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

Increased Vinyl Surface Energy through Plasticizer Choice

Bruce Streeter, May 2001

Printing on flexible PVC can be a problem due to the low surface energy of the vinyl compound. Many of the additives commonly used in vinyl will lower the relatively high surface energy of PVC. The increasing use of water based inks has increased the demand for higher surface energy flexible vinyl compounds. Velsicol Chemical has developed two new polymeric plasticizers that are capable of increasing the surface energy of flexible vinyl film and sheet by as much as 4 dynes/cm. The two plasticizers offer the same surface energy improvement in a high molecular weight-high permanence version and a lower viscosity easier handling version. The improvement offered by the new plasticizers can be reduced or eliminated by the improper choice of lubricant. This study shows that the choice of one compounding ingredient, the plasticizer, can increase the surface energy of a flexible PVC film by up to 4 dynes/cm. In addition it demonstrates the negative impact of a commonly used lubricant on printability. As a lubricant, stearic acid is a very common additive but studies have shown that it can also be generated in the vinyl product from some thermal stabilizers commonly used in vinyl (1).

Machine Innovation and Elementary Steps

Zehev Tadmor, May 2001

The systematic scientific analysis of polymer processing machines leads to the definition of a small number of elementary steps, which in chemical engineering terminology are the 'unit operations' of these machines that transcend individual machine configuration and reflect the common experience of the processed material in any type of machine. The elementary steps reveal the detailed specific physical mechanisms that take place in these machines. These mechanisms, in turn, are powerful tools that when properly used can trigger machine innovation. Moreover, with proper abstraction they can also lead to a formal methodology for invention of new machine configurations. In this paper both processes of innovation and invention will be described through a few selected case studies.

The Carbon Dioxide Technology Platform

Joseph M. DeSimone, May 2001

What if the electronics industry used specially designed photoresists that could be deposited using a spin coating process based upon liquid CO2 instead of organic solvents? Also what if this industry didn’t have to use hundreds of millions of gallons of water per day to remove sub-micron particles during the manufacture of integrated circuits and flat panel displays? Imagine polymerizing monomers in a continuous stirred tank reactor with the resulting polymers instantly dry, avoiding the trillions of BTUs needed every year to dry commercial polymers made in aqueous reaction media. Imagine an automotive industry that doesn’t expose its employees to toxic chlorinated solvents during metal degreasing processes. Imagine a textile industry that doesn’t need to use 100 lbs of water for every 1 lb of yarn that was dyed. Imagine local dry cleaners that don’t need to clean garments in perchloroethylene and local businesses that don’t need to pay exorbitant, newly enacted taxes on solvent use or carry newly mandated liability insurance policies. What if the demands on municipal water systems and municipal waste water systems could be dramatically reduced by changes in manufacturing technology? Imagine an educational environment where students become grounded in the fundamentals of their core disciplines, are exposed to cutting-edge, multidisciplinary science, and can experience the satisfaction and excitement that comes from doing research that makes a difference to society. The discussion will focus on the latest developments from the NSF Science & Technology Center for Environmentally Responsible Solvents and Processes. In particular, the detailed synthesis and CO2 solution properties of fluorinated and siloxanebased homopolymers and block copolymers will be discussed. The utility of such macromolecules will also be demonstrated for use in coatings (photoresists and textiles), separations, stabilizers for polymerizations, and scaffolds for catalysis. Particular attention w

Analysis of the Failure of a Polyethylene Natural Gas Service Line

Donald E. Duvall, May 2000

Leaking natural gas from a 23 year old polyethylene pipe service line migrated into the basement of a public building. The explosion which occurred upon ignition of the gas destroyed the building and killed six of the seven occupants. Fracture of the line was found to have occurred at the connection of the polyethylene pipe to a service tap on a steel gas main. The critical issue of this investigation was understanding whether the pipe resin had acceptable creep rupture strength for the application and was over stressed or had inadequate long term strength to resist typical stresses to which buried polyethylene gas lines are exposed. This presentation will examine some of the considerations involved in arriving at a conclusion as to which condition existed in this incident.

Polyurethane and Silicone as Non-Allergenic Alternatives to Latex for Medical Balloons

Tilak M. Shah, May 2000

Recent developments in the formulation and processing of polyurethane and silicone have resulted in making these polymers viable non-allergenic alternatives to natural latex in the medical products field. Advancements in the dip molding of polyurethane and silicone enable a variety of products to be produced in volume, including low-pressure balloons for cardiovascular, oncology, and urology products, as well as gloves, condoms, stent coatings, scope tubing, and multifunctional sleeves. These polymers can provide the same advantages offered by latex, without the negatives, and are especially well-suited for medical balloons.

Design of Stiffening Features in Rotationally Moulded Plastic Parts

R.J. Crawford, May 2000

Polyethylene is a very convenient and popular material for rotational moulding because it is readily available in powder form and it has good thermal stability. Unfortunately polyethylene is one of the least strong plastics and it has a low modulus. It is a feature of rotationally moulded parts that designers have to use shape very effectively in order to impart stiffness to the end product. This is not a straightforward matter because rotational moulding does not easily create features such as ribs. Increasing the wall thickness of the part is often the simple solution but more cost-effective designs involve the use of corrugations or unique configurations such as kiss-off" points. This paper describes the results of experimental and analytical studies to optimise the design of corrugated sections for rotationally moulded parts. Factors such as corrugation shape width depth spacing etc are considered and designs are optimised to give maximum axial and transverse stiffness for minimum weight. The use of a solid skin with a foamed core is also considered particularly in regard to the best ratios of skin to core thickness. Charts are provided to assist designers in deciding the best shapes for rotationally moulded parts."

Are You Ready to Sell in the Next Millennium? Identifying the 12 Key Functions of Selling, Rating Them and Improving Them

Martin K. Pottle, May 2000

Successful managers and their companies continually (and holistically) assess the effectiveness of their organizations. This paper addresses the 12 separate functions within a firm’s sales and marketing structures and explains how other companies rate whether any or all of these areas: 1) fall below acceptable standards; 2) can be enhanced with small improvements; or 3) are in excellent shape. From this information and insight, readers will be able to go back to their companies armed with new and better techniques to spot sales shortfalls and their causes.

Bank Measurement Leads to Improved Quality of Extruded Sheets or Films

Heinz G. Gross, May 2000

High quality thermoplastic films and sheets are run through a nip of a polishing roll stack while being produced. During the extruding procedure the quality is decisively affected by the size and distribution of the bank of melt which builds up in front of the nip of the polishing rolls. Thus it is extremely important to measure the bank and optimize it. With the help of the new developed measuring system WUMSY the size and the exact location of the bank can be measured for the first time. Based on the exact knowledge of the bank size and the bank distribution over the width of the roll stack the operating people can further optimize the production line. As a result of this optimization differences for instance in the thermoforming behavior over the width of the product, as often occur with conventional extrusion techniques, can be reduced by eliminating bank differences in the nip. Thus films or sheets with a more isotropic behavior will be achieved.

An Experimental Investigation on the Influence of Barrel Temperatures on the Output of a Constant Depth Screw with Grooved Barrel Feeding

Timothy W. Womer, John R. Wagner, Jr., Gary Harrah, Dean Reber, May 2000

Output for a grooved feed extruder with constant channel depth of 0.210 [5.33mm] was measured for the extrusion of a LDPE and found to be influenced by grooved feed bushing temperatures below 100°F [38°C]. Comparison to an earlier work shows reasonable agreement between experimental and calculated outputs. Further work needs to be done at deeper screw channel depths."

Dispersion in High Viscosity Ratio Polyolefin Blends

Michel A. Huneault, Frej Mighri, Glen H. Ko, Fuminao Watanabe, May 2000

This study will focus on dispersion in high viscosity, low interfacial tension PE/PP and PP/PP blends. Typically, in high viscosity ratio blends, the particle size distribution can be wide ranging, with particles as large as a hundred microns and finer dispersed ones in the sub-micron range. In this study, the dispersion state will be examined by several techniques to measure particle size from the sub-micron to the 500 mm range. The effect of material and processing parameters will be investigated.

Die Geometry and Polymer Processing Additive (PPA) Efficiency

Claude Lavallée, Susan S. Woods, May 2000

The effect of varying: • Die Gap, • Shear Rate, • Backpressure, and • Output on the ability of Dynamar™ PPA to eliminate melt fracture from linear low density polyethylene (LLDPE) blown film was evaluated. Correlations between time for melt fracture elimination and the various process parameters were made.

Latest Developments Concerning Slit Dies with Integrated Flexible Adjusting Membranes

Heinz G. Gross, May 2000

The successful development of the Membrane Technology which more and more replaces conventional restrictor bar dies started in the beginning of the nineties. The first membrane die was presented to the public on a running pilot line during the 18th Kolloquium of the Institut für Kunststoffverarbeitung (IKV) in Aachen (Germany) 1994. The technique is now protected by various patents being granted in most of the important industrial countries and it is distributed all over the world by eight licensees. The basic construction ideas are explained by describing some important practical industrial applications. Finally the actual situation of the development of the third generation of the Membrane Technology is explained.

Anticipated Electrical Guidelines for the Upcoming Mold Safety Standard

Thomas P. Linehan, May 2000

The Society of Plastics Industry (SPI) has a working committee to address safety issues with injection molds. Part of this committee's work is to address electrical aspects of safety. To do this, a Mold Electrical Safety Sub Committee has been created under the Committee on Mold Safety specifically to review electrical standards for injection molds. Proper design of hot runner system wiring is one of the key areas of focus because of the adverse environment these systems operate in. This paper will seek to give a heads-up" in what to expect in one part of the electrical safety standard that is to be released in the next couple of years. A proposed method for proper selection of heater conductors (wires) will be reviewed as there are no existing guidelines for applications that expose wire to this high a temperature and conductor bundle size (number of conductors)."

The Effect of Feeding Mode on Dispersive Mixing Efficiency in Single-Screw Extrusion

P.H.M. Elemans, J.M. van Wunnik, May 2000

In the case of dry colour compounds, where polymer granules are coated with a pigment powder, the latter tends to form agglomerates during extrusion, due to the hydrostatic pressure that prevails in the screw channels. In single-screw extruders, this pressure is due to the Coulombic frictional transport in the solids conveying zone. The formation of agglomerates can be prevented to a considerable extent by operating the extruder in an underfed mode. This result has emerged from a study of the problems encountered when dispersing pigments in poly(butylene terephthalate) (PBT), but can also be applied in the case of numerous compounds where a fine dispersion of solids in polymers is required.

Enhancing Dry-Colour Efficiency in Starve-Fed Injection Moulding

P.H.M. Elemans, May 2000

As in the case of extrusion, the formation of agglomerates can be avoided to a significant degree in the injection moulding of dry colour compounds by starve-feeding the machine. This involves dispensing of the granules (powder-coated with pigment in these tests) to the screw by means of a vibrating trough while the screw is rotating; during the injection phase, the feed is zero. A measure of the filled length is the plasticating time, which is greater in the case of starve-feeding than if the machine were to be operated in a flood-fed mode. Experiments reveal that, using a plasticating unit having a standard three-zone screw, products can be obtained which have a good (albeit still not perfect) pigment dispersion, which is markedly better than in the case of conventional injection moulding. This process offers application possibilities in the field of coloured formulation development.

Electron-Beam Processing of Plastics: An Alternative to Chemical Additives

Michael Stern, May 2000

Modifications in polymeric structure of plastic materials can be brought about either by conventional chemical means, usually involving silanes or peroxides, or by exposure to ionizing radiation from either radioactive sources, or highly accelerated electrons. Chemical cross-linking typically involves the generation of noxious fumes and sensitizing by-products of peroxide degradation. Increased utilization of electron-beams (e-beams) for modification and enhancement of polymer properties has been well documented over the past forty years. Of specific interest to the plastics industry has been the use of e-beam processing (EBP) to improve thermal, chemical, barrier, impact, wear, and other properties of inexpensive commodity thermoplastics, extending their utility to demanding applications typically dominated by higher-cost engineered materials. EBP of cross-linkable plastics has yielded materials with improved dimensional stability, reduced stress cracking, higher service temperatures, reduced solvent and water permeability, and significant improvements in other thermomechanical properties. The purpose of this paper is to review the basic effects EBP on polymers, as well as to highlight several specific recent cases of its utilization to improve key properties of selected plastic products.

The Three-Level Stack Mold

Joseph R. Klanfar, Henry Rozema, Vincent Travaglini, May 2000

Development of new technologies is crucial for the injection molding industry as a whole. This is especially true when Rigid Thin-Walled Disposable Packaging is concerned. Increased competition in this market has led to the evolution of stack molds. The goal: to produce a product of higher quality, in a shorter time and at a lower price. In this industry, where profit margins are measured by fraction of a second, innovation is the key to success.

Production of Profiles from Thermoplastic Composite Towpregs

J.N. Mota, J.P. Nunes, A.S. Pouzada, May 2000

The production of towpregs of continuous fibers and thermoplastic matrix is a convenient way of impregnating thermoplastics in fiber tows. The processing of these towpregs brings about technical difficulties when producing end user products. A pultrusion head was developed and tested for the producing of a U-shape profile of continuous carbon fibers and polycarbonate matrix. The methodology and theoretical models used to design pultrusion head and the results of preliminary tests made to pultruded the U-shape profiles are presented and discussed.

The Advantages of Direct In-Line Compounding Systems

Marvin J. Voelker, Charles D. Weber, May 2000

Composite Products, Inc. has commercialized in-line compounding technology to produce thermoplastic composites. Turnkey systems continuously compound thermoplastic resin with reinforcements i.e. ½ inch chopped glass, carbon or natural fibers to produce finished composites with outstanding toughness. Coloring, recycling of plant regrinds and use of recyclates are accomplished in-line with the molding process. The patented technology provides molders the ability to contain costs and simplify complex scheduling logistics to meet Just-In-Time shipping schedules.

Backmixing in Screw Extruders

Chris Rauwendaal, Paul Gramann, May 2000

Mixing is a critical function in most extrusion operations. One of the most difficult mixing tasks is backmixing. An extrusion operation where good backmixing is very important is when a low percentage color concentrate, CC, is added to a virgin polymer. In this case, the initial distance between the CC pellets may be 100 mm or greater. If the final striation thickness needs to be reduced to the micron level, the reduction of the striation thickness needs to be at least five orders of magnitude - this is quite a tough task! This paper will analyze how the velocity profiles, axial mixing, and residence time distribution are related. It will be shown why simple conveying screws have poor axial mixing capability. New mixer geometries that are specifically designed to improve backmixing will be discussed. Results from extrusion experiments will be presented.