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 Quick, Precise, but not Cold
17.05.2017 | Fraunhofer-Institut für Lasertechnik ILT

nachricht A laser for divers
03.05.2017 | 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: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Innovative LED High Power Light Source for UV

22.06.2017 | Physics and Astronomy

Mathematical confirmation: Rewiring financial networks reduces systemic risk

22.06.2017 | Business and Finance

Spin liquids − back to the roots

22.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>