The rubber(R) phase and polystyrene (PS) phase of high impact poly-styrene(HIPS)prepolymer were separated by means of ultracentrifuge

in order to investigate their rheological behavior separately. Below 17% conversion

the rheological behavior of the PS phase is Newtonian

and this viscosity can be estimated by where CPS and Mw

are

respectively

wt% concentration and weight-average molecular weight of PS in the PS phase

while above 17% conversion

the PS phase begins to exhibit pseudoplastic behavior

with its apparent viscosity rising drastically as the conversion increases. On the other hand

the R phase shows pseudoplastic behavior during the whole range of prepol-ymerization

and its apparent viscosity can be correlated with the graft de-gree(E)and the concentration(CR)of rubber as well as shear rate(r)bywhere The influence of conversion and shear rate on the two-phase viscosity ratio (ηR/ηps)were also discussed. Finally

viscosities of the prepolymer system and of its two phases were correlated by the following equation

which was derived from an alternative layer model Where A and B are adjustable parameters

φPS is volumetric fraction ot polystyrene.