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For at least several years I'be been storing various chloride solutions with methanol as a solute in Nalgene containers, which I believe are made from high density polyethylene (HDP).

But recently two of these containers had failed. On these containers the plastic seems to have hardened and cracked (see photographs below).

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The other containers still seem to be pliable, in good shape. I thought that HDPE would be resilient to methanol and provide indefinite storage. Was I wrong? Or is it perhaps the methanol in combination with the particular salt that led to failure of the container? The failed containers had strontium and potassium chloride solution. Others like lithium, sodium and copper solutions are OK.

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HDPE should be fairly stable to MeOH, but it crazes in the presence of UV, when subject to oxidization or to environmental stress.

Since only some of the containers failed, were those subjected to more UV (e.g. placed by windows or at the front of a shelf in a well-lit location), placed near oxidizers, such as bleaches or were they subject to higher temperature, which would have caused the methanol liquid and vapor to expand, increasing pressure and stressing the container?

My experience has also been that apparently identical polyethylene containers have different failure rates, perhaps due to subtle differences during synthesis or manufacture.

Given polyethylene's tendency to craze, it might be best to use another type of container for long-term storage.

Note, though, that ~50% MeOH/water solution used for windshield antifreeze is usually shipped in polyethylene containers. Though the water lowers the vapor pressure, perhaps the UV susceptibility is addressed with additives.

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  • $\begingroup$ The containers may have been exposed to higher than normal room temps this last summer, and correspondingly pressure, but ALL of them were. Perhaps these two were at higher pressure. But there is a marked difference in the brittleness of the failed containers compared to the ones that didn't fail which are more pliable. Which leads me to believe failure was more due to change in material property than stress itself. It also occurred to me that these containers were all reused and maybe there was something in these particular containers that led to brittleness. $\endgroup$ – docscience Dec 30 '17 at 18:28
  • $\begingroup$ In any event whether stress or material change, this gives impetus to regular, periodic inspection of ALL chemical storage containers, especially in the case of risking release of hazardous substances. $\endgroup$ – docscience Dec 30 '17 at 18:30
  • $\begingroup$ @docscience, I strongly agree: do inspect HM storage regularly. Steel shelving can be corroded by acid vapors, bottles can crack as contents crystallize and there are many other failure modes. It is also a good opportunity to rotate usage, so oldest, most likely to be weak or contaminated, are used up or discarded. $\endgroup$ – DrMoishe Pippik Dec 30 '17 at 22:40
  • $\begingroup$ Once stored metallic calcium in what I thought was an airtight glass container. The oxidation expanded internal volume and shattered the jar. $\endgroup$ – docscience Dec 31 '17 at 16:56
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PE has a strong tendency for cold flow under (esp. extensional) stress. When it yields, it recrystallises, becoming more brittle. The crack position at the edge, where the highest local stress occurs, would support that this is what happened.

Different PE types (LDPE; LLDPE; HDPE; and more subtle differences in branching, comonomer content etc.), slightly different temperature, pressure, filling height, previous UV exposure, etc. made the difference for your containers. Once it's started, the crazing is likely to continue, because the anisotropic density change during recrystallisation produces even more local stress in the material.

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