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

Warpage Comparison between Microcellular and Conventional Injection Molding

Adam Kramschuster, Ryan Cavitt, Donald Ermer, Zhongbao Chen, Lih-Sheng Turng, May 2005

This research investigated the effects of processing conditions on the shrinkage and warpage (S&W) behavior of a box-shaped part using conventional and microcellular injection molding. Two sets of 26-1 fractional factorial DOE were employed to perform and analyze the experiments. After the machine and material reached the steady state condition, molded samples were collected and measured using an optical coordinate measuring machine (CMM). The results suggest that the supercritical fluid (SCF) content (in terms of SCF dosage time) and the injection speed affect the S&W of microcellular injection molded parts the most, whereas hold pressure and hold time have a greater influence on the S&W of conventional injection molded parts. This study also quantitatively showed that, within the processing range studied, an increase in dimensional stability could be achieved with the microcellular injection molding process.

Biobased Polylactide (PLA) Nanocomposites

Tongnian Li, Shaoqin Gong, Lih-Sheng Turng, May 2005

Three types of polylactide (PLA) composites, namely, PLA/nanoclay, PLA/core-shell rubber, and PLA/nanoclay/ core-shell rubber were melt compounded via a co-rotating twin-screw extruder. The effects of two types of organically modified nanoclay (i.e., Cloisite®30B and 20A), two types of core-shell rubber (i.e., Paraloid EXL2330 and EXL2314), and the combination of nanoclay and rubber on the mechanical properties of the composites were investigated. In comparison with pure PLA, both types of PLA/5wt% nanoclay composites showed an increased modulus, a slightly reduced tensile strength, a similar impact strength, and a significantly reduced strain at break. PLA/EXL2330 composites with a rubber loading level of 10wt% or higher exhibited much higher impact strength but lower modulus and strength when compared to pure PLA. The simultaneous addition of 5wt% nanoclay (Cloisite®30B) and 20wt% EXL2330 resulted in a PLA composite with a 134% increase in impact strength, a 6% increase in strain at break, a similar modulus, and a 28% reduction in tensile strength as compared to pure PLA.

Simulations of Grafting Monomers and Associated Degradation of Polypropylene in a Modular Co-Rotating Twin Screw Extruder

Jongmin Keum, James L. White, May 2005

Kinetic models of grafting MAH and MMA on polypropylene(PP) were developed for screw extrusion. However the kinetic models are insufficient to explain the grafting reactions along the length of modular co-rotating twin screw extruders, because rheological properties and the residence time of PP changed by degradation of PP during the grafting reaction. In order to model this for a modular co-rotating twin screw extruder, the kinetic model of grafting reaction and models of degradation of PP are combined with fluid mechanics and heat transfer. Given the geometrical configurations of the screw and the operating conditions and the physical properties of the polypropylene, the simulations predict variation of molecular weight and mean residence time by degradation of PP. The weight percent of grafted MAH or MMA on PP profiles along the screw axis are also calculated in the simulation. These predictions are compared with experimental data for various operating conditions.

Compounding Wood Polymer Composites with In-Line Drying Technology

Ralph Cutillo, Steven Jackson, May 2005

Composite decking has moved into the mainstream of commercialization. Manufacturers must have a process that can achieve high rates for a reasonable capital investment. The equipment must also be able to process a variety of materials so as to take advantage of formulation changes that increase quality and/or reduce costs.A single step process will be discussed that converts nondried cellulosic fibers and polyolefin resins into finished retail decking. The effect on process conditions, particularly moisture removal, will be presented. Technical as well as commercial issues will be addressed. The focus of the presentation will be the need for an integrated manufacturing system to provide the maximum economic return on investment.

First Principles Cause of Melt Fracture in LLDPE

Dave Smith, Mike Andrews, May 2005

Ever since the introduction of LLDPE, the industry has had to deal with problems caused by melt fracture in many processing situations, with the worst problems typically occurring in the production of blown film. Over the years, many mechanisms have been proposed in an attempt to explain the cause and therefore possible cures for melt fracture, but none of these mechanisms has been able to adequately explain the observed phenomena or provide sufficient insight to develop a cure for the problem. Based on experimental observations, a new mechanism based on volatile induced flow defects has been proposed that explains many of the observations that could not previously be explained. This mechanism has allowed us to predict new methods for reducing melt fracture, and tests have proven these predictions to be correct. SEM photos of film samples provide additional evidence in support of this proposed mechanism.

Novel Gauging Technology for Contact-Sensitive Blown Films

Bill Hellmuth, May 2005

There are many challenges to on-line thickness measurement for blown films, some of which are:Getting data fast enough to make timely thickness profile corrections. This can be a problem with down stream stationary gauges.Measuring soft, tacky films or high optic films with gauges that ride in contact with the filmMeasuring films containing polyamide (nylon) with an “on-the-bubble” capacitance gauge. The capacitance of nylon changes rapidly in the temperature range of the cooling bubble just above the frost line (60 – 100°C / 140 – 210°F) causing inaccurate thickness readings. This precludes the use of capacitance gauges until the film is cooled below 40°C (100°F). (Fig. 1)To address these issues, a relatively new on-line technology utilizes a non-contact scanning gauge mounted downstream of the primary hauloff to measure the layflat web (double sheet). A novel software algorithm separates the double sheet measurements into full circumference profile scans. The data can then be used to take corrective action on average thickness or thickness profile variation. European patent EP 1 207 368 A2 provides a description of one of several possible methods used to implement this technology.1By measuring the layflat with a scanning gauge head, data collection rate becomes nearly independent of the process oscillation time. This addresses the first challenge. NOTE: the oscillating die or hauloff must be moving for the technology to work. Also, the oscillator must traverse far enough to generate sufficient variation in the data to perform the separation function (this distance varies according to each supplier’s experience).Using a non-contact transmission gauge (e.g. nuclear, X-Ray, IR, or capacitance) handles the second challenge -- problems associated with contacting the film.Measuring nylon films downstream of the hauloff, where the web is cooler, allows the use of a capacitance gauge in addition to nuclear, X-Ray or IR gauges. This addresses the third issue.

Study of Polypropylene Morphology to Obtain Porous Membranes by Stretching

F. Sadeghi, A. Ajji, P.J. Carreau, May 2005

Four different polypropylene resins were extruded using the tubular and the cast film processes. The morphology of the films was observed by SEM and the effect of extrusion processing variables on the morphology was investigated. Melt rheological experiments were carried out to characterize the behavior of the polymers. It was found that the molecular weight distribution and the chain structure as well as the processing conditions had important effects on the morphology. Efforts focused on obtaining a lamellar crystalline morphology by controlling the processing conditions. The possibility of generating a porous membrane from the initial morphology using a stretching technique was evaluated. The initial lamellae arrangement of the precursor film is shown to play a significant role in obtaining a porous structure.

New Approach to Noise Reduction in Plastic Gears

Nimish C Gandhi, May 2005

The Gear noise was studied in an individual gear mesh for a two shot molded gear. The two layers comprised of a hard core and softer tooth of the gear. PBT, PA 66 and POM were used as the hard core and TPE for the softer skin. This experiment was limited only to the noise of the gear mesh using a sound meter and not the wear of the gear teeth. The “softer” teeth demonstrated smoother and quieter gear meshes with straight PA 66 and POM parts. It was found that the noise levels reduced as much as 25% when one of the driver/driven gear had softer teeth. The sound of the driving motor was isolated from the test gears using the acoustical fiberglass shield.

Preparation and Characterization of Polyimide Nanocomposites

D.M. Delozier, K.A. Watson, J.G. Smith, J.W. Connell, Aiping Yu, E. Bekyarova, R.C. Haddon, May 2005

Electrical conductivity needed to dissipate electrostatic charge (ESC) build-up that occurs on polymeric surfaces in the space environment can be achieved through the use of single-walled carbon nanotubes (SWNTs). This study presents two samples of SWNTs prepared by two different processes and their effect upon macroscopic polyimide properties. The neat SWNTs were characterized by ultraviolet/visible (UV/Vis) and fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and thermogravimetric analysis (TGA) prior to addition to the polymer through a surface coating process and bulk inclusion. The nanocomposites were evaluated for nanotube dispersion, electrical conductivity, mechanical, and optical properties.

Investigating Flow Behavior of Wood-Plastic Composites

Andrew Yacykewych, May 2005

The trend toward increased usage of renewable resources has led to the growing popularity of wood-filled materials. These emerging materials require extensive testing – beginning with formulation and ending with the final manufactured product. In the early stages of development, it is possible to acquire data comparing differences between recipes utilizing a Mixer/Measuring Head. The given blend can be compounded with a customized twin screw extruder and torque rheometer. Finally, a single screw extruder can quantify the rheology of the compound using a capillary die. The objective of this work is to investigate the behavior of a polyolefin based wood-filled compound using a torque rheometer.

"Reach-RS:" A Model Outreach Program

Christopher C. Ibeh, Derek Weber, Obi Okafor, May 2005

The pilot “REACH-RS” program was implemented in the summer of 2004. The PSU “REACH-RS” program is the culmination and result of the interactions between the director of the PSU/NSFREU/ RET program and high school science teachers, counselors and administrators. This interaction identified the need for an academically-oriented summer program for talented high school juniors and seniors. Selected high school students are invited to participate in a series of seven-day, hands on-oriented workshop with in-lab activities in such subject areas as “SMET of Materials Identification,” “Computerized Materials Selection Techniques,” “Toy Manufacturing Via Rotational Molding,” “Foam Production Technology,” “Ultra-sonic Bonding Techniques,” “Injection Molded Electrically Conductive Plastics In EMI Applications,” etc. Each experiment is designed to inculcate and reinforce in the student the practical applications of scientific, mathematical, engineering and technological concepts. Program sponsorship was accomplished via funding provided by 3M Foundation. Program outcome include but not limited to: preview and introduction to college life, improvement of communication and inter-personal skills, acquisition of technical proficiency in the areas of materials, nanomaterials and processing for the participants, and the development of academia-industry partnerships.

Graphite Platelet/Nylon Nanocomposites

Hiroyuki Fukushima, Sung Ho Lee, Lawrence T. Drzal, September 2004

Natural crystalline graphite based graphite intercalated compounds [GICs] were exfoliated into sub-micron graphite flakes. Graphite nanocomposites were fabricated by combining the exfoliated graphite flakes with nylon66 resin. The mechanical properties of these composites showed considerably higher modulus than those of composites made with commercially available carbon reinforcing materials (i.e. CF VGCF and Carbon Black). Also the electrical property was improved by adopting appropriate fabrication conditions.

Carbon Fiber Tie Rods for Heavy-Duty Truck Applications

David Witucki, September 2004

A joint effort between Delphi Corporation Hendrickson International and Oak Ridge National Laboratory has led to the development of carbon fiber reinforced polymeric tie rod for use in heavy-duty truck suspension systems. The composite tie rod tube assembly is 65% lighter than current metal tubes with equivalent or improved performance. This paper will summarize the design and test methodology which have led to successful implementation of this product for heavy truck applications.

Sensing When the Molding Cycle is Over: Using In-Mold Impedance Sensors in Thermoset Molding

Jim Diehr, September 2004

SmartTrac impedance sensing technology provides an important new method for thermoset molders to improve cure process productivity and quality. Similar to dielectric cure monitoring impedance technology uses the changing electrical properties of the thermoset as it cures to determine the optimum time to end the cure. This paper reviews the implementation of impedance sensing technology in SMC and phenolic and presents results from several production and lab applications.

Door Module from Fibre Reinforced Plastics - A Positive Contribution to Car Manufacturing

Dr. Matteo Terrangi, September 2004

PowerPoint Presentation at ACCE 2004.

GM Moves Toward Composite Transmission Cross Member for Full-Size Trucks

Adam D. Myers, September 2004

General Motors’ next generation full-size truck frames are currently 80 pounds over their targeted weight. By replacing the current steel transmission cross-member on General Motors’ full-size trucks through the application of a composite material transmission cross-member a substantial weight reduction will be achieved. Reducing the weight of General Motors’ full-size trucks will consequently increase the fleet-wide fuel economy for the company’s truck line allowing CAFE requirements to be met more easily.

Advanced GMT Applications in the Automotive Industry

Richard Broo, September 2004

PowerPoint Presentation at ACCE 2004.

D-LFT Process: In-Line Compounding & Compression Molding of Long-Glass-Fiber-Reinforced Polymers

Daniel Schwendemann, Gerald Münz, September 2004

Long fiber-reinforced thermoplastics have excellent mechanical properties and stiffness / weight ratio which is of particular interest to the automotive industry. The new in-line compounding processes for long-fiber materials offers users more flexibility as they are able to both compound and process such materials in accordance with their own formulation and also use ready-made compounds.

UV Cure: The Microwave Popcorn of the Composites Industry

Paul Mills, September 2004

Recent developments in the area of UV cured fiberglass resins and gel coats may provide significant advantages to composite parts manufacturers. These advantages lie in the area of greater speed better efficiency and the significant reduction in styrene. Interest in this later advantage has spurred commercialization of UV cured composites where regulatory pressure has required a different approach that traditional peroxide cure mechanisms.

Natural Fibers Thinking Out of the Box

Garry E. Balthes, Harry R. Hickey, September 2004

Most people are aware of what natural fibers are but few know of the diverse capability of this natural resource and unfortunately industry pressures over the past several years to reduce costs focused on trying to refine well established technologies using glass or wood fibers or to a certain extent injected molded polymers. It has only been through recent pressure by some of the larger OEM’s that natural fibers have been gaining broader interest for both their performance and environmental benefits as compared to older more comfortable based technologies. Cost versus performance is a delicate balancing act. Fortunately natural fibers go a long way on striking a balance between both of these most common demands. When considering performance natural fibers offer an unlimited range of lighter weight possibilities for interior and exterior applications. Most common today natural fibers are commingled into a nonwoven mat with fiberized thermo plastic polymers such as polypropylene and polyester for use in common interior applications that include door panels center consoles pillars and inserts. However advancements in the range of available natural fibers and specialty polymers along with a continuous improvement of the nonwoven process are now providing for greater heat stability to meet the elevated requirements for over head systems package trays and topper pads. Increased demands for occupant safety give further reason to consider natural fibers as few other materials provide the same impact characteristics with the base material. For exterior applications natural fiber mats used as the base material in sheet molding compounds will find their way into bumper reinforcements wheel well liners and under hood applications. The industry historically focused on direct material cost. In this simplified approach natural fibers seldom will come out to be the low cost alternative but when considering the benefits derived from one-step processing the end cost of the finis