1. for example: here is the monomer of polyethylene
Polymer
a substance composed of repeating structural units, or monomers, connected by covalent chemical bonds
for example: here is the monomer of polyethylene

2. Monomers can be chemically joined in one of two ways:
Polymerization
Monomers can be chemically joined in one of two ways:
1.Addition Polymerization (Acrylics, polyethylene, polystyrene)
Addition Polymerization – 3 step process
Initiation
Propagation
Termination
e.g. During polymerization of ethylene “mers”, the double bonds break and bond together, propagation continues monomer bonding and when all monomers are used up Rxn terminates

3. 2. Condensation Polymerization
During the chemical Rxn, a small molecule is eliminated as monomers are joined together
An example is the polymerization reaction involving terephthalic acid and ethylene glycol eliminating a water molecule to form an ester.
The eventual result is a polyester called poly(ethylene terephthalate) or more commonly, PET

4. Many Addition Polymers are Thermoplastics
Majority of today’s polymers are thermoplastic
Easily processed, reprocessed or recycled
Condensation Polymers can be Thermoplastic or Thermosetting
Condensation polymers include nylons and urethanes

5. Thermoplastics vs. Thermosets
Thermoplastic: polymers that can be repeatedly softened or melted by heating
Ex. Polyethylene, acrylic, polyester, PVC
Thermoset: cross-linked polymers that do NOT soften when heated because strands are not free to move
Ex. Bakelite, vulcanized rubber

6. What Is Thermosetting and Thermosoftening Polymers |
Chemistry for All | FuseSchool

7. Thermoset: Polyisoprene chains ( natural rubber) + sulfur

8. Thermoplastics
Remember the analogy to a plate of cooked spaghetti v. cold spaghetti

9. Thermosets:

10. Crosslinking polymers with organic peroxides

11. HDPE High-density polyethylene
Uses after recycled:
plastic pipes, lumber, flower pots, trash cans, or formed back into non food application bottles.
Properties – stiffness, strength, resistance to chemicals & moisture, ease of forming
Applications - Milk, water, detergent bottles, shampoo bottles, yogurt, retail bags

12. LDPE Low-density Polyethylene
Properties – ease of processing, strength, toughness, flexibility, ease of sealing, resistance to acids & bases
Applications - Dry cleaning, frozen food, bread bags, squeezable plastic bottles, household garbage
Uses after recycled:
Plastic trash bags, plastic tubing, grocery sacks, floor tile, furniture