Saturday, June 17, 2023

what is the most unfavorable imp material by the patient due to bad taste.. polysulfide



what is the most unfavorable imp material by the patient due to bad taste:

  • a- agar
  • b- silicone
  • c- polyether
  • d- polysulfide***

polyphenyl sulphide:

PPS (polyphenyl sulphide) phenylene polysulfide was introduced in 1968 and was initially used primarily in aircraft construction.
The PPS, developed by Dr. H. Wayne Jr. Hill and Mr. James T. Edmonds Phillips Petroleum Co., was commercially launched in 1973 by Phillips under the name of Ryton, whose patents became public in 1987.

crystalline polysulfide:

PPS is a crystalline polysulfide formed of a chain of benzene rings joined together by a sulfur atom. It is obtained by reacting paradichlorobenzene with sodium sulphide in a polar solvent, such as N-methylpyrrolidone, stable at the high temperatures necessary for synthesis and solvent both intermediate oligomers.

The directly obtained product is a low molecular weight PPS, well suited for use as a coating. However, to mold it, the PPS must be heated in oxygen to obtain a higher molecular weight. This heating also makes it possible to obtain a crosslinked PPS.

The PPS can be in different forms:

  • powdered, especially for coatings;
  • crosslinked, of improved thermal and dimensional stability, for coatings and injection;
  • linear, one-step product with improved impact resistance for compounds for injection;
  • modified, especially for extrusion of films.
The PPS is most often reinforced by glass fibers, generally 40 to 65%, carbon fibers, or loaded with mineral fillers, talc ...