Handbook of Solvents - George Wypych - ChemTech - Ventech!

688 George Wypych
Viscosity, Poise
10 6
10 5
10 4
1 10 100 1000
individual polymers does not necessarily have a bearing on the viscosity of their solutions.
Both poly(ethylene oxide) and poly(propylene oxide) are not affected by solution pH but,
when used in combination, they become sensitive to solution pH. A rapid increase of viscosity
at a lower pH is ascribed to intermolecular complex formation. This behavior can be
used for thickening of formulations. 8
Figures 12.1.9 and 12.1.10 show one potential application in which a small quantity of
solvents can be used to lower melt viscosity during polymer processing. Figure 12.1.9
shows that not only can melt viscosity be reduced but also that the viscosity is almost independent
of shear rate. 10 In environmentally friendly process supercritical fluids can be used
to reduce melt viscosity.
The above data illustrate that the real behavior of solutions is much more complex than
it is intuitively predicted based on simple models and relationships. The proper selection of
solvent can be used to tailor the properties of formulation to the processing and application
needs. Solution viscosity can be either increased or decreased to meet process technology
requirements or to give the desired material properties.
REFERENCES
Shear rate, s -1
20% solvent
no solvent
Figure 12.1.9. Apparent melt viscosity of original PET
and PET containing 20% 1-methyl naphthalene vs.
shear rate. [Adapted, by permission, from S Tate,
S Chiba, K Tani, Polymer, 37, No.19, 4421-4 (1996).]
1000
100
10 100 1000
1 A Ya Malkin, Rheology Fundamentals, ChemTec Publishing, Toronto, 1994.
2 Ch W Macosko, Rheology. Principles, Measurements, and Applications, VCH Publishers, New York,
1994.
3 R I Tanner, K. Walters, Rheology: an Historical Perspective, Elsevier, Amsterdam, 1998.
4 C R Schultheisz, G B McKenna, Antec ‘99, SPE, New York, 1999, p 1125.
5 F Motamedi, M Isomaki, M S Trimmer, Antec ‘98, SPE, Atlanta, 1998, p. 1772.
6 G D J Phillies, Macromolecules, 28, No.24, 8198-208 (1995).
7 M Ponitsch, T Hollfelder, J Springer, Polym. Bull., 40, No.2-3, 345-52 (1998).
8 I C De Witte, B G Bogdanov, E J Goethals, Macromol. Symp., 118, 237-46 (1997).
9 H Raval, S Devi, Angew. Makromol. Chem., 227, 27-34 (1995).
Viscosity, Pa s
10 4
Shear rate, s -1
4wt%CO 2
no CO 2
Figure 12.1.10. Viscosity behavior of PS with and
without CO 2. [Data from M Lee, C Tzoganikis,
C B Park, Antec ‘99, SPE, New York, 1999, p 2806.]