Plastic
[8] Dozens of different types of plastics are produced today, such as polyethylene, which is widely used in product packaging, and polyvinyl chloride (PVC), used in construction and pipes because of its strength and durability.
[13] They can also be classified by their physical properties, including hardness, density, tensile strength, thermal resistance, and glass transition temperature.
Plastics can additionally be classified by their resistance and reactions to various substances and processes, such as exposure to organic solvents, oxidation, and ionizing radiation.
Before heating in the presence of sulfur, natural rubber (polyisoprene) is a sticky, slightly runny material, and after vulcanization, the product is dry and rigid.
Crystalline plastics exhibit a pattern of more regularly spaced atoms, such as high-density polyethylene (HDPE), polybutylene terephthalate (PBT), and polyether ether ketone (PEEK).
In contrast, global production of polyethylene (PE) and polypropylene (PP), the world's leading petrochemical-derived polyolefins, was estimated at over 150 million tonnes in 2015.
[31] Regional differences in the volume of plastics production are driven by user demand, the price of fossil fuel feedstocks, and investments made in the petrochemical industry.
In the European Union (EU), too, heavy investments have been made in the plastics industry, which employs over 1.6-million people with a turnover of more than 360 billion euros per year.
These are added during the compounding stage and include substances such as stabilizers, plasticizers and dyes, which are intended to improve the lifespan, workability or appearance of the final item.
Masterbatch granules can be mixed with cheaper bulk polymer and will release their additives during processing to give a homogeneous final product.
For thermosetting materials the process is slightly different, as the plastics are liquid to begin with and but must be cured to give solid products, but much of the equipment is broadly similar.
[5]The largest application for plastics is as packaging materials, but they are used in a wide range of other sectors, including: construction (pipes, gutters, door and windows), textiles (stretchable fabrics, fleece), consumer goods (toys, tableware, toothbrushes), transportation (headlights, bumpers, body panels, wing mirrors), electronics (phones, computers, televisions) and as machine parts.
Although additives are blended into plastic they remain chemically distinct from it and can gradually leach back out during normal use, when in landfills, or following improper disposal in the environment.
Flame retardants are a group of chemicals used in electronic and electrical equipment, textiles, furniture and construction materials which should not be present in food packaging or child care products.
Some compounds leaching from polystyrene food containers have been proposed to interfere with hormone functions and are suspected human carcinogens (cancer-causing substances).
For example, the World Health Organization's International Agency for Research on Cancer (IARC) has recognized vinyl chloride, the precursor to PVC, as a human carcinogen.
[48] A more recent animal study suggests that even low-level exposure to BPA results in insulin resistance, which can lead to inflammation and heart disease.
[49] As of January 2010, the Los Angeles Times reported that the US Food and Drug Administration (FDA) is spending $30 million to investigate indications of BPA's link to cancer.
[54] The rivers Yangtze, Indus, Yellow, Hai, Nile, Ganges, Pearl, Amur, Niger, and Mekong "transport 88% to 95% of the global [plastics] load into the sea.
[64] They cause pollution by entering natural ecosystems from a variety of sources, including cosmetics, clothing, construction, renovation, food packaging, and industrial processes.
Because plastics degrade slowly (often over hundreds to thousands of years),[74][75] microplastics have a high probability of ingestion, incorporation into, and accumulation in the bodies and tissues of many organisms.
[57] Recent studies have shown, however, that plastics in the ocean decompose faster than had been previously thought, due to exposure to the sun, rain, and other environmental conditions, resulting in the release of toxic chemicals such as bisphenol A.
[102][103][104] Recycling can reduce dependence on landfills, conserve resources and protect the environment from plastic pollution and greenhouse gas emissions.
Alternatively, plastic can be burned in place of fossil fuels in energy recovery facilities, or biochemically converted into other useful chemicals for industry.
[123] According to the Organisation for Economic Co-operation and Development, plastic contributed greenhouse gases in the equivalent of 1.8 billion tons of carbon dioxide (CO2) to the atmosphere in 2019, 3.4% of global emissions.
and that the study involving European researchers found, "15 of the 16 applications a plastic product incurs fewer greenhouse gas emissions than their alternatives.
The output of the process (commonly known as cellulose nitrate or pyroxilin) could be dissolved in alcohol and hardened into a transparent and elastic material that could be molded when heated.
[135] In 1893, French chemist Auguste Trillat discovered the means to insolubilize casein (milk proteins) by immersion in formaldehyde, producing material marketed as galalith.
[6] The discovery of polyethylene terephthalate (PETE) is credited to employees of the Calico Printers' Association in the UK in 1941; it was licensed to DuPont for the US and ICI otherwise, and as one of the few plastics appropriate as a replacement for glass in many circumstances, resulting in widespread use for bottles in Europe.
On March 2, 2022, UN Member States voted at the resumed fifth UN Environment Assembly (UNEA-5.2) to establish an Intergovernmental Negotiating Committee (INC) with the mandate of advancing a legally-binding international agreement on plastics.
