Plastics Flashcards
List, identify and know the main types of plastics and their properties. You should be able to give examples of applications where plastics are used.
What are plastics?
- A group of materials made up of long chains of molecules.
- Many of them are known as hydrocarbons because the long-chain molecules consist of hydrogen and carbon atoms in various combinations with other atoms.
- Some plastics have been created from natural sources.
What is the correct name for plastic materials?
Polymers
Why are plastics so popular?
They have several advantages over many more traditional materials:
- lightweight
- self-coloured
- electrical insulator
- thermal insulator
- ability to be formed into complex shapes
- good strength to weight ratio
- good atmospheric and chemical corrosion resistance
What are the main sources of raw materials used in manufacturing plastics?
- Animal and vegetable by-products are used in semi-synthetic polymers eg. cellulose (from plant fibres) is mixed with acetic acid to produce cellulose acetate.
- Coal, oil and gas, through a process called thermal cracking, are the source for synthetic plastics. This accounts for the majority of modern plastics.
What are the three groups of plastics and their main properties?
- Thermoplastics - These materials can be repeatedly reheated and remoulded.
- Thermosets - These undergo a chemical change resulting in them becoming permanently rigid. They cannot be reheated and reshaped.
- Elastomers - Polymers that have good elasticity. They can be distorted under pressure but will return to their original shape when the pressure is removed.
Draw the structure of a Thermoplastic.
Thermoplastic
Draw the structure of a Thermosetting plastic.
Thermosetting Plastic
Draw the structure of an Elastomer.
Elastomer
Additives are a way of improving the properties of plastics. Name five additives.
- Fillers
- Flame-retardants
- Anti-static agents
- Plasticiser
- Stabilisers
What do fillers do when added to plastics?
- Fillers reduce the bulk of the plastic.
- Fillers are cheap and therefore reduce the cost of the plastic.
- Some fillers can increase strength and hardness by removing brittleness.
- Examples of fillers include saqwdust, crushed quartz and limestone.
What does a flame retardant reduce the risk of, when added to plastic? How does it actually work?
- Flame retardants reduce the risk of combustion and therefore fire.
- The retardant produces a chemical reaction that slows and stifles combustion.
- A good example of the use of flame retardants is in foam filled cushions.
Name a product made from synthetic materials that would benefit from anti-static agents being added to it.
Carpets made from nylon and polyester.
How does an additive that is a plasticiser improve plastic manufacturing processes?
- Plasticisers improve the flow properties of plastics when being moulded.
- Plasticisers also reduce the softening temperature.
In what types of plastic products are stabilisers used in and why?
- Products such as window frames, doors and conservatories use stabilisers.
- Stabilisers reduce the effect of ultraviolet light by making the plastic more resistant to being “broken down” by sunlight.
- Stabilisers are important for the aesthetic and structural integrity of the product.
What are biodegradeable plastics?
Biodegradable plastics are designed to degrade (break down) under biologically and enviromentally rich conditions (such as rain and sun) unlike conventional plastics which clog up landfill sites.
