Polymers - Classification

  • Based on Mechanical Behaviour

Polymers Classification based on Mechanical Behaviour

  • Elastomers
  • Fibers
  • Plastics

Elastomers

  • Exhibit high elasticity
  • Return to their original shape after deformation
  • Examples: Natural rubber, Synthetic rubber (Neoprene)

Fibers

  • Have high tensile strength
  • Used in making textiles
  • Examples: Nylon, Polyester, Silk

Plastics

  • Possess low strength in comparison to fibers and elastomers
  • Can be molded into various shapes
  • Examples: Polyethylene, Polypropylene, PVC

Polymers - Classification

  • Based on Structure

Polymers Classification based on Structure

  • Linear Polymers
  • Branched Polymers
  • Cross-linked Polymers
  • Network Polymers

Linear Polymers

  • Consist of long linear chains
  • Examples: Polyethylene, Polypropylene

Branched Polymers

  • Have additional branches off the main chain
  • Examples: Low-density Polyethylene (LDPE), Polyvinyl Chloride (PVC)

Cross-linked Polymers

  • Chains connected through covalent bonds
  • Cannot be melted or dissolved
  • Examples: Vulcanized rubber, Epoxy resin

Polymers - Classification

  • (e) Based on Mechanical Behaviour

Polymers Classification based on Mechanical Behaviour

  • Elastomers
  • Fibers
  • Plastics

Elastomers

  • Exhibit high elasticity
  • Return to their original shape after deformation
  • Examples: Natural rubber, Synthetic rubber (Neoprene)

Fibers

  • Have high tensile strength
  • Used in making textiles
  • Examples: Nylon, Polyester, Silk

Plastics

  • Possess low strength in comparison to fibers and elastomers
  • Can be molded into various shapes
  • Examples: Polyethylene, Polypropylene, PVC

Polymers - Classification

  • (f) Based on Structure

Polymers Classification based on Structure

  • Linear Polymers
  • Branched Polymers
  • Cross-linked Polymers
  • Network Polymers

Linear Polymers

  • Consist of long linear chains
  • Examples: Polyethylene, Polypropylene

Branched Polymers

  • Have additional branches off the main chain
  • Examples: Low-density Polyethylene (LDPE), Polyvinyl Chloride (PVC)

Cross-linked Polymers

  • Chains connected through covalent bonds
  • Cannot be melted or dissolved
  • Examples: Vulcanized rubber, Epoxy resin

Crystalline and Amorphous Polymers

  • Crystalline Polymers
    • Ordered arrangement of polymer chains
    • Have a melting point and sharp melting range
    • Example: Polyethylene
  • Amorphous Polymers
    • Random arrangement of polymer chains
    • Do not have a well-defined melting point
    • Example: Polystyrene

Addition Polymerization

  • Monomers contain a double bond
  • Double bond breaks, and new bonds form between monomers
  • No small by-products are formed
  • Examples: Polyethylene, Polypropylene

Condensation Polymerization

  • Monomers contain functional groups
  • Bond formation occurs with the elimination of small molecules such as water or alcohol
  • Examples: Nylon, Polyester

Polymer Properties - Molecular Weight

  • Determined by the degree of polymerization
  • Higher molecular weight corresponds to longer polymer chains
  • Affects properties such as melting point, strength, and flexibility

Tacticity

  • Arrangement of side groups on a polymer chain
  • Isotactic: Side groups are on the same side of the chain
  • Syndiotactic: Side groups alternate on the chain
  • Atactic: Side groups are randomly arranged on the chain

Copolymers

  • Composed of two or more different monomers
  • Can be prepared by copolymerization of monomers
  • Examples: Styrene-butadiene rubber (SBR), Ethylene-vinyl acetate (EVA)

Biodegradable Polymers

  • Break down naturally by the action of microorganisms
  • Reduce environmental pollution
  • Examples: Polylactic acid (PLA), Polyhydroxyalkanoates (PHA)

Polymer Additives

  • Added to modify the properties of polymers
  • Examples:
    • Plasticizers: Improve flexibility
    • Stabilizers: Prevent degradation by heat or light
    • Flame retardants: Reduce flammability

Recycling of Polymers

  • Reduce waste and environmental impact
  • Techniques: Mechanical recycling, Chemical recycling, Energy recovery
  • Examples: PET bottles recycled into polyester fibers, HDPE containers recycled into new plastic products

Applications of Polymers

  • Packaging materials: Films, Bottles, Containers
  • Construction materials: Pipes, Insulation, Flooring
  • Automotive: Tires, Belts, Seals
  • Healthcare: Prosthetics, Drug delivery systems
  • Textiles: Clothing, Fabrics