Polymer Chemistry 9j Flashcards
addition polymers
no loss of atoms during the process
monomer usually contains C=C double bond, which forma single C=C bond after the reaction
backbone chain is usually only C atoms
condensation polymers
a small molecule such as H2O or HCl condenses out.
usually made of polyesters or polyamides
monomers likely contain two different functional groups
backbone chain usually has O or N, other than C.
differentiating thermoplastics from thermosets
by their physical response to heating:
thermoplastics are softer and melt with heat while thermoplastics do not melt with heat
by their rigidity:
thermoplastics have lower rigidity, but have high strength, hence are more flexible without breaking. Thermosets have higher rigidity and more more brittle.
thermoplastics characteristics
held together by weak intermolecular attractions/ dispersion forces. they do not have covalent bonds.
they can be melted, moulded and cooled to Harden, hence are recyclable.
thermosets characteristics
since the polymer chains are cross-linked, hence the harden permanently.
the cross-linked chain resist heat, hence, they cannot be melted and cannot be recycled.
LDPE and HDPE
LDPE: more irregularly tangled together, highly branched, look like veins
HDPE: packed closely together, more regular structure. more points of contact, hence more intermolecular dispersion forces form.
physical properties of polymers: chain length
mp increases with the increase in chain length
physical properties of polymers: packing of chains
the more closely packed the chains are, the more intermolecular forces that form, hence the mp increases.
physical properties of polymers: branching
LDPE and HDPE
physical properties of polymers: monomer units (what it is composed of)
depends on whether the molecules can form hydrogen bonding or not
physical properties of polymers: cross linking
when there are more cross linking, the polymer becomes more hard and brittle.
