Backing material for a one-shot mold?

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A user seeks advice on how to support a fragile metallic cylindrical mold during injection molding of a thermoplastic polymer at high pressure (150 MPa), which exceeds the mold's rupture stress. The user is looking for a removable backing solution that can be dissolved with a solvent and does not require temperatures above 150°C for removal. Initial thoughts on using epoxy were dismissed due to the need for heat to remove thermosets. Suggestions include using a two-part firm silicone, commonly used in dentistry, which provides temporary support and can be easily removed after the process. Concerns are raised about the high injection pressure potentially damaging other materials, such as cement, and questions are posed about the necessity of using the current mold versus creating a stronger one from more durable materials. Further inquiries about the thermoplastic type and mold dimensions are also made.
PhilMeagher
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Hi,

I currently have a fragile metallic cylindrical mold (wall thickness ~1 micron) into which I want to injection mold a thermoplastic polymer at about 150 MPa (3.14 Mlb/sq.ft). The mold and polymer together will form the final part. However, such injection pressure far outstrips the rupture stress of the mould; so I'm looking for some sort of backing which I could use to support the mold while injecting; but which I can then remove afterwards - ideally via some kind of solvent.

Unfortunately, due to the nature of the mold material, I can not use anything which requires a temperature >150°C (>300°F) to remove it.

Initially I considered some sort of epoxy, but it seems the only way to remove a crosslinked thermoset is via heat; and that really doesn't suit at all.


Any suggestions?



All the best,

Phil
 
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How about a 2-part firm silicone? It's used in dentristry, is pretty inexpensive if you hunt around, and gives you a few minutes of very soft pliability (warm plasticine) before setting to the firmness of a shoe sole in under 10 mins. It'll provide 1-time support and slip off a treat when you're done.

http://www.amazon.com/dp/B007DKSH9Q/?tag=pfamazon01-20 for instance
 
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I don't know 150MPa is really high. As in you'd have to be careful even with cement.

http://www.theconcreteportal.com/images/constrelation/stressstrain2.JPG

21755 psi. That would break apart a cement mold. Is there a reason you have to use this mold? Sounds like recreating it out of stronger materials would be better.

Normally large volume plastic molds are made from machined steel.
 
Do u want to use a solvent to lower viscosity of melt ? what is the radius of the mold?
which is the thermoplastic ?
 

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