SPE Library

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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Conference Proceedings

The Effect of Surface Energy of Boron Nitride on Polymer Processability

Nimish S. Rathod, Savvas G. Hatzikiriakos, May 2004

Fluoropolymers have long been used as processing aids for surface melt fracture treatment of polyolefin extrudates. Recent developments have shown that a small amount of Boron Nitride powder successfully eliminates surface melt fracture and also delays the onset of gross melt fracture. Study of surface energy helps in understanding the different mechanisms of these two processing aids in eliminating extrudate melt fracture.

Fundamentals of Melt Fracture Elimination Using Fluoropolymer Process Aids

S.R. Oriani, G.R. Chapman, May 2004

Fluoropolymer process aids are widely used in polyolefin blown films to eliminate melt fracture. These process aids function by depositing a thin fluoropolymer layer on internal die surfaces, and promoting slip at the fluoropolymer – polyethylene interface. The present work describes how the morphology of fluoropolymer – polyethylene blends can be controlled to increase fluoropolymer deposition rate by using a new, rheology-modified fluoropolymer in combination with an interfacial agent.

Blown Film Characterisation

G.D. Smith, R. Spares, M.T. Martyn, M. Woodhead, P.D. Coates, P. Lafuente, B del Amo Fernández, May 2004

Effects of process changes on polyethylene blown films were studied using profile analysis techniques. The relationship between process parameters, barrel temperature, haul off rate and die gap, and film properties, thickness, blow up ratio (BUR), freeze line height, consistency of bubble profile were studied. An optical analysis system was developed which allowed film characteristics to be monitored during processing.

The Effect of Orientation on the Mechanical Performance and Thermal Properties of Extrusion Cast Metallocene Polyethylenes

B.G. Millar, G.M. Mc Nally, W.R. Murphy, May 2004

Cast films were prepared using a Killion single screw extruder, from a range of metallocene PEs of varied comonomer types (hexene, octene), using different haul off speeds (8-4m/min) and die gaps (700-250?m). It was found that samples with greater orientation in one direction had increased tensile strength and shrinkage in that direction. DSC analysis showed crystallinity to decrease with decreasing haul off speed.

An Investigation into the Cooling of Blown Film

Gregory A. Campbell, N. Ganesh, Sara W. Campbell, Lana Burl, May 2004

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

Joo Sung Lee, Hyun Wook Jung, Jae Chun Hyun, May 2004

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.

Novel Barrel Heating with Natural Gas

Johannes Wortberg, Thorsten Schroer, May 2004

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

Hongbing Chen, Uttandaraman Sundararaj, Krishnaswamy Nandakumar, Mark D. Wetzel, May 2004

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

Jongmin Keum, James L. White, May 2004

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

Anne Martine de Vries Robbé, David B. Todd, Léon P.B.M. Janssen, May 2004

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.

Polytetrafluoroethylene (PTFE) Paste Preforming: The Effects of Viscosity and Surface Tension of Lubricants

Isaias Ochoa, Savvas G. Hatzikiriakos, May 2004

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.

Temperature Gradients in the Channels of a Single-Screw Extruder

Mark A. Spalding, Daniel W. Baugh, Kurt A. Koppi, Walter C. Buzanowski, Anthony J. Bur, S.C. Roth, May 2004

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

Marion McAfee, Linda Caldwell, Steve Thompson, Gerry McNally, May 2004

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

Stephen J. Derezinski, May 2004

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

Mark A. Spalding, Kun Sup Hyun, May 2004

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

Anthony C. Neubauer, Seung J. Rhee, Gary L. Smitherman, May 2004

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.

Basic Extrusion Models as Diagnostic Tools in Extrusion Trouble Shooting

Eldridge M. Mount III, May 2004

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

Sehyun Kim, Victor M. DiNardo, May 2004

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

Edmund Haberstroh, Arndt Kremers, May 2004

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.

Simultaneous Characterization of Dispersive and Distributive Mixing in a Single Screw Extruder

Kirill Alemaskin, Ica Manas-Zloczower, Miron Kaufman, May 2004

Simulation of the dispersion of solid agglomerates along their trajectories in a single screw extruder with sequential tracking of parents and fragments allow us to assess conditions appropriate for dispersive mixing and simultaneously account for the spatial distribution of all particles in the system. A new mixing index based on the calculation of Shannon entropy for different size fractions of the minor component present in the system and giving preference to smaller sizes was developed.