[mandy_rh]

I am a medical student working on some experiments on synthetic plaster casts.
I am trying to soften a cured cast.  I have tried several things already and wondered if anyone had any suggestions.  I am not trying to unwind the cast just make it softer.


The two casts I have been working with have the following components:

cast 1: polypropylene polyol, diphenyl methane, di-isocyante prepolymer, methylene bisphenyl, silicone trace, synthetic rubber, polyester knit fabric and a polyethylene core.

cast 2: Diphenylmethane Di-iscocyante (MDI), Polypropylene Glycol, Polyethylene Oxide, Polyurethane prepolymer and Fibreglass.

Any suggestions of chemicals that may have a softening of the cured cast would be most helpful, if it is at all possible?
Also someone had suggested increasing the polyols in the cast, does anyone know how I would do this?

[fledarmus]

Once the cast has cured, there is very little that you can do to soften it. There are solvents that you might be able to add that would make the polymers swell up and possibly get a little more flexible, but I doubt you would want those next to the skin.

Your best chance for softening the cast would be to add components to your polymerizing mixture that were more flexible or that would reduce the areas of crystallinity in the polymer. For example, polypropylene glycol, since it has a pendant methyl group, packs to form a less rigid polymer than polyethylene oxide - increasing the proportions of polypropylene would increase the flexibility of the resulting cast. You could also add plasticizers or add more flexible fillers.

Without knowing the proportions of the components in the mixture and the structure they are forming, it is very difficult to give suggestions.

[mandy_rh]

Thanks