Your phone case, the pen you’ve clicked three times in your hand, even the wrapper from that snack you swore you weren’t going to cave to. It is everywhere, but rarely does anyone stop to ask how it actually gets made. It is a surprisingly detailed process, and it shapes everything from water bottles to specialty seals used in heavy machinery and thermoplastic mechanical components.
Raw Materials
Most plastics begin with oil or natural gas pulled from deep underground. These fuels aren’t just burned for energy. They are broken down and refined into lighter parts that serve as the starting point for plastic. Petroleum-based plastics still dominate the market, but some companies are pushing plant-based plastics for a greener approach.
Building a Foundation
This stage of plastic production is similar to that unit in science class you took about how atoms bond together to form molecules. This differs in that it happens on an industrial scale with large equipment running around the clock. After oil or natural gas goes through refining, it is broken down into smaller, simpler molecules called monomers.
Two key players in this process are the monomers ethylene and propylene. They act as the raw building blocks for a large range of plastics. Independently, they may seem unimpressive. They lack the strength or shape you’d expect from something like a plastic bottle or car bumper. However, once these monomers undergo further processing, they can link together in repeating chains. The chains become polymers, and that’s when the material begins to take the strength and versatility recognized in plastic products.
Polymerization
This is the stage where joining takes place, the heart of plastic production. Different polymers are used to make different products:
- Polyethylene is what grocery bags and film wrap are composed of.
- Polypropylene can be found in food containers, medical devices, and engineered thermoplastic mechanical components.
- Polystyrene, though a less popular option available, is used in manufacturing, packaging, and insulation.
Manufacturers perform controlled chemical reactions to lock these chains together. The end result is exceptionally different than the gas or oil that it began as.
The Extras
This is the part of the operation where characterizations become more distinct through additives. Additives take the form of raw plastic pellets called resins. These raw pellets do not perform well on their own. To get the final product, manufacturers combine them with additives:
- Colorants: Change appearance.
- Plasticizers: Make rigid plastics flexible.
- Stabilizers: Help resist heat or UV light.
That’s the reason your water bottle feels different from your phone case. Each batch is curated to yield a specific, predetermined result. For example, specialty seals demand plastics that won’t wear down under heat or pressure, just like your pop bottle needs to hold carbonation without leaking.
Shaping the Plastic
Once pellets and additives have been determined and are ready, they are heated and molded into their desired shape. This can be accomplished in a handful of different ways:
- Extrusion: typically used to make pipes or straws, the melted plastic is pushed through a mold.
- Injection molding: plastic is heated in the hopper of the press, then injected into a mold, and then cooled. This method is generally used for making toys, bottle caps, or automobile parts like coolant fans.
- Blow molding: utilizes air pressure to form hollow shapes like your water bottle.
Coming Together
Plastic passes through stages, from cornfields to resin, until it lands in your hands. Beginning as raw fuels, then monomers, then polymers, additives, and shaping. This chain is the process by which plastic is created.
If you take a minute to look around the room right now, you are sure to find more plastic than you realized. Plastic is an important part of daily life, and the process from which it is made is interesting.
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Reference:
Plastics Europe. (n.d.). How Plastics Are Made.
