January 2009

January Workshop
Extrusion Basics

DON’T MISS IT!.....One Day classroom and hands on demonstration

President’s Message

Happy New Year! On behalf of the South Texas SPE board of directors I hope that you and your family enjoyed a fun and restful holiday. Thank you to all who supported our December program Plastics for Corrosion Protection and Prevention. We had 46 people attend the program that was led by Tom Baus of Ticona. Tom spoke about the advancements in PPS Polyphenyl Sulfide that has been accepted as a material to extend the life or replace steel in harsh petroleum environments. I want to recognize the companies that supported the program with table top displays. Blackwell Plastics, Deep Flex, Great Western Supply, Lubrizol Advanced Materials, Smart Pipe, Southwest Impreglon, Tiaero, Ticona, Vertec Polymers and Western Falcon. The format allowed time to network and have business discussions with various plastic technologies that included material suppliers, injection molding, extrusion, coatings, composite pipe manufacturers, and distributors.

The South Texas SPE section has nearly 600 members that hit every area of our industry. We are working very hard to develop programs that serve the diverse geographic and professional needs of our membership. We kick off our program year with a great social networking opportunity as we celebrate the plastics industry with the Houston Astros. We sought to engage our regional processors with hands-on interactive training for injection molding and extrusion. We have remained true to our technical roots with programs diving deep into the chemistry of specific polymers and supported design and industry trends to explore “green” or renewable polymers. The Polyolefins Committee will host the largest international conference dedicated to polyolefins. This conference has historically provided operating funds for student SPE chapters at eight universities. We are also excited to bring commercial opportunities to our industry professionals by including programs with regional industries such as Houston’s medical and petroleum industries where we present solutions to challenges faced in these industries. The Directors and Committee Chairpersons are doing a great job meeting so many of our membership needs.

January will be a fantastic opportunity to get involved with the SPE. Join us at these events:
• January 6 – Breakfast bunch at the I-Hop I-10 and Washington
• January 13 – Basics of Extrusion at Killion Laboratories on I-10 and Chimney Rock
• January 16 – Lunch bunch at the Steel City Pizzeria in the Woodlands

The Basics of Extrusion program will provide the opportunity to experience a combination of classroom and live demonstration of the extrusion process. We will review the basics of the extruder, screw design, die, and downstream equipment. So come and join us, meet industry professionals, learn something new, and possibly grow your business with new relationships. I will conclude this new year letter with a challenge. Make a resolution to come to at least one SPE event that meets your needs. It could be social, technical education, business networking or golf. The SPE is a valuable resource that will provide a great return on the time you invest.

Wishing you all the best in 2009!

Jeff Applegate
SPE South Texas President 2008-2009

Plastics Information: Check it Out

The Houston Public Library on McKinney has resources on plastics and polymers. Check out their catalog at www.hpl.lib.tx.us. If you are not near the McKinney location, you can arrange to pick up your books at your local branch.

The Fondren Library at Rice University has the most complete collection of books on plastics and polymers. This is also a prime resource for patent and trademark information, as well as other US Government documents. You cannot check out books there unless you join Fondren Library [$50], but you can arrange for books to be sent to your library by inter-library loan. Use their catalog at http://library.rice.edu/.

The next best place to browse is at the MD Anderson Library at the University of Houston central campus. South Texas Section has donated many plastics books to this library. If you plan ahead, you can get a TexShare library card from a library where you are a member, which will allow you to check out books from any U of H library. Their catalog is at www.library.uh.edu/.

Bulletin Board

Education Committee Meeting Notes

Education Committee Met on November 17, 2008

The South Texas Section Education Committee held its Fall meeting on November 17th. Ten committee members attended as well as one guest. Following are the meeting highlights.

1. Approximately $45,000.00 of the $82,250.00 education budget for year 2008/2009 has been disbursed. an additional $13,000.00 is expected to be disbursed by the end of 2008. The remainder is on schedule to be used on programs during the winter and spring of 2009.
2. The Lamar Endowed Scholarship contract was signed by Jeff Applegate and Marty Husti, and returned to Lamar. Once the signed contract is returned to the Section, the initial payment of $12,500.00 will be forwarded to Lamar. Total endowment funding is $25,000.00 which will be completed during the 2009/2010 year.
3. Padula Award checks for Student Chapter operation have been sent to all qualified Universities except Lamar. We are still waiting for the Lamar Student Chapter roster before sending the check. Also, UT-Austin will receive a Padula Award once they reactivate their Student Chapter.
4. The UH Student Chapter request for speakers for their meetings was most successful. Ted Marker agreed to distribute the speakers lists so other Student Chapters could make use of it. Suzanne Biggs agreed to post it to the Section’s data base.
5. Andy Chatterjee announced that the Polyolefins scholarships available through the TPM&F Division will be awarded to UH and UH-Downtown for 2009. Ted Marker will inform UH and Iman Bahrani will inform UH-Downtown.
6. Baylor University is working to expand their undergraduate ME program to include polymers studies. Prof. Walter Bradley has requested assistance from the Section in advising the best use of $40,000 in funds that has been made available by Baylor to set up a polymers lab. The Section will work with Baylor in this regard as well as help them develop a Student Chapter as their program develops.
7. The Science Fair will take place during March, 2009. Bill Talbot will enlist the services of Alvin Community College’s Public Affairs expertise to generate publicity for this event. Mark Demark will coordinate the efforts at Alvin CC.
8. Carlos Dela Rosa and Shawn Smith are working to make the February, 2009 Essay Contest a success. The resources at Alvin CC for publicity will also be used.
9. Guest – Jason Mann – presented an outline on how the Section can make use of Facebook to open up contact and communications with younger members and potential SPE members. A poll showed that two of the Education Committee members already had Facebook accounts. Eight additional members at the meeting stated that they would set up account. This is an initiative that will be pursued by the Section Board with full support of the Education Committee.
10. Next Education Committee Meeting will be held during the Spring, 2009 to set the 2009/2010 budget.

International Polyolefins Conference

February 22-26, 2009
North Houston Hilton Hotel

(make room reservations SPE rate directly with hotel at 281-875-2222)

On-line Conference Registration is now open at South Texas Section web site (http://www.spe-stx.org/PolyolefinsRegistration.cfm) or at www.4spe.org

Features and Activities:

• Over 80 peer reviewed papers Feb. 22-25
• 70 Booths with the latest commercial developments.
• SPE International Seminars Feb. 25-26 giving full day instruction on important related topics
• Monday evening networking reception sponsored by PMC Group
• Sunday afternoon golf outing
• Sunday afternoon tutorial on Fundamentals of Polyolefins
• Extensive program and scholarships for students

Sponsored by South Texas Section, Flexible Packaging Division, Thermoplastic Materials and Foams Division, Polymer Modifiers and Additives Division.

SPE Polyolefins Preliminary Program

As of December 1, 2008

February 22-25, 2008
Hilton Hotel North Houston, Houston, Texas, USA
To register go to the following website: http://www.spe-stx.org/PolyolefinsConference.htm

Book Bag

	Chemical Resistance of Plastics and Elastomers, 4th Edition Edited by William Woishnis, 2008, CDROM Price: $625.00 The 4th edition of this CDROM contains the world’s largest database of information on the effects of thousands of reagents, the environment, and other exposure media on the properties and characteristics of plastics and elastomers. Hard-to-find information has been normalized to quickly provide answers to questions; PDL ratings are included to provide answers as to whether a material is suitable for further research. Extensive data is given for exposure conditions and the results of exposure. The CDROM format incorporates over 194,000 records into an easy-to-use package with an interface that permits basic search via keyword; advanced search using three distinct Boolean operators; or browsing via name of material or reagent.
	Essentials of Polymer Science and Engineering Paul C. Painter & Michael M. Coleman, 2009, 525 pages Price: $190.00 This book is both an introduction to polymers and an imaginative invitation to the field of polymer science and engineering as a whole, including plastics and plastics processing. The text explains and helps students as well as professionals appreciate all major topics in polymer chemistry and engineering: polymerization synthesis and kinetics, applications of probability theory, structure and morphology, thermal and solution properties, mechanical properties, biological properties, and plastics-processing methods. Designed to supersede many standard texts (including the authors’), Essentials of Polymer Science and Engineering is unique in a number of ways. Special attention has been paid to explaining fundamentals and providing high-level visuals. In addition, the text is replete with engaging profiles of polymer chemists and their discoveries. The book explains the science of polymer engineering and tells the story of the field from its beginnings to the present, indicating when and how polymer discoveries have played a role in history and society. In addition it contains study questions and problems.
	Extrusion: The Definitive Processing Guide and Handbook Harold F. Giles, Jr., John R. Wagner, Jr., Eldridge M. Mount, III, 2005, 600 pages Price: $315 Why is it important to get to equilibrium and how long does it take? Are there problems running polypropylene profiles on a single screw extruder? Does the job involve compounding color concentrates on a corotating twin screw extruder? This unique reference work is designed to aid operators, engineers, and managers in quickly answering practical day-to-day questions in extrusion processing. This comprehensive volume is divided into 7 Parts. It contains detailed reference data on such important operating conditions as temperatures, start-up procedures, shear rates, pressure drops, and safety.

SPE-STX Board Meeting

Location: via Teleconference
Date: December 8, 2008

Technical Article – From ANTEC 2006
A “See-Through” Extruder to Teach Principles of Polymer Melt Extrusion

David E. Higbee,¹ Hemina KrishnaBachia,² and Rajendra K. Krishnaswamy¹*

¹Chevron Phillips Chemical Company, LP Bldg 94-G, Research and Technology Center Bartlesville, OK 74004
²ConocoPhillips Company Bartlesville, OK 74004

* Corresponding Author (krishrk@cpchem.com)

Key-Words: Extrusion, Transparent, Visual-Aid

Abstract

The design and construction of a simple and inexpensive single screw extruder with a transparent quartz barrel is presented. The utility of such an extruder as an effective teaching tool to visually portray the mechanisms of polymer melting and mixing during extrusion is outlined.

Background

The plastics industry in the USA employs more then 2.2 million people, which represents about 2 percent of the workforce. Revenue generated from shipment of plastics and plastic products exceeds $ 400 billion, which positions this industry as the nation’s fourth largest in terms of manufacturing (1). The plastics industry continues to grow at about 2 % annually.

Extrusion is the most popular process used to fabricate plastic parts. Product quality and production rate are the two most important aspects of the fabrication process (25). Solid pellets of a polymer are fed to an extruder through a pellet hopper. These pellets are conveyed forward through the action of a rotating screw. The screw is encased in a barrel that is generally heated to temperatures above the melting point of the polymer. The screw is designed such that the gap between the screw flight and the barrel wall, referred to as the “screw flight clearance” is very small (~0.1 mm). Further, the depth of the channel between adjacent screw flights decreases continuously between the region of the screw where the solid pellets enter the extruder and the region where a homogenous melt is formed. This decrease in channel depth helps in building pressure and in melting the polymer.

Downstream of the pellet hopper, the extrusion process can, for the sake of simplicity, be divided into three major sections: (a)Solids Conveying or Feed; (b) Melting & Compaction and (c) Metering. The factors that enhance the solids conveying efficiency in the feed section of an extruder are: (i) large screw channel area relative to pellet size; (ii) low rubbing force or friction between the solid pellets and the screw surface (well-polished screw surface); (iii) high rubbing force between the solid pellets and the barrel surface; (iv) long feed section and (v) minimal compaction in feed section.

The melting efficiency of an extruder is influenced by the temperature profile, the screw type, the melting characteristics of the polymer and the viscous heat generated. These parameters also dictate the relative contributions of the dissipative and conducting melting mechanisms to the overall melting process.

The primary function of the melt metering section is to convey a homogenous melt to an appropriate die. Momentum and mass balance across the metering section indicate that the metering rate of an extruder can be increased by increasing the channel depth, decreasing the screw flight surface area, lowering the pressure drop across this section and by increasing the polymer viscosity. While the factors that drive these individual sections of an extruder have been reasonably well characterized, the output or production rate of an extruder is dependent not only on the dynamics of each of these three extrusion zones but also on the interactions between them.

There have been various attempts to understand the dynamics of the extrusion process, from both theoretical and experimental perspectives. Prof. Chung’s textbook (2) is an excellent reference for senior undergraduate and graduate engineering students who want to learn the basic principles of polymer melt extrusion.

In this report, we wish to discuss a visual tool that can be used to teach the basic principles of polymer melt extrusion. Specifically, we will highlight the construction and utilization of a simple and inexpensive single-screw extruder built with a transparent barrel such that the dynamics of extrusion may be examined (visually) and explained with greater ease.

Design and Construction of the Extruder

The starting point for building the subject extruder is a “Mini-X Extrusion Welder” from Plastic Welding Technologies (Diamond Springs, California). This welder is designed to accept feedstock in the form of rods or cylinders. The rod is conveyed horizontally to the extruder and subsequent melting occurs due to the applied heat and viscous dissipation. External heat to the extruder is provided through coil heaters that wrap the steel barrel. Rotation of the variable speed screw aids in the melting and metering of the polymeric rod feedstock. As the melt exits the extruder, it is further heated by a hot-air jet such that the viscosity of the extrudate is lowered considerably just prior to its application. In order to convert this design into one that mimics conventional plastics melt extrusion, the hot air jet was removed. A vertical hopper was designed to feed either pellets and/or powder directly into the extruder. A programmable temperature controller was added to enable the extrusion of a wide variety of polymers.

The barrel of the extrusion welder was constructed with stainless steel. In order to provide a visual insight into the extrusion process, we replaced the steel barrel with a quartz tube. Figure 1 shows the original steel barrel and the new quartz barrel. The standard compression screw is clearly visible through the quartz barrel. The location of the feed hopper (hole where the vertical hopper slots in) is also evident in this figure.

In Figure 2, all the primary components of the modified extrusion welder is shown. The original coil heaters, that are tightly wound, are shown above the quartz barrel. Obviously, we cannot use this coil heater as it covers the transparent quartz barrel completely such that the extrusion process is no longer visible. Therefore, the coil heater was removed and the heating was accomplished by a tape heater, a bundle of which is also shown in the same figure (lower left corner). The tape-heating element was wound on the quartz barrel such that there were sufficient gaps between adjacent loops. These gaps essentially serve as optical windows that enable us to view the extrusion process.

Figure 3 shows a portion of the quartz barrel during the extrusion of poly (ethylene oxide). The gaps between adjacent loops of the tape heater are our windows to polymer melt extrusion. Figure 4 is a picture of the die that is mounted flush with the end of the screw. The die is essentially a Teflon capillary that rests snugly between the screw tip and the curved barrel tip. The diameter of the capillary die can be changed to alter the back pressure experienced during the extrusion process.

Potential Applications

Figure 5 is a picture of PEO extrudate from our modified extrusion welder; the extrusion was carried out at a set temperature of about 100 °C and at 75 rpm screw speed. We find that poly (ethylene oxide) or PEO is an ideal polymer for our “see-through” extruder because of the following reasons: (1) low melting temperature such that a setting of 100 °C is more than adequate; (2) easy availability of PEO of varying molecular weight (100,000 g/mol to 1,000,000 g/mol) from PolySciences, Inc.; and (3) the generally low melt pressure exerted by this polymer. Low-melting polyolefin waxes are also good candidate polymers for this extruder.

In Figure 5, a transition from red-colored extrudate to a white-colored extrudate is evident. The red color is from small amounts of a red wax crayon (in the form of shavings) blended with the PEO. The uniformity of the redness suggests good mixing of PEO with the red wax; in other words, the wax appears to be reasonably well dispersed within the PEO matrix. This is a general confirmation of the overall quality of the extrudate during normal operation.

Based on our limited experience with this extruder, we suggest the following experiments that may serve to elucidate the principles of extrusion to young students of science: (1) As the solid powder is conveyed forward, the transition from solid to liquid state is visually evident. Specifically, the dissipative melting mechanism of the polymer is very apparent. In other words, the transition from solid to liquid state along the barrel wall is evident as is the collection of the melt pool ahead of the screw flight. (2) This extruder may be used to study the residence time distribution and its dependence on the melt rheology and melting characteristics of polymers. (3) Mixing/Blending of polymers of different viscosity is also another subject that can be visually explained using this extruder; this is particularly effective if one of the blend components contains a pigment or dye of some sort. (4) Non-Newtonian effects, such as extrudate swell, memory retention and so on may be studied and explained by examining the extrudate of various polymer melts that differ in their melt elasticity.

In summary, we offer a simple and inexpensive extruder with a transparent barrel that allows one to visually observe the extrusion of polymer melts. This extruder may be used as an effective teaching tool, particularly for high school seniors and college freshmen and sophomores with the objective of exposing such students to careers in the science and engineering of polymers. The authors are willing to work with and help anyone that has an interest in building such an extruder.

Acknowledgements

We would like to acknowledge the Society of Plastics Engineers, specifically the Education committee, for the Husky Education Award that enabled us to pursue this idea. We also acknowledge Cris Bonnet of Plastic Welding Technologies for his support and assistance with this project as well.

References

[1]. Society of Plastics Industry Report: “Size and Impact of the Plastics Industry on the U.S. Economy” (2003).
[2]. C. I. Chung, “Extrusion of Polymers: Theory & Practice”, Hanser Gardner, Cincinnati, (2000).
[3]. J. M Dealy & K. F. Wissbrun, Melt Rheology & its Role in Plastics Processing: Theory & Applications, Chapman & Hall, New York (1995).
[4]. D. G. Baird & D. I. Collias, Polymer Processing: Principles & Design, John Wiley & Sons, New York (1998).
[5]. R. K. Krishnaswamy, D. C. Rohlfing, A. M. Sukhadia, K. L. Slusarz, Polymer Engineering and Science, 44, 2266 (2004)