Natural environment, depolymerization

Applications in the Natural Environment. Considerable attention has been focused on degradable plastics especially in the natural environment. Depolymerization has a number of practical applications, including degradable plastics. In particular, the applications of biodegradable plastics have been extensively reviewed as the desirable polymer waste management (68-70). The depolymerization in the environment occurs by two distinct mechanisms... 

The external effects of the environment on polymer blends are chemical in nature, and normally lead to degradation of the polymers. Chain scission, depolymerization and reactions on the side-chain substituents all contribute to overall deterioration of blend properties. These are described for blends containing polyvinyl chloride, polystyrene, acrylics and polyolefins mixed with a variety of other polymers. The general feamres of radiation damage and the detrimental effects of processing are reviewed. 

The alkalinity of soluble silicates is their primary hazard. Contact exposure effects can range from irritation to corrosion. Inhaled or ingested sodium silicates are rapidly eliminated in the urine. Trace quantities of dissolved silica are essential to nutrition, but if normal dietary amounts are exceeded, siliceous urinary calculi may result. Dissolved silica is a minor but ubiquitous constituent of the environment. When dissolved silica becomes depleted in natural waters, diatoms are displaced by species that accelerate eutrophication. Commercial soluble silicates rapidly depolymerize upon dilution to molecular species indistinguishable from natural dissolved silica. 

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