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CO2 Refrigeration

Date:2011/1/10 From:AetClose

    Scientists use carbon dioxide to create novel plastics

Researchers from the Fraunhofer Institute for Environmental, Safety and Energy Technology in Oberhausen, Germany discovered a new use for carbon dioxide – for creating plastic with antibacterial properties.
The scientists infused compressed carbon dioxide into plastics, which they said could lead to new products ranging from colored contact lenses to bacteria-resistant door handles. Carbon dioxide is one of the most potent greenhouse gases that contribute to global warming.
   At a temperature of 30.1oCelsius and a pressure of 73.8 bar, the carbon dioxide goes into a supercritical state that gives it 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.
The team pumped liquid carbon dioxide into a high-pressure container with the plastic components to be filled. They then gradually increased the temperature and pressure until the gas reached the supercritical state.
     Once the state is reached, they continue to increase the pressure to 170 bar, in which pigment in powder form dissolves completely in the carbon dioxide and then diffuses with the gas into the plastic. The whole process reportedly takes only a few minutes to execute.
     The scientists used this process to infuse polycarbonate with nanoparticles that give it antibacterial properties. They also conducted tests with silica and the anti-inflammatory active pharmaceutical ingredient flurbiprofen, which were also successful.
  “Our method allows us to customize high-value plastic components and lifestyle products such as mobile phone shells,” explained Manfred Renner, a scientist at the institute.
 “The best about it is that color, additive or active ingredient is introduced into layers near the surface at temperatures far below the material’s melting point, in an environmentally friendly manner that does away with the need for aggressive solvents,” he continued.
   The process holds enormous potential because while carbon dioxide shows solvent-like characteristics, it does not have the same harmful effects on health and on the environment like solvents used in paints.

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