I agree with Patrick

There is some useful information online here: http://www.bd.com/vacutainer/faqs/

And here: http://www.bd.com/vacutainer/pdfs/VDP40161.pdf 

I don't know about the tube glass, but regarding the sample there would be a lot of cell lysis, including red blood cells, which would mess up your samples pretty badly. For most applications you would want to separate the plasma from the cells, and/or the buffy coat from the RBC's, before freezing stuff down. 

Thanks to all who gave their suggestions. I gave it a try and the tubes stored at -80C did not crack after the first freeze thaw cycle. However, I noticed that when the same tubes were freeze thawed a second time after a few months, they definitely cracked and the tubes did leak when the samples melted at room temperature. So it's safe for the first freeze thaw, but if you want to reuse the remaining sample, chances are the tube will not withstand a second first freeze thaw cycle.

In case anyone else comes to this question, we had some blood samples frozen in a  -20C freezer for about 2-4 years. Some of the tubes cracked, but not all of them (some of the blood turned to powder and most was unusable). If anyone has tried putting them into the -80C, I'd be curious to know how long they lasted. 

We have since started using specific plastic tubes for freezing samples at -80C, but they haven't been there long enough for me to say how they hold up over time.

Linda Koshy and Marília Bonelli - thanks for sharing your experiences. Did you use glass or plastic BD EDTA tubes?

Thanks!

I had used plastic BD EDTA Vaccutainers.

The ones that cracked in the -20C freezer (after 2+ years) were glass EDTA vacutainer tubes.

Thank you for this discussion and sharing your experiences.