Module 8: Plastics and Recycling

How do you interpret skeletal structures of molecules?

• Each line endpoint or vertex = a carbon atom.

• Hydrogens on carbon are implied (fill to 4 bonds).

• Heteroatoms (O, N, Cl, etc.) are written explicitly.

• Multiple lines = double or triple bonds.

What is a monomer?

A small molecule that can join with others to form a polymer.

What is a polymer?

A long chain made of repeating monomer units.

How is the mass of polymer molecules expressed?

• In grams per mole (g/mol) or

• Daltons (Da), where 1 Da ≈ 1 g/mol per molecule.
  Polymer chains can be thousands to millions of Daltons.

Where do most plastics and synthetic polymers come from?

Crude oil → refined → cracked into smaller molecules → polymerized into plastics

What is addition polymerization?

A reaction where monomers with double bonds open up and link together without losing atoms.

Do addition polymers retain all atoms of their monomers?

Yes—every atom from the monomer appears in the polymer chain.

How do you convert between monomer and repeating unit structures?

• Monomer → remove double bond and connect ends to form repeating unit.

• Repeating unit → add a double bond back to recreate the monomer.

What are the Big Six polymers?

• Polyethylene (HDPE, LDPE)

• Polypropylene (PP)

• Polystyrene (PS)

• Polyvinyl chloride (PVC)

• Polyethylene terephthalate (PET)
  These account for ~75% of plastics in the U.S. and Europe.

What are thermoplastics?

Plastics that can be melted, reshaped, and reused—common in recycling.

What do crystalline regions do in a polymer?

Ordered, tightly packed → provide strength and rigidity.

What do amorphous regions do?

Loosely packed → provide flexibility.

What percentage of plastic waste in the U.S. is actually recycled?

Only about 5%.

What are microplastics?

Plastic particles less than 5 mm in size, often produced by breakdown of larger plastics or manufactured intentionally (microbeads).

Strategies to reduce microplastic exposure?

• Use natural-fiber clothing.

• Reduce single-use plastics.

• Avoid products with microbeads.

• Use filters on washing machines.

• Choose reusable containers instead of disposables.