Strength - Max. service temperature

General Information

• Strength measures the resistance of a material to failure, given by the applied stress (or load per unit area)
• The chart shows yield strength in tension for all materials, except for ceramics for which compressive strength is shown (their tensile strength being much lower)
• Maximum service temperature indicates the maximum temperature at which a material can be used in engineering – above this its strength rapidly decreases
• This chart is useful for identifying materials for components which operate at temperatures above room temperature, e.g. cooking utensils, car engines and exhausts
• Polymers are limited to low temperatures, metals to intermediate temperatures, and only ceramics can withstand very high temperatures.

Physical Insights

• Thermoplastic polymers operate at lower temperatures than thermosets because only weak Van der Waals forces hold the chains together
• Ceramics can operate at high temperature because covalent bonds are very stable
• Polystyrene has a maximum use temperature below 100^oC - which explains why polystyrene coffee cups go out of shape

Example Uses

• Teflon as a non stick surface for frying pans
• Ceramic for fire bricks and for coatings for jet engine blades
• Tungsten for light bulb filaments

Simple Questions

• Why is lead-tin used for solder?
• Select materials for a saucepan.
• Select materials for a mould for casting aluminium parts (melting temp 660^oC)
• Select materials for a mould for casting steel parts (melting temp 1540^oC)

Further Questions

• Why can polymers operate only at low temperatures when their polymer chains contain covalent bonds like ceramics?
• What is the operating temperature of a light bulb filament?

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