Topic 3 Polymers

Topic 3: Polymers

3.1 Overview of Polymers

• Definition of Polymer: A polymer is a long-chained molecule or macromolecule formed by chemical bonding of repeating units called monomers.

• Greek Origin: "Poly" means "many" and "mer" means "unit"; hence, polymers are collections of many units.

3.2 Molecular Structures and Properties of Polymers

• Types of Polymers:

  • Homopolymers: Comprised of one type of monomer.

  • Copolymers: Made from two or more different monomers.

• Polymer Chain Structures:

  • Linear, Branched, Crosslinked, Network.

• Crystallinity:

  • Amorphous: No ordered molecular arrangement, lacks a definite melting point.

  • Crystalline: Ordered arrangement, distinct melting point.

• Molecular Weight: Influences properties like ductility, tensile strength, viscosity, and chemical resistance.

3.3 Additives to Polymers

• Additives modify properties:

  • Fillers: Increase bulk, reduce costs.

  • Plasticizers: Improve ductility and softness.

  • Stabilizers: Prevent degradation.

  • Colorants: Provide color.

  • Lubricants: Reduce friction.

  • Flame Retardants: Decrease flammability.

3.4 Common Polymers and Applications

• Polyethylene (PE): Used in bags and containers.

• Polyvinyl Chloride (PVC): Used for pipes and coatings.

• Polypropylene (PP): Found in containers and chemical tanks.

• Nylon: Used in gears and bristles.

• Polystyrene (PS): Found in toys and radios.

3.5 Processing of Polymers

• Plastic Manufacturing Processes include:

  • Injection Moulding: Melting and injecting thermoplastics into molds.

  • Extrusion: Processing polymer into continuous shapes.

  • Compression Moulding: Molding thermosets under heat and pressure.

  • Transfer Moulding: Good for intricate shapes using thermoset materials.

Key Takeaways

• Polymers are essential materials in technology and manufacturing, with specific properties influenced by their structures and the additives used in their formulation.