Shaking up injection molding with dynamic melt manipulation,
micro/nanoscale technology with standard BOY machines.

The Manufacturing Science Lab at Lehigh University
is exploring new frontiers.

Science has always been about trial and error, but in an era of high-stakes foundation grants, corporate sponsorships, and computer modeling, it is easy to lose sight that round after deliberative round of experiments in the lab is the best way to prove (or disprove) any theory. The professors, research assistants, and students of the P.C. Rossin College of Engineering and Applied Science at Lehigh University certainly haven’t. Their focus on discovering material and processing advantages through persistent, systematic experimentation using current, widely available processing machinery is a testament to scientific methods.

Melt manipulation has been a key area of interest to Lehigh, which has conducted a decade’s worth of research supported by National Science Foundation grants, Society of Plastics Engineers assistance, and a host of process machinery manufacturers. One of these companies is BOY Machines Inc., the Exton, PA-based supplier of injection molding machines up to 100 tons capacity. Lehigh’s efforts, using two conventionally equipped model BOYs, has led to many surprising breakthroughs.

The traditional route to polymers with enhanced properties is through the use of fillers and additives to create engineered plastics. John P. Coulter, Professor and Associate Dean of the P.C. Rossin College of Engineering and Applied Science at Lehigh, has been encouraging his students and associates down another path. “You don’t always have to reinvent the wheel to achieve new results. We have been working with a variety of different size, commercially available injection molding machines, then applying fundamental science to achieve new material results. By manipulating the melt through changes in flow, shear, molecular alignment, and thermal conditions, we’ve managed to enhance the end product or develop a processing advantage.”

Most of the recent melt manipulation efforts have been in the area of vibration assisted injection molding processing — using low frequency pulsation to better line up molecules — and these efforts have led to some noteworthy advances. They have also caught the attention of the plastics industry, as evidenced by Lehigh’s winning of the best injection molding research paper at the most recent International Society of Plastics Engineers ANTEC conference. It detailed the use of pulsations to oscillate the injection pressure to better align molecules and improve part strength.

“We took a 15-ton BOY injection molding machine and hooked up our own PC control of the injection and packing stages. Other than that, we made no physical changes to the machine itself. Then, we introduced low frequency oscillation of the injection screw to enhance specific properties of the material being processed,” notes Coulter. “For instance, tensile strength can be dramatically increased in this manner.”

From a processor’s standpoint, Lehigh has experimented with many end use application areas. In one example, the Lehigh group used melt manipulation to enhance the tensile strength of different grades of polystyrene. Employing vibrational methods, it produced parts made of a 50/50 recycled blend of PS that were stronger than 100% virgin blend processed conventionally. The ability to use regrind and still improve specific properties represents a great deal of financial opportunity for processors competing in a global plastics economy.

Lehigh has even been able to document some of its processing achievements on videotape, using a special mold fitted with transparent windows facilitating in-situ observation of specimen birefringence during mold filling. “It’s been fascinating to see some of these changes taking place,” says Coulter. One such experiment did not require vibration at all. Through trial and error and visual monitoring, Coulter’s group has determined how to control the location of weld lines as well as molecular orientation associated weaknesses within molded parts. “In this fashion, we can put the strongest and/or weakest spot on a part wherever it makes the most sense.”

All of these exceptional experiments have been a dramatic prelude to a new area of research that Lehigh is currently actively engaged in — nanotechnology, the engineering and custom design of materials and devices at the molecular scale. The goals are to create new high-performance products, eradicate illnesses through sub cellular control, and extend development limits. Currently, Lehigh Professors John Coulter and Padma Rajagopalan have a grant proposal in front of the National Science Foundation entitled “Molecular Orientation Focused Dynamic Polymer Melt Control for Tailored Blood Interaction and Biodegradability.” The goal is to fully explore this complex technology in order to develop precision medical products that can yield significant advances in health, new telecommunications devices, computing products, and environmental sensing units.

Recently, Lehigh’s Center for Advanced Materials and Nanotechnology received $900,000 for the Materials Research Science and Engineering Centers as part of a Pennsylvania statewide $11 million investment in nanotechnology initiatives. Under this program Lehigh and Carnegie Mellon University have developed a strong infrastructure in nanocharacterization, with major enhancements to programs and facilities that support interdisciplinary research and interactions with large and small companies across the commonwealth. Lehigh’s Center for Optical Technologies also received $500,000 for Nanophotonics, which will support both research and enhancements in industrial and educational outreach programs. Lehigh will use this funding to support their infrastructure in optical and optoelectronic technologies, advanced optical, electronic and optoelectronic materials, and a host of related advanced nanocharacterization and nanotechnologies.

“What we have found thus far as a result of our cross-disciplinary research,” says Coulter is that “traditional math models don’t apply when you are operating at the molecular level, so we are developing new math models with our research. Establishing a new science base, if you will.”

One of Coulter’s Research Assistants, Aleksandar Angelov, has been experimenting with nano-scale molding on BOY’s smallest machine, the 12A, equipped with a 12 mm screw and molds made out of silicon with standard micro fabrication techniques. The parts he has been producing are unbelievably small, but measurable with an electron microscope. One example is a molded tag of the BOY logo that is only 50 microns (a micron is one-thousandth of a millimeter). It is actually smaller than the AIDS virus, which is the smallest virus known to man. Further evidence of the Lehigh Manufacturing Science Laboratory’s nano-molding work can be found at a “Lehigh Micro/Nanoscale Image of the Week” web site developed by Professor Jim Gilchrist. Posted on it are striking examples of the research being done at this level by various research groups at Lehigh University. A similar development shown on the site is a three-dimensional polymer designed in the shape of the Lehigh University logo, replicated from an etched silicon substrate at the nanoscale. Each letter in the word LEHIGH is, at 15 micrometers, roughly the size of a human blood cell. An even more detailed inset reveals an even closer magnification of the Lehigh shield — the tiny hash marks represent a 500 nm (nanometer) measurement. The most recent work by the Lehigh molding group accomplished the reliable and accurate molding of nanoposts down to the 50 nm scale. They are actually smaller than the AIDS virus, which is approximately 100 nm.

“We couldn’t be more excited by these innovative programs and the way our machines are being used in them,” states Robert Koch, President of BOY Machines Inc. “Lehigh is at the leading edge of so much manufacturing technology. We hope to work together from here to help BOY customers utilize melt manipulation techniques to gain material advantages. As for nanomolding, it holds tremendous promise and because our machines are so well suited to the molding of miniaturized parts, we expect them to be vital to advances going forward.”

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