Plastic water containers. Plastic packaging. Plastic cups, plates, spoon, fork, and utensils. Plastic chairs and tables. Plastic bags. Plastic pots. Plastic bottles, and too many to mention. Plastics are everywhere. Perhaps, when you look around now, you can name at least ten things made of plastics. No wonder, plastics are dramatically a growing segment of municipal waste (MSW). According to the United States Environmental protection Agency (EPA) report, plastics used in containers and packaging had the most plastic tonnage at over 14 million tons in 2017.
The term “plastics” refers to a wide range of materials, including those that are composed of various elements such as carbon, hydrogen, oxygen, nitrogen, chlorine, and sulfur. Typically, plastics have high molecular weight, which means each molecule can have thousands of atoms bound together. Naturally occurring materials that contain high molecular weight are wood, horn, and rosin. Plastics, manufactured or synthetic, are often designed to mimic the properties of natural materials. Plastics, also known as polymers, are produced by converting natural products or by the synthesis from primary chemicals generally coming from organic materials like natural gas, cellulose, salt, or coal, cellulose, and crude oil.
Before crude oil can be utilized, it needs to undergo processing as it is composed of a mixture of thousands of compounds. The production of plastics starts with crude oil’s distillation in an oil refinery. The process separates the heavy crude oil into fractions or groups of lighter components.
Each fraction is made of hydrocarbon chains varying in size (chemical compounds made up of carbon and hydrogen) and molecular structure. Naphtha, one of these fractions, is the crucial compound for the production of plastics.
To produce plastics, there are two main processes involved: Polymerization and polycondensation, which both require specific catalysts.
The monomers in a polymerization reactor, such as ethylene and propylene, are linked together, forming the long polymer’s chains. Each polymer has its particular property, size, and structure-dependent on the type of basic monomer used.
Plastics are categorized differently and can be grouped into two main polymer families: Thermoplastics (which soften on heating and then harden again on cooling) and the Thermosets (which never soften once they have been molded).
You can remelt and reuse thermoplastics while thermoset plastics can be ground up and used as filler; however, the material’s purity tends to degrade with each reuse cycle. There are some methods to break down plastics to a feedstock state.
Although silicones are an exception with silicon atoms, most plastics are based on the carbon atom that can be linked to other atoms with up to four chemical bonds.
Diamonds, graphite, or carbon black soot may be the result when all of the bonds are to other carbon atoms. On the other hand, plastics are produced when carbon atoms are connected to hydrogen, oxygen, nitrogen, chlorine, or sulfur.
When the linking of atoms results in long chains, such as pearls on a string of pearls, the polymer is called a thermoplastic. One notable characteristic of thermoplastics is it can be melted. The thermoplastics all have repeat units called unit cells, the smallest section of the chain that is identical. The vast majority of plastics, about 92%, are thermoplastics.
Who discovered the first plastic?
The first plastic was discovered in 1907 by Leo Hendrik Baekeland, a Belgian-born American living in New York. The plastic was based on a synthetic polymer made from phenol and formaldehyde, with the first viable and cheap synthesis methods invented in 1907.
On his search for an insulating shellac to coat wires in electric motors and generators, Baekeland found that combining phenol (C6H5OH) and formaldehyde (HCOH) formed a sticky mass. Later, he discovered that the material could be mixed with wood flour, asbestos, or slate dust to make secure and fire-resistant “composite” materials.
During synthesis, the new material tended to foam. Baekeland built pressure vessels to force out the bubbles and provide a smooth, uniform product, as he announced in a meeting of the American Chemical Society in 1909.
Baekeland then named it Baekelite, also known as bakelite. It was the first plastic created from synthetic components. It was a thermosetting phenol formaldehyde resin formed from a condensation reaction phenol with formaldehyde. The product was initially used for electrical and mechanical parts, which eventually became widespread for consumer goods and jewelry in the 1920s.
Related Links:
https://plastics.americanchemistry.com/How-Plastics-Are-Made/