polymers Flashcards
the extent to which all (entire) monomer is polymerized
degree of conversion
Two molecules react to form a larger molecules with
elimination of a small molecule
condensation polymerization
free radicals react with double bond of a monomer for
crosslinking
– is activated with light
camphoroquinone (CQ)
added to polymer to modify the physical properties
plasticizer
Minimize or prevent spontaneous or accidental
polymerization of monomers
inhibitors
Polymers containing two or more chemically different
types of monomer units to create different polymer
properties
copolymer
low MW monomer =
diluent
condensation polymerization –> like water and alcohols
byproducts
condensation polymerization –> – dimensional stability
low (shrinkage)
Two molecules react to form a larger molecule without
the elimination of a small molecule
additional polymerization (no byproduct)
additional polymerization –> – in composition
no change
additional polymerization –> – dimensional stability
better
examples of additional polymerization
free-radical and ring opening
most dental resins are formed from –
additional polymerization
silicone impression material
condensation polymerization
most common type of additional polymerization
free radical
CQ absorbs light and –
releases free radicals
activator of CQ
blue light
accelerator of CQ
DMAM
Do plasticizers participate in the polymerization rxn?
no
do plasticizers become part of polymer chain?
no
plasticizers – attraction between polymer chains
reduce
plasticizers – the polymer
softens (more flexible)
dibutyl phthalate makes denture polymer rubbery
plasticizer
free radical scavengers
oxygen, HQ, MEHQ, BHT
main inhibitor for most systems
oxygen
very efficient inhibitor but causes discoloration
HQ
MEHQ is an –
excellent inhibitor
BHT produces – discoloration
less
MMA + Butyl methacrylate –> –
denture bases
resist fracture
MMA + Octyl methacrylate –> –
soft and flexible (denture soft
liner)
MMA + Hydroxyethyl methacrylate –>
increased wettability
patients with xerostomia; dry mouth
most common high MW monomer
Bis-GMA
core Bisphenol-A of Bis-GMA provides
high strength
terminal methacrylate groups of Bis-GMA provide sites for –
free radical polymerization
– need to be diluted with a thinning monomer to be easily placed and manipulated
Bis-GMA
Low MW monomers
MMA and TEGDMA
what is CQ and BPO?
initiators
high degree of conversion
fewer residual monomers
low degree of conversion
more residual monomers
most common acrylic polymer
PMMA
PMMA was introduced as –
denture base materials
