I work in the plastics industry.
There is no problem with the plastic bottles used for powders, they will seal tighter than a tin can and there is no porosity of the plastic that will allow moisture to gain access to the inside of the bottle.
Those bottles have an added anti-static compound as part of the High Density Poly Ethylene matrix the bottle is made from.
Matter of fact, direct discharge of static electricity won't ignite a free standing pile of powder.
If there was an issue of "oils" excepting ambient moisture while stored in plastic containers, the plastic may have been susceptible to the oils or there was an issue with the spouts/lids for the containers. If they where "gallon" plastic containers, my guess is they where like a jug for anti-freeze that have a paper seal inside the cap,, that seal probably gave out/ rotted because of the oil's properties.
This is not the case with plastic powder bottles.
It's always interesting to see folks concerned with this plastic bottle stuff, when the same folks will use the same plastic containers to store gasoline in their garage without a second thought.
That's not directed at you David, it's just that this topic is notorious for rearing it's head every few months for years now.
