November 2009

November Meeting

PEEK in the Oil Patch
Metal Alternative: Process-Optimization of PEEK Properties

Speaker: Dr. Alan Wood
The American Institute of Chemical Engineers and the South Texas Section of the Society of Plastic Engineers will be co-hosting a technical meeting On thermoplastics in the oilfield industry. Dr. Alan Wood, the Principal Scientist in the Global Applied Technology team at Victrex Headquarters, UK, will be preset topics on the Optimization of the properties of PEEK, the applications and the developing technologies. In addition to the Keynote speaker, break-out sessions presented by other speakers will be held before dinner. These sessions will include Thermoplastic Composites and Pipe as well as Refrigerated Vapor Recovery Systems and Resume Design. See the schedule below for details..

President’s Message

Greetings!

Even during a Houston downpour we had a standing room only program for our October meeting to see reaction injection molding at VTech Industries. Pat Webster, Product Manager for BASF, provided a technical presentation on the RIM materials and properties. Art Valentz, CEO of VTech Industries was an outstanding host and opened up his facilities for all of us to see the manufacturing process first hand.  VTech Industries manufactures skylights for commercial and residential buildings. Our meeting was followed by a fajita dinner at the original Ninfa’s on Navigation.

Kurt Hayden has been working diligently to put together an outstanding joint technical program with the AICHE on November 5th at the Pellazio. Victrex will be presenting on PEEK in the Oil Patch. Metal alternative: Process optimization of PEAK properties. We expect a great turnout from both Professional Societies with good technical presentation and relationship building opportunities. Please join us for this exciting event.

The mission of the SPE is to promote scientific and engineering knowledge relating to plastics. In addition to our professional technical programs, we continue our commitment to support local SPE student chapters, scholarships and grants at 10 colleges and Universities in our region.

On behalf of all of the directors and chairpersons, we look forward to serving you in a way that will grow our businesses, expand our technical knowledge and our relationships.

Best wishes!

Jeff Applegate
SPE South Texas President 2009-2010

Extrusion of Engineering Plastics Seminar

November 9, 2009 9:00am–November 11, 2009 4:30pm
Instructor: Dr. Pravin Shah
Houston, Texas USA
Expertise Level: II

Purpose & Overview
This seminar, developed for plant managers, production engineers and process engineers as well as extrusion supervisors and technicians, provides a simplified and thorough treatment of the extrusion of engineering plastics and exotic polymers, with major emphasis on:

(1) How to select the right grade of each material to extrude strip, tubing, profile, and rod.

(2) How to develop critical process parameters such as barrel temperature profile and screw design requirements for extruding exotic materials of today, using melt rheology as a practical tool.

Utilizing a workshop approach this seminar teaches how to correlate materials, process, and equipment parameters for extruding engineering plastics into various shapes. Attendees learn how to improve extrusion of current and new engineering plastics, reduce scrap and downtime, and improve yield and output rates.

The laboratory session will take place at Killion Laboratories and will focus on extrusion runs with engineering or novel polymers; attendees receive hands-on training.

Instructor:
Dr. Pravin Shah - Biography

Seminar Content
• Introduction to Engineering Plastics
• Basic Understanding of the Extrusion Process
• A Simple Guide to Selecting Critical Materials and Extrusion Parameters From Melt Rheology Data
• Introduction to Die Design (for Tubing, Blown Film, Flat Film, and Sheet)
• A Processor’s Guide to Extrusion of Engineering Plastics
• A Workshop Session to Solve Extrusion Problems

Hotel Information:
Sheraton Houston Brookhollow Hotel
3000 North Loop West Freeway
Houston, Texas 77092
+1 888-627-8196
Rate: $129.00 plus tax
Attendees are responsible for making their own hotel reservations.

Transportation:
The Sheraton Houston Brookhollow Hotel is located approximately 30 minutes from George Bush International Airport and approximately 45 minutes from Hobby Airport in Houston. Transportation to the hotel from these airports should be arranged through your travel agent.

Seminar Hours:
Monday, November 9: 9:00 a.m. to 4:30 p.m. with lunch from 12:00 p.m. to 1:00 p.m
Tuesday, November 10: 9:00 a.m. to 4:30 p.m. with lunch from 12:00 p.m. to 1:00 p.m.
Wednesday, November 11: 9:00 a.m. to 3:00 p.m.
Please schedule your departures after this 3:00 p.m. ending time.

Suggested Attire:
Casual Business attire is appropriate. Please be prepared for moderate temperature variations in the seminar room.

Seminar Cancellation Policy:
Refunds will not be granted five (5) days prior to seminar. Substitutes may be sent in place of the registrant with prior notification to SPE. Cancellations are subject to a $100 processing fee. Written cancellations must be received at SPE headquarters prior to the seminar.

SPE reserves the right to cancel a seminar or substitute instructors. If SPE should cancel, the attendee will be contacted as soon as possible prior to the seminar. It is recommended that a refundable airline ticket be purchased. SPE is not responsible for penalty fees or any costs incurred by the attendee due to cancellation of the seminar.

Registration Fees:
Your registration fee covers classroom instruction, educational materials, transportation to and from the laboratory session at Davis-Standard, refreshment breaks, and lunch on Monday and Tuesday. It does not include hotel accommodations.

Registration Information:
You may register for this seminar online or by phone +1 203-740-5403.

Registration is limited and on a first-come, first-served basis. Early registration is strongly recommended.

Polyolefins Conference and FlexPackCon – Mark your calendars!

The 2010 International Polyolefins Conference and FlexPackCon will be held at the Hilton Houston North (formerly known as the Wyndham), Feb 22-24, 2010. 

This year’s program will again include both the traditional Polyolefins focus as well as the Flexible Packaging program. One of the themes for FlexPackCon will be sustainability and will include talks by Chet Rutledge, Director of Packaging Procurement,WalMart; Larry Dull, Partner, Packing Knowledge Group (PKG) LLC; and Victor A. Bell, President, Environmental Packaging International. They will discuss the WalMart scorecard and it’s extensions, how to used the scorecard to evaluate new opportunities, and packaging Life Cycle Analysis. FlexPackCon will also provide updates on food law (e.g. FDA) and potential regulatory expansions.

If you know of particular developments which should be presented at the conference, please contact Robert Portnoy for Polyolefins rportnoy@portnoytechnicalservices.com) or Andy Christie (andy@optexprocesssolutions.com) for FlexPackCon.  If you’d like to sponsor a coffee break or exhibit, please contact Emery Jorgenson (emery@jorgensonmachinery.com).

We look forward to seeing you at the conference!

http://www.linkedin.com/groups?gid=2073302&trk=hb_side_g

Join the South Texas Section of the Society of Plastics Engineers on Linked-In. Click on the above link and you will be directed to group page. Linked-In will serve as another communication tool for SPE-STX.

Linked-In  is a free web site for professional networking with over 40 million members as of May 2009.

Linked-In enables discussions and networking between SPE-STX members and those related to the plastics industry. Linked-In compliments the current SPE-STX web and membership to Linked-In is free. 

News Highlight
Linked-In SPE-STX group currently has 116 member as of 1 October. To date, the tool has been used primarily to promotes and discuss SPE-STX meetings. 

Members are also notified of meetings from board members plus email blasts sent by SPE International.  

As always, both the monthly newsletter and STPE-STX web site are the leading source of information on SPE-STX activities.  

Bulletin Board

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/.

Book Bag

	Plastic Conversion Processes: A Concise and Applied Guide Eric Cybulski, 2009; 165 pages $70.00 Many books describe a single plastic-conversion process, like injection molding, but until now, none has described and compared several processes. This book provides a basic overview of seven conversion processes used in the industry. These processes account for more than 97% of all plastic products. Each chapter begins with a process attribute table to serve as a quick guide. The particular conversion process is then briefly described, along with a short history. To better explain each process, sections detailing equipment, tooling, and materials have been added. Also included are sections on design guidelines and on how to identify which process was used to manufacture a plastic part. Contents: Injection Molding Plastic Extrusion Blow Molding Thermoforming Reaction Injection Molding Rotational Molding Compression Molding
	Mixing and Compounding of Polymers: Theory and Practice, 2nd Edition Ica Manas-Zloczower, 2009; 850 pages ISBN: 978-1-56990-424-4 $249.00 Finally available in its second edition, this classic monograph covers everything from the basic principles to the various practical applications of state-of-the-art mixing and compounding. It discusses the basic mixing mechanisms encountered in polymer processing; the latest results in modeling, flow simulation and visualization, and scale-up rules for the most important batch and continuous mixers; the properties of various additives used in the plastics and rubber industry and their effects on the properties of the compound; working principles and practices for reactive polymer compounding; compatibilization mechanisms applicable to blends and composites; mixing practices in the current commercial mixing devices; key aspects of mixing at nanoscale; and scale-down of mixing equipment and fundamentals of microfluidics. Contents: Part I: Mechanisms and Theory Basic Concepts - Mixing of Miscible Fluids - Mixing of Immiscible Fluids - Dispersive Mixing of Solid Additives - Distributive Mixing - Distribution Functions and Measures of Mixing Part II: Mixing Equipment - Modeling, Simulation, Visualization Batch Equipment Simulation - Batch Equipment Visualization - Continuous Equipment Simulation - Dispersive Mixing Devices in Single Screw - Twin Rotor Mixers - Co-Kneader - Visualization - Scale-up of Mixing Equipment - Scale-down of Mixing Equipment Part III: Material Consideration, Properties and Characterization Solid additives (inorganic) - Solid additives (organic) - Compatibilizers (mechanisms, theory) - Material Consideration for Mixing at Nanoscale - Effect of Mixing on Properties of Compounds - Effect of Mixing on Rubber Properties Part IV: Mixing Practices Internal Mixers - Single Screw Extruders - Twin Screw Extruders - Intermeshing Twin Screw Extruders - Reciprocating Screws - Reactive Compounding - Farrel Continuous Mixer
	Injection Molding: Fundamentals and Applications Musa R. Kamal, Avram I. Isayev, S. Liu, 2009; 800 pages ISBN: 978-1-56990-434-3   $249.00 This book surveys the state of the science and technology of the injection molding process. It represents a comprehensive, balanced mix of practical and theoretical aspects for a wide range of injection molding applications. The authors of the 21 chapters are experts and leaders in their respective areas of specialization in the injection molding field. While it is not possible to cover all aspects of such a dynamic growing field, readers should find sufficient information and background to become acquainted, at various levels of depth, with key components of the science and technology of injection molding. Contents: Injection Molding: Introduction and General Background Injection Molding Machines, Tools, and Processes The Plasticating System for Injection Molding Machines Non-Conventional Injection Molds Gas Assisted Injection Molding Water Injection Techniques (WIT) Flow Induced Fiber Micro-Structure in Injection Molding of Fiber Reinforced Materials Injection Foam Molding Powder Metal Injection Molding Micro Injection Molding Internal Visualization of Mold Cavity and Heating Cylinder Injection Molding Control Optimal Design for Injection Molding Development of Injection Molding Simulation Three-Dimensional Injection Molding Simulation Viscoelastic Instabilities in Injection Molding Evolution of Structural Hierarchy in Injection Molded Semicrystalline Polymers Modeling Aspects of Post-Filling Steps in Injection Molding Volumetric and Anisotropic Shrinkage in Injection Moldings of Thermoplastics Three-Dimensional Simulation of Gas-Assisted and Co-Injection Molding Processes Co-Injection Molding of Polymers
	ANTEC™@NPE 2009 Conference Proceedings - Thumb Drive SPE, Chicago, Illinois USA, June 2009, Thumb Drive $250.00 In Chicago in 2009, ANTEC® (Annual Technical Conference), sponsored by the Society of Plastics Engineers, celebrated its 67th year of excellence. The largest peer-reviewed technical conference serving the plastics industry, ANTEC® is perfectly positioned to help the plastics specialist achieve new levels of professional development. Order the ANTEC® 2009 proceedings on thumb drive or CD-ROM. Includes 700+ papers detailing the latest developments in: Alloys and Blends, Applied Rheology, Automotive, Biopolymers, Blow Molding, Color and Appearance, Composites, Decorating and Assembly, Electrical and Electronic, Engineering Properties and Structure, Extrusion, Failure Analysis and Prevention, Flexible Packaging, Injection Molding, Joining of Plastics and Composites, Marketing and Management, Medical Plastics, Mold Making and Mold Design, Nano/Micro Molding, Plastic Pipe & Fittings, Plastics in Building and Construction, Plastics Environmental, Polymer Analysis, Polymer Modifiers and Additives, Process Monitoring and Control, Product Design and Development, Radiation Processing of Polymers, Rotational Molding, Thermoforming, Thermoplastic Elastomers, Thermoplastic Materials and Foams, Thermoset, and Vinyl Plastics.
	Injection Molding - Thumb Drive SPE, Chicago, Illinois USA, June 2009, Thumb Drive $50.00 Injection Molding Titles Include: Optimizing the Molding Process — Chapter from Plastics Technician’s TOOLBOX, by Jerry Golmanavich, Golmanavich Enterprises Shear Induced Imbalances and MeltFlipper® Technology, by John P. Beaumont, Penn State Erie & Beaumont Technologies, Inc. The Warpage Simulation with In-mold Constraint Effect in Injection Molding, by Dr. Venny Yang, CoreTech System Co., Ltd. The Investigation of Flow Behavior of Polymeric Melts in Water Assisted Injection Molding, by Dr. Chao-Tsai Huang, CoreTech System Co., Ltd. Injection Molding of Woodfiber Plastics Composites, by Michael Burgoyne State of the Art of Electric injection Molding, by M. Barr Klaus, Electric Injection Services, Inc. Mold Ejector Pin Melt Flow Volume Sensor, by Fred Buja, FjB PlasTechnology Water up to 400°F – The Best Way To Heat up Your Mold, by Anna Birkhofer, consultant Asia Tooling and Molding: How To Be Successful, D.B. "Dusty" Rhodes, Waypoint Bellwether, Inc. It Is as Easy To Be an Injection Molding Compounder as It Is To Be an Injection Molder, by Peter Lipp, Krauss-Maffei Corporation Effect of Injection Molding Process Parameters on the Morphology and Quality of Microcellular Foams, by Jingyi Xu Microcellular Injection Molding of Polylactide-Montmorillonite Nanocomposites, by Sarah Gong, Assistant Professor, University of Wisconsin-Milwaukee
	Qualifications, Startups and Tryouts of Injection Molds W. J. Tobin, 2003, All inclusive CD $32.00 The truth is you don’t need fancy gizmos to do scientific molding. All you need is a machine where you can read the settings, an accurate weigh scale, and a computer. A universal setup guide only needs a little homework on your part to read each machine’s manual and the ability to read the settings. If you had a few days and an engineering textbook you could actually write these spreadsheets yourself! It is NOT MAGIC. This CD uses a practical, down to earth, easy to use approach to bringing a mold on-line and producing consistently good parts. CD contains both filled in tutorials showing what inputs are required and worksheets for you to fill in. CD Contents: Contents of the 90 page book. Spreadsheets in Microsoft Excel .xls files: Optimum fill calculation – the melt viscosity curve, Gate Freeze off, Cooling time, Cavity balance for multi cavity tools, Cp CpK calculator, Universal setup sheet – includes how to translate from one machine to another, a waterline map, Runner size optimization, and a calculator to determine your process window settings. Microsoft Word .doc Files: Mold Check List, Mold History / Maintenance forms. The text includes a complete explanation of the experiments to optimize your injection molding cycle. Other Topics are: Mold Maintenance – Inspection and General Maintenance, Mold hang and Mold Pull procedures, Mold Storage, Basic Chemistry, Quality Control/ Quality Assurance – Cp and CpK explained and how to use them, Sizing Sprues, Nozzles and Runners for your mold, Hard Copy of the Mold Check List, Mold History and a Data Form to fill out for the experiments, and how to calculate a process window that will allow you to adjust the process as it drifts and still make acceptable parts.
	Additives for Polyolefins Michael Tolinski, 304 pages, Jul-2009 ISBN-13: 978-0-8155-2051-1 $150.00 This book focuses on the polyolefin additives that are currently important in the plastics industry, alongside new additives of increasing interest, such as nanofillers and environmentally sustainable materials. As much as possible, each chapter emphasizes the performance of the additives in the polymer, and the value each relevant additive brings to polypropylene or polyethylene. Where possible, similar additives are compared by capability and relative cost. With major sections for each additive function, this book provides a highly practical guide for engineers and scientists creating and using polyolefin compounds, who will find in this book a wealth of detail and practical guidance. This unique resource will enable them to make practical decisions about the use of the various additives, fillers, and reinforcements specific to this family of materials. Contents: SECTION I: OVERVIEW OF POLYOLEFINS AND ADDITIVES 1 Introduction 2 Trends in polyolefin & additive use SECTION II: ENVIRONMENTAL RESISTANCE 3 Antioxidants and heat stabilization 4 Ultraviolet light protection & stabilization 5 Flame-retarding additives 6 Additives for modifying electrical properties SECTION III: MECHANICAL PROPERTY ENHANCEMENT 7 Overview of fillers & fibers 8 Factors determining selection of fillers and fibers SECTION IV: APPEARANCE ENHANCEMENT 9 Colorants 10 Nucleation and clarity SECTION V: PROCESSING AIDS 11 Processing aids for molding 12 Processing aids for extrusion SECTION VI: OTHER MODIFICATIONS OF FORM AND FUNCTION 13 Reducing density: Polyolefin foams 14 Coupling, compatibilizing, recycling, and biodegradability 15 Cross-linking 16 Sterilization & radiation resistance 17 Aesthetics enhancement and surface modification SECTION VII: CONCLUSION: INCORPORATING ADDITIVES 18 Adding Additives to resin References Index

SPE-STX Board Meeting

Location: Teleconference
Date: September 18, 2009

Influence of Composition on Deformation Behavior of Blend of Poly(Ether Ether Ketone) and Poly(Ether Imide)

Jatin Panchal and Miko Cakmak*
Polymer Engineering Institute, College of Polymer Engineering and Polymer Science, University of Akron, Akron, OH 44304-0301, USA

Abstract

Uniaxial deformation behavior of varying composition of binary blend of PEEK and PEI was investigated at temperatures T_g< T_p < T_cc and the effect of composition, temperature, stretching rate and development of crystallinity were studied. The compositions studied were PEEK/PEI 100/0, 90/10, 80/20, 72.5/27.5, 65/35 and 50/50 resp. Increasing the PEI content shifts the T_g and cold crystallization temperature of the blend to higher temperature, however, this rule of increase of T_cc is faster than that of T_g. As a result the process temperature window (T_cc-T_g) widens. PEI retards the crystallization process of PEEK allowing the blend to be stretched at higher stretch ratio's at lower stresses at the relative processing temperature of T_g+10/20.

Introduction

The materials used in this study are PEEK (Poly Ether Ether Ketone)/PEI (Poly Ether Imide). PEEK (Poly Ether Ether Ketone) is a tough polymer with highly aromatic backbone with properties that make it very attractive for use as high quality engineering thermoplastic. It is semi-crystalline polymer with a crystalline melting point around 335°C and glass transition at around 145°C. PEEK (Poly Ether Ether Ketone) can be quenched-cooled from the melt into glassy state and can therefore be prepared in the crystalline form either by heating up from glassy state or by cooling down from the melt state.

PEI is a linear amorphous high performance polymer with a glass transition of 215°C. PEI has the advantage of good mechanical properties and thermal stability, but its solvent resistance is rather poor, which limits its use particularly in aerospace application.

Miscibility of polymer pairs has been demonstrated123to play an important role in controlling properties such as viscosity, crystallinity, tensile modulus etc. Generally, a lack of miscibility will lead to phase separation and poor interfacial bonding. The blend of PEEK/PEI have been subject of several studies in past. It has been shown that PEEK/PEI are melt miscible over all the composition range.^4,5

The goal of this study is to find the optimum composition of PEEK and PEI that enhances the thermal properties of the blend by shifting the glass transition temperature and cold crystallization process to higher temperature thereby opening the “Rubbery” state processing window (=T_cc-T_g) for ease of film manufacturing, while preventing possible premature thermal crystallization, which is prevelent in 100% PEEK.

Experimental

Materials:The polymers used for this study are: Poly{Oxy-1,4-Phenylene Oxy- 1,4-Phenylene Carbonyl-1,4Phenylene) and Poly{2,2-Bis[4-(3,4-Dicarboxy Phenoxy) Phenyl]propane-m-Phenylene Bis-Imide}, trade name VICTREX 380G, commonly known as PEEK (Poly Ether Ether Ketone) with Molecular Weight ranging from 14000 ± 6000 and PEI (Poly Ether Imide), trade name ULTEM 1000, with Molecular Weight ranging from 30000 ± 1000 resp.

Blend Preparation/ Film Preparation and Uniaxial Stretching
Blends of PEEK/PEI of different compositions were prepared by melt mixing, using Labotex 30 Twin Screw Extruder (TEX 30, HSS-32.5, PW-2V). The barrel temperature was set at 370°C and Die temperature at 380°C. The filaments of 1.5-mm diameter were extruded, quenched into cold water tank and pelletized.

Thin films of different compositions of PEEK (Poly Ether Ether Ketone)/PEEK (Poly Ether Imide) blend was prepared using Compression Molding Machine. The pellets were dried in vacuum oven at - 30 in.Hg at 120 oC for a 12 Hrs in order to eliminate air bubbles in the molded samples.

The mold used was a square metal picture frame mold, which had inner dimensions of 120 mm x 120 mm x 0.5 mm. The resin was processed at 390°C and 2000 Psi. In order to produce completely amorphous sample, films removed from the mold was immediately quenched into chilled water. Rectangular samples, 20 mm x 80mm, were cut from the compression molded films. The thickness of the samples were measured at 18 points on the gauge length with a resolution of 2um. Standard Deviation was calculated using equation

Where, y_i is the thickness at the i^th points and <y_i> is the average of y_i’s.

Instron Tensile Testing machine (Model 4204) was used along with the Temperature controlling chamber (Instron-3119-009), for uniaxial stretching. The stretching temperature used for a particular blend was Tg+10/20, preventing the samples from undergoing thermal crystallization.

Thermal Analysis
Thermal analysis of blend pellets, molded samples, stretched and annealed samples were performed using a Dupont 9900 Differential Scanning Calorimeter. All runs were made at a heating rate of 20°C/min. The samples were heated in dry nitrogen atmosphere using standard DSC program included with the DUPONT 9900. The % Crystallinity was calculated using the equation 2.

% Crystallinity=••M-•HC/130 (2) 100 % crystallinity of PEEK (as reported by Blundell and Osborn) used was 130 J/gms.

Wide Angle X-Ray Scattering
To study the crystallinity development, WAXS patterns were obtained using General Electric X-ray generator. Monochromatization of the incident beam

was accomplished using nickel filter. Sample thickness was maintained around 1 mm, by stacking 2-3 layers together. WAXS pattern were generally obtained with X-ray beam perpendicular to the film surface

Orientation Factor Measurement
The samples were mounted such that the long axis is along the stretching direction when chi angle is rotated to 90°. With chi angle 90°, the samples were scanned at varying 2-theta angle from 15° to 30° in order to find the maximum peak position of (110) and (200) planes for different blends with varying PEI contents and varying stretch ratio. Fixing 2-theta at maximum peak position for (110) and (200) planes as determined by 2 theta scans, respectively and chi angle was varied 0° to 90°, using an automated quarter circle GE goniometer. The intensity results obtained were used for orientation factor measurement. A GE XRD-6 X-Ray generator equipped with Cu target tube provided the X-rays that were monochromatized using a detector side graphite crystal monochromator. To obtain the orientation factor, scattered intensities were measured and Stein's generalization of Herman's orientation factor as in equation 3 was used.

where is the angle between the i crystallographic axis and the machine direction z.

The for PEEK can be expressed as in eq.4

Results and Discussion

Thermal behavior of the blends
D.S.C. thermograms of the blended pellets as prepared by the twin screw extruder are shown in fig1. The occurrence of single T_g proves the miscibility of the two polymers over the entire composition range. The glass transition temperature increases with the increasing PEI content and it closely follows the T_g as predicted by Fox equation, T_g = W₁/T_g1+W₂/T_g2, as shown in fig 1 (Inset)

The cold crystalline peak shifts to the higher temperature with increasing PEI content, as the chain requires higher energy to crystallize due to the constrained environment imposed by stiff PEI chains. Therefore, the PEEK chains advancing to the growth front requires to overcome higher energy barrier. The area under the crystalline peak decreases, indicating the decrease in the crystallinity of the blend, as shown in fig 2 (Inset), which is due to the dilution effect of the viscous PEI which hinders the crystallization of PEEK by reducing the diffusion of the chains to the crystal growth front. As PEEK is the only crystallizable component of the blend the melting peak remains unaltered.

As shown in Fig 2, the processing window for the film stretching i.e. the difference between T_cc and T_g increases from 27°C to 50°C with the increasing PEI content.

Effect of temperature on the deformation
So as to analyze the results and to establish a common ground to compare results obtained by stretching different blends having different glass transition and cold crystallization temperatures, based on the past experience, we decided to stretch the binary blend at temperature T_g + 10 and T_g+20 using different stretch rates: 5 mm/s and 10mm/s. It is evident from the stress-strain curves as shown in fig 3 and 4, that stress level is dramatically influenced by the change in temperature. The blend reveals a typical stress-strain behavior shown by most crystallizable amorphous thermoplastics. The stress-
strain curve is linear within the elastic limits and beyond that the polymer undergoes elongation at almost constant stress. On stress hardening, there is an abrupt change in the slope and stresses increase exponentially. On increase of stretching temperature, whole stress-strain curve shifts to lower stresses and the critical stretch ratio at which stress hardening occurs shifts to higher stretch ratio's for a particular blend. With the increase in temperature, the polymer chains get higher energy and become more mobile and `rubber' like, which reduces their capabilities to strain harden and crystallize and therefore deforms to higher stretch ratio's at lower stress level. This is partly due to reduction of crystallizability due to dilution effect.

Effect of stretch rate on the deformation
Increase of stretching rates from 5mm/s to 10mm/s at T_g+10, results in increase in the stresses for same deformation, which can be attributed to onset on stress hardening at lower stretch ratio's. The shift of the stress hardening to lower stretch ratio with the increase in the stretching rates is not significant, however, it becomes more evident during commercial production when the level of stresses are many times higher than that used for this experiment.

Effect of composition on the deformation
The effect of composition on the deformation is shown in fig 3 and 4. As the PEI content increases, stresses at lower deformation increases due to the increasing presence of the stiffer PEI chains however, the critical point of stress hardening is shifted to higher stretch ratio's due to dilution effect of PEI which retards the stress induced crystallization of PEEK which is responsible for causing stress hardening and subsequent increase in the stress level.

Thermal behavior of stretched films
Thermal behavior of PEEK/PEI 100/0 stretched films is shown in fig 5. With the increase in stretch ratio, the glass transition and the melting temperature of the blend remains unaltered. The cold crystallization peak shifts to lower temperature and the area under the cold crystallization peak decreases. With increase in stretch ratio, the polymer chains are alligned in the stretching direction and undergoes stress induced crystallization. When additional heat is supplied, the already oriented chains which didn't undergo stress induced crystallization, crystallizes immediately which is evident from the shift of T_cc to lower temperature. As the stress induced crystallization process dominates with higher stretching ratio's the uncrystallized chains left for thermal crystallization decreases which explains lowering of the area under the crystallization peak. Increase in crystallinity with increasing the stretch ratio are as shown in fig5 (Inset).

Effect of deformation on the development of crystalline lattice and orientation
In order to determine the structural evolution, WAXS patterns were obtained. The unstretched films are essentially amorphous. Fig 6 shows the plot of stress-strain curve and the corresponding stretch ratio where WAXS pattern were determined. At stretch ratio of 2x (11O) and (2OO) planes are seen embedded in the amorphous background which indicates the orientation of the chains in the stretching direction. Beyond the stress induced crystallization, where the stress rises exponentially, the (110) and (200) peaks gets highly defined and off equatorial planes becomes more defined confirming the packing of the chain in third direction forming the three dimensional order in the crystalline regions. The orientation factor measurements are shown in fig7. With the increase in stretch ratio the c axis approaches f_c = 1, indicating allignment of the c axis along the stretching direction. The b and a axis approaches the value of f_c = 0.5 indicating the orientation of b and a axis perpendicular to stretching direction.

Conclusion

The deformation behavior of blend of PEEK/PEI with increasing composition of PEI was studied. Increasing the PEI content results in widening of the process window (T_cc-T_g) and delays the stress induced crystallization to higher stretch ratio's and lower stresses. PEI also reduces the crystallization process of PEEK. The effect of increasing temperature is to allow stretching of the films at lower stresses at the cost of crystallinity allowing the film to be stretched to higher stretch ratio's before undergoing stress induced crystallization. The c axis orientation factor was found to be quite high and the addition of PEI was found to retard the chain orientation in PEEK regions.

References

1 Olabisi, O., Robeson, L. M., and Shaw, M. T., Polymer-Polymer Miscibility, Academic Press, NY 1979.

2 Paul, D. R., in Polymer Blends, Newmans Academic Press, NY 1978.

3 Utracki, L. A., Polymer Alloys and Blends, Hanser Publications, NY 1990.

4 Harris, J. E. and Robeson, L. M., J. of Applied Polymer science, 35, 1877, 1988.

5 Crevecoeur, G. and Groeninek, G., Macromolecule,, 24, 1190, 1991.