What's Oxo-degradable plastics
Oxo-degradable plastics are actually conventional plastics, such as PE, PP, PS, and PET, in which additives that can cause the plastic to degrade by a process initiated by oxygen and accelerated by light and/or heat have been added.
The additives are typically metal salts of carboxylic acids or Dithiocarbamates based on cobalt (Co), iron (Fe), manganese (Mn) or nickel (Ni). The oxidation process, usually under UV light and/or being heated for a long time period, causes cleavage of polymer chains, which leads to the oxo-degradable plastic losing strength and subsequently fragmentation.
In their useful life, oxo-degradable plastics are as stable and durable as regular plastics. Once when they are exposed to UV lights and/or prolonged heating, oxo-degradation starts. As the oxo-degradation continues, the fragments become smaller and smaller, and finally disappear from our naked sight.
In theory, if the molecular weight of the cleaved polymer chains are small enough then assimilation by microorganisms can occur, which leads to true biodegradation, leaving carbon dioxide, water, biomass behind. However, the truth is that, in most cases if not all, the fragmentation results in millions of small particles, in other words, micro-plastics or micro-fibres, which cannot further biodegrade by microorganisms due to its intrinsic nature of non-biodegradability.
This is more harmful to our environment than the un-degraded form since micro-plastics are found everywhere, even in our drinking water and food chains. As a consequence, many countries have started or is considering banning the use of oxo-degradable plastics.
In conclusion, oxo-degradable plastics are made by non-biodegradable polymers with an additive containing transition-metals. When treated properly, they can degrade at a fast rate, fragment into tiny particles. These tiny plastic particles are unnecessary able to further biodegrade, which will cause another unwanted micro-plastic pollution.
