4.2 d Flashcards
monomer
molecule that can be bonded to other monomers, to form a polymer
polymer
large molecules made up of repeating units called monomers
are all polymers = plastics?
no
simplified plastic extraction process
oil (raw material) extracted in a location
exported to another location
oil is converted to plastic
sold
3 main plastic types
natural
semi synthetic
synthetic
natural plastic type
naturally occuring materials that can be moulded by heat (eg latex from tree sap)
semi synthetic plastic type
naturally occurring materials that have been modified or changed by mixing other materials with them
synthetic plastic type
materials derived from breaking down carbon based materials (usually crude oil, coal or gas) so that their molecular structure changes
thermoplastics
linear chain molecules with weak secondary bonds between the adjacent chains.
can be melted and reformed => makes it easy to recycle
thermosetting plastics
linear chain molecules with strong primary bonds between the adjacent chains.
on first heating, softens and can be moulded into shape. heat triggers chemical reaction, and it cannot be reshaped.
will burn if heated => makes it difficult to recycle. to recycle they need to be ground into a powder which adds time and costs, so are often sent to landfill
list thermoplastics
PP – easily formed, low cost, tough, light
(HD/LD)PE – low cost, very flexible (LD), transparent
PET – very low cost, light, tough, shatter resistant
PVC – tough, light, durable, range of colors, waterproof
HIPS (PS) – low cost, impact resistant
ABS – tough, light, high impact strength, durable
list types of thermoset polymers
polyurethane
urea-formaldehyde
melamine resin
epoxy resin
polyurethane properties
high abrasion resistance
high load bearing
strong electrical insulator
can be flexible and elastic, hard like fibreglass or soft and spongy
urea-formaldehyde
good electrical resistivity
doesnt distort from heat
high surface hardness
melamine resin
highly durable
hard (one of the hardest)
lightweight in comparison
high electrical and heat resistivity
epoxy resin
tough
electrical insulation
high thermal resistance
bioplastics
developed to reduce the problems of disposing of plastics they can be designed to be biodegradable
