2.2 Applications of Polymers Flashcards
What are the two main types of polymers?
Thermoforming and thermosetting
What is a thermoplastic/forming polymer?
Polymers which can be formed using heat and reshaped many times without changing properties
What is a thermosetting polymer?
They cure initially with a chemical catalyst and then will not soften when heated (this reaction is exothermic)
What is the difference between natural and synthetic polymers?
- Synthetic polymers are produced from finite resources such as coal, gas and oil
- Natural polymers come from sources such as rubber and amber, which come from trees
What is fractional distillation
When crude oil is heated in the crude oil distillation unit - each fuel has different sized molecules with different boiling points and different types of polymers are made from the different fuels
What is cracking
Heat and pressure are used to convert the large hydrocarbon molecules into smaller, more useful versions as the large molecules do not flow very well and are not suitable to be converted into plastics
What is polymerisation?
After hydrocarbons are obtained from cracking, they are then chemically processed: Monomers join together end to end to form long chains, called polymers
What is the structure of a thermoplastic/forming polymer?
They have long chains of molecules, tangled together with no fixed structure or pattern
Name the thermoplastic/forming polymers
- Low density polyethylene LDPE
- High density polyethylene HDPE
- Polypropylene PP
- High Impact Polystyrene HIPS
- Acrylonitrile Butadiene Styrene ABS
- Polymethyl methacrylate PMMA (Acrylic)
- Nylon
- Polyvinyl chloride PVC
What are the properties of LDPE?
- It’s quite flexible, but also tough
- Has excellent resistance to chemicals
- It can be either translucent or opaque
- Used for squeezy bottles and snap-on lids and carrier bags
What are the properties of HDPE?
- It’s tough and has a higher strength-to-weight ratio than LDPE
- It also has good chemical resistance
- Used for bottles containing chemicals, rigid plastic toys, storage boxes, buckets and garden bins
What are the properties of PP?
- It’s tough, flexible and has an excellent fatigue resistance
- It’s resistant to chemicals and solvents
- It is available in translucent form and in a range of colours
- Used for food packaging, medical equipment, hinged lids, moulded furniture and rope
What are the properties of HIPS?
- It’s rigid, lightweight and has a high impact strength
- It has the ability to retain heat without deformation
- It’s food safe
- Used for yoghurt pots, single-use coffee cups and plastic cutlery
What are the properties of ABS?
- It’s hard and tough with an excellent impact strength
- It has very good resistance to acids, alkalis, oils and grease
- Used for domestic appliance casings, computer screen housings, rigid suitcases, safety helmets, car bumpers and wing mirrors
What are the properties of Acrylic?
- It’s a tough lightweight material
- It can be a clear plastic but is available in a very wide range of colours
- It has relatively poor resistance to chemicals
- Used as an alternative to glass, for shower trays, baths, car lamp covers and lenses in glasses
What are the properties of Nylon?
- It has a low coefficient of friction
- It’s durable and resistant to abrasion
- It is heat resistant
- Used for mechanical components, woven textiles such as rope, parachutes, tents, seat belts and carpets
What are the properties of PVC?
- It can be both rigid and flexible
- Rigid PVC is tough, hard and used for plumbing pipes as well as guttering and down pipes
- It has good chemical and weather resistance
- Flexible PVC is used for hose pipes, clothing and as an alternative to leather
What is the structure of thermosetting polymers?
Long chains of molecules are cross-linked and form a very rigid molecular structure
