A level Product Design Unit 2 Polymers A level Product Design Unit 2

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 ?

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 ?

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 ?

Fully uncoiled, one polymer molecule’s chain length may be 10,000 times the diameter of the chain The length of the chain gives the material flexibility Many other material properties are dependent on the chain length Tg = glass transition temperature Temperature at which polymer moves from a hard glass like state to a softer rubbery state Polymer Properties

Plastic Additives Polymer molecules Reinforcement Plasticizer Filler Added to improve material strength properties Plasticizer Added to change natural material properties Makes material easier to process Filler Added to replace polymer Cost reduction measure Stabilizers Stop deterioriating over time Heat, UV, Biodegradation Foamants Increases volume Gives more elasticity under compression Plastic Additives Typical PVC Content

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

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

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

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

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

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

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

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

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

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

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

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: -500C Max Temp: 1700C Glass transition temperature: 82oC. Melting point: 250oC. Material Properties: PET

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: -1000C 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

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: -250C Glass temp (Tg): 830C Material Properties: PVC PVC Applications (2000)

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

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 1350C Min temp 00C Melting point: 1700C Glass temp: -180C Material Properties: PP

Material Properties: PS Amorphous Flammable Excellent thermal insulation Used in fridge linings Solid: Light, Hard, Stiff, Brittle Expanded: Light, Bouyant, Crumbles Min temp: -400C Max temp: 600c Glass transition point: 1000C Material Properties: PS

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

Some acrylic Products

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

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

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

Guess the plastic ….

Guess the plastic …..

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HDPE ABS PVC Acrylic Answers!