I know poly-ethylene is safe, but dont know about poly urethane. But I'll happily vape diketones; so, go figure.
But does it actually release diketones? I am not having luck finding anything
kterka24 is quite right; I meant that I'll vape flavors which contain diketones. I did find this warning from http://ecologycenter.org/factsheets/adverse-health-effects-of-plastics/ "Can release toluene diisocyanate which can produce severe lung problems". now this is from exposure to polyurethane in couch cushions, but now that I've read this I'll be more cautious of the plastics I use.
I use them for simple syrups in my home bar, and they work fine. They're actually food-grade, but Harbor Freight is practicing CYA. I just wouldn't put anything acidic in them.
How do you know they are food grade if they label says not for food?
I just don't put acidic juices in them.
Also may want to make sure they won't melt in a dish washer.
What are some acidic juices?
May be just me but I wouldn't use them. I personally use mason jars for storing large(800 mil) batches of juice. They are a pain to pour from into 30mil bottles but with some practice I seldom waste any now.
I use the picnic/restaurant stye ketchup and mustard squeeze bottles for my VG, PG, and VG Nic. You can find them in Walmart for about a buck a piece.
Store them in glass bottles. Some users have mentioned that plastic allows flavor to escape. Don't know that for a fact, but I did search around for good bottles and really the best I could find were these 200ml vials which are popular among DIYers in my country. And really, you can't beat the price (IIRC 0.60€/unit) I'm sure you can buy something similar, you'll just have to drink the contents first. Look for it in the bottled water section.
Look for an identification code on the bottom. Wouldn't be 1, but a 2 or 4 would be usable. Anything else, or if there is no code, I'd be wary. If they are actually polyurethane, it'd be a 7 if marked.