Polymers Flashcards
What is a crystalline structure?
Any structure of ions, atoms, molecules that are held together in a regular/ three dimensional arrangement
What is low density polyethene?
Is made up of Polymer chains that have side branches.
These side branches stop the polymer molecules from lining up regularly.
This structure is not crystalline since it is not formed in a regular pattern.
Less strong than HDPE since it has a lower melting point due to the forces of attraction between the polymer molecules to be weakened.
What is HDPE? High density poly ethene?
Polymer chains that have no side branches.
Polymer molecules are able to line up regularly to give a crystalline structure.
HDPE has strong forces of attraction between the polymer molecules, causing it to have higher melting point than LDPE.
Has a higher density than LDPE.
Has stronger material.
What are the conditions that ethene molecules need to be added whilst making LDPE and HDPE-
LDPE-
Temp- 200 degrees
Pressure- 2000 atmospheres
Catalyst- none used
HDPE-
Temp- about 60 degrees
Pressure- very low (10 to 80 atmospheres)
Catalyst- titanium chloride or titanium tetrachloride
Explain and describe the thermosoftening polymers-
Soften when heated up, and can be reshaped when theyre hot.
They become hardened when they’re cooled down, but can still be reshaped if they were heated up again.
Why is thermosoftenting polymers a flexible material? Name one thermosoftening polymer-
Its tangled polymer chains slide over eachother, making it a flexible material.
Polyethene is a thermosoftening polymer
Why are thermosoftening polymers able to slide over eachother?
Due to them having weak intermolecular forces of attraction between the polymer chains.
Explain and describe thermosetting polymers-
Once shaped and moulded, theyre not able to be soften by getting heated up again, and cannot be reshaped.
They can be heated up one time and shaped one time, then the other times it won’t be soften to be able to reshape.
the polymer chains will join together/ be held by permanent bonds. These cross links (permenant bonds) form when they’re heated. They hold the polymer chains in position so they’re not able to slide over eachother easily.
Name one thermoset used, and what is it used for?
Vulcanized rubber, used for tyres
How are the chains fixed together in thermosetting polymers?
By strong covalent bonds between the polymer molecules and the cross links.
What happens between the polymer molecules in thermosoftening polymers when they’re cooled down and are heated again?
The intermolecular forces between Polymer molecules pull the polymer molecules back into place and back together.
Exam style- The thermosetting polymer does not melt when heated- use ur knowledge of bonding and structure to explain why- 4 marks
Large molecules that have covalent bonds between polymer molecules which are strong, which does not allow for the polymer molecules to move past eachother.
Or
There are Cross links between polymer chains, which are STRONG and cannot be easily broken down when heated.
Exam style- Describe the structure and bonding of a thermosoftening polymer- 4 marker
Structure- large polymer molecules that are held by weak intermolecular forces between the polymer chains.
Bonding- so these polymer molecules can be easily broken down when heated.
What are smart polymers? Name a few-
Smart polymers are polymers that change in response to a stimulus.
Examples-
Hydrogels, light sensitive plasters, shape memory polymers, dental polymers, would dressings,etc.
Explain 3 examples of smart polymers and how are they used?
Light sensitive platers- adhesive in the plasters respond to light, it becomes less sticky when exposed to light, so that it can be easy to remove.
New shape polymer- was developed to keep the stitch closed. It responds to body temperature and tightens, leading to the polymer closing up the wound.
Hydrogels- is used for wound dressing, it helps keep moist and sterile conditions whilst healing, since it has a matrix which traps in water (since hydrogels have polymer chains which have cross links between them, making them strong)
Shape memory polymers-
Between thermoset and thermosoft.
Soften when heated and can be shaped (stretched or defined/deformed)
Upon cooling, it remains in the shape that it was in upon reshaping.
When heated again, the polymer is able to return to its old/ original shape.
(Braces, stents)
Why are some polymers not biodegradable? What could happen if they weren’t biodegradable?
Since they have not been broken down by microbes.
It can cause problems with waste disposal.
What are the problems caused in landfill sites due to non- biodegradable plastics?
Non biodegradable plastics have not been broken down by microorganisms, so they can stay on the landfill sites for years.
Overtime, they can release harmful chemicals to the soil and water, causing soil pollution and water pollution.
As plastics do not decompose, they prevent organic material from being broken down properly by microorganisms, so there would be less methane gas being produced, which is needed in some landfill sites for energy recovery, leading to less renewable energy produced.
“Explain how non-biodegradable plastics affect the efficiency of landfill sites.” ( 5-6 marks)
Or:
“Describe the impact of non-biodegradable plastics on methane gas production in landfill sites.”
Non biodegradable plastics do not decompose (theyre not broken down by microorganisms) this creates a barrier around the organic waste in landfill sites.
Because, as waste is piled up, organic material is buried down or is between layers of plastic, and these layers of plastic acts a seal (so microorganisms can’t reach organic material) because plastics have long polymer chains, creating a dense structure, preventing water/ air molecules from entering.
This prevents the microorganisms from breaking down the organic material, which reduces methane gas production, leading to less energy recovery (converting organic material to renewable sources) to be available. Making landfill sites less efficient.
