Materials: Glass & Ceramics

Glass, Ceramics and Textiles

1.1 Materials and Applications

  • Focus on glass, ceramics, and textiles.

Learning Outcomes

  • Knowledge and understanding of:
    • What glass is and its uses.
    • How plastics have replaced glass in products.
    • How glass is made.
    • A range of ceramics and products made from them.
    • A range of natural and synthetic textiles.
    • How textiles are used in products, fashion, and interiors.

Material Categories

  • Other Materials:
    • Glass: Sand-based materials.
    • Ceramic: Clay-based (Pottery, earthenware).
    • Textiles: Fibres (Cotton, silk, polyester, nylon).

Glass

  • Definition: Material used for glazing windows, manufacturing bottles, etc.
  • AQA Course: Not currently listed but may be relevant in examination and coursework when discussing traditional materials replaced by alternatives.
  • Understanding composition and properties is crucial.

Manufacturing with Glass

Lime-Soda Glass

  • Composition: Mixture of sand, lime, and sodium carbonate.
  • Process: Heated to 1500 degrees C in a furnace.
  • Continuous flow: Molten material is tapped off.
  • Floatation: Floated on a tank of molten tin to form glass plate.
  • Annealing: Reduces stresses built up in the material during the process.
  • Cutting: Cut to size using diamond wheel cutters.
  • Recycled Materials: Made from a mixture of new and recycled materials (cullets) which can be up to 90\%.

Glass Blowing

  • Used for manufacturing hollow objects such as bottles
  • Mouth Blowing: Traditional method for expensive glassware
  • Everyday projects: A 'gob' of glass is formed by pressing/blowing into a mold

Slumping

  • Process: Glass is heated until soft and then molded
  • Application: Car windscreens

Annealing

  • Issue: Glass contracts on cooling, causing internal stresses.
  • Solution: Slow cooling in an oven to avoid stress.

Properties of Glass

  • Brittleness: Breaks if dropped or hit suddenly; shatters if heated or cooled rapidly.
  • Strength: Stronger in compression than tension.
  • Chemical Resistance: Excellent chemical resistance.
  • Optical Properties: Better than clear plastic, making it a premium material.

Toughened Glass

  • Modification: Makes glass harder to break.
  • Process: Reheating followed by rapid air cooling, creating compressive forces.
  • Limitation: Cannot be cut or drilled after toughening.

Coloured Glass

  • Method: Colour introduced during manufacture with Copper, Iron, or Nickel.

Lead Crystal

  • Addition: Lead oxide is added to increase light reflection.
  • Use: In 'cut glass'.

Pyrex

  • Definition: Brand name for heat-resistant glass products made from boro-silicate glass.
  • Properties: Resists very high temperatures.
  • Applications: Cookware and lab equipment.

Laminated Glass

  • Structure: Composite material with two thin sheets of plate glass.
  • Layer: Tough polymer layer sandwiched between the glass sheets.
  • Safety: Polymer layer holds shards together if broken.
  • Applications: Security purposes.

K Glass

  • Manufacturer: Pilkingtons (UK).
  • Function: Thermal insulator.
  • Benefit: Allows sunlight while reducing heat loss.

Self Cleaning Glass

  • Application: Useful for hard-to-clean windows (e.g., tall buildings).
  • Coating: Hydrophobic coating prevents droplet formation.
  • Mechanism: Interacts with UV light to break down organic dirt into washable compounds.
  • Similar coatings: Used on modern smartphone screens (hydrophobic and oleophobic).

Glass vs Polymer

  • Common Exam Question: Why plastic has replaced glass in applications.
  • Comparison requires knowledge of properties of each material.

Advantages of Using Polymers

  • Lightweight: Easier for transportation.
  • Lower Melting Point: Easier for recycling.
  • Impervious to Gas: Better for carbonated drinks.
  • Impact Resistance: Can be squashed without breaking, enhancing safety.
  • Convenience: Screw tops can be used.

Advantages of Using Glass

  • Rigidity and Durability: More rigid and durable than thermosetting plastics.
  • Scratch Resistance: More resistant to scratches.
  • Optical Properties: Better transparency.
  • Heat Resistance: Not deformed by heat; suitable for heat-resistant applications.
  • Perception: Gives a sense of quality due to weight and visual properties.

Disadvantages of Glass

  • Weight: More expensive to transport.
  • Safety: Less safe when damaged.
  • Recycling: Requires a lot of energy to melt down, despite being recyclable. Although, it is proven that it requires less energy to recycle glass than to create new glass from the base components.