Material Choice and Properties

Material Choice

  • Polymers: Made from monomers; include natural and synthetic types.

  • Polymers Properties:

    • HDPE: Stronger & stiffer with higher crystallinity.

    • LDPE: Weaker & more flexible with lower crystallinity.

Ceramics

  • Common types: Soda-lime glass and borosilicate glass.

  • Clay ceramics formed by shaping wet clay and heating in a furnace.

Composites

  • Composed of two materials: reinforcement fibers and a matrix (binder).

  • Examples:

    • Concrete: cement + sand + crushed rock.

    • Composite wood: wood fibers + adhesives.

Alloys

  • Mixture of metals to enhance properties.

  • Examples: Gold (with other metals), Steel, Bronze, Brass.

Using Impurities to Strengthen Iron

  • Pure iron is soft; adding impurities increases strength.

Making Steel

  • Varying carbon content changes properties: low carbon = ductile, high carbon = hard but brittle.

Monomers and Polymers

  • Ethene as a monomer; used in addition polymerization to form polyethene.

  • General formula: n \text{C}2\text{H}4 leads to polyethene.

Condensation Polymerization

  • Involves two functional groups; water is lost as a byproduct.

  • Example: Formation of polyesters and polyamides.

Natural Polymers

  • DNA: polymer of nucleotides; stores genetic information.

  • Other examples: starch, proteins.

Amino Acids and Proteins

  • Amino acids linked via condensation polymerization to form proteins; example: glycine.

Carbon Compounds

  • Carbon forms various compounds (polymers, diamond, fullerenes).

Different Structures of Elements

  • Giant Ionic Structures: High melting/boiling points due to ionic bonds.

  • Giant Covalent Structures: Examples include diamond and graphite.

  • Metallic Bonding: Delocalized electrons allow for conductivity.

  • Simple Covalent Molecules: Low melting/boiling points due to weak intermolecular forces.

Rusting and Redox Reactions

  • Rust formation: iron + oxygen + water = hydrated iron(III) oxide.

  • Redox: oxidation is the loss of electrons; reduction is the gain.

Preventing Rust

  • Methods: electroplating, sacrificial protection, oil/grease, painting.

Life Cycle Assessments (LCAs)

  • Assess environmental impact across raw material use, energy consumption, and disposal.

Recycling

  • Reduces landfill use, energy consumption, and resource extraction.

  • Factors affecting viability: economic, environmental, and raw material availability.