Intro to Polymers Flashcards
Isomerism
Spatial arrangement of reactive groups on a Monomer, where different orientations yield different properties
Isotactic
All reactive groups on the same side
Syndiotactic
Alternating side reactive groups
Metallic bonding
Sea of delocalized electrons
Ionic bonding
Transfer of electrons
3-D sharing of electrons
Covalent bonding (thermosets and crosslinking)
1-D sharing of electrons
Covalent bonding, thermoplastics
Hydrogen bonding
Covalent primary, Van der Waals secondary
Dipole to dipole
Van der waals bonds, secondary e sharing
Amorphous Polymers
1-D chains-covalent bonding with van der Waals between chains.
Glassy, amorphous, and brittle at room temp.
Example is PMMA
Semi-Crystalline Polymers (Thermoplastics)
1-D chains, covalently bonded with van der Waals between chains.
Both crystalline and amorphous regions.
Tg is typically below 0 deg C, leathery, rubber at room temp.
High ductility and toughness, with good chemical resistance
Examples: PE, PETE, PP, PVC, Nylon, Teflon
Elastomers
3-D covalently bonderd, lightly crosslinked, long chain.
Irreversible Curing.
Lower modulus but moderate tensile strength.
Tg below 0 deg C, leathery/rubbery at room temp.
Examples: Vulcanized rubber, silicones
Thermosets
3-D covalently bonded, highly cross-linked.
Reactive elements added between adjacent chains, covalent bonding between polymer chains.
Cannot be recycled.
Brittle fracture: high modulus and minimal plastic deformation.
Highest Tg due to curing reactions and highly crosslinked chains.
Examples: Epoxy, cynate ester, bakelite.
Free radical
Atom or group with a dangling covalent bond
Addition polymerization
Initiation: Free radical attaches to monomer
Propagation: Free radical monomer combines with additional monomers
Termination: Free radicals combine or transfer to other chains
