Lecture Notes on Polymers

Introduction to Polymers

• Definition: Polymers are macromolecules made of many repeating units called monomers.
• Properties Determinants:
  • Types of monomer units
  • Linkages between monomers
  • Inter- and intramolecular forces

Classes of Polymers

• Thermosoftening Polymers
• Thermosetting Polymers

Thermosoftening Polymers

• Characteristics:
  • Soften when heated
  • Can be molded when soft into various shapes
  • Not linked together, only interact via weak intermolecular forces
  • Low melting points
• Examples:
  • Polyethylene
  • Polypropylene
  • Polyvinyl chloride
  • Polystyrene
  • Polytetrafluoroethylene
• Applications:
  • Used in everyday items such as window and door frames, pipes, wiring insulation, and waterproof clothing

Thermosetting Polymers

• Characteristics:
  • Do not soften when heated
  • Cross-linked structure provides rigidity
• Example:
  • Vulcanized rubber (polymer of isoprene)
    • Sulfur added to create disulfide bridges during vulcanization, increasing strength
  • Substance used for old TV sets
  • Certain types of strong glue

Conclusion

• Comparison:
  • Thermosoftening plastics: soft and meltable upon heating
  • Thermosetting plastics: hard and retain shape when heated

Key Takeaway

• Understanding the structure and behavior of polymers under heat is crucial for their application in real-life products.