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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Modeling of Viscoelastic Coextrusion Flows in Multi-Manifold Flat Dies
A recently proposed modification of the viscoelastic Leonov model is employed as a stress calculator in FEM analysis with a full u-v-p-? numerical scheme of the coextrusion flow in multi-manifold flat dies with 30 and 90 degree entrance angles. It is shown that the predicted stresses, interface location and streamlines fields are in a good agreement with the measurements. It is also revealed that the extensional viscosity has to be used in the modeling of the coextrusion flow to confirm experimental data.
Elongational Flow in Multiple Screw Extruders
Flows of a low-density polyethylene in a co-rotating twin-screw extruder and in a twelve-screw ring extruder are compared. Effect of the shear as well as elongational viscosity of the low-density polyethylene is included in the simulation. Even though the velocity and pressure distributions in the two extruders have many similarities, because the intermeshing regions constitute a larger fraction of the ring extruder than that of the twin-screw extruder, the degree of elongation, and hence, the quality of mixing, is found to be better in the ring extruder.
Kinematics Model of Solids Conveying of LDPE
The kinematics model of solids conveying shows that the solids advance angle is a single empirical factor of solids flow in lieu of friction factors. Furthermore, solids advance angle can be linearly correlated with pressure for LDPE. The linear functions that approximate the solids angle are used with the kinematics model to calculate solids flow of LDPE. The calculations are compared to data to demonstrate the accuracy of the model.
Entropic Mixing Characterization in a Single Screw Extruder
The quality of distributive mixing is evaluated via an entropic measure of color homogeneity. We first illustrate this technique in a numerically built rectangular channel representing the unwounded channel of a single screw extruder. We also apply this method for assessing mixing quality of experimentally obtained samples when mixing a color concentrate in ABS resin in a single screw extruder. We discuss application of this technique in numerical simulations of processing equipment.
Melt Temperature Homogeneity in Single Screw Extrusion: Effect of Material Type and Screw Geometry
Thermocouple meshes have successfully been used to measure melt temperature across the material exiting from a 60mm single screw extruder. Temperature profiles are shown to be dependent on screw geometry, set wall temperatures, throughput and material type. Differences in average temperature profile and transient fluctuations have been determined.
Design and Validation of Self-Compensating Melt Regulator for Plastics Extrusion
A design for a self-adjusting melt pressure regulator is presented for use between an extruder and one or more dies. The regulator is derived from a low force valve design that enables the outlet pressure to be directly regulated by a provided force on a valve pin without need for pressure sensors or a closed loop control system. Analytical and experimental results indicate an excellent level of response and consistency given the simplicity of the design.
Experimental Observations of LDPE Melt Flow in Coextrusion Geometries
Flow visualisation studies are preformed to determine the effects of die geometry on interfacial instabilities in coextrusion flows of a LDPE melt. Slit coextrusion visualisation cells with 30° and 90° convergent stream angles are used in this study. Stream ratios leading to interfacial instability in the LDPE melt are quantified and compared for each geometry.
Experimental and Numerical Studies of Blown Film Cooling
Studies of blown film cooling were carried out to investigate interaction of cooling air flow and the heat transfer processes. Instabilities in the air flow were detected at several point in the cooling region which influences the local heat transfer.The results indicates the development of temperature fluctuation in the bubble which seem to be one of the main reasons for the formation of film thickness profile in extrusion direction.
The Effect of Extrusion Conditions and Material Properties on the Gas Permeation Properties of LDPE/LLDPE Silage Wrap Films
This work investigates the effect of extrusion processing conditions and co-monomer type on the gas permeation properties of LLDPE films containing polyisobutylene (PIB). The results show improved gas barrier properties with increasing polymer density and increase in film crystallinity and orientation as a result of extrusion processing conditions such as blow up ratios.
A Modeling of the Film Blowing Process by using Variational Principles
A simple equation with only four physical parameters for the description of the bubble shape (including HDPE wine-glass shape) has been derived from variational principles. The proposed equation was used in modeling of the film blowing process for a variety of process conditions and polymer melts, and a very good agreement between measured and simulated data was found.
Influence of Processing Conditions on the Mechanical Properties of Nylon 12 and LDPE Tubing
The effect of extrusion processing conditions on the mechanical and morphological properties of a range of nylon 12s and LDPEs was investigated. The results indicate that processing conditions had a more pronounced effect on the mechanical properties of nylon 12 tubes, in comparison to those produced from LDPE.
A Study on the Thermal Performance of Calibrators
In this work a numerical code able to model the heat transfer in calibrators for extruded profiles is described and validated. For assessment purposes the numerical predictions are compared with analytical models and numerical results obtained with a commercial software. The routines developed are then used to identify the main process parameters and to estimate their relative importance.
Analysis of Flow in a Spiral Mandrel Die
For rheological design of spiral mandrel dies the most common calculation methods are segmenting the die into simplified geometries and calculating the characteristics of each flow segment analytically. In the past, one-dimensional flow was considered, but this assumption is deficient especially for low depth segments. In recent investigations IKV has studied three-dimensional flow conditions in a transparent test die and in 3D-FEA calculations. The results of these studies give the key to improve the calculation of spiral mandrel dies significantly.
Screw Design for Cooling Extruders
This paper presents a theoretical approach to the prediction of melt temperature profiles in cooling extruders. The effect of screw design on cooling performance in discussed. A new screw geometry is presented will substantially improved cooling capability. Initial performance data on a 200-mm cooling extruder are presented.
Gentle Compounding of Natural Fiber Filled PVC Composites
Compounding of thermoplastics with wood flour or natural fibers presents a number of challenges. The temperature and shear sensitivity of the thermoplastic matrix such as PVC, presence of moisture in the cellulosics, and the critical process temperature limitations of the composite are some of them. Lower shear history and melt temperature during primary compounding operations of such composites generally result in better mechanical properties of the finished product. This paper investigates the suitability of CK Continuous Kneader to surmount the imposed process limitations effectively.
Processing Polyethylene Terephthalate on a Single Screw Extruder without Predrying Using Hopper- and Melt Degassing
Conventional PET processing requires pre-drying, an energy- and cost-consuming process limiting production flexibility. The paper presents combined hopper- and melt degassing in a single screw extruder as a real alternative to predrying and investigates the influence of extrusion- and degassing parameters, screw-design and water content on both intrinsic- and melt viscosity.
Practical Approach to Screw Breakage and How to Avoid Failures
The use of practical mathematical expressions can be used to evaluate the mechanical strength of a rotating shaft. Similar expressions can be used in the design of a feedscrew. The purpose of this paper is to investigate the factors that influence the mechanical strength of a feedscrew and to show how to use these expressions from a practical standpoint to avoid failure during operation.
Effect of Screw Surface Properties on Extruder Performance
The surface condition of the screw and die can have a significant effect on extruder performance; however, little information about these effects is available in the open literature. This paper discusses various aspects of the screw surface conditions and how these can change the characteristics of the process and extruded product quality.
Die Lip Sensitivity in Cast Film Dies
Die designs for production of cast polymer films typically include a flex lip for varying the geometry of the lip opening. The cast film process requires die lip gaps ranging from 0.4 mm to 0.8mm. Flex lip gap and the adjustment of said gap becomes increasingly difficult to control as it is reduced. An examination is made of the issue of die lip sensitivity with different polymers extruded at different lip openings.
Metering Channel Flows and Troubleshooting Single-Screw Extruders
The manufacturing costs for a process depend highly on the proper operation of the extrusion equipment. In general, proper operation requires that the metering section of the screw be the rate-limiting step. Using drag flow and pressure flow calculations for the metering section is a simple method to determine if the section is the limiting step. This paper shows how these types of calculations can be used to determine if the screw and process are functioning properly.
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