ENME307: Polymer structure

Bonds within polymer molecules

covalent

Bonds between polymer molecules

van der walls

Aliphatic

linear, less stable derived from methane

Aromatic

ring, more stable, derived from benzene

Radicals

species that have 1 or more unpaired e-, initiates polymerisation but remains unchanged

Functional group

group responsible for chemical characteristics

Electro Negativity

ability to pull e- towards nucleus

Polarity

amide > carboxylic acid > alcohol > ketone/aldehyde > amine > ester > ether > alkane

Monomers

repeating units

Isomers

same composition, different structure, different properties

Cis

rigid

Trans

flexible

Polyethylene (PE)

CH4

Polyvinyl chloride (PVC)

CH3Cl

Teflon

CF4

Polypropylene (PP)

CH3CH3

Polystyrene (PS)

CH3 benzene ring

Addition/Chain

add mer group (Teflon, PP), faster weight growth

Condensation/Step

chem reaction with H2O byproduct (epoxy, PE), slower weight growth

Monofunctional

1 functional group

Difunctional

2 functional groups, needed for polymerisation

Short DP

softer material

HD

high density

LD

low density

LLL

linear low density

UHMW

ultra high molecular weight

A

amorphous

X

cross linked

Ligamers

like monomers but longer

Reactants

unsaturated polymer, styrene, curing agent

Curing agent

opens up double bonds, contains radicles

Crosslinked polymers

thermoset (resin), elastomers

Gel point

where resin becomes unworkable and every component is crosslinked

Vitrification

rubber to glassy/rigid