PMMA Flashcards
what are the steps in acrylic polymerisation
activation
initiation
propagation termination
what occurs during the activation stage of acrylic polymerisation
activation of initiator to provide free radicals
what occurs during the initiation stage of acrylic polymerisation
free radicals break the C-C double bonds in the monomer and transfer the free radicals
what occurs during the propagation stage of acrylic polymerisation
the polymer chain grows
what is the initiator in heat cured acrylic powder
benzoyl peroxide
what is the function of the plasticiser in heat cured acrylic powder
allows quicker dissolving in the monomer liquid
what is the inhibitor in heat cured acrylic powder
hydroquinone which prolongs shelf life - reacts with any free radicals produced by heat
what is the function of the co-polymers in heat cured acrylic powder
improves the mechanical properties - particularly cross linking of the polymers
why is efficient polymerisation vert important in acrylic heat curing
the efficient polymerisation gives high molecular weight polymer which in turn gives good mechanical properties
is acrylic non-toxic and non-irritant
yes, non-irritant if no monomer is released but a few patients are allergic
what does high hardness and abrasion resistance qualities of acrylic mean
it retains a good polish, some wear
does acrylic have high or low thermal activity
it has low thermal activity which is poor
what is the advantage of acrylic having low density
it’s lightweight in the patient’s mouth but need to increase bulk to overcome poor mechanical properties
does acrylic have a high or low softening temperature
high - which makes it okay to ingest hot fluids but do not use boiling water for cleaning
how is benzoyl peroxide activated by promoter in self curing acrylic
tertiary amine in liquid
what is the promotor in self cure acrylic
dimethyl-para-toluidine
is the temperature of self cure acrylic lower or higher
lower which means less thermal contraction and better dimensional accuracy
why is the chemical activation of self cue acrylics less efficient
more unreacted monomer which acts as plasticiser, reducing transverse strength and compromising biocompatibility
is there more unreacted monomer when acrylic is self cured or heat cured
self cured
does the acrylic fit the cast better if its heat cured or self cured
self cured
what rubber toughening agent is added in an attempt to strengthen acrylic
butadien styrene which stops crack propagation and long time fatigue problems
what are pour and cure resins
similar to self cure but have smaller powder particles - have good fitting but poor mechanical properties
what components are in light activated denture resins
urethance dimethacrylate
what are alternatives to polymers
nylons and vinyl polymers and polycarbonates
