Scale-up consideration for polymerization in a twin-screw extruder using 3-D numerical simulation
Scaling up a polymerization process in the fully filled screw elements of co-rotating twin-screw ... more Scaling up a polymerization process in the fully filled screw elements of co-rotating twin-screw extruders was investigated with a 3-D Finite Volume Method. The simulation results show that, with identical mean residence time in the screw elements, the polymerization progression is accelerated when the screw diameter is increased. Moreover, the difference in conversion based on 1-D and 3-D models becomes more significant with increasing screw dimension, indicating that 1-D model can not predict the polymerization progression correctly in large extruders. The polymerization requires short screw length (LID) to complete when the screw diameter is increased. This may be due to the fact that the heat loss through the barrel surface is more difficult to occur, and the non-uniformity in temperatures at the cross section of screw elements becomes more pronounced after scaling up.
A new type of hydrogels based on poly(styrene-alt-maleic anhydride) (PSMA) was prepared via Diels... more A new type of hydrogels based on poly(styrene-alt-maleic anhydride) (PSMA) was prepared via Diels-Alder click chemistry. The formulations consisting of tetrazine-functionalized PSMA as a multi-clickable polymer and norbornene-terminated poly(ethylene glycol) (PEG) as a polymeric cross-linker were used as precursors to give ultrafast hydrogels with controlled structures. The hydrogels formed within several minutes under a physiological condition without any catalyst, and their storage modulus (G′) values were in the range 0.3-1.7 kPa suitable for bio-applications. The pore structure and the release profile of doxorubicin hydrochloride (DOX•HCl) of the hydrogels could be manipulated by the molecular weight of PEG. The precursors exhibited practically no depressing effect of the normal HEK293 growth, while the DOX•HCl-loaded hydrogel presented significant anticancer activity towards HeLa cells. The results suggested this biocompatible hydrogel as a potential injectable drug depot for tumor sites.
Melt rheology of vinylidene chloride‐vinyl chloride copolymers
Journal of Vinyl Technology, 1986
A continuous extruder slit‐die rheometer system determines the rheological properties of thermall... more A continuous extruder slit‐die rheometer system determines the rheological properties of thermally sensitive copolymers of vinylidene chloride and vinyl chloride to aid the design of processing screws, melt dies, and coextrusion feed blocks for the production of barrier film. The flow of VDC‐VC copolymers was dependent on molecular weight, temperature, and shear rate. Increased chain mobility causes low‐melting‐temperature copolymers to flow more easily. Liquid additives also reduce viscosity.
This report introduces a new Engineering approach for the scale-up of high performances screws in... more This report introduces a new Engineering approach for the scale-up of high performances screws in Tandem extruder system for Polystyrene Foam manufacturing.
Industrial & Engineering Chemistry Process Design and Development, 1966
When mixing solids, it is desirable to be able to evaluate the performance of a mixer in terms of... more When mixing solids, it is desirable to be able to evaluate the performance of a mixer in terms of its ability to produce mixtures that approach the theoretical limit of uniformity. Although a satisfactory correlation exists for mixtures where the particles are of uniform size, none has yet been developed for multisized particles. A mathematical definition of a perfect mixture of three sizes of particles is proposed. The principles employed can be extended to any number of sizes, but the complexity of the equations increases rapidly. Agreement with experimental results appears substantially better than that obtained by previous investigators.
Gear pump assisted extrusion is becoming popular in the plastics processing industries. The growt... more Gear pump assisted extrusion is becoming popular in the plastics processing industries. The growth has been tremendous since 1980. In this study, the benefits of gear pump assisted extrusion, especially in single screw applications, is critically reviewed, and a method of predicting the operational conditions of the gear pump assisted extrusion system is discussed. Further, shortening the length to diameter ratio of the extruder in gear pump assisted extrusion was analyzed and found to produce a reduction in energy consumption, provided melting is completed.
abstrzu;t; Undemanding how polymers will process in such as extruders, injection molding machines... more abstrzu;t; Undemanding how polymers will process in such as extruders, injection molding machines, and dies can be met through academic-industry cooperation. With declining R&D budgets and globalization of businesses, this cooperation is extremely valuable for continuing fundamental research in polymer processing and fabrication technologies. This paper illustrates some examples and suggests how industry can best benefit from these programs
Rheological Properties of Molten Polymers. III. Shear-Dependent Melt Viscosity
Transactions of the Society of Rheology, 1969
The steady-state capillary flow data for several commercial polystyrene melts have been analyzed,... more The steady-state capillary flow data for several commercial polystyrene melts have been analyzed, and the shear-dependency of viscosity for these melts has been compared with theoretical results from Pao’s nonlinear hydrodynamic theory. Pao’s theory allows one to calculate the shear-dependent viscosity in terms of viscoelastic constants, such as retardation times and shear compliances which can be obtained from tensile creep experiments. Using the viscoelastic data obtained in Part II of this series in Pao’s equation, a semiquantitative agreement has been obtained. In most cases, the agreement was within a factor of two in the range where experimental data were available. Introducing a modifying factor common to several commercial polystyrene melts in calculating the retardation spectrum has improved the agreement between experimental data and theoretical results.
Investigation of mixing mechanisms and energy balance in reactive extrusion using three-dimensional numerical simulation method
International Journal of Heat and Mass Transfer, 2005
ABSTRACT The polymerization of ε-caprolactone in fully-filled conveying elements of co-rotating t... more ABSTRACT The polymerization of ε-caprolactone in fully-filled conveying elements of co-rotating twin-screw extruders was analyzed with three-dimensional numerical simulation method. The effects of screw rotational speed, geometry of screw element, and initial conversion at the channel inlet on polymerization progression were studied. The simulation results show that polymerization is accelerated with increasing screw pitch, due to the increase in mixing intensity. With increasing screw rotational speed, the reaction could either slow down or speed up, depending on the viscosity of the reaction system. It is found that the advancement of polymerization depends on the competition among heat from reaction, viscous dissipation and heat loss through the wall surfaces.
Theoretical and Experimental Analysis of Solids Conveying in Single-Screw Extruders
Journal of Reinforced Plastics and Composites, 1997
Solids conveying is the least understood process for single-screw extruders. This lack of underst... more Solids conveying is the least understood process for single-screw extruders. This lack of understanding was caused by the unavailability of solids conveying rate data. A new device has been developed to measure solids conveying rates as a function of barrel and screw temperatures, screw speed, and discharge pressure. These data along with friction and bulk density data will be used to determine the accuracy of several solids conveying models.
Barrier flighted screws have been used for many years to increase rates, to eliminate flow surgin... more Barrier flighted screws have been used for many years to increase rates, to eliminate flow surging due to solid bed break up, to lower melt temperatures, and to minimize temperature fluctuations in the extrudate. For most barrier screws, the melt separation flight starts at a location where the melt pool starts to accumulate. However, if the start of melting occurs downstream from this point, compacted solid polymer can be wedged into the start of the barrier entrance. For some barrier screws, this wedging can lead to a restriction in the flow, decreasing the rate of extrusion by up to 30%. This paper will discuss the phenomenon and show how to eliminate the problem.
The size of flight radii on the screw channel is important for the proper performance of a single... more The size of flight radii on the screw channel is important for the proper performance of a single-screw extruder. SPI guidelines state that the root radii should not be less than half the depth of the channel. Improper design or fabrication, however, often results in radii that are less than half that for the metering and transition sections, leading to regions with long residence time and material degradation. For optimal solids conveying, however, the effect of flight radii is considerably more complicated. This paper will present experimental and numerical data that indicate how to specify the flight radii for all sections of the screw.
Frictional Behavior of Polyethylenes with Respect to Density and Melting Characteristics
Metallocene Catalyzed Polymers, 1998
The frictional behavior of 12 polyethylene samples with densities ranging from 0.963 down to 0.87... more The frictional behavior of 12 polyethylene samples with densities ranging from 0.963 down to 0.870 g/cc on a metal surface was studied. The samples with densities higher than 0.908 g/cc behaved as rigid plastics, sliding on the metal surface. The samples with densities lower than 0.905 g/cc behaved as elastomers, strongly adhering on the metal surface and tearing within the polymer. Melting occurred when the metal was heated to a temperature above the melting range of the sample. The frictional behavior of a polyethylene can be understood in terms of the density and melting temperature range of the sample.
This report introduces a new Engineering approach for heat transfer mechanism to improve and deve... more This report introduces a new Engineering approach for heat transfer mechanism to improve and develop the manufacturing process of XPS Polystyrene form. The success in this process will trickle down to other foam processes to improve the productivity and energy savings.
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Papers by Kun Hyun