Polymers wace Flashcards
Define a polymer.
Describe it’s structure
very large molecules made when hundreds of monomers join to form a long chain
-monomers are small units joined together by covalent bonds to create polymer
-polymerisation
Contrast between synthetic and natural polymers
Natural:
-polymers occur naturally (silk, carbs, protein, cotton)
Synthetic:
-man made
-tailored for specific purpose
Describe how polymers compare and contrast to metals
-both are can be hard, strong, malleable and ductile
-polymers are lighter and are insulators of heat and electricity
Describe how structural feature of length effects polymer
-increase in length of chain=increase in dispersion forces
-cause polymer to be harder, more rigid
Describe how structural feature of branching effects polymer
-polymer spaced further apart=less dense material
-greater difference =decrease intermolecular forces
-increases flexibility of material
Describe how structural feature of crosslinking effects polymer
-crosslinks between polymer chains are covalent bonds=polymer network
-cannot be liquid but are hard, rigid
-burn and melt when heated
Describe how structural feature of elastomers effects polymer
-have elasticity
-found when only occasional crosslinks
-can still flex but returns to original state once stretch force is released
-weak vanderwaals forces bwn polymer chains=flexibility
Define thermoplastics as polymers
Properties?
Give an examples
-no covalent cross-links
-flexible, stretchy and have low boiling point
-therefore, can be moulded + shaped/recycled
-bonds between chains must be hydrogen, dipole dipole, or weak dispersion
e.g. polyethene, natural rubber
Describe how density is affected by the structure of polymer chains
-branching makes plastics light, soft, easy to melt (low density)
-lined up chains make plastic dense, rigid, and harder to melt (high density)
Define thermosetting plastics as polymers
Properties?
-strong intermolecualr forces (crosslinsk)holding chains in place
-polymers chains cannot slide past eachother
-cannot be stretched (little elasticity), rigid, high melting point
-decomposes/burns when heated (can’t soften/melt)
-cannot be recycled
Define elastomers
Properties?
-formed when occasional crosslinks are present
-elasticity as chains can move past each-other, but returns to original state due to crosslinks
-crosslinks prevent complete melting and makes recycling difficult
Describe the basics of addition polymerisation
provide and example of how to represent the product
-requires monomers that are unsaturated (double/triple bonds)
-during process, bond is broken and single bonds are formed between monomers
Explain addition polymerisation of polyethene
-monomers of ethene added together to form polymer
-non-polar and exhibits only strong dispersion forces
Describe what difference occur between low density and high density polyethene
Properties for low density
Read over structure
-due to high temp and pressure polymer is formed rapidly where free radicals break attach sides of polymer chain=significant branching
-low density molecule as a result, causing decrease in dispersion forces (weaker intermolecular forces)
-soft, flexible structure w/low bp and mp
Describe what difference occur between low density and high density polyethene
Properties for high density
-lower pressure and temp conditions w/specialised catalyst=fewer branches
-pack tighter together=increase density and more orderly arrangement
-increase dispersion forced=hard, higher mp and bp, non-conductor
Explain addition polymerisation of polytetrafluoroethene (PTFE)
Properties?
Read over structure
-teflon
-non-stick (low friction co-efficient)
-heat/flame resistant
-chemical resistant
-strong and durable
Describe condensation polymerisation and it’s basics
Provide two common examples
-occurs bwn 2 different monomer that each have 2reactive functional groups
-large polymer formed containing 2 reactive functional groups, while small water molecules eliminated
e.g. carboxylic acid and alcohol=ester
carboxylic acid and amine=amide
Compare addition and condensation polymers
Addition:
-monomers must be unsaturated
-no by-products produced
-polymer backbone=long C chain
Condensation:
-monomers contains 2 reactive functional groups
-small water molecules produced
-polymer backbone contains 2 functional groups
Determine the basics of a polyester
Provide and example
-formed through condensation reac.
-ester formed bwn alcohol + carboxylic acid
-monomer are alcohol w/2 hydroxy group (diol) and acid w/2 carboxyl groups (diacid)
e.g. polyethylene teraphthalate (PET)
Describe PET and it’s properties
Add an example or two
-polyethylene terephthalate
-strong due to polar ester groups therefore can form dip-dipole attraction bwn chains
-hard, strong, stable material absorbs little water
-good gas barrier properties and chem resistance
e.g. fabrics and packaging
Determine the basics of a polyamides
Provide and example
-2 amino groups (diamine)
in amine
-2 carboxyl group (diacid) in acid
-stronger than polyesters as they can form H bonds between amine groups on neighbouring polymer chains
Describe nylon (6, 6) and it’s properties
Add an example or two
-polyamides can form H bonds bwn lone pairs of e- on oxygen of (C=O) and H atom from (N-H) group
-ability to increase tensile strength and stiffness
-strong, lightweight
-hard, tough, rigid
-fatigue and wear resistance
-sliding properties
