F5chapter 7

Topic 7 Synthetic Materials In
Industry

7.1 Understanding synthetic polymers

ITeach – Science Form 5

All these things are made of
polymers.

What is polymer?

A polymer is a long chain molecules consisting
of many small molecules ( monomers)

Polymerization

Depolymerization

1.

a) Monomer – small molecules which combine to
form long chain molecules.

b) Polymer – long chain molecules consisting of
small interconnecting molecules

c) Polymerization – combination process of small
molecules to form long chain molecules.

d) Depolymerization – decomposition process of
polymer molecules to its monomers.

Polymerization

Two types of polymers

1. Natural 天然的 polymers
2. Synthetic 人造的 polymers

Natural polymers

 Produces naturally by plants or animals.
 Examples:
1. Starch 淀粉
2. Protein 蛋白质
3. Silk 丝
4. Cellulose 纤维素
5. Fat
6. Natural rubber 橡胶
7. Cotton wool 棉花

Glucose monomers combine to form
starch polymer.

Synthetic 人造的 polymers

Made by human through chemical reactions.
Examples:
1.Nylon 尼龙
2.Polystyrene 保丽龙
3. Neoprene
4. Perspex
5. Polythene
6.Polyvinyl chloride

(PVC)

Natural Polymer Synthetic polymer
1. Protein 1. Nylon
2.Starch
3. cellulose 2. Polystyrene
4. Fat 3. Neoprene
5. rubber 4. Perspex
5. Polythene
6. Cotton wool 6. Polyvinyl chloride

7. silk (PVC)

Natural Polymers and monomers

Polymers Monomers
1. Protein Amino acid
2.Starch
3. cellulose Glucose
Glucose
4. Fat Fatty acid and glycerol
5. Natural rubber Isoprene

Synthetic rubber and monomers

Polymers Monomers

1. Polystyrene styrene

2. Neoprene chloroprene

3. Perspex Methyl methacrylate

4. Polythene ethene

5. Polyvinyl chloride chloroethene
(PVC)

Do you still see these items
today?

 lighter and easy to use

Synthetic polymers

Plastic pail

Plastic iron

Examples of synthetic polymers

Synthetic polymers -made from
chemical substances from petroleum.

Synthetic polymers can be classified into 3 groups:

Examples of items made from synthetic
rubber.

Examples of items made from plastics.

Examples of items made from synthetic fibre.

The process of making synthetic
polymer

A large number of monomers are combined to
form a long chain of molecules.

Polymerization

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Example:

Ethene
Polythene

Other examples of synthetic polymers
and their monomers

Polymer Monomer
Polyvinyl chloride chloroethene

Perspex methyl methacrylate

Neoprene chloroprene

Polypropene propene

Types of synthetic rubber

1. Neoprene

 Non-flammable

 Heat resistant

 Resistance to Bunsen burner tube

water, oil, Electrical wire insulator

sunlight, oxygen

Rubber pipe

gloves

2. Styrene butadiene rubber (SBR)
Easily vulcanised

Car tyre Shoe sole

3. Thiokol
High resistance to oil and solvents

Petrol hose Tank lining for
storing petrol

4. Silicone rubber
Can withstand high temperatures

Keyboard

teat sealants
Lining in cooking utensils

Understanding Synthetic Polymers Topic 7 Synthetic mate

General characteristics of synthetic polymers

Thermal and Light weight Able to be
electrical moulded into
insulator various shapes

Durable General Heat resistant
characteristi
Impact Resistant to
resistant cs of chemicals
(can withstand synthetic
shock) polymers

Safe and
hygience

Comparison between characteristics of
natural rubber and synthetic rubber

Understanding Synthetic Polymers Topic 7 Synthetic mate

Comparison between synthetic rubber and natural
rubber

Synthetic rubber Natural rubber

Similarities • Both are polymers
• Can be vulcanised to become stronger

• Higher heat resistance • Less heat resistance

• Better heat and electrical • Good heat and electrical
insulator insulator

• More resistance to acids, • Less resistance to acids,
alkalis, oil alkalis, oil

• Low ability to absorb sound, • High ability to absorb sound,
vibration, shock, pressure vibration, shock, pressure

• Less elasticity • More elasticity

• Harder • Softer

Topic 7 Synthetic Materials In
Industry

7.2 Analysing Plastics

ITeach – Science Form 5

What are these objects made of ?

PLASTICS

Can you give other uses
of plastic in our daily life?



Plastic

Is plastic a natural polymer/ synthetic polymer?
Synthetic polymer – made up of chemical
substances from ???

petroleum
Produced through polymerization process.

Different monomers
form different
polymers of plastics.

2 main groups of plastics

Thermoplastic 热塑性塑料

 Can be soften/ melted by heat- low resistance
to heat

 Can be remoulded/ recycled – new things
 Can dissolve in organic solvent

Why thermoplastic can be soften/
remoulded easily?

Thermoplastic molecules do not have cross-
links between polymer chains.

When heated, the polymer chains easily slide
over each other- soft/ melt

Examples of thermoplastics

1. Polythene
2. Polystyrene
3. Polyvinyl chloride (PVC)
4. Perspex
5. Polyamide(Nylon)
6. Polypropylene

Types of plastics

Polythene

1. Low density – soft
Uses: plastic bags, raincoats

2. High density – hard
Uses: pails, plastic bottles, food containers,, toys

Polystyrene

- Good heat insulator
Uses:
Ice box
Packaging materials
Food boxes

Protective packaging for electronic
goods

Polyvinylchloride(PVC)

Uses:
Water pipe/ water tap
electrical cables

PVC cards

Perspex

-Transparent plastic

Uses:
Lenses of glasses/ contact lenses
Photo frame
Safety screen
Airplane windows

CD casings

Polyamide (Nylon)

Uses:
Ropes
Bristle of toothbrush
Jacket
Socks
parachute

Polypropylene

Uses:
Food tray
Rope
Chairs
Milk / drink bottle

Thermosetting plastics 热固性塑
料

 Hard
 Heat-resistant ( high melting point)
 Cannot dissolve in any organic solvent
 Cannot be soften by heat
 Cannot be remoulded