How Plastic Is Made
The days of plastic straws and other everyday utensils may be long gone, plastic production is still a rapidly growing segment. This should come as no surprise seeing as most household items contain an element of plastic. Everything from containers to trash bags and even furniture is composed of plastic, making it one of the most versatile materials that we know of. According to the American Chemistry Association, in 2018, plastics generation was 35.7 million tons in the United States. This is an astounding 12.2% of municipal solid waste! You may find yourself wondering how plastic is made and I am here to answer that for you with a simple step-by-step guide. You could also watch this video by Ted about how plastic is made - the history.
How Plastic Is Made: The Origin of Plastic
Originally meaning “pliable and easily shaped”, plastic is now a name for a category of materials called “polymers”. The term polymer means “of many parts” and is made by forming a long chain of molecules.
In 1869, John Wesley Hyatt invented the first synthetic polymer. He was inspired by a New York Firm’s offer of $10,000 for anyone who could find a replacement for ivory. Due to the ever-growing popularity of billiards, a strain had been put on the supply of naturally obtained ivory through the slaughter of wild elephants. Hyatt discovered that through blending cellulose, derived from cotton fiber, with camphor (a waxy, flammable, transparent solid), plastic could be created that could then be crafted into a variety of shapes. This substance could then be used to imitate natural substances such as ivory, tortoiseshell, and linen.
It goes without saying that this discovery was utterly revolutionary. Human manufacturing was no longer held back by nature’s limitations and mother nature could retain her supplies. This creation also helped liberate people from the economic and social constraints that the scarcity of natural resources presented. The plastic revolution had begun.
How Plastic Is Made: Different Types of Plastic
Let’s start with the different types of plastic. While you may not be able to pronounce all of them (I certainly can’t), it may interest you to know what each one is used for:
Polyethylene Terephthalate (PETE or PET): This is by far the most common type of plastic due to its versatility. Examples of items containing this plastic include water bottles, jars, sleeping bags, and protective packaging.
High-Density Polyethylene (HDPE): This type of plastic has a very high strength to density ratio, making it a common material in corrosion-resistant piping, geomembranes, and plastic lumber.
Polyvinyl Chloride (PVC): You have probably heard of this one. PVC is used in a vast array of products such as window frames, drainage pipes, water service pipes, medical devices, and blood storage bags.
Low-Density Polyethylene (LDPE): While its most common use is plastic bags, LDPE is also used in the production of dispensing bottles, various molded laboratory equipment, and plastic parts for computer components.
Polypropylene (PP): PP is renowned for being a very tough, heat-resistant plastic that is capable of retaining its shape even after undergoing a lot of torsion and bending. It is predominantly used in outdoor furniture, luggage, and car parts.
Polystyrene or Styrofoam (PS): Known as a synthetic aromatic hydrocarbon polymer, PS can be more than 95% air. It is widely used to make lightweight protective packaging, home and appliance insulation, and even surfboards.
Miscellaneous plastics (includes: polycarbonate, polylactide, acrylic, acrylonitrile butadiene, styrene, fiberglass, and nylon)
How Plastic Is Made
How Plastic is Made: The pellitizing process.
All the above plastics are either ‘synthetic’ or ‘biobased’. The former is derived from natural gas, coal, or crude oil, while the latter comes from renewable products such as starch, carbohydrates, vegetable fats and oils, and other biological substances.
Due to the ease of manufacturing methods, most plastic we see today is made synthetically. However, due to the growing demand for limited oil-reserves, there is a need for more biobased plastics within the industry.
How Plastic is Made: Step by step
Extraction of Raw Materials: This is mostly crude oil and natural gas, but also some coal. There complex mixture of compounds means they then need to be processed.
The Refining Process: This is simply where the crude oil is turned into different petroleum products which are then converted to produce useful chemicals including “monomers”. This is done by heating the crude oil in a furnace, which is then transported to the distillation unit where the heavy crude oil is separated into lighter components called fractions.
Polymerization: This is essentially the process where light olefin gases (gasoline) are converted into polymers by chemically bonding monomers into chains. There are two different ways of achieving this:
Addition Polymerisation: This describes the connection between one monomer to the next one (and so on), and is attained by introducing a catalyst, typically a peroxide. This particular process is called chain-growth polymers as it only adds one monomer at a time. Examples of these types of polymers are polyethylene and polystyrene.
Condensation Polymerization: By removing small molecules such as water, two or more different monomers may attach themselves. Just like addition polymerization, this also requires a catalyst in order to spark a reaction between adjacent monomers. This process is known as step-growth. Examples of these types of polymers include polyester and nylon.
Compounding / Processing: This describes the process of blending various materials by melting them to make formulations for plastics. Through various molding processes such as pellitization, this is transformed into pellets which are then turned into the finished (or semi-finished) product. Machines known as extruders are then responsible for turning these into the products we see on the shelves.
