Elastomeric impressions Flashcards
What kind of dimentional stability does putty have?
High
What kind of dimentional stability does light bodied have?
Low
If something has high dimentional stability what kind of detail does it have?
Poor detail
What 2 pastes are in polysulphides?
Base paste (White) containing SH groups and Tio2 Catalyst paste (dark brown)
What kind of setting reaction is a polysulphide material?
Condensation polymerisation
What kind of tear resistance does polysulphide have?
High
Silicone condensation rubbers have what kind of setting reaction?
Cross linking of polydimethylsiloxane chains (increasing elasticity and viscosity)
What is the catalyst in the silicone condenstion rubbers??
Tin
What is the cross linking agent in the silicone condensation reaction?
Alkyl silicate
What is the by production in silicone condentation reaction and what problem does it cause?
Alcohol (ethanol) making it volatile meaning it will evaporate in normal temperatures therefore it must be poured asap
Is sillicone rubbers hydrophobic or hydrophillic?
Hydrophobic
Silicone rubbers (Addition) come in 2 pastes- what is in the first paste?
Filler
Liquid silicone prepolymer
Platinum catalyst
What is in the second paste in the addition sillicone rubber reaction?
Filler
Liquid sillicone prepolymer
polydimethylsiloxane prepolymer
What initiates the Addition polymerisation reaction in the sillicone rubbers?
H2 is left wandering so it interacts with the platinum catalyst creating the platinum catalysed addition polymerisation reaction.
What kind of setting reaction occurs in polyethers?
Ring opening addition polymerisation
