Letter 19254

Problem with Black Delrin Mold

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Hi,

I use a black Delrin mold in a cell biology lab. The mold is used to make a gel that has cells in it. The reason we chose Delrin was because of it's very unreactive. We had no problem until recently when all cells dye when poured in the mold. If seems that there is something in the delrin or bound to the surface that is killing the cells. There is no visible chalking or corrosion and I keep scrubbing it to clean it. In the past, I have left the delrin in dilute bleach solution or alcohol solution to sterilize it. Does anyone know if this could be the cause of my problem and if so how can I possibly solve the problem? Is there some biologically friendly coating that I can put on the Delrin?

Thanks,

Morad Askari
University of Pittsburgh - Pittsburgh, PA, USA

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Probably, some chemical permeated into the Delrin (acetal polymer) and leaches out into the gel. This material is not recommended for bleach solutions. Try boiling in DI water to leach out the chemical, and use hot DI for future sterilizations. Delrin isn’t recommended for use above 185 F, so this is a bit of an experiment.

Ken Vlach
- Goleta, California

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Hi-

One of the components of acetel (Delrin) plastics is formaldehyde. When you machine Delrin, the shavings give off a strong odor of formaldehyde. The MSDS (material safety data sheet) also shows formaldehyde emission when the plastic is overheated or burned. Perhaps in your scrubbing you have released enough formaldehyde to cause your cell cultures to die.

Best regards,

Tony Archer
- Provo, Utah

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If you can get a block of solid PTFE (Teflon (r)) or UHMW PE, (ultra-high molecular weight polyethylene) for your cell culture molds, that might be even better than acetal /Delrin (r). Both of these plastics are fairly friendly to machine and survive much higher working temps.

In fact, bulk PTFE is so nice to work I've carved it with a pocket knife! Hope it isn't too soft. Filled PTFE may be an option, too.

T. Dowling.

Thomas W. Dowling
- Metuchen, New Jersey

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