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CO2 could be used in 'green' plastic production

By

January 4, 2011

A plastic part colored using the CO2 impregnation process (Photo: Fraunhofer)

A plastic part colored using the CO2 impregnation process (Photo: Fraunhofer)

Excess carbon dioxide in the atmosphere has certainly become an environmental concern in recent years, but researchers from Germany’s Fraunhofer Institute for Environmental, Safety and Energy Technology are now experimenting with a process that uses CO2 to process plastic products in an environmentally-friendly fashion. They have discovered that by compressing the gas, it can be used to impregnate plastic objects with dyes, antibacterial compounds, or other substances. Traditionally, toxic solvents have been used for coloring plastic items.

The Fraunhofer team pump CO2 into a high-pressure container already containing the plastic parts and powdered pigment, then heat it to 30.1C (86.18F) and compress it to 73.8 bar. At this point, it goes into a supercritical state and takes on solvent-like properties. The team then continue to increase the pressure, until at 170 bar the pigment dissolves into the CO2, and then proceeds to diffuse into the plastic. The whole process only takes a few minutes, and while the gas itself escapes from the plastic afterward, the pigment stays in and cannot be wiped off.

The researchers have also successfully impregnated plastics with antibacterial nanoparticles, silica, and the anti-inflammatory active pharmaceutical ingredient flurbiprofen.

The process is said to work on partially crystalline and amorphous polymers (such as nylon and polycarbonate), but not on crystalline polymers. Unlike some traditional plastic impregnation technologies, it doesn’t cause dyes to change color, heat-sensitive substances (such as fire retardants or UV stabilizers) can be introduced, and the plastic comes nowhere near its melting point.

The CO2 itself is non-flammable, non-toxic and inexpensive. While the Fraunhofer process doesn’t capture carbon dioxide, there are experimental plastic production systems that do – perhaps the escaped gases from the one could find their way into the other.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
3 Comments

It's the way to go, to view CO2 and Methane Calthracites (?) as valuable resources, for conversion back into fuels AND raw carbon for sequestation into bio char for global soil fertility.

Mr Stiffy
4th January, 2011 @ 11:18 pm PST

I saw the headline and thought 'why not just plant a tree?', but this is actually a very interesting application of supercritical CO2, there will be many more applications besides for the unique properties of CO2 in its supercritical state...

PeetEngineer
5th January, 2011 @ 08:26 am PST

The same principle is used in decaf cofee production. The supercritical CO2 dissolves and extracts the caffeine from the cofee beans.

cachurro
18th April, 2012 @ 08:01 pm PDT
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