Heat-Cure Acrylic Resin Processing: From Mixing to Final Stages

Manipulation Of Heatcure Acrylic Resin

Write about manipulation of heat-cure resin in detail.
Answer:

Manipulation of Heat-cure Resin:

Mix the correct proportion of polymer and monomer, i.e. polymer/monomer ratio is 3 to 3.5/1 by volume or 2.5/1 by weight.
First, the liquid monomer is poured in a thick, clean glass jar and then the powder is added slowly to it.
After all powder is added the mix is stirred and vibrated thoroughly so that mechanical mixed pigments and dyes are dispensed evenly throughout the material.
On completion of stirring, a light lid must be placed on the glass jar to prevent evaporation of the monomer.
When polymer and monomer mix is allowed to stand in a closed container it undergoes physical changes due to the interaction of monomer to polymer.

Heat-Cure Acrylic Resin Processing From Mixing To Final Stages

The following are the physical stages:

Stage I: Wet Sand Stage; Polymer gradually settles into the monomer forming a fluid incoherent mass.
Stage II: Sticky Stage: Monomer attacks the polymer by penetrating into the polymer. The mass is sticky and stringy (cobweb-like) when touched or pulled apart.
Stage III: Dough or Gel Stage: As the monomer diffuses into the polymer, it becomes smooth and dough-like. It does not adhere to the walls of the jar. It consists of undissolved polymer particles suspended in a plastic matrix of monomer and dissolved polymer. The mass is plastic and homogenous and can be packed into the mold at this stage.
Stage IV: Rubbery Stage: Monomer disappears by further penetration into the polymer for evaporation. The mass is rubber–like, non-plastic, and cannot be moulded.
Stage V: Stiff Stage: Formed mass is totally unworkable and should be discarded.