Chemgineer
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Storage of pine oil and beta pinene.
I distilled some turpentine a while ago and ended up with alpha and beta pinene plus some heavier pine oil.
I've been storing the beta pinene and the oil in 2 hdpe plastic bottles, both of them have now sucked the bottles in permanently like there is a
vacuum.
I am wondering if this is due to pressure changes due to expansion of the liquids or if the 2 products are reacting with the hdpe?
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Sulaiman
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I assume that oxygen has combined with the contents.
you could test for reduced (not necessarily zero) oxygen concentration in the air in the bottles.?
(the classic 'burning splint' burns less intensely)
PS who has splints?'
[Edited on 9-3-2025 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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Chemgineer
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I will transfer it to a glass bottle but was just concerned about a vacuum on the glass if it was being caused by temperature/volume changes.
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Sulaiman
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IF the negative pressure is/was due to oxygen consumption
then 'worst' vacuum will be -0.2 atmosphere (20% oxygen)
which I think would be ok for 1 litre glass bottles.
PS the pressure on the glass is independent of the relative volume of the head space.
(if all oxygen is consumed from atmospheric air, and the bottle was sealed.
Edit: some trivia that I just calculated::
1 litre air is 20% of 1/24 mole = 0.008333 mole = 0.27g of O2 = enough to oxidise 0.1g of carbon to CO2
[Edited on 9-3-2025 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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teodor
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Probably all terpenes have this feature. They eagerly dissolve nitrogen. I don't know the mechamism, but it is definitely nitrogen which disappears.
@Fery was the first on this forum as I am aware of who made this observation. He paid my attention once that the volume of air which disappears from a
bottle corresponds not only to oxygen.
[Edited on 10-3-2025 by teodor]
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Deathunter88
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Hydrocarbons vapors diffuse through HDPE pretty easily and also soften it over time. For hydrocarbons with a low vapor pressure (like terpentine,
kerosene, mineral spirits), you'll form a partial vacuum in the bottle as more vapor is lost than can be replaced by the vapor pressure of the liquid
itself. This, combined with the softened HDPE, will cause the bottle to collapse.
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Chemgineer
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Quote: Originally posted by Deathunter88  | | Hydrocarbons vapors diffuse through HDPE pretty easily and also soften it over time. For hydrocarbons with a low vapor pressure (like terpentine,
kerosene, mineral spirits), you'll form a partial vacuum in the bottle as more vapor is lost than can be replaced by the vapor pressure of the liquid
itself. This, combined with the softened HDPE, will cause the bottle to collapse. |
Thanks for the great explanation, on that basis my products should still be fine and will store better in glass.
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Fery
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My both 5 L plastic barrels with alpha pinene are completely without air after few years. Not only O2 consumed but also inert N2 disappeared and walls
are bent inwards. If I turn them upside down, there is even no single air bubble under the lid. Very strange and I cannot explain. There should be at
least some argon in a tiny bubble which is almost 1% of air.
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teodor
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| Quote: Originally posted by Chemgineer | | Quote: Originally posted by Deathunter88 | | Hydrocarbons vapors diffuse through HDPE pretty easily and also soften it over time. For hydrocarbons with a low vapor pressure (like terpentine,
kerosene, mineral spirits), you'll form a partial vacuum in the bottle as more vapor is lost than can be replaced by the vapor pressure of the liquid
itself. This, combined with the softened HDPE, will cause the bottle to collapse. |
Thanks for the great explanation, on that basis my products should still be fine and will store better in glass. |
After some time you'll find the vacuum formed in the glass bottle as well. So, probably you'll find the explanation about diffision is not
satisfactory. Try.
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walruslover69
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This is likely due to the terpenes swelling the plastic. Many oils and organic compounds can do this to plastic. Some of the solvent is absorbed into
the plastic and it expands. As the plastic expands it either needs to bulge inward or outward, usually inward. Whenever I order terpenes from a
supplier, they ship them in either glass or aluminum bottles.
This is also why many terpenes can be so hard on seals/gaskets. imagine an O ring expanding and not being able to fit it's original circumference
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