History and Background of GreenPla(R)
When you look around in your daily life, you'll notice that plastics are used everywhere. Plastics, which are light in weight, can be easily processed into various shapes and colors, and are available at low costs, are a typical example of outstanding benefits of advanced science and technology. We are enjoying comfortable modern lives brought about by the plastics.
Stability and durability of plastics are very useful characteristics when the plastics are in use. However, the strength of plastics could cause some reverse problems; the issue of plastic waste s. Plastic wastes tend to be conspicuous at landfill sites and, since plastics in general are light in specific weight, volumetric percentage of waste plastics in the total waste is relatively high. Waste plastics have been sometimes regarded as the major cause of rapid depletion of available landfill sites.
Once discharged into natural environment, some of the plastics are very difficult to retrieve. Stories of fishing line tangled on seabird's legs and plastic bags found in stomach of sea turtle are, for example, very often carried in news papers. We are now facing the fact, more often than ever, that waste plastics discharged as the result of human activities are threatening the wild lives and damaging the environment.
Biodegradable plastics ( GreenPla(R) ) have been developed as one of the solutions to the problems. Biodegradable plastics can be used in the same way as conventional plastics under ordinary conditions, but they are degraded by microorganisms like woods and cotton once they have become disused. GreenPla, which is eventually degraded to carbon dioxide and water in the natural cycle, is the first plastics that take into account the treatment and final disposal after used.
The term "Biodegradability" is defined as the characteristics of material that can be microbiologically degraded to the final products of carbon dioxide and water, which in turn are recycled in the nature. Biodegradation should be distinguished from disintegration which simply means the material is broken into small and separate pieces. Biodegradability of plastics is determined by the ISO methods and evaluated based upon the pre-established criteria. Only biodegradable plastics that meet the rigorous criteria such as contents of heavy metals and safe intermediate reaction products may be classified as GreenPla(R).
GreenPlas of natural organics origin include chitosan/ cellulose/starch
compound, cellulose acetateand denatured starch with thermal plasticity
are typical examples of this type of GreenPla.