Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


NC State Researchers Develop New Plastic Recycling Process


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.” | NC State University
Further information:

More articles from Process Engineering:

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

nachricht New process for cell transfection in high-throughput screening
21.03.2016 | 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: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>