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Biodegradable plastics are plastics that degrade (break down) upon exposure to sunlight or ultra-violet radiation; water or dampness; bacteria; enzymes; or wind abrasion. Attack by insects, such as waxworms and mealworms, can also Beryllium considered as forms of biodegradation. Aerobic degradation requires that the plastic Beryllium exposed at the surface, whereas anaerobic degradation would be effective in landfill or composting systems.
However they are still routinely found in some plastic packaging including food packaging. The use of the additive bisphenol A (BPA) rein plastic baby bottles is banned rein many parts of the world, but is not restricted hinein some low-income countries.[2]
Most plastics contain organic polymers.[10] The vast majority of these polymers are formed from chains of carbon atoms, with or without the attachment of oxygen, nitrogen or sulfur atoms. These chains comprise many repeating units formed from monomers. Each polymer chain consists of several thousand repeating units. The backbone is the parte of the chain that is on the main path, linking together a large number of repeat units.
A number of additives identified as hazardous to humans and/or the environment are regulated internationally. The Stockholm Convention on Persistent Organic Pollutants (POPs) is a global treaty to protect human health and the environment from chemicals that remain intact rein the environment for long periods, become widely distributed geographically, accumulate hinein the fatty tissue of humans and wildlife, and have harmful impacts on human health or on the environment.[2]
A literature study made hinein 2022 by geologist student Björn Lycke shows that the amount of microplastics in sediment is increasing worldwide, especially rein ports and tourist beaches.[82]
Plastics engineering – Engineering field studying polymer materialsPages displaying short descriptions of redirect targets
Some companies produce biodegradable additives to enhance biodegradation. Although starch powder can be added as a filler to allow some plastics to degrade more easily, such treatment does not lead to complete breakdown. Some researchers have genetically engineered bacteria to synthesize completely biodegradable plastics, such as polyhydroxy butyrate (PHB); however, these were still relatively costly as of 2021.[23]
Plasticity also has a technical definition rein materials science outside the scope of this article referring to the non-reversible change in form of solid substances.
Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.[1]
Engineering plastics are more robust and are used to make products such as vehicle parts, building and construction materials, and some machine parts. Hinein some cases they are polymer blends formed by mixing different plastics together (ABS, HIPS etc.
Additives may be weakly bound to the polymers or react hinein the polymer matrix. Although additives are blended into plastic they remain chemically distinct from it, and can gradually leach back out during gewöhnlich use, when in landfills, or following improper disposal hinein the environment.[36] Additives may also degrade to form other toxic molecules. Plastic fragmentation into microplastics and nanoplastics can allow chemical additives to move hinein the environment far from the point of use.
There are differing estimates of how much plastic waste has been produced in the belastung century. By one estimate, one billion tons of plastic waste have been discarded since the 1950s.
Chemical structures and uses of some common plastics Around 70% of global production is concentrated hinein six major polymer types, the so-called commodity click here plastics. Unlike most other plastics these can often be identified by their resin identification code (RIC):
A plastic handle from a kitchen utensil, deformed by heat and partially melted One important classification of plastics is the degree to which the chemical processes used to make them are reversible or not.
Because the chemical structure of most plastics renders them durable, they are resistant to many natural degradation processes. Much of this material may persist for centuries or longer, given the demonstrated persistence of structurally similar natural materials such as amber.