of [
] are reciprocal concentration and are commonly quoted in
cubic centimeters per gram (cm
3
/g) or deciliters per gram (dL/g). [A deciliter (dL)
equals 100 cm
3
.] The units of
K
in
Eq. (3-71)
must correspond to those of [
η
η
].
The viscosities we have been using in this section are conventional dynamic
viscosities with units of poises or Pas. They are to be distinguished from kinematic
viscosities which have units in stokes and equal the dynamic viscosity divided by
the density of the liquid. The latter are widely used in technology where the mass
flow rate is measured in preference to the volumetric flow rate of
Eq. (3-87)
.
3.3.6
Solution Viscosities in Polymer Quality Control
Solution viscosities are involved in quality control of a number of commercial
polymers. Production of poly(vinyl chloride) polymers is usually monitored in
terms of relative viscosity (
η
/
η
0
) while that of some fiber-forming species is
Table 3.2
Solution Viscosity Nomenclature
Name
Symbol
Definition
Solution viscosity
η
Solvent viscosity
η
0
Relative viscosity
η
r
η/η
0
Specific viscosity
η
sp
η
r
2 15η/η
0
21
Reduced specific viscosity
η
sp
/c
(η
r
2 1)/c
c
21
ln η
r
5
c
21
ln(η/η
0
)
Inherent viscosity
η
inh
Intrinsic viscosity
[η]
c
21
lim
c-0
ðη=η
0
21Þ
