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Dmat3

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robbypowell's version from 2016-09-17 00:28

Section

Question Answer
the elements usually comprising polymers are ____, ____, and _____,,, and sometimes _____ and _____Carbon, Hydrogen, and Oxygen; sometimes Phosphorus and Nitrogen
polymers have very strong ______-chain bonds and weak ______-chain bondsstrong INTRA; weak INTER
(Isotropic/Anisotropic) polymers have different properties in different directionsAnisotropic
(Isotropic/Anisotropic) polymers have similar properties in all directionsIsotropic
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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
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characteristics of the setting polymer

Question Answer
components inside the UNIT store energy and release it to speed up the polymerization reaction... this generates ____ and so is an _______ reactionheat; exothermic
2 examples where heat generation from exothermic polymerization is clinically relevant concerndirect denture reline; PMMA provisional
contraction, or dimensional change with cure, usually results in about ____% shrinkage of dental polymers4%
a major consequence of polymerization _____ is evident when composite at pulpal floor debonds and this leads to sensitivityshrinkage (aka contraction)
The more ______ atoms that react with each other, the more shrinkage (contraction) will result from polymerizationCarbon
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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
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