Polymers Flashcards
What are Polymers
Polymers are covalent molecular substances composed of many small molecules (monomers) joined together by covalent bonds through the process of polymerisation
- All plastics are synthetic polymers but not all synthetic polymers are plastics
What are Thermosoftening polymers?
-Polymers soften on heating, easily recycled because can be melted / remoulded
Structure:
- Tangled polymer chains
- No cross-links between chains
- Weak forces of attraction between chains
What are Thermosetting Polymers?
- Don’t melt when heated, not easily recycled. More durable, stronger and chemically resistant Structure: - Polymer chains held together by strong covalent cross-linking bonds that does not break on heating.
What are Addition Polymers
Addition polymers form by adding together. The monomer must have a double bond between C atoms
- No loss of molecules and no Formation of Biproducts
What is Ethylene
Ethelyne is made from crude oil (ethene)
Crude oil -> Fraction distillation (seperates mixture based on BP’s) -> Cracking (makes makes small hydrocarbons)
What is the Difference between LDPE and HDPE
LDPE: (Low density polyethylene)
- Made using high temp / high pressure
- Branching alkyl groups (amorphous)
- Weaker Dispersion forces
- Lower density, Low MP’s, Flexible
HDPE: (High density polyethylene)
- Made throygh Zieglar- Natta process:
- Low temp/ Low pressure + Catalyst (Titanium (3) chloride / Trialkyl aluminium)
- Unbranced (Crystalline) Chains which pack closely together
- Stronger disperion forces
- Higher MP’s / Less flexible
What is Polyfluroethylene (PTFE)
Also known as Teflon
- Made from monomer: Tetrafluroethene (all H atoms replaced by Fluroine)
- Strong and tough due to polar C - F bonds and dipole-dipole interactions between polymer chains
- Non stick pans
- Thermosetting
What is Polyvinyl Chloride (PVC)
Made from monomer vinyl chloride (chloroethene)
- Mainly amorphous due to the way Cl atoms stick out from the chain
- Rigid / Thermosoftening
- Dipole-Dipole interactions add to the dispersion forces between polymer chains holding them strongly together
What is Polystyrene
Made from monomer styrene (ethylbenzene) which is an alkene where the phenol group (-C6H5) has been substituted for one of the H atoms
- Amorphous structure because rings sticks out of chain and prevents chains packing closely together
- Symmetry of Phenyl rings means they are non-polar therefore only weak dispersion forces hold chains together
- Thermosoftening, Used for packaging
Describe the Biodegradability of Polymers
- Most synthetic polymers are strong covalent C-H or C-C Bonds so polyers are stablea nd don’t break down
- PVC has C-Cl Bonds which are weaker and break down in the presence of UV Light
What are Condensation Polymers? and how are they formed?
Condensation polymers are polymers formed through a condensation reaction, where molecules join together, losing small molecules as byproducts such as water or methanol.
Formation Requirements:
- Monomers must have 2 functional groups (one on each end of the monomer)
- Neighbouring monomers must have different functional groups, when these 2 monomers chemically react, a different functional group is formed in the process
- Biproduct formed (usually water)
What are Polyesters and how are they formed?
Polymers in which the monomers are joined by an ester link
- One monomer molecule with a carboxylic acid functional group must react with another monomer which has an alcohol function group at each end of the monomer.
- OH group on Carboxylic acid disappears
- H atom comes off of the alcohol functional group
- Monomers single bond at O atom on alcohol monomer
- Biodegradable because bacteria can break down the ester links (carbon double bonded to Oxygen and single bonded to another oxygen)
What are Polyamides (Nylon) and How are they formed
Polymers made from amide (carbon bonded to NH2 and double bonded to Oxygen) links
- Nylon made from a monomer containing an amine functional group and reacting with a neighbouring monomer containing a carboxyl (carboxlic acid) group
- OH functional group comes off of carboxylic monomer
- one H atom comes off amine functional group
- Monomers join by single bonding to N atom (creating an amide group)
