Ch. 10- Polymers Flashcards
polymer
a molecule with a large molecular mass that is formed by repeating smaller units (monomers)
monomer
a substance of relatively low molecular mass; the building blocks of polymers
polymerization
a process by which monomers are made into polymers
celluloid
cellulose nitrate, derived from natural cellulose by treating it with nitric acid; earliest synthetic attempt to improve on natural polymers
what do we use celluloid for?
as a substitute for more expensive materials like ivory, amber, and tortoise shell; used to make billiards balls, movie film, & stiff shirt collars
why don’t we use celluloid as much?
it’s highly flammable and difficult to preserve
what was the first truly synthetic polymer?
Bakelite, made from phenol & formaldehyde
what is the simplest and least expensive synthetic polymer?
polyethylene
why was polyethylene so important for the Battle of Britain?
it was invented just before the war, and was used as an electric insulator; without it, the British would have had to use what they had at the time (cotton braid + rubber paint) for electric wires, which was very ineffective for their radar; if their radar wasn’t as effective as it was with polyethylene, they could’ve lost the battle
what is the source of most synthetic polymers?
petroleum & natural gas
copolymer
a polymer formed by the combination of two (or more) different monomers
what are the 3 main types of polyethylene
- high-density polyethylene (HDPE)
- low-density polyethylene (LDPE)
- linear low-density polyethylene (LLDPE)
properties of high-density polyethylene (HDPE)
- has mostly linear molecules that pack tightly in a crystalline structure
- rigid & strong plastics
- have densities of 0.94-0.96 g/cm3
- hold shape in boiling water
how do we use HDPE?
- threaded bottle caps
- toys
- detergent bottles
- milk jugs
properties of low-density polyethylene (LDPE)
- has many side chains branching off the polymer molecules, preventing the molecules to tightly pack & assume crystalline structure
- waxy, bendable plastics
- have densities of 0.91-0.94 g/cm3
- severely deform in boiling water
how do we use LDPE?
- plastic bags & film
- squeeze bottles
- electric wire insulation
- common household products that require flexibility
how do we make linear low-density polyethylene (LLDPE)?
by polymerizing ethylene with a branched-chain alkene
how do we use LLDPE?
- plastic films for landfill liners
- trash cans
- tubing
- automotive parts
thermosetting polymer
a polymer that cannot be softened and remolded; very high temperatures cause them to discolor and decompose