• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.260-265
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• 2007

Rubber compounds have high viscoelastic property. One of the viscoelastic behaviors during profile extrusion is the swelling of extrudate. In this study, die swells of rubber compounds at the capillary die have been investigated through experiment and computer simulation. Experiments and simulations have been performed using fluidity tester and commercial CFD code, Polyflow respectively. Die swells of rubber compounds in a capillary die were predicted using non-linear differential viscoelastic model, Phan-Thien-Tanner(PTT) model for various relaxation times and relaxation modes. The results of simulation were compared with the experiments. Pressure and velocity distribution, and circulation flows at the comer of capillary die have been investigated through computer simulation. It is concluded that the PTT model successfully represented the amount of the die swell of rubber compounds for various relaxation times at different modes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.209-212
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• 2007

Rubber compounds have high viscoelastic property. One of the viscoelastic behaviors during profile extrusion is the swelling of extrudate. In this study, die swell of rubber compounds at the capillary die have been investigated through an experiment and computer simulation. They have been performed using fluidity tester in experiment and commercial CFD code, Polyflow in computer simulation. Die swell of rubber compounds for relaxation time at several modes under same conditions with the experiment were predicted using non-linear differential viscoelastic model, Phan-Thien-Tanner (PTT) model. The simulation was analyzed compared with the experiment. Viscoelastic behaviors for pressure, velocity and shear rate distribution were analyzed at the capillary die. It is concluded that the PTT model successfully represented the amount of the optimal die swell of rubber compounds for relaxation time at different modes.

• Elastomers and Composites
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• v.41 no.4
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• pp.223-230
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• 2006

Rubber compounds have a high viscoelastic property. One of the viscoelastic behaviors during profile extrusion is the swelling of extrudate, and the amount of swelling varies with operational conditions in extrusion. It is well recognized that the elastic portion in the viscoelastic property plays an important role in the extrudate swell. In this study computer simulation of the die swell at the capillary die for several rubber compounds has been performed using commercial CFD code, Polyflow. A non-linear differential viscoelastic model, Phan-Thien-Tanner (PTT) model, was used in the computer simulation. Non-isothermal behavior was considered in the calculation. Distribution of pressure, velocity and temperature in the reservoir and capillary die, and extrudate profiles were predicted through the simulation. The amount of the die swell fur the different rubber compounds was investigated for various flow rates and three types of length to diameter of the capillary die. It is concluded that the PTT model successfully represented viscoelastic behavior of rubber compounds.

• Elastomers and Composites
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• v.22 no.3
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• pp.213-218
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• 1987

In this study, the rheological properties of a partially valcanized black filled EPDM were investigated as a function of degree of crosslinks using capillary rheometer. In order to obtain the samples having various degree of crosslinks between 0 and 6 percent, the vulcanization kinetics was also studied by Monsanto rheometer. The results showed that the die swell ana the pressure drop at the capillary entrance and exit increase nearly linearly with the increase in degree of crosslinks. However, melt fracture occurred at a lower shear rate for the samples of higher degree of crosslinks. These results were discussed in terms of the melt elasticity produced at the entrance region of capillary by the partial vulcanization. It is also interesting to note that the fluctuation of die swell during the practical extrusion or calendering process in the factories can be caused by the partial vulcanization occurred during the process.

• Design & Manufacturing
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• v.14 no.3
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• pp.31-36
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• 2020

In injection molding processes, the property of molten resin should be characterized accurately. Among several properties, the PvT state is the most important one, since it affects the shrinkage, warpage, molded weight, and the part density. Thus, the PvT data is crucial to the simulation of the injection molding process. This work shows how such a measurement can be performed for a semi-crystalline and amorphous polymers. The PvT measurement has been conducted using a capillary rheometer using a suitable accessory that blocks the capillary. The results have shown that the PvT data can be obtained using such a rheometer and then the PvT coefficients of the Tait equation can be reached.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.92-96
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• 2019

In the presence of ${\mu}-tip$ embedded in a slot-die head for stripe coatings, there arises the capillary flow that limits an increase of the stripe density, which is required for the potential applications in organic light-emitting diode displays. With an attempt to suppress it, we have employed a computational fluid dynamics software and performed simulations by varying the ${\mu}-tip$ length and the contact angles of the head lip and ${\mu}-tip$. We have first demonstrated that such a capillary flow phenomenon (a spread of solution along the head lip) observed experimentally can be reproduced by the computational fluid dynamics software. Through simulations, we have found that stronger capillary flow is observed in the hydrophilic head lip with a smaller contact angle and it is suppressed effectively as the contact angle increases. When the contact angle of the head lip increases from $16^{\circ}$ to $130^{\circ}$, the distance a solution can reach decreases sharply from $256{\mu}m$ to $44{\mu}m$. With increasing contact angle of the ${\mu}-tip$, however, the solution flow along the ${\mu}-tip$ is disturbed and thus the capillary flow phenomenon becomes more severe. If the ${\mu}-tip$ is long, the capillary flow also appears strong due to an increase of flow resistance (electronic-hydraulic analogy). It can be suppressed by reducing the ${\mu}-tip$ length, but not as effectively as reducing the contact angle of the head lip.

• Proceedings of the Korean Society of Rheology Conference
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• 2002.05a
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• pp.149-152
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• 2002

• Journal of the Semiconductor & Display Technology
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• v.18 no.2
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• pp.6-10
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• 2019

In the presence of $\mu-tip$ for narrow stripe coating, there appears lateral capillary flow along the hydrophilic head lip because the $\mu-tip$ has some resistance to flow. It was known to be suppressed by increasing the contact angle of the head lip. In this paper, we have demonstrated by computational fluid dynamics(CFD) simulations that it can also be suppressed by the formation of micro-patterns on the shim and meniscus guide embedded into the slot-die head. To optimize the micro-patterned structure, we have performed simulations by varying the groove width, depth, and clearance. In the absence of micro-patterns, it is shown by experiment and simulation that the solution spreads to a distance of $1,300{\mu}m$ from the ${\mu}-tip$. In the presence of micro-patterns with the groove width and clearance of $50{\mu}m$, the distance the solution spreads is reduced to $260{\mu}m$. However, no further suppression in the capillary flow is observed with micro-patterns with the groove width of $40{\mu}m$ or less. It is also observed that the capillary flow is not affected by the groove depth if it is larger than $10{\mu}m$. We have shown that the distance the solution spreads can be reduced further to $204{\mu}m$ by coating a hydrophobic material (contact angle of $104^{\circ}$) on the surface of micro-patterns having the groove width and clearance of $50{\mu}m$.

• Elastomers and Composites
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• v.46 no.1
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• pp.54-59
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• 2011

One of the viscoelastic flow behaviors during profile extrusion is the swelling of extrudate. In this study, die swell of rubber compound in the capillary die have been investigated through experiment and computer simulation. Simplified viscoelastic model and non-linear differential viscoelastic model such as PTT model have been used in the computer simulation. The simulation results have been compared with experimental data. Experiment and simulation have been performed using fluidity tester and commercial CFD code, Polyflow respectively. Die swells predicted by two models showed good agreement with experimental results. Pressure and velocity distribution, and circulation flow at the corner of reservoir have been well predicted by PTT model. Simplified viscoelastic model can not predict circulation flow at the corner of reservoir. However this model has an advantage in computation time compare with full viscoelastic model, PTT model.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.351-363
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• 2001

This paper presents an experimental investigation on the heat trensfer characteristic of micro pipe (MHP) array with 38 triangular microgrooves. A heat pipe is an effective heat exchanger operating without external power. The heat pipe transfers heat by means of the latent heat of vaporization and two-phase fluid flow driven by the capillary force. The overall size of the MHP array can be put undermeath a microelectonic die and integrated into the electrronic package of a microelectronin device to dissipate the heat from the die. The MHP array is fabricated by micromachining with a silicon wafer and a glass substrate. The MHP was filled with water and sealed. The experimental results show the temperature decrease of 12.1$^{\circ}C$ at the evaporator section for the input power of 5.9 W and the improvement of 28% in the heat transfer rate.