Condensation silicones Flashcards
1
Q
base paste
A
- polydimethyl siloxane
- colloidal silica or micro sized metal oxide filler:
- putty viscosity 60-70%
- medium viscosity 35-75 fillers
- low viscosity 5-15
- color pigments
2
Q
base paste
A
- polydimethyl siloxane
- colloidal silica or micro sized metal oxide filler:
- putty viscosity 60-70%
- medium viscosity 35-75 fillers
- low viscosity 5-15
- color pigments
3
Q
accelerator paste
A
- alkyl silicate like orthoethyl silicate(cross-linking agent)
- stannous octoate-catalyst
4
Q
setting rxn
A
- condensation rxn
- crosslinking bet orthoethyl silicate and dimethyl siloxane
- exothermic 1 deg increase
- ethyl alchohol forms byproduct for shrinkage
- 8-9 min
- mixing 45 sec
5
Q
advantages
A
- adequate working and setting time
- pleasant odor no staining
- adequate tear strength
- better elastic properties on removal
- less distortion on removal
6
Q
advantages
A
- adequate working and setting time
- pleasant odor no staining
- adequate tear strength
- better elastic properties on removal
- less distortion on removal
7
Q
accelerator paste
A
- alkyl silicate like orthoethyl silicate(cross-linking agent)
- stannous octoate-catalyst
8
Q
setting rxn
A
- condensation rxn
- crosslinking bet orthoethyl silicate and dimethyl siloxane
- exothermic 1 deg increase
- ethyl alchohol forms byproduct for shrinkage
- 8-9 min
- mixing 45 sec
9
Q
other characteristic
A
- excellent detail reproduction
- high curing shrinkage
- permanent deformation 1-3%
- tear strength: 3000 gm/cm lower than polysulfides
- stiffer and harder than polysulfide
- hydrophobic
- electroplated w/ silver and copper
- shelf life: less than 2 years
10
Q
advantages
A
- adequate working and setting time
- pleasant odor no staining
- adequate tear strength
- better elastic properties on removal
- less distortion on removal
11
Q
disadvantages
A
- adequate accuracy if poured immediately
- poor dimensional stability
- potential for significant distortion
- slightly more expensive
