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.