Much attention has been paid on the R&D of chemical recycling of waste plastics in recent years from the view point of preservation of natural resources and environmental protection of the earth. There are several kinds of recycling techniques of plastics: material recycling, thermal recycling and chemical recycling. Which recycling method is used depends on the countries. In Japan, the thermal recycling combined with an electric power generation is popular because Japan has a lot of municipal waste incineration facilities. However, as burning waste plastics causes the dioxin problem, new recycling techniques have to be introduced in near future. Chemical recycling, which depolymerizes plastics into the monomers of raw materials or the oligomers of fuel oil, is expected to be a safe and environment-friendly technique of waste plastic treatment. In this work, we present the recent progress on the chemical recycling of waste plastics using sub-and supercritical fluids: the kinetic study on the depolymerization of condensation polymer of polyethylene terephthalate (PET) to the constituent monomers with supercritical methanol, and the decomposition of thermosetting plastics of brominated epoxy resin with subcritical water.
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