Addition and Condensation Reactions Flashcards
Example of a typical free radical
benzyl peroxide
Two types of initiation reaction
Free radical and anionic polymerization
Propagation reactions
Free radical driven: runs as long as there is easy access to free radicals.
Common orientation is head to tail, but sometimes head to tail occurs
Two types of termination
1) Disproportionation:
Poly 1 has a new H atom
Poly 2 has a new double bond
2) Chain transfer: Induces side chain branching
Vinyl Type Polymers
Basic structure is 2 carbons, 3 hydrogens + 1 reactive group
Semicrystalline or amorphous
Examples: polyethylene, polypropylene, polyvinylchloride, polystyrene
Vinylidne
Two reactive groups instead of one. The reactive groups can be the same or different.
Examples: PMMa or PVDC
Miscellaneous addition type polymers
2 carbons + more than 2 non-hydrogens elements/groups. Example: Teflon
Dienes
Basic structure:
4 carbons, 5 hydrogens, 1 reactive group.
Crosslinkable to form elastomers
Heat, pressure, time
Examples: Polybutadiene, polyisoprene, polycloroprene
Crosslinking
Replaces weaker van der waals bonds between polymer chains with covalent bonds between chains.
Formula for % crosslinking
% crosslinking = moles of crosslinking element/moles of mers in polymer batch
Effect of crosslinking on elastomers
Higher % CL increases Tg and E
Addition polymer processing methods
Extrusion, injection molding, injection blow molding, blown-film molding, sheet forming or calendaring, vacuum thermoforming,
Condensation polymerization
End groups react to form characteristic linkages, leaving behind a condensate
Condensation polymerization processing methods
Compression molding, transfer molding, fiberizing, reaction injection molding,
