Benefits and Disadvantages of Plastics

• Plastics have various advantages and disadvantages that impact society, environment, and economy.

Overview of Polymers in Society

• Topic covered:

  • VCE Chemistry Unit 1 Area of Study 2

  • How are materials quantified and classified?

• Presented by Louise Lennard

Study Design Outline

• Key points of study:

  1. Formation of addition polymers

  2. Properties of addition polymers

  3. Thermoplastic versus thermosetting polymers

  4. Types of polymerisation reactions

  • Differences between addition and condensation reactions in producing natural and manufactured polymers from monomers.

Representing Polymers

• Scientific Writing Conventions:

  • The repeating unit is defined as a monomer.

  • Monomers are depicted with open brackets to indicate their repeating nature in the polymer.

  • An ‘n’ represents the number of monomers linked in the polymer chain.

Terminology:

• Monomer (n.): Molecule that reacts with other molecules to form larger molecules (polymers).

• Polymer (n.): Molecule produced naturally or synthetically from monomers bonded together.

• n: Represents the number of monomers linked in the polymer, indicating molecule length continues.

Addition Polymerisation

• The core building blocks of addition polymers are introduced.

  • Monomers:

  • Must contain a carbon-carbon (C=C) double bond or a carbon-carbon (C≡C) triple bond.

  • Example:

    • Monomers: Alkenes or alkynes.

    • Undergo an addition polymerisation reaction.

    • Result: One product formed, named from monomer (e.g., if the monomer is ethene, the polymer is called ‘polyethene’).

Definitions:

• Alkene (n.): Hydrocarbon with at least one double carbon-to-carbon bond.

• Alkyne (n.): Hydrocarbon with at least one triple carbon-to-carbon bond.

• Addition Polymerisation (n.): The chemical reaction between monomers that results in a polymer.

Condensation Polymerisation

• Explanation of condensation polymers:

  • Building blocks called monomers contain functional groups that can cause condensation.

  • Monomers:

  • Generally consist of two functional groups, such as hydroxyl/amine and carboxyl groups.

  • Result: Two products formed - the condensation polymer and a small molecule (typically water).

Deep Dive on Functional Groups:

• Functional Group (n.): Specific group of atoms defining the properties of a compound.

• Condensation Polymerisation (n.): Chemical reaction leading to a polymer formation plus water.

  • R A H + R B OH → R A B R + H2O

Natural Condensation Polymerisation

• Natural polymerisation occurs in organisms, such as:

  • Example: Formation of proteins and carbohydrates.

Key Takeaway on Natural Condensation:

• Polymer (n.): Molecule produced naturally or synthetically from bonded monomers.

• Example:

  • Amino acids can condense to form proteins (Amino acid monomer → Polymer + H2O = Protein).

Artificial Condensation Polymerisation

• Overview of synthetically produced plastics:

  • Not all polymers are classified as plastics; polymers can be both natural or synthetic.

  • Plastic (n.): Molecule produced synthetically from bonded monomers.

Example of Artificial Condensation:

• Production of polyesters used in fabrics:

  • HO - OH + C - C OH + n → a dicarboxylic acid + a polyester + a dialcohol

Multiple Choice Activity

• Identify the type of polymerisation reaction and name a functional group in one of the monomers.

• Example Reaction:

  • O OH + OH → HO C C HO

Properties of Addition Polymers

• Non-polar monomers produce non-polar polymers:

  • Intermolecular forces: Dispersion forces are the strongest between chains.

  • Properties: Relatively flexible.

Deep Dive Examples:

• Ethene → Polyethene:

  • Weak dispersion force between chains.

• Chloroethene → Polychloroethene (PVC):

  • Strong dipole-dipole forces between polychloroethene chains.

Properties of Polar Polymers

• Polar monomers lead to polar polymers:

  • Stronger intermolecular forces such as dipole-dipole attractions or hydrogen bonds.

  • More rigid compared to non-polar polymers.

Deep Dive on Polar Example:

• Kevlar Chains:

  • Hydrogen bonding within polymer chains.

Types of Polyethene

• Low Density Polyethene (LDPE):

  • Formed under high temperature and pressure; branched structures result in lower density.

  • Properties:

  • Lower density than HDPE

  • Soft, opaque, but transparent in thin forms

  • Insulator of electricity

• High Density Polyethene (HDPE):

  • Produced under low temperature and pressure with less branching.

  • Properties:

  • Higher density than LDPE

  • Hard and allows light to pass through

  • Insulator of electricity

Summary of Polyethene Properties:

• LDPE:

  • Density: ext{density} = rac{ ext{mass}}{ ext{volume}}

• HDPE:

  • Tightly packed polymer structure with minimal branching.

Thermoplastic vs. Thermosetting Polymers

• Thermoplastics:

  • Linear polymers that soften when heated, allowing for reshaping.

  • Weak intermolecular forces.

Thermosets:

• Cross-linked polymers that do not melt on heating due to strong covalent cross-links.

• Example: Bowling ball.

• Elastomers:

  • Contain some cross-links allowing elasticity without complete rigidity.

Multiple Choice Activity on Elastomers

• Identify incorrect statements on elastomers from given options.

Final Summary

• Addition polymers derive from alkene or alkyne monomers with one product forming.

• Condensation polymers from monomers with functional groups, producing two products.

Key Terms

• Monomer

• Alkene

• Alkyne

• Addition Polymerisation

• Condensation Polymerisation

• Functional Group

• Polymer

• Plastic

• LDPE

• HDPE

• Linear (Thermoplastic) Polymer

• Cross-linked (Thermosetting) Polymer

• Cross-link

• Elastomer

• Density

Note: To fully understand types of materials and polymer properties, the study content indicates practical examples and connection to real life applications.