polymers Flashcards
expanded polystyrene
- comprehensible and lightweight (N2 gas pockets)
- maintains shape
- heat and sound insulation (N2 gas pockets)
- opaque (high light scattering)
- used for packaging material
what are polymers
are molecules which are composed of many identical, repeating subunits known of monomers
- can be formed through addition polymerisation or condensation polymerisation
- total addition of all monomers is the total mass of the polymer
low density polyethylene (LDPE)
is characterised by extensive chain branching and low density formed at high temperature and pressure
- chemically unreactive (saturated hydrocarbon)
- soft and flexible (not tightly packed)
- transparent (low degree of light scattering)
- low melting point (weak dispersion forces)
- used for plastic shopping bags
what is a polyvinyl chloride
polyvinyl chloride (polychloroethene, PVC) is an addition polymer from chloroethene monomers (vinyl chloride)
- are stiffer than polyethylene (Cl>H)
- held together by stronger dipole dipole and dispersion forces (Cl>H)
- brittle
- PVC + UV absorber prevents sun degradation,
- PVC + heat stabiliser improves performance at high temperatures
- PVC + plasticer softens
- used for banks cards, water pipes
what is polyethylene (polyethene)
ethene (ethylene) is important feedback to produce addition polymers
- ethene are monomers
- 2 types of polyethylene (LDPE, HDPE)
biodegradability of all polymers
- increase in polarity of bonds = increase in biodegradability
- increase in CH bonds
- C-Cl, C=O, C-N, C-O are easier to biodegrade
- condensation polymers are easier to biodegrade than addition polymers
high density polyethylene (HDPE)
is characterised by minimal chain branching and long linear polymer molecules and formed at low temperature and pressure and with Zieglar-Natta catalyst.
- chemically unreactive (saturated hydrocarbon)
- highly rigid (tight packing, strong dispersion forces)
- opaque (high light scattering)
- high BP/MP
- used for chairs
what is nylon
synthetic linear polyamide and type of condensation polymer
- the most common is nylon-6,6 made from hexane-1, 6-diamine and hexanedioic acid co-monomers
- high tensile strengnth
- rigid
- resistant to chemical and thermal degredation
- used for car engines
determining structure of addition polymer from monomer
- identify double or triple bond
- redraw monomer to make the double or triple bond central
- bond individual monomers to the carbon atoms involved in double/triple bonds
- all other atoms are side chains
crystal polystyrene
- rigid (stiffness from bulky benzene rings)
- brittle
- transparent (low light scattering)
- 100C deforming temperature
- used for CD cases
what is polystyrene
polystyrene (polyethenylbenzene, PS) is an addition polymer produced from styrene (ethenylbenzene) monomers
- are 2 forms: crystal and expanded
what is a polyamide
is formed by the repeated condensation reaction of dicarboxylic acid and diamine co-monomers
chemical structure of all polymers
- increase chain length = increase dispersion forces and rigidity and BP
- increase in crystalline (opposite is amorphous) = increase in intermolecular force strength and density/rigidity and BP
- chain branching = loose packing and amorphous molecules
- chain stiffening from large side chains = increase rigidity
what is polytetrafluoroethylene
polytetrafluoroethylene (polytetrafluoroethene, PTFE) is an addition polymer produced from tetrafluoroethylene (tetrafluoroethene) monomers
- rigid and durable (H<F<Cl)
- chemically unreactive (C-F is strongest carbon bond)
- high BP
- hydrophobic (non-polar)
- lipophobic = non stick and low friction (weak dispersion forces)
- used for non stick frypans
