POLYSULFIDE ELASTOMERIC IMPRESSION MATERIAL:
First elastomeric impression material to be introduced, also known as mercaptan / thymol, it is a type of Rubber based impression material
- Base paste (white)
- Accelerator (brown/grey)
Available in 3 viscosities:
- Light bodied
- Medium bodied
- Heavy bodied
- Liquid polysulfide polymer 80-85%
- Inert fillers (titanium oxide, zinc sulfate, silica) 16-18%
- Lead dioxide 60-69%
- Dibutyl phthalate 30-35%
- Sulfur 3%
- Other substances (like magnesium stearate) 2%
- and deodorants
HS – R – SH ———-PbO2+ S—-> HS – R- S – S – R – SH + H2O
1) Setting time – 5-8 min.
- colder climate increases setting time.
- Drop of water accelerates the reaction.
2) Excellent detail reproduction.
3) Dimensional stability
- curing shrinkage – 0.45% due to continued reaction.
- Shrinkage due to loss of byproduct.
4) Permanent deformation – 3-5%
- highest amongst elastomers.
5) High tear strength – 7000gm/cm2
6) Good flexibility of 7%, allows elastic recovery of the material.
7) Hydrophobic- tissue should be thoroughly dried before making the impression.
8) Can be electroplated with copper.
- long working time.
- proven accuracy
- high tear resistance.
- inexpensive to use
- less hydrophobic
- longer shelf life.
- must be poured with dental stone immediately.
- potential for significant distortion.
- odor is offensive.
- messy & stains clothes.
- second pour is less accurate.