Ceramics, composites and polymers

Question 1

What are ceramics and their properties?

Answer 1

• Ceramics are a group of hard, brittle, heat-resistant and corrosion-resistant materials
• They are made by shaping and then firing nonmetallic materials, such as clay, at high temperatures

Question 2

What are the two groups of ceramics?

Answer 2

• Clay ceramics
• Glass

Question 3

Clay ceramics - definition and properties

Answer 3

• Include brick, china and porcelain
• Made by shaping wet clay while its soft and then heating it to a high temperature in a furnace for it to harden
• They have high compressive strength

Question 4

Glass - types and properties

Answer 4

• Soda-lime glass: made by melting a mix of sand, sodium carbonate and limestone, then allowing the molten liquid to cool and solidify
• Borosilicate glass: made by heating sand with boron trioxide, has much higher melting point than soda-lime glass
• Gass is transparent, strong and a good thermal insulator

Question 5

What is a composite?

Answer 5

• A composite material consists of two or more materials with different properties
• They are combined to make a material with more desirable properties

Question 6

What components are in most composite materials?

Answer 6

• The reinforcement: often long solid fibres or fragments
• The matrix: binds the reinforcements together. Usually something that starts soft and hardens

Question 7

What are polymers?

Answer 7

• Large molecules of high relative molecular mass that are made by joining together smaller molecules, known as monomers

Question 8

What are polymers dependent on and their normal properties?

Answer 8

• The properties of a polymer depend on the monomers from which they were made and the conditions of the chemical reaction
• They are normally flexible, easily shaped and good insulators of heat and electricity

Question 9

High vs low density polymers

Answer 9

• Low density polymers: made in moderate temperatures, high pressures and in the presence of a catalyst. They are more flexible but weaker and are used in carrier bags
• High density polymers: made in low temperatures, low pressures and in the presence of a catalyst. They are more rigid but stronger and are used in drainpipes

Question 10

What are therosoftening polymers and how do they work?

Answer 10

• Made from lots of polymer chains which are held together by weak intermollecular forces
• These forces are easily overcome, so the polymers melt easily
• Can be remoulded into different shapes & will harden when cooled

Question 11

What are thermosetting polymers and how do they work?

Answer 11

• Made from lots of polymer chains which are held together by strong covalant bonds
• These require lots of energy to break so do not soften when heated
• These polymers are hard, strong and rigid