📖 In-Depth Theory
Ceramics
CERAMICS are non-metallic, inorganic solids made by heating materials at high temperatures.
SODA-LIME GLASS:
Made by heating a mixture of sand (SiO₂), sodium carbonate (Na₂CO₃) and limestone (CaCO₃).
Transparent, rigid, brittle.
Used in: windows, bottles, jars.
BOROSILICATE GLASS:
Made from sand and boron trioxide (B₂O₃).
Higher melting point than soda-lime glass.
More resistant to thermal shock (sudden temperature changes).
Used in: laboratory glassware (Pyrex), ovenproof dishes, telescope mirrors.
CLAY CERAMICS:
Pottery, bricks, tiles — shaped wet clay then heated (fired) in a furnace/kiln.
Hard, brittle, poor conductors of heat and electricity.
Used in: construction (bricks), electrical insulators, sanitary ware.
PROPERTIES OF CERAMICS:
Hard, rigid, brittle.
High melting points — good for high-temperature applications.
Electrical and thermal insulators.
Chemically resistant — unreactive with most substances.
Polymers
POLYMERS have a wide range of properties depending on their structure.
LOW-DENSITY POLY(ETHENE) (LDPE):
Branched chains — cannot pack closely.
Low density, flexible, soft.
Used in: plastic bags, cling film.
HIGH-DENSITY POLY(ETHENE) (HDPE):
Unbranched chains — pack closely together.
Higher density, stiffer, stronger.
Used in: milk bottles, drain pipes.
THERMOSETTING POLYMERS:
Cross-links between chains — form a rigid 3D network.
Do NOT melt when heated — decompose instead.
Very hard and rigid.
Used in: electrical fittings, heat-resistant handles, resin glues.
THERMOPLASTIC POLYMERS:
No cross-links — chains can slide past each other when heated.
Soften and melt when heated — can be reshaped and recycled.
Hard when cool, flexible when warm.
Used in: bottles, bags, most common plastics.
Composites
COMPOSITES contain two or more materials — one embedded in the other.
Properties of the composite are superior to either material alone.
STRUCTURE:
MATRIX: the continuous phase (surrounding material).
REINFORCEMENT: fibres or particles embedded in the matrix.
The reinforcement provides strength; the matrix holds everything together.
EXAMPLES:
CARBON FIBRE REINFORCED PLASTIC (CFRP):
Carbon fibres in a polymer matrix.
Very high strength, very low density — stronger than steel, lighter than aluminium.
Used in: aircraft, racing cars, bicycles, tennis rackets, wind turbines.
GLASS-REINFORCED PLASTIC (GRP, FIBREGLASS):
Glass fibres in a polymer matrix.
Lighter and stronger than glass alone — flexible.
Used in: boats, car bodies, helmets, baths.
CONCRETE:
Aggregates (gravel, sand) in a cement matrix.
Strong under compression, weak under tension.
REINFORCED CONCRETE: steel rods embedded in concrete — strong under both compression AND tension.
BONE:
Collagen fibres (protein) in a calcium phosphate matrix.
Natural composite — flexible and strong.
⚠️ Common Mistake
Borosilicate glass has a HIGHER melting point than soda-lime glass — that's why it's used in laboratory equipment. Thermosetting polymers have CROSS-LINKS — they don't melt. Thermoplastic polymers have NO cross-links — they can be melted and recycled. Composites are SUPERIOR to either component alone in at least one property.