How CO2 can be used to impregnate plastics

WASHINGTON - Despite being the main contributor to global warming, carbon dioxide really does have some beneficial features.

Scientists are impregnating plastics with compressed CO2 in a process that may lead to new applications ranging from colored contact lenses to bacteria-resistant door handles.

Researchers at the Fraunhofer Institute for Environmental, Safety and Energy Technology (UMSICHT) in Oberhausen are pursuing a new idea by testing how carbon dioxide can be used to impregnate plastics.

At a temperature of 30.1 degrees Celsius and a pressure of 73.8 bar, CO2 goes into a supercritical state that gives the gas solvent-like properties.

In this state, it can be introduced into polymers, or act as a “carrier” in which dyes, additives, medical compounds and other substances can be dissolved.

In tests, the researchers have even managed to impregnate polycarbonate with nanoparticles that give it antibacterial properties.

E-coli bacteria, placed on the plastic’s surface in the institute’s own high-pressure laboratory, were killed off completely - a useful function that could be applied to door handles impregnated with the same nanoparticles.

The process holds enormous potential, as carbon dioxide is non-flammable, non-toxic and inexpensive.

Whilst it shows solvent-like properties, it does not have the same harmful effects on health and on the environment as the solvents that are used in paints, for example.

“Our method allows us to customize high-value plastic components and lifestyle products such as mobile phone shells. The best about it is that the color, additive or active ingredient is introduced into layers near the surface at temperatures far below the material’s melting point, in an environ mentally friendly manner that does away with the need for aggressive solvents,” said Dipl.-Ing. Manfred Renner, a scientist at Fraunhofer UMSICHT. (ANI)