How its Made

How plastic is made

As we’ve learned, Plasitc Polymers are made up from chains of monomers.

Most monomers are hydrocarbons

• molecules built from hydrogen and carbon atoms

They are extracted from things like petroleum, natural gas, or coal.

Steps to creation

To make plastics, chemists and chemical engineers must do the following on an industrial scale:

1. Prepare raw materials and monomers
2. Carry out polymerizations reactions
3. Process the polymers into final polymer resins
4. Produce finished products

1. Prepare raw materials and monomers

First, they must start with various raw materials that make up the monomers.

Ethylene and propylene come from crude oil which contains the hydrocarbons that make up the monomers.

The hydrocarbon raw materials are obtained from the "cracking process" used in refining oil and natural gas.

See How Oil Refining Works here:

• https://science.howstuffworks.com/environmental/energy/oil-refining.htm

Read an excerpt below from: https://www.explainthatstuff.com/plastics.

• Crude oil drilled from the land or sea is a thick gloopy mixture that contains thousands of different hydrocarbons, which have to be separated out before we can use them. That happens in an oil refinery, through a process called fractional distillation. It's a more involved version of the distillation you might have used to purify water. If we heat water, it eventually turns into steam, which we can then collect, cool, and condense back to water; that's distillation, and it produces highly purified or "distilled" water. We can heat and distill crude oil the same way, but all those many hydrocarbons it contains have molecules that are different sizes and weights, so they boil off and condense at different temperatures. Collecting and distilling the different parts of crude oil at different temperatures gives us a bunch of simpler mixtures of hydrocarbons, called fractions, which we can then use for making different types of plastics.

Once various hydrocarbons are obtained from cracking, they are chemically processed to make hydrocarbon monomers and other carbon monomers used in plastics.

like styrene, vinyl chloride, and acrylonitrile

More on types of plastic in the next section: (Kinds of plastics link)

Hydrocarbon monomers made in this way are the raw materials for polymerization, the next step in the process of chemical reactions to make plastic polymers.

2. Carry out polymerizations reactions

The hydrocarbon monomers carry out polymerization reactions in large polymerization plants.

• The monomers combine to create the polymers used for the plastic.

  • "Some polymers are made simply by fastening hydrocarbon monomers together, like daisy chains, which is a process called addition polymerization.
  • Others are made by joining together two small hydrocarbon chains and removing a water molecule (two hydrogen atoms and one oxygen), making a bigger hydrocarbon chain in a process known as condensation polymerization.
  • The more often you repeat this, the longer the polymer gets."

• Chemists combine various types of monomers in different arrangements.

  • other ingredients are introduced to the basic hydrocarbons to produce a polymer with exact chemical and physical properties.

• This allows an almost infinite variety of plastics with different chemical properties

• Each is a polymer.

3. Process the polymers into final polymer resins

Processing can include the addition of

• Dyes

  • Turn the plastics into any color.

• Plasticizers

  • Make plastics more flexible, viscous, and easier to shape

• Stabilizers

  • Prevent plastics from breaking apart in sunlight and heat
  • Things like flame-retardant chemicals

• Fillers

  • low-cost minerals to replace the expensive, oil-based hydrocarbons. This makes final plastic product less expensive.

The final polymer resins are now in the form of pellets, powders, or grains.

4. Produce finished products

Finally, the polymer resins are processed into final plastic products.

Polymer resin is loaded into a machine, heated, and then shaped by one or more processes to make our finished plastic product.

How every day objects are made

Almost everything around you is made from plastic or contains traces of it.

Below are some of the ways plastic resin pellets are changed into our every day products:

Extrusion

• Pellets are heated and mechanically mixed in a long chamber, forced through a small opening and cooled with air or water.

Calendaring

• Squashing melted plastic between heavy roller
  • This process is used to make plastic sheets or films

Injection molding

• The resin pellets are heated and mechanically mixed in a chamber and then forced under high pressure into a cooled mold.
  • This process is used for containers like butter and yogurt tubs.

Blow molding

• This technique is used in conjunction with extrusion or injection molding.
• The resin goes into the chilled mold, and compressed air gets blown into the resin tube.
• The air expands the resin against the walls of the mold.
  • This process is used to make plastic bottles.

Rotational molding:

• The resin pellets are heated and cooled in a mold that can be rotated in three dimensions.
• The rotation evenly distributes the plastic along the walls of the mold.
• This technique is used to make large, hollow plastic items
  • Toys, furniture, sporting equipment, septic tanks, garbage cans, kayaks

Spinneret molding

• The resin pellets are forced through a kind of microscopically small sieve, called a spinneret, to make thin fibers.
  • This process is used to make things like toothbrushes or nylon stockings.

Learn more about these process here:

• https://science.howstuffworks.com/plastic.htm
• https://www.explainthatstuff.com/plastics.html