Die swell behaviour of polypropylene ? An experimental investigation

Effects of the actual diameters and diameter ratios of barrels and dies on the elastic swell and entrance pressure drop of natural rubber in capillary die flow

“…The test temperature during the extrudate swell measurement was 80°C, and the shear rate ranged from 2 to 50 s −1 . Because the t r value of the material flowing in the die is related to the relaxation of the polymer molecules, it is regarded as one of the major factors influencing the extrudate swell t r can be determined with the die dimensions ( L / D ) and wall shear rate (γ w ):16 …”

State of the‐Art for Extrudate Swell of Molten Polymers: From Fundamental Understanding at Molecular Scale toward Optimal Die Design at Final Product Scale

“…Polymer melts are forced to enter the die from the (extrusion equipment) reservoir by contraction flow so that complex flow behavior including extensional and shear flow variations is realized. The characteristics or dimensions of the die geometry such as the lL/D, [23,28] the die entrance angle, [20,23] and the ratio between the diameter of reservoir and the die [21,84] play a significant role in affecting the swelling behavior of viscoelastic flows. Moreover, there can be a difference in the overall geometry with the two important classes being capillary and slit dies.…”

“…Anand and Bhardwaj [28] reported the extrudate swelling of two types of PP melts through capillary dies with various L/D values. They found that in case the die diameter was set to 5 mm with L/D ratios of 4, 9, 14, and 23, the swelling ratio decreased with the increase of L/D ratio at a given shear rate.…”

“…[20][21][22][23][24] The earlier studies related to extrudate swell of polymers focused on utilizing the capillary rheometer with a circular or slit die to experimentally study the effect of processing parameters, flow geometry, molecular characteristics, and filler content. [25][26][27][28][29][30] However, measuring the extrudate swell is a tough task because of its susceptibility to measurement conditions, such as sagging or gravity influences and ambient temperature variations. Therefore, a highly precise measurement method is always an important element regarding the study of the swell behavior of polymer melts.…”

Extrudate swell in some dilute elastic solutions

“…The capillary length was governed by the requirement that fully developed flow exists well upstream of the exit plane. In the experiments an L/d ratio of 27.95 was used, which, assuming the capillary to have consistent bore dimensions, ensured fully developed flow well upstream of the exit plane [17][18][19]. The capillary exit was machined to achieve an exit shape approximating that of the assumed knife edge.…”