Boys with toys + two conclusions

The remains of a PET bottle

Twenty minutes of absence from the lab was enough time for two of my male colleagues to start experimenting with the dry ice leftovers, or better said, to start exploding bottles! Two useful conclusions were drawn, however, by pushing these poor bottles to their extremes.

Samples 31 and 32 didn't make it

Bottle type "6" (no.31), for example, was an overdosed sample sealed normally (no Teflon tape around the threads). In antithesis with case 8 and 9, where the same type of bottle was sealed with Teflon tape and exploded due to cap failure, here the cap stayed in place and the base bursted. Without the tape, the sealing was firmer and so the collapse occurred at the base of the bottle, which proved to be weaker than the walls. The failure of the base was intensified by the large quantity of inserted dry ice that was in contact with this surface, causing it to frost (this sample was not placed in warm water to accelerate sublimation). The temperature of the solid CO2 (-79 C) exceeded the minimum service temperature of the PET bottle (-58 to -38 C) and thus the base became brittle and incapable to withstand the internal pressure.

This test showed therefor that type "6" should not be excluded from the samples list (the PET surface itself is strong), but rather a new way of sealing the cap should be introduced, to prevent leakage. Furthermore, it indicated that special attention should be given during the sublimation of the dry ice in the bottles, so that frost is avoided.

Similar were the results from the rest damaged bottles that were collected from the lab's floor...