Introduction to Polymers

Introduction to Polymers

• Polymers are long molecules formed by joining thousands of small molecules.
• Macromolecules are another name for polymers.
• Polymerization is the chemical process forming polymers.
• Degree of polymerization is the number of monomer units in a polymer.
• Monomers are small molecules that combine to form polymer molecules.

Nomenclature

• Homopolymer: Polymer containing identical monomer units (e.g., PE, PVC, PVA, PMMA).
• Copolymer: Polymer containing different monomer units (e.g., BUNA-S, BUNA-N, Thiokol).
• Alternate copolymer: Monomers arranged in regular, alternating fashion.
• Block copolymer: Blocks of repeating monomer units followed by blocks of another monomer unit.
• Random copolymer: Monomers randomly distributed along the chain.
• Graft copolymer: Branched structures with different monomer segments on the backbone and branches.
• Functionality: Number of bonding sites in a monomer.

Homochain and Heterochain Polymers

• Homochain polymer: Polymer chains with the same atom type (e.g., PE, PVC).
• Heterochain polymer: Polymer chains with different atom types (e.g., Nylon, Polyester, PU).

Classification of Polymers (Based on various factors)

• Structure/Shape: Linear, Branched, Cross-linked, Atactic, Isotactic, Syndiotactic
• Physical State: Amorphous, Crystalline
• Heat Response: Thermoplastic (soften on heating), Thermosetting (harden on heating, irreversible)
• Conductance: Insulators or Conductors
• Origin: Natural (e.g., cellulose), and Synthetic

Advantages of Polymers over other materials

• Low density leads to the reduction in weight & cost of materials.
• Excellent corrosion resistance.
• Good thermal and electrical insulators.
• Flexible and moldable into desired shapes.
• Low processing temperature.
• Variety of colors & properties.
• Good resistance to chemicals compared to other materials.

Uses of Polymers

• Homes (Windows, flooring, etc.), Vehicles (Windshields, parts), Clothing (Fabrics), Furniture, Appliances, etc.

Polymerisation (Addition/Chain growth & Condensation/Step growth)

• Addition Polymerization chain growth where monomers add to form long chains without elimination of smaller molecules.
• Condensation Polymerization or step growth polymerization.
• Condensation polymerization forms polymers by eliminating small molecules (water, HCl) during the combination of monomers.

Free Radical, Cationic, and Anionic Polymerization

• Free Radical Polymerization: Polymer chains grow through the addition of free radicals.
• Cationic Polymerization: Polymer chains grow through the addition of carbocations.
• Anionic Polymerization: Polymer chains grow through the addition of carbanions.

Plastics

• Plastics are organic materials exhibiting plasticity (moldable).
• Merits: Lightweight, abrasion-resistant, shock-absorbent, inexpensive fabrication, etc.
• Demerits: Low heat resistance, poor ductility, embrittlement at low temperatures, non-biodegradable.
• Classification into Thermoplastic (soften on heating) and thermosetting plastics (rigid and irreversable hardening on heat).

Polyvinyl Chloride (PVC)

• Properties: Hard, stiff, chlorine atom, insoluble, etc.
• Applications: Shoes, pipes, drainage, bottles, car parts, etc.

Phenol Formaldehyde Resin (Bakelite)

• Properties: Hard, rigid, strong, good dielectric properties, heat and moisture resistant, etc.
• Applications: Domestic plugs & switches, handles, adhesives, etc.

Polytetrafluoroethylene (PTFE)

• Properties: Excellent toughness, heat resistant, non-adhesive, etc.
• Applications: Wire insulation, non-stick pans, coating., gaskets, etc.

Fiber Reinforced Plastics (FRP)

• Properties: Excellent strength-to-weight ratio, corrosion resistance, ease of fabrication.
• Preparation: Combination of fibers and resin matrix cured under pressure and/or heat.
• Uses: Aircraft parts, boat hulls, etc.

Elastomers

• Elastomers are polymers with long flexible chains with weak intermolecular forces, they can stretch and return.
• Natural Rubber is a polymer made of isoprene, used in tires, etc.
• Vulcanization involves the treatment of vulcanization with sulfur to improve strength and durability.

Conducting Polymers

• Conducting polymers can conduct electricity.
• Intrinsically conducting polymers: Conjugation in the backbone allows conductance.
• Extrinsically conducting polymers: Conductivity from added conducting elements.
• Applications are in electrochromic displays, solar cells, and sensors.

Biodegradable Polymers

• Biodegradable polymers break down through the action of microorganisms.
• Examples include starch, cellulose, chitin.

Polylactic Acid (PLA)

• Properties: Biocompatibility, processability, high strength.
• Applications: Sutures, stents, food packaging, disposable tableware.

Polyvinyl Acetate (PVA)

• Properties: Transparent, amorphous, chemically resistant.
• Applications: Adhesives, coatings, paints.

Explore the fascinating world of polymers in this quiz. You'll learn about the different types of polymers, their formation processes, and essential terminology such as homopolymer and copolymer. Test your knowledge and see how well you understand these vital macromolecules.