The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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An Investigation into the Cooling of Blown Film
The focus of this investigation was develop a relatively simple model which could be used in blown film simulation. We desired to have the model represent the major contributors to the heat transfer for blown film. Our experimental results suggested that the heat transfer coefficient went through a maximum as the the bubble expanded. We have proposed a physical model which is consistent with our experimental observations. The model is based on a 3D representation of the boundary layer of ain around the bubble.
Process Stability Enhancement by Encapsulation Extrusion Method
A film casting simulation has been used to demonstrate why the encapsulation extrusion process is so effective industrially in enhancing the stability of the extrusion. In the present study, it is intended to explain theoretically why and how the coextrusion of LDPE in encapsulation dies improves the HDPE process. The undesirable neck-in and draw resonance phenomena frequently occurring in the extrusion of HDPE are shown due to its low-melt-strength property, and consequently can be alleviated using high-melt-strength materials in the encapsulating dies.
Performance Analysis of a Variable Barrier Energy Transfer Screw
High plastication rates and high quality extrudates are often difficult to produce using single-screw extruders, especially at low discharge temperatures. A new screw called a variable barrier energy transfer (VBET) screw was recently developed to plasticate at high rates, low discharge temperatures, and with high melt qualities. The fundamental operation of the screw along with performance aspects will be presented. A comparison is made between the melting, pumping, and mixing characteristics of an Energy Transfer (ET) screw and VBET screw.
Novel Barrel Heating with Natural Gas
Normally for direct heating of barrels in plastic processing machines electrical resistance heaters are used. A newly developed heating/cooling system uses natural gas. This paper explains the design and realization of a unit where the exhaust air from a radial burner heats the barrel by convection and radiation. Integrated cooling possibility by a tangential incoming airflow also meets practical requirements. Transforming basic energy is not necessary, which leads to CO2 reduction and lower energy costs for the processors.
On-Line Visualization of PS/PP Melting Mechanisms in a Twin-Screw Extruder
The melting and deformation mechanisms of polystyrene (PS) and polypropylene (PP) blends were investigated through on-line visualization of the co-rotating twin-screw extrusion process. A sliding barrel technique was used to realize the on-line visualization with one glass window in the barrel. The axial temperature and pressure profiles along the screw channel were measured using the same sliding technique. Different melting mechanisms were found for the PP/PS (80:20) blend and PS/PP (80:20) blend.
Engineering Analysis of Devolatilization of Additives in Intermeshing Co-Rotating Twin Screw Extruders
An experimental study of various operation conditions and screw configurations was made to understand and solve devolatilization problems in intermeshing co-rotating twin screw extruders. This includes studying additives (Nonane, Hexanol, p-Xylene) of polyethylene. We describe devolatilization through a model of interfacial area and mass transfer coefficients in an intermeshing co-rotating twin screw extruder.
Flow Behavior of Newtonian Fluid through Conveying Elements and Kneading Blocks
The flow behavior of a Newtonian fluid through conveying elements and kneading blocks in a co-rotating twin screw extruder was examined by drag and pressure flow experiments. These results are compared with existing computer models. Also the flow behavior of the different kneading blocks and the conveying elements are compared with each other. The results can guide when to decide which mixing elements to use and can help with future computer modeling.
Modeling of Polymer Drop Deformation and Breakup during Melting under Shear Flow Using Volume-Of-Fluid Method
Polyethylene (PE) or polycarbonate (PC) drop breakup process in PE melt under shear flow was investigated using volume-of-fluid method. Real properties of polymers, and temperature and shear rate dependent viscosity model were incorporated in the modeling. An erosion mechanism was found for both PE and PC drops. Local flow information, such as shear rate, viscosity and shear stress, was obtained from the simulation results. Highest shear stress was observed at the interface, which could explain the erosion breakup mechanism.
New Intermeshing Pin Mixer for Extrusion
It is well known that reorientation of interfaces is key to efficient distributive mixing. However, how to achieve reorientation is not well known. This paper describes how interfaces can be reoriented in screw extruders and which method leads to the most effective reorientation. A new mixing device was developed to achieve highly efficient reorientation by utilizing an intermeshing mixing action between the screw and a floating sleeve. Test results indicate that the intermeshing pin mixer can produce excellent mixing quality over a short axial length, as short as one diameter.
Polytetrafluoroethylene (PTFE) Paste Preforming: The Effects of Viscosity and Surface Tension of Lubricants
Conventional processing methods are not applicable to PTFE due to its high melting point (342°C). Therefore, PTFE is processed by means of paste extrusion (extrusion of a mixture of PTFE powder with a lubricant). The physical properties of this new phase (lubricant) influence both the preforming stage as well as the rheology of the paste. In this paper, the effects of the physical properties of lubricant (viscosity and surface tension) on the preforming and extrusion pressure of PTFE paste are examined.
Extrusion Characteristics of HDPE-Wood Composites
Extrusion characteristics, such as output, pressure profiles and melting profiles, were investigated in a Brampton Engineering single screw extruder with two screw geometries. It was found that for the wood-HDPE1 composite, the channels were not fully filled until the melting process was completed in both screw geometries. The actual experimental results were compared to those simulated using a commercially available software program. It was found that the current extrusion theories do not predict the pressure profiles generated even for the virgin HDPE1 material for one of the screw geometries.
Temperature Gradients in the Channels of a Single-Screw Extruder
A novel fluorescence analytical technique was used to measure the polymer temperature inside an operating extruder. The method allowed the temperature measurement of the polymer without interference from the surrounding metal parts. This paper will show some temperature data for molten polycarbonate in a single-screw extruder under processing conditions.
Design of a Soft Sensor for Polymer Extrusion
The application of closed-loop viscosity control to polymer extrusion is desirable to achieve a consistent quality product. However, incorporation of such techniques is limited by the difficulties in obtaining an accurate, real-time indication of the melt viscosity. This paper outlines the design of an in-line viscosity sensor based on a capillary die and the use of software algorithms generated from off-line data. The use of data acquisition software to analyse and correct for errors is explored.
Kinematics of Solids Conveying
Solids conveying is typically calculated using friction factors. The friction factors depend on material and conditions, are difficult to measure, and the calculation is extremely sensitive to their value. Kinematic analysis of solids conveying is shown to yield the “solids lead angle” for the resin solids plug that does not require friction factors. Solids lead angle for different polymers are shown, and the data are used to make predictions of solids conveying performance without evaluation of friction factors.
Troubleshooting Mixing Problems in Single-Screw Extruders
Mixing processes are very important for plasticating, single-screw extrusion operations. Numerous mixing processes can occur including pre-blending prior to feeding to the hopper, during melting, trapping and melting of solid fragments, mixing of fully molten resins, and mixing downstream from the extruder. This paper focuses on the mixing processes that occur during melting and the handling of solid fragments. Troubleshooting guidelines are presented to mitigate these mixing problems.
Troubleshooting Underwater Pelletization Processes
The fundamental parameters governing the underwater pelletizing process are proposed and confirmed based upon actual observations during process and mechanical troubleshooting of high capacity pelletizing systems.
Production of Compounds with High Filler or Fiber Loading on Screw Kneaders
The production of filled and reinforced compounds has a high economic importance mainly because fillers and reinforcing fibers render the final product to serve very specific applications. In order to understand such operations more the term “highly filled” will be explained and critical aspects analyzed. In essence two different type of compounding machines are utilized for such compounding tasks, the co-rotating twin-screw and the reciprocating single screw (kneader). Fundamental differences of these systems are analyzed and compared. Examples of compounding processes are described.
Basic Extrusion Models as Diagnostic Tools in Extrusion Trouble Shooting
Use of the basic mathematical expressions of the solids conveying, melting, metering and mixing theories for single screw extruders permits the rapid understanding of the functions of an extruder and the interrelationship of polymer properties and process conditions. Understanding the algebra of these models allows for the development of corrective actions and then interpreting the result of the changes permits a new insight into the root cause of the problem.
Effect of Xylene Solubles in Biaxially Oriented Polypropylene
Xylene soluble is an atactic polypropylene and usually produced as a by-product during the polymerization of an isotactic polypropylene. Some amount of xylene soluble polypropylene is known to play a role in orientation of polypropylene to produce film. In this study, isotactic polypropylenes with various amounts of xylene solubles were prepared. The characteristics of these polymers and their performance on the TM long film stretcher were determined, as well as some structure-processing-property relationships.
Matching of Vulcanization with Blowing Reaction in Sponge Rubber Compounds
Sponge rubber is a porous material, that is foamed by the decomposition of a chemical blowing agent. The blowing up of the profiles takes place inside the vulcanization unit parallel to the curing reaction. Both reactions are thermally activated processes, that interact regarding their kinetics. To simplify process design and optimization, a FEA model for the calculation of the local curing rate is presented and a new test method is introduced that enables a process oriented characterization of sponge rubber compounds.
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