olola's version from 2016-09-19 09:46

steps in polymerization

Question Answer
1st step, creation of a "species" that starts the reaction; free-radical formation (nothing to do with monomer)Activation
the only step of polymerization that is under the clinician's controlActivation
an unpaired electron seeks out something electron rich to form a covalent bondActivation
reaction of active species with first MER unitInitiation
reaction of activated MER unit with something electron rich (and it keeps doing this)Propagation
quenching of the propagation process (some may form rings or tangle with each other)Termination

characteristics of the formed polymer

Question Answer
degree of ________: number of individual MER units in an average chain (avg chain length in # units)Degree of Polymerization
degree of ________: portion of total reactive units that have been used to form the polymer (number used/total available=%)Degree of Conversion
What type of polymer chain shape has the strongest physical properties?Cross-linked
cross-linking increases physical properties of polymers except for _____ which decreasesflexibility
________ can cause polymers to undergo softening, increased flexibility, and swelling ((leaching of components, staining, lowering propertiesFLUIDS
________ agents can interfere with hydrogen bonding between chains of a polymer, but when the agent leaves, hydrogen bonding comes backPlasticizing agents
PVS has cross-linking in a ______ amount cross-linkinglow; (want flexibility)
vacuum form matrix has what polymeric shape?Linear (low flowing temp)
Resin composite has a _____ amount of polymeric cross-linkingHIGH
when a polymer is moldable with temperature and retains shape upon cooling it is ______thermoplastic
when a polymer does not soften with heating... it is ______thermoset
contraction, or dimensional change with cure, usually results in about ____% shrinkage of dental polymers4%