Stress relaxation characteristics and extrudate swell of the IUPAC-LDPE melt

Prediction of extrudate swell in polymer melt extrusion using an Arbitrary Lagrangian Eulerian (ALE) based finite element method

“…Later, more realistic constitutive equations such as the integral K-BKZ model [5][6][7][8][9][10][11][12][13] and the differential PTT model [14][15][16] were used. Different types of damping functions such as the Wagner irreversible and reversible [9][10][11] damping functions, the Papanastasiou-Scriven-Macosko (PSM) type damping function [5][6][7][8], the Osaki twin exponential damping function [17] and a new three-parameter damping function suggested by Huang and Lu [13], have been used in conjunction with the K-BKZ model to study the effect of rheological non-linearities on extrudate swell. Similarly, the effect of second normal stress difference was considered in addition to the dominant effect of the first normal stress difference [6,10].…”

“…A review of more recent literature on extrudate swell simulations has been given by Huang and Lu [13]. Some of the numerical studies on extrudate swell are based on the Streamline Finite Element Method (SFEM) introduced by Luo and Tanner [5].…”

Die Swell of Complex Polymeric Systems

“…In testing the validity of the model for a system with large L/D, the rheometric and swell data of a pure IUPAC-LDPE standard was used as shown in Figures 1 and 2 [77,78]. The capillary had die diameter 3.00 Dm m  and experiments were carried out at 150℃.…”

“…The test temperature was 190 o C, and apparent shear rates were varied from 50 to10 -4 s -1 . experimental data for LDPE [77] of   and 1Ñ  .…”

“…The dashed curves in Figure 2 present the experimental data [77] Figure 2) and by Eq. (5) (as shown by the solid curves in Figure 2).…”