Experimental and Numerical Simulation Study of Devolatilization in a Self-Wiping Corotating Parallel Twin-Screw Extruder

Devolatilization is an important process for separating and removing unnecessary residual volatile substances or solvents during the production of polymers using twin-screw extruders. Latinen proposed a surface renewal model to determine the concentration of volatile components in the extrudate of a single-screw extruder. When a twin-screw extruder is used to calculate the concentration, it is necessary to use the exposed surface area of the resin in the starved region of Latinen’s model, which, however, is difficult to estimate. In our previous work, we numerically determined resin profiles of the screws using the 2.5D Hele–Shaw flow model and the finite element method, which helps in estimating the surface area of devolatilization. In this study, we numerically analyzed the volatile concentration of the extrudate in a self-wiping corotating twin-screw extruder using Latinen’s surface renewal model along with our resin profile calculation method. The experimental results of the concentrations of the volatile component (toluene) in the extrudate of polypropylene agreed well with its numerical calculation with a relative error of 6.5% (except for the data of the lowest rotational speed). Our results also showed that decreasing the flow rate and increasing the pump capacity were effective for removing the volatile component. The screw pitch of a full-flight screw was not affected by the devolatilization efficiency with a fixed flow rate and screw speed.

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The Comparison of Water Absorption Analysis between Counterrotating and Corotating Twin-Screw Extruders with Different Antioxidants Content in Wood Plastic Composites

Advances in Materials Science and Engineering ◽

10.1155/2011/406284 ◽

2011 ◽

Vol 2011 ◽

pp. 1-4 ◽

Cited By ~ 11

Author(s):

Mohd Hafizuddin Ab Ghani ◽

Sahrim Ahmad

Keyword(s):

Water Absorption ◽

Twin Screw Extruder ◽

Screw Extruder ◽

Wood Plastic Composites ◽

Twin Screw Extruders ◽

Plastic Composites ◽

Study Results ◽

Significant Difference ◽

Twin Screw ◽

Screw Extruders

Water absorption is a major concern for natural fibers as reinforcement in wood plastic composites (WPCs). This paper presents a study on the comparison analysis of water absorption between two types of twin-screw extruders, namely, counterrotating and corotating with presence of variable antioxidants content. Composites of mixed fibres between rice husk and saw dust with recycled high-density polyethylene (rHDPE) were prepared with two different extruder machines, namely, counterrotating and corotating twin screw, respectively. The contents of matrix (30 wt%) and fibres (62 wt%) were mixed with additives (8 wt%) and compounded using compounder before extruded using both of the machines. Samples were immersed in distilled water according to ASTM D 570-98. From the study, results indicated a significant difference among samples extruded by counterrotating and corotating twin-screw extruders. The counterrotating twin-screw extruder gives the smallest value of water absorption compared to corotating twin-screw extruder. This indicates that the types of screw play an important role in water uptake by improving the adhesion between natural fillers and the polymer matrix.

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Numerical Simulation of Effect of Slip Conditions on PVC Co-Rotating Twin-Screw Extrusion

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.189-193.1946 ◽

2011 ◽

Vol 189-193 ◽

pp. 1946-1954 ◽

Cited By ~ 1

Author(s):

Ying Han Cao ◽

Jin Nan Chen

Keyword(s):

Flow Rate ◽

Volumetric Flow Rate ◽

Wall Slip ◽

Slip Condition ◽

Twin Screw Extruder ◽

Slip Coefficient ◽

Twin Screw Extrusion ◽

Screw Extruder ◽

Slip Conditions ◽

Twin Screw

The effect of wall conditions on the co-rotating parallel twin-screw extrusion of rigid polyvinyl chloride (RPVC) is studied. The relationship between the shear stress at the screw wall and the slip velocity of the flowing melt obeys Navier’s linear law. At zero pressure difference between the entrance and exit of the melting section of twin-screw extruder, the volumetric flow rate and 3D isothermal flow fields of RPVC are calculated under different wall slip conditions in the metering section of the twin-screw extruder by using the evolution technique in POLYFLOW. The results show that when the slip coefficient is smaller than 104Pa*s/m , the volumetric flow rate of the melt is constant, corresponding to the full slip condition. When the slip coefficient is larger than 104Pa*s/m , with the slip coefficient decreasing, the volumetric flow rate and viscosity increase, but the gradients of velocity, pressure, and shear rate decrease. The residual stress of the product is thus reduced. Therefore, increasing wall slip is good for the stability of polymer extrusion and the product quality. The dispersive and the distributive mixing of the twin-screw extruder under full slip and no slip conditions are also studied. Results show that the mixing performance under no-slip condition is better than under full-slip condition, but slip at the wall is good for the extrusion of heat-sensitive materials.

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Non-Isothermal Simulation of Melting Process in Twin Screw Extruder Based on Two Typical Screw Configurations

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.130-134.2273 ◽

2011 ◽

Vol 130-134 ◽

pp. 2273-2279

Author(s):

Chang Liang ◽

Bing Luo ◽

Kui Sheng Wang

Keyword(s):

Liquid Fraction ◽

Melting Process ◽

Melting Zone ◽

Twin Screw Extruder ◽

Screw Extruder ◽

Twin Screw Extruders ◽

Twin Screw ◽

Higher Temperature ◽

Study Heat Transfer ◽

Screw Extruders

In this study, heat transfer and melting process in a co-rotating twin screw extruder are studied based on two typical screw configurations, screw element and kneading blocks staggered 45°. In order to estimate the melting ability of two configurations quantitatively, FEM software, FLUENT is adopted to simulate the cases. It could be concluded that kneading blocks have higher temperature rise and more liquid fraction than screw element, and it takes less time and less distance for kneading blocks to finish melting. Simulation results also show that kneading blocks have more viscous dissipation than screw element. Therefore, we can come to the conclusion that the kneading blocks are more suitable for the melting zone of co-rotating twin screw extruders.

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Numerical Simulation of Mixing Performance of Intermeshing Co-Rotating Tri-Screw and Twin-Screw Extruders

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.468-471.2211 ◽

2012 ◽

Vol 468-471 ◽

pp. 2211-2214 ◽

Cited By ~ 1

Author(s):

G. Wang ◽

X.Z. Zhu ◽

Chun Yi Sun

Keyword(s):

Shear Rate ◽

Polymer Melt ◽

Polymer Processing ◽

Mixing Efficiency ◽

Twin Screw Extruder ◽

Screw Extruder ◽

Twin Screw Extruders ◽

Mixing Performance ◽

Twin Screw ◽

Dispersive Mixing

Parallel arranged tri-screw extruder (PATSE) is a new machine of polymer processing and first manufactured in recent years in China. Compared with the traditional twin-screw extruder, PATSE adds a screw, and added an intermeshing region. It is well known that material going though intermeshing region will acquire higher shear rate and stretching rate, which is beneficial to mixing processing. In order to know the mixing performance in cross-section for PATSE, polymer melt flow field simulation and mixing simulation were conducted on PATSE with 2D model and a Carreau flow model to evaluate velocity profiles, particle trajectories, max shear rate, max stretching rate, dispersive mixing, distributive mixing, segregation scale, length of stretch, mixing efficiency with the commercial CFD package Polyflow and compared with those of twin screw extruder (TSE). The results show that PATSE has better mixing performance than TSE.

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