What comes to mind when you think of the uses of plastic? Many people think of bags and packaging, plastic cutlery, containers, or other kitchenware, and toys. Not many of us think of sweaters, food, or wood furniture. Unbeknownst to many, all of these things are made from polymers; some are called plastics and some are not and the distinction can be arbitrary.
Plastics consist primarily of polymer molecules made of carbon. Similar to a bicycle chain, the links of the polymer are attached together. Polymers are a broad category that include plastics and silicones. Silicones are based on silicon rather than carbon. Polymers also include DNA.
The shape of polymers gives plastics their elasticity which allows them to be molded into shape. We have used naturally derived plastics for many years. In Mexico, the Olmecs played with balls made of rubber which is a natural polymer. They did this a millennium and a half before Christ. Uses of plastic go back even before the use by the Olmecs though. Wood contains cellulose which is a polymer that give plants tough cell walls. The cellulose gives wood its stiffness and durability. The long strands of cellulose are separated at pulping mills and that is what gives paper its strength.
Cellulose also provided the raw material for another breakthrough in plastic. Parkesine is a material that has been used in many products including cutlery, buttons, and combs. Two Americans took Parkesine and added camphor to it which made it more malleable and they renamed it celluloid. This became a raw material used in the film industry.
In the 18th Century, French explorer Charles-Marie de la Condamine discovered that there was a rubber tree in the Amazon basin. It was not until the 1840s that American Charles Goodyear and British born Thomas Hancock took out patents for vulcanized rubber – rubber which was treated with Sulphur to make it more durable.
Rubber also made electrification possible as it was used to insulate electrical switches. The big breakthrough which is considered the birth of modern plastics came in 1907 when Leo Baekeland invented Bakelite. Bakelite is one of the first plastics that is made from synthetic components; it was made from fossil fuels.
More synthetic plastics followed with polystyrene in 1929, polyester in 1930, polyvinylchloride and polythene in 1933, and nylon in 1935. The plastic industry grew during the war effort when they were used in everything including military vehicles and radar insulation.
Companies were building plants where they could turn crude oil into plastics. In 1948 new products such as Tupperware were becoming available.
Polyethylene terephthalate (PET) was a versatile product that was invented in 1941. It can be used to make many different things such as drink bottles, winter gloves, and plastic for packaging flowers. The only difference is the way the material is cast.
Properties and uses of plastics can be changed by altering their structure just a little bit. The plastic that a milk bottle is made of can be changed from polyethylene to polypropylene (a stronger material) simply by adding one carbon to it. The material made by adding a carbon can strengthen the plastic enough to make things like sippy cups for toddlers.
Some polymers are compostable and over months or years they will be broken down by microbes. Some plastics however do no break down and cause an environmental concern.
It may become more difficult to get plastics. Most currently come from oil and gas but these sources could run out and we will have to go back to using biological sources. Some plastics that have been derived from crude oil are now being produced from sugar cane.
Oil may become too expensive to use. At that point things may turn to industrial bio-technology for the manufacture of plastics.
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