Chemistry - 15 Using Our Resources - 15.3 The Properties of Polymers & 15.4 Glass, Ceramics and Composites

Polymer

large compound formed from combinations of many monomers

The properties of a polymer depend on [2]:

• monomers comprising it

• conditions of manufacture

Types of poly(ethene) [2]

• LDPE

• HDPE

LDPE stands for:

Low-Density Poly(Ethene)

HDPE stands for:

High-Density Poly(Ethene)

Structure of LDPE [3]

• randomly branched

• more spaces within the material

• low density

Structure of HDPE [3]

• regularly branched and interlocked

• less spaces within the material

• high density

Conditions to make LDPE [2]:

• high pressure

• trace of oxygen

Conditions to make HDPE [2]

• slightly raised pressure

• 50°C catalyst

Thermosoftening

plastic that is able to be repeatedly melted and reshaped

Thermosetting

plastic that will not melt and will instead char/burn

What makes a plastic thermosoftening?

molecules held together by intermolecular forces

What makes a plastic thermosetting?

molecules held together by covalent bonds

What is the main chemical component of sand?

silicon dioxide

What is the chemical name of limestone?

calcium carbonate

What is the chemical name of soda?

sodium carbonate

What is the most common form of glass?

soda-lime glass

Soda-lime glass components [3]

- sand

How is soda-lime glass made? [2]

• components are heated to 1500°C

• they melt and react

Molecular structure of glass

randomly arranged particles

like a molten material stuck in place

Chemical name for boron trioxide

B₂O₃

What is the technical name for toughened glass?

borosilicate glass

What is borosilicate glass used for? Why? [3]

• test tubes

• ovenware

• as it melts at higher temperatures than other glass

Borosilicate glass components [2]

- sand

Ceramic

made of clay and hardened by heat in a furnace

What is the molecular structure of clay? [5]

• contains compounds of metals (e.g. Al and K) and compounds of non-metals (e.g. Si and O)

• ionic bonding between ions

• covalent bonding between non-metals

• ions and atoms arranged in giant structures forming layers

• water molecules interrupt layers

Why is unfired clay slimy?

water molecules interrupt the layers

Why does firing clay make it hard? [2]

• water molecules are driven out from between the layers

• strong bonds form between the layers of clay

How are ceramics made? [2]

• clay is made into desired shape

• fired at around 1000°C in a kiln or furnace

Why are ceramics brittle? [2]

• sharp blows distort layers so that ions with like charges are next to one another

• ions repel

Properties of ceramics [4]

• hard

• brittle

• electrical insulators

• resistant to chemicals

What are ceramics used for? [3]

• bricks and tiles

• crockery

• sinks

Composite

products made from multiple materials

What are the components of a composite? [2]

• matrix/binder

• reinforcement

What is the matrix/binder in a composite?

material that the reinforcement is suspended in

What is the reinforcement in a composite?

fibres or fragments of another material

Examples of composites [4]:

• fibreglass

• plywood

• MDF

• concrete

Fibreglass

lightweight material made from glass fibres embedded in a polymer resin matrix

Plywood

thin sheets of wood glued together so the grain runs perpendicular

MDF

medium-density fibreboard

Concrete

hard material made from cement