Rheological properties, extrudate swell, and die entry extrusion flow marker experiments for rubber–carbon black compounds

ABSTRACT:The effects of the actual diameters and diameter ratios of barrels and dies on the elastic swell and entrance pressure drop of natural rubber compounds in an extrusion capillary rheometer were investigated. Either the barrel diameter or the die diameter was altered so that diameter was fixed, the relationship between the entrance pressure drop and the extrudate swell was linear up to a certain value of the barrel diameter greater than 30 mm. Beyond this critical barrel value, the relationship became nonlinear and associated with the shearing stress generated by the formation of semipluglike flow patterns and the residence time of the material. For a constant barrel diameter, the smaller the die diameter was, the greater the extrudate swell was because of the increases in the extensional deformation and wall shear rate coupled with a reduction in the material residence time.

Section: Introductionmentioning

confidence: 99%

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

Sombatsompop

Dangtangee

2002

“…The results indicated that the elastomers exhibited streamline flow into the entrance in all cases except degraded rubber, which gave evidence of vortices in the die corners. Song et al6 conducted flow marker experiments of various rubber compounds, including natural rubber (NR), styrene butadiene rubber (SBR), and ethylene propylene‐diene monomer (EPDM), in the barrel of a capillary rheometer using a wide range of die designs. They found that the radial flow simply moved inward to the capillary die as the ram moved down the barrel, with no evidence of secondary flows.…”

Section: Introductionmentioning

confidence: 99%

Flow visualization and extrudate swell of natural rubber in a capillary rheometer: Effect of die/barrel system

Sombatsompop

Dangtungee

2001

An investigation was carried out to examine the effect of die/barrel system on the flow patterns and extrudate swell of natural rubber in the barrel of a capillary rheometer, using a colored tracer as the visualization technique. The capillary rheometer used in this work had two dies located along the barrel, which is novel in rheometer design. The flow of the rubber in the upper barrel was dependent on the piston/barrel action and changed with piston displacement, whereas the complexity of the flow in the lower barrel was dependent not only on the piston displacement, but also on the geometry of the upper die design. The flow patterns that developed in the whole barrel were independent of the die located at the bottom of the barrel. In addition, the change in extrudate swell was associated with the flow occurring in the barrel, residence time, elastic characteristic, and the temperature rise during the flow. It was concluded that the general style of the flow patterns of natural rubber was greatly dependent on the die geometry that the material had previously moved past.

“…It is worth mentioning that the upper limit of the validated shear rate range,

1.57 \times 10^{2} 1 / s

, is high enough to cover the maximum shear rate in the numerical work. Due to the difficulties inherent to the rheological measurements of filled elastomers, the lower limit of the validated range reaches only

1.57 \times 10^{- 1} 1 / s

. We have to admit that, within the computational domain, there are regions in which the shear rates could be lower than this value.…”

Section: Resultsmentioning

confidence: 98%

An integrated numerical study of coextrusion flow inside and outside the die

Yang¹,

2016

The three-dimensional coextrusion flow of two polymer melts is solved over the die-extrudate region using the finite element method. As elastic recovery is known to be the main source of extrudate swelling, a viscoelastic constitutive model (the Phan-Thien-Tanner or PTT model) is adopted to characterize the rheological behavior of the elastomers. A major challenge in the simulation of multilayer flow inside and outside the die is to update multiple moving surfaces (material interface and extrudate free surface) simultaneously. This difficulty is resolved by introducing a two-step updating algorithm which decouples the iterations of the interface and the free surface. The effects of extrudate swelling and bending on interface deformation are investigated herein, together with the interface shape dependency on flow elasticity. The numerical method is also applied to an industrial profile and the simulation result is in quantitative agreement with the experimental coextrusion data. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43522.