PET/PETE and autoclaving

[osp001]

For tissue culture, it is important to use products that can be autoclaved (121-123 C, 15-30 minutes). I have some old containers that I've been wondering what they were (they have no recycling logo or anything like that), and I suspect they're PET. I asked a few tissue culture people if they've ever used PET containers, and the only reply I got noted that they've melted in the dishwasher, which would presumably rule out autoclaving.

But Wikipedia (great source, I know) suggests the softening temperature (as gauged by the Vicat B scale) is well above that required for autoclaving, AT 170 c.

While I appreciate that PET bottles are more that PET, I would think it would be a major structural component of the bottle, and resist melting at "typical" dishwasher temperatures.

So, in short- any idea if PET plastic would deform under its own weight (i.e., no significant weight added by any contents) at up to, say, 125 C for 20 minutes? TIA.

 

[Demon3]

The HDT and Vicat will depend upon whether the PET has crystallized or not. This could explain the conflicting message you are getting.

Look up HDT of PET at

http://www.matweb.com

(free)

Make sure you look at non-filled PET as addition of filler to semi-crystalline PET will dramatically increase the Vicat and HDT.

For non-crystalline PET the HDT and Vicat will be just below the glass transition temperature, Tg, which you can look up through Mr. Google. I would do it but my dinner is calling.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[osp001]

Phew. OK; that makes sense.

Any idea how to tell whether this old (pre-recycling logo) container I have is made from polycarbonate or PET or something else? Alas, I no longer have a DSC available to me.

 

[patprimmer]

PC dissolves in aromatic or chlorinated hydrocarbons. PET does not. Test a small piece in methylene chloride.

If the part is clear the PET will be amorphous. If it is amorphous it will deform at about 90 deg C.

Even crystallised and glass fibre reinforced PET and PC both hydrolyse fairly quickly at 125deg C so they will become brittle and cracked after a few reuses.

How many hours at 125deg C do you require.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[osp001]

Autoclave time for disinfection is typically 15-30 minutes, so sub-hour, certainly. The main requirement is for clarity; water-clear polycarbonate is the standard for some applications. The old containers I have are water-clear, but they're certainly not made up to modern standards.

 

[Demon3]

PC stress cracks if you place a drop of acetone on it. I don't think PET will.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry