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 Etching Microstructures with Lasers
25.10.2016 | Fraunhofer-Institut für Lasertechnik ILT

nachricht Applying electron beams to 3-D objects
23.09.2016 | Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>