Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NC State Researchers Develop New Plastic Recycling Process

16.04.2003


Plastics are everywhere these days, but current recycling techniques allow only a very limited portion to be reclaimed after initial use. Researchers in the Department of Chemical Engineering at North Carolina State University, working to change that, have developed a unique recycling process for some of the most common kinds of polymers.


Joan Patterson, doctoral student in chemical engineering at North Carolina State University, demonstrates the twin-screw extruder that will be used to recycle PET plastic bottles into plastic pellets, in bag at left.
© NC State University



The familiar soda bottle is made of a plastic called polyethylene terephthalate (PET). These bottles are ubiquitous, yet recycling them poses challenges, primarily because of contaminants or impurities. Dr. George W. Roberts, professor of chemical engineering, Dr. Saad A. Khan, professor of chemical engineering and director of the chemical engineering graduate program, and Joan Patterson, doctoral student in chemical engineering, are working on a project designed to address this problem.

“We’re trying to develop a process where we can take waste polymer and convert it back into the material from which it was made. In the process, all the impurities are removed from the polymer,” said Roberts. “Ideally, this should be done in a single step because the economics have to make sense for the process to have widespread applicability.”


The process, according to Roberts, has two unique elements. “First we run the process in a machine called a twin-screw extruder, which has high throughput. A lot of polymer can be processed in a very short time,” he said. “The extruder melts the PET and creates very thin films so we can interface the high molecular weight polymer with another material, either ethylene
glycol or methanol, that will reduce the molecular weight of the polymer substantially.”

Second, supercritical carbon dioxide (CO2) is combined with the ethylene glycol or methanol, which reduces the viscosity, or stickiness, of the polymer, making it easier to process and allowing better contact between the materials. At the end of the process, the CO2 is vented from the extruder and run through a condenser, where dissolved impurities can be removed. The CO2 is then recycled.

The process has several advantages. The conversion is done under efficient processing conditions and is a one-step, environmentally benign procedure. In addition, the process can be tailor-made for materials of different molecular weights.

A single-screw extruder has been used successfully in the research laboratory at NC State for this procedure. Now Roberts and his team are looking for ways to make this process economically feasible for an industrial-scale operation. “The basic reaction of ethylene glycol with the polymer is known, but our preliminary data say that this enhanced reaction is several orders of magnitude faster when done in the extruder with supercritical CO2 than if it is run conventionally,” said Roberts.“That translates into lower cost.”

According to Khan, twin-screw extruders are common in the workplace, so these machines can be reconfigured to use supercritical CO2. First, the research team must determine how variables – including rate of flow of polymer; the amounts of CO2, ethylene glycol or methanol; temperature; pressure of CO2; and machine configuration – affect the processing.

“To our knowledge, the machines in the marketplace have never been used for this purpose, but they can be modified for this process,” said Roberts. “Part of our research involves configuring the existing machines so they can give optimal performance.”

groberts@eos.ncsu.edu | NC State University
Further information:
http://www.ncsu.edu/news/press_releases/03_04/114.htm

More articles from Process Engineering:

nachricht CeGlaFlex project: wafer-thin, unbreakable and flexible ceramic and glass
25.04.2017 | Fraunhofer-Institut für Lasertechnik ILT

nachricht Additive manufacturing, from macro to nano
11.04.2017 | Laser Zentrum Hannover e.V.

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>