Bite into it


Concepts Shown:

Crosslinking polymerization


automixing system, penny mold, mold with 50 and 70 um impressions, polymer mold of jaw (green and orange).


Explain function and relation of materials to crosslinking polymerization and thermosetting polymers.


Polymerization: The process of monomer units becoming chemically linked together to form high molecular weight molecules. Addition reaction: Adding monomers together without by-products. Ionic polymerization: An addition reaction that proceeds by ionic reactions. Polyvinylsiloxane impression system: It is used to make impressions of dental features. It comes in different consistencies and colors. It has low dimensional change, short working time, and high stiffness. It is on ionic addition polymerization reaction. 2-part system: base and catalyst base: moderately low molecular weight silane containing hydrogen terminal groups catalyst: low molecular weight polymer with vinyl terminal groups and chloroplantinic acid catalyst. [eq]. Result: Cross-linked, thermosetting, high molecular weight rubber. Crosslinking: Tying together polymer chains. Equipment: Base and catalyst contained in two separate cartridges in auto-mixing gun. Plungers extrude equal amounts of past when compressed. The two pastes are folder over each other and exit the tip in a mixed condition with minimal air bubbles. [eq]. Polyvinylsiloxanes can reproduce .02 mm lines. Included are 50 um and 70 um lines replicated by the polymer. It has low deformation, low strain in compression, minimal flow, and moderate tear strength. Comments: Plaster cast of teeth is fragile. Handle with care.


Marcia Muller

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