4.4 Materials Flashcards
Explain the advantages of using composite materials
- Part consolidation
- Dimensional Stability (stable in all conditions)
- Non Conductive
- Non Magnetic
- Radar Transparent (not detected by radars)
- Low thermal Conductivity
- Durable
- Light weight
- High Strength
- High strength to weight ratio
- Corrosion resistant
- high impact strength
- Design flexibility (easily moulded)
Explain the difficulties associated with recycling composite materials
- currently no commercial operations for economic recycling
- heterogeneous hybrid structure
Explain the advantages of recycling materials
Converts waste into usable materials ensures sustainable use of resources Protects environment Helps to reduce: - Energy usage - consumption of raw fresh materials - Air pollution and water pollution by reducing landfill - Greenhouse gas emissions
Explain the difference in ease of recycling thermoset v thermoplastic polymers
Thermoplastic - 100% recyclable
Thermoset - form permanent chemical bonds
- prolonged heating will not change shape
- can be shredded to be used in other applications
Explain why some polymers are biodegradable and other are not.
Enzymes and microorganisms that breakdown polymers have evolved with natural polymers.
Plastics have been around for only 70 years thus microorganisms have not evolved to break them down naturally
To be biodegradable, polymers must have similar structures to natural polymers like starch or cellulose.
Explain the advantages of polymers being biodegradable
- Take less time to breakdown
- Use biomass which is a renewable resource
- better for the environment with minimal GHG
- Require less energy to manufacture
- Non toxic
- reduce the cost of waste disposal
- divert waste from already overflowing landfills
State the basic stages in metal production
- Concentration of metals
- conversion in reducible compound
- reduction
- refinement/purification
Advantages and disadvantages of Thermoset
Advantages
- Light
- Low processing costs
- Highly recyclable
- High-Impact resistance
- Reshaping capabilities
- Aesthetically superior finishes
Disadvantages
- Melt
- Deformed when exposed to high levels of stress
- Chemical leaching
Advantages and disadvantages of Thermoplastic
Advantages
- Retain their strength and shape even when heating
- Highly flexible design
- Thick to thin wall capabilities
- High levels of dimensional stability
- Cost-effective
Disadvantages
- Cannot be recycled
- Cannot be re-moulded or reshaped
Advantages and disadvantages of Elastomer
Advantages
- Recyclable material
- Resistant
- Soft
Disadvantages
- Relatively high cost
- If heated to a relatively high temperature they tend to lose their rubbery property
Advantages and disadvantages of Synthetic fibres
Advantages
- Cheaper than natural fibre
- Easier to wash and dry up quickly
Disadvantages
- Synthetic fibres burn more easily
- Damage by hot washing
Compare the effects of heat on thermoset v thermoplastic polymers.
Why is this the case?
Thermoset - Plastic remain in permanent solid state once hardened.
Highly cross-linked networks that must be shaped during polymerisation
Thermoplastic - Can be melted and reshaped
Only HB and DF holding chains together thus heat can disturb the bonding
Compare the physical properties of chains with different degrees of cross linkage
As cross linking increase polymer:
- becomes more rigid (Movement and flexibility is reduced)
- increase in melting point (primary bonds must now be broken to metal)
- become more dense as chains are brought closer together with cross links
Advantages and disadvantages of making polymers from fossil fuels
Advantages
- Petroleum and natural gases are abundant and accessible
- Can be produced from by-products of other processes
- Wide variety of plastics can be produced, suitable for different uses
Disadvantages
- Use non-renewable crude oil
- End up as litter on land/ in water for 100s of years
- toxic to many animals
- Aren’t easily biodegradable
Advantages and disadvantages of making polymers from renewable materials
Advantages
- reduced CO2 emissions in comparison to processing normal plastics
- Carbs, proteins and oils are relatively abundant and renewable
- Biopolymers are general cheaper than normal plastics
- Completely degradable
Disadvantages
- Functionality is compromised (e.g. sugarcane bottles cannot hold carbonated drinks)
- Limited range is currently available
- Pressure on farmland to grow material takes away natural resources for food
- Recycling needs to occur separately from current plastics
