Bk. Aral et Dm. Kalyon, VISCOELASTIC MATERIAL FUNCTIONS OF NONCOLLOIDAL SUSPENSIONS WITH SPHERICAL-PARTICLES, Journal of rheology, 41(3), 1997, pp. 599-620
We have characterized various steady and time-dependent material funct
ions of suspensions of a non-Newtonian binder, poly(dimethyl siloxane)
, incorporated with 10%-60% by volume of hollow and spherical glass be
ads. The material functions included storage and the loss moduli, shea
r stress and first normal stress difference growth and relaxation, rel
axation modulus upon step strain and creep and recovery behavior. Both
constant shear stress and shear rate experiments were carried out usi
ng multiple rheometers over a broad temperature range (-35 to 40 degre
es C) while following sample fracture and wall slip effects. With incr
easing volume fraction, phi, of the noncolloidal particles, the strain
range, over which linear viscoelastic behavior is observed, became na
rrower and the relaxation time of the suspension increased. Increasing
solid content gave rise to the development of the yield stress and th
e dependence of large amplitude oscillatory shear properties on time a
nd deformation history. The yield stress values increased with phi, bu
t were not sensitive to temperature. For phi greater than or equal to
0.3 the first normal stress difference values reached reproducible and
steady negative values (with tensile force positive). Larger negative
values of the first normal stress difference were observed with incre
asing deformation rate and solid concentration. The manifestations of
the material functions resulting from the incorporation of the solids
into the non-Newtonian binder included the suppression of the extrudat
e swell and the dipping of the free surface in the Weissenberg experim
ent. (C) 1997 The Society of Rheology.