1. A level Product Design Unit 2
Polymers
A level Product Design
Unit 2

3. Material
Properties
Uses

4. Whats the difference between a plastic & a polymer ?
Plasticity is a material property & not a material
“the ability to be shaped or formed”
Plastic Materials
Bone
Horn
Clay
Concrete
A polymer is a certain type of material
There are natural & synthethic polymers
We are only interested in synthetic polymers
Whats the difference between a plastic & a polymer ?

5. an individual chemical molecule is called a monomer
When many monomers are linked together to form a chain, a polymer molecule is formed
A plastic consists of many large polymer molecules
What is a Polymer ?

6. A chemical reaction forms the polymer molecule (makes the chain)
polymerisation
Normally, chains are randomly arranged and form a 3d pattern
Imagine a piece of string scrunched up into a ball
What is a polymer ?

7. Synthetic Polymer Categories
Long chain polymers
Crosslinked polymers
Thermoplastics
Thermosetting
Plastics
Elastomers
Semi-crystalline
amorphous
Synthetic Polymer Categories

8. Crosslinked Polymers Very strong Level of crosslinking determines Tg
Strong bonds between chains (crosslinks) and intra-chain
Level of crosslinking determines Tg
Thermosetting plastics (eg Araldite) are highly linked
Chemical reaction forms the links
One way process – cannot be reversed
Will not soften with heat - very high Tg
Araldite is a tradename for a resin based polymer
The resin is mixed with an activator to start curing
Materials like rubbers are lightly crosslinked
Tg is below freezing ie. Is in a rubbery state at all temperatures above 0
Below Tg, material is hard & brittle (useless)
Crosslinked Polymers

9. Thermoplastics Strong covalent bonds Weak bonds between chains
Bonds between individual chain elements
Weak bonds between chains
These bonds can be easily broken with heat
Breaking all bonds causes return to original shape
Recyclable by re-heating
Energy cost !
Contamination is a big issue
Thermoplastics

10. Thermoplastics Amorphous thermoplastics Semi-crystaline thermoplastics
Chains are randomly entangled
Generally transparent
Eg. PolyCarbonate (CDs)
Glass transition temperature (Tg) is a key property
Semi-crystaline thermoplastics
Cooling causes molecules to fold in a regular structure and form a crystal
Crystal is dense and so plastic is opaque
Eg. Polyethylene (gas and water pipes)
Have a definate meting point (Tm)
Thermoplastics

11. Semi-Crystalline Thermoplastics
The more crystalline a material is:
The stronger it gets
It has more resistance to solvents
Solvents need to dissolve into a material
Amorphous plastics have greater free space
Higher density
Higher modulus (stiffness)
Higher melting point (Tm)
The lower its transparency
Reduced impact resistance (brittle)
Reduced ductility
Ability to be deformed without cracking
Semi-Crystalline Thermoplastics

12. Effect of temperature on thermoplasticsTg
(glass to rubber) Tm
(melting point)
Stiffness
(modulus)
Temperature
Amorphous thermoplastic
Semi-crystalline thermoplastic
Effect of temperature on thermoplastics

13. Thermosetting Plastics
15% of plastic production
Polyurethane
Carpet underlay
bed foam
Urea formaldehyde (UF)
Mains plugs/sockets/light switches
Phenol Formaldehyde (PF)
Tradename: Bakelite
Epoxy Resin
Tradename: Araldite
Used as coatings & adhesives or to form composites eg. Carbon fibre
Can cause health problems
Melamine formaldhyde
Work top laminates
Office furniture
Thermosetting Plastics

14. Sources of Polymers Oil (carbon) Sustainable sources (biopolymers)
4% of crude oil is used for plastics
Sustainable sources (biopolymers)
Wheat & corn
Carrot
Recycling
Difficult: all recycled items must be of the same polymer
Mixed plastics can be used for low level products such as road surfacing, wood replacement
Sources of Polymers

15. Carbon Based Polymers PolyPropylene (PP) Poly Vinyl Chloride (PVC)
Tupperware (lunch boxes)
Poly Vinyl Chloride (PVC)
Window frames
PolyStyrene (PS)
Packaging
Yoghurt pots / vending machine cups
Carbon Based Polymers

16. Carbon Based Polymers Acrylic Paint Point of sale displays Baths
Car lights
HDPE (High Density PE)
Bottles (biggest application)
milk bottles (largest bottle sector)
LDPE (low Density PE)
Supermarket carrier bags
Packaging film (eg. cling film)
Washing up liquid bottles
PET (PE Terephthalate)
fizzy drinks bottles
Carbonation makes HDPE unsuitable
Space blankets
ABS (Acrylonitrile Butadiene Styrene)
Car batteries
Calculators / mobile phones
Safety helmets
Carbon Based Polymers

17. Material Properties: ABS
Amorphous
Good resistance against medium temperatures (< 1000C)
Hard
tough
antistatic.
good resistance against chemicals.
Poor resistance to UV-light
Can be painted
Min temp: -250C
Max Temp: 800C
Glass Temp: 1100C
Material Properties: ABS

18. Material Properties: PET
Very light
AKA: Polyester
Can stand high tensile stress
Often used for magnetic tape
hard, stiff, strong
dimensionally stable
absorbs very little water
good chemical resistance except to alkalis
Medium resistance to UV
most commonly recycled plastic
drinks bottles are made from PET
Semi-crystaline
Must be rapid cooled to make it amorphous & transparent
Can degrade & become discoloured during heat treatment
Adds an unwanted flavour to food (can be compensated for at addition cost)
Min Temp: C
Max Temp: C
Glass transition temperature: 82oC.
Melting point: oC.
Material Properties: PET

19. Material Properties: HDPE
Excellent for any food related products
Not microwaveable
Machines extremely well (cut, bond, drill etc.)
Good chemical resistance
Good impact resistance
light weight
Poor UV tolerance
very low moisture absorption
high tensile strength
Not a good candidate for gluing.
Primarily used for blow moulding
Colours fade over time
Min Temp: C
Max temp: 1100C
Melting point: 1300C
Glass temp: -95
Applications
Milk bottles
trays and tanks
pipe fittings, wear plates, hinges
cutting boards.
Material Properties: HDPE

20. Material Properties: PVC
Amorphous (transparent)
Is typically coloured to make opaque
Good UV resistance
Excellent chemical resistance
glue able and weld able
easily machine able & heat bends nicely
Stiff
Tough
hard
Tg can be reduced down to -400c by adding plasticizer
Makes PVC suitable for hose pipes etc
Max Temp: 600C
Min Temp: C
Glass temp (Tg): 830C
Material Properties: PVC
PVC Applications (2000)

21. Material Properties: LDPE
Lower density & chemical resistance than HDPE
More transparent than HDPE
Less expensive than HDPE
Colours fade over time
Poor UV tolerance
Very soft & pliable
Max temp 700c
Min temp -50oc
Melting point 1200c
Glass temp: -1100C
Material Properties: LDPE

22. Material Properties: PP
Poor UV resistance
Translucent (semi-crystaline)
Rigid
Very light
Excellent chemical resistance
food storage applications
Medical applications (syringes)
Carpets
Microwaveable
Max temp C
Min temp 00C
Melting point: 1700C
Glass temp: -180C
Material Properties: PP

23. Material Properties: PS
Amorphous
Flammable
Excellent thermal insulation
Used in fridge linings
Solid:
Light, Hard, Stiff, Brittle
Expanded:
Light, Bouyant, Crumbles
Min temp: C
Max temp: c
Glass transition point: 1000C
Material Properties: PS

24. Material Properties: Acrylic
amporphous
Trade names: perspex & plexiglass
Weather resistant (Can withstand sunlight for long durations)
Difficult to recycle
Can be done but is very expensive (not cost effective)
Stiff (Flexible compared to glass)
Less breakable than glass
Scratches easily
brittle
Resistant to most chemicals and industrial fumes
Can be cut by various methods
Corrosion resistant
Good electrical insulator
Min Temp: 50C
Max temp: 410C
Glass temperature : 1100C
Material Properties: Acrylic

25. Some acrylic Products

26. Issues Safety Life Cycle Sustainability Energy for manufacture
Many chemical plastisizers contain oestrogen
Gender bending chemical
Some plastics (eg. PET) degrade & emit cancerous material over time
Life Cycle
Carbon based plastics take thousands of years to degrade
Biodegradeable plastics are being researched now
Sustainability
What would land used to grow organic polymers normally be used for ?
Are organic polymers at the expense of food grade crop ?
Today: a 500ML water bottle takes 3 fl/oz of crude oil to produce (+ energy to manufacture)
Energy for manufacture
All polymers (apart from elastomers) require heat to make them plastic
All plastics must be sorted and washed before being recycled
Where does this energy come from ?
Plastic is itself a fuel and can be incinerated
Toxic fumes are a consequence
Plastic can also be manufactured into a synthetic oil
Issues

27. Issues Sources of rubbish (2006)
Plastic mining of landfill sites may become a future industry
The price of plastic is linked to the price of oil
Issues

28. http://www.dynalabcorp.com/files/Use and Care of Plastics.pdf
Useful Web Sites

29. Guess the plastic ….

30. Guess the plastic …..

31. Guess the plastic ……

32. Guess the plastic ….

33. HDPE
ABS
PVC
Acrylic
Answers!

34. Exam Question...

35. Exam Question...