How Plastics and Composites Have Changed Our World

By Carl Avery Nov11,2020

Look around your home. How many items can you find that are either made entirely from plastic or have plastic parts? While you’re looking, pay attention to composite materials as well. You may not see as many composites, but you will probably see more today than if you had looked 10 years ago.

Plastics and composites have dramatically changed the world. You might not fully understand just how much if you were born in the 1980s or later. That is because plastics have been a part of mainline manufacturing for last 40 years. Prior to that though, plastics were not nearly as commonplace.

How Do You Like Your Milk?

We buy milk in plastic containers today. But imagine buying it in a paper carton. Even better, imagine milk being sold in glass bottles. Prior to the mid-1970s, glass bottles were the primary receptacle for milk sold at retail. When the milkman came to drop off your daily allotment, he left glass bottles behind.

By the way, the milk box on the front porch was likely made of wood. It may have been encased in thin, aluminum sheeting to protect it against the weather, but the main structure was pine or some other inexpensive wood. The mailbox hanging just above it was aluminum or tin.

We do not use milk boxes today. If we did, they would be made of plastic. Our mailboxes are made of plastic more often than not. And we could go on and on. Cola comes in plastic bottles where it used to be sold in glass. Today’s composite floors were made of natural hardwoods 40 years ago.

Carbon Fiber and Plastic

Today’s plastics are now being replaced with carbon fiber and other composites. In reality however, a carbon fiber product is really a carbon fiber reinforced plastic (CFRP). What is the difference? Reinforcement.

A plastic is essentially a polymer. In almost every case, plastics are synthetic polymers made from petrochemicals. There are as many different kinds of plastic as there are applications. So what about carbon fiber? It is a polymer reinforced by carbon fibers.

Take a carbon fiber bike, for example. The tubes that make up the bike frame begin as threads made from carbon fibers spun together. The threads are twisted together to create larger threads rolled onto spools. The spools are loaded onto a filament winding machine and threads fed through a die. They are then wound around a mandrel and impregnated with an epoxy resin.

The epoxy resin is the key here. As explained by Salt Lake City’s Rock West Composites, the epoxy resin becomes a plastic once it fully cures. As a plastic, it is reinforced by the fibers embedded in it.

Like Rebar on Steroids

If you are still not understanding the concept behind carbon fiber reinforced plastics, think of concrete and rebar. Concrete is a pretty strong material all by itself. But it is porous and brittle. So for applications requiring extra strength, it is reinforced by rebar. Construction workers build a rebar frame and then pour concrete around it.

A CFRP is the same sort of thing, but a lot stronger. The carbon fibers embedded in the cured plastic give the final product exceptional strength and rigidity. CFRPs are so strong they can replace steel.

A lot has changed in the last 50 years. In the arena of manufacturing, plastics and composites have made a world of difference. We take them for granted because they are so commonplace, but there was a time when neither plastics nor composites existed. It was a vastly different world back then.

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