Eperimental studies were performed on a series of degraded PP resins obtained by repeated extrusion for 0 to 8 times at 250℃. By means of a capillary extrusion rheometer with various entry angles and length/diameter ratios (L/D=1

2

5

10

20

40) of the capillaries as well as a falling sphere viscometer

the following rheological quantities were measured: zero shear rate viscosity η0

apparent viscosity η

entrance pressure loss ΔP0 and extrudate swell.Both the narrowing of the molecular weight distribution and the lowering of the molecular weight during the degradation process have profound effects on the previous flow behavours. It is suggested that stress t1/2(wheren=n0/2)

the value e(e=△Po/2t)and the die swell from a very short die can be used to characterize the existence of high molecular tail of MWD

which greatly influences the processability of the melts.