The reflux will not happen with this device if, when extended, there are ribbs present where liquid can collect.
It will act as a steam collection device requiring an occasional shake.
As for the material, well it is made for a sink. Most likely the tub type you would see in a shop or in an art shop. I installed on at a friends art studio once. Have you ever heard or read here on the hive or elsewhere anyone complaining that the pipes under the sink that they dump shit in giving out? Now before I get verbal lashing, I do not condone such sensless polluting but we know it happens.
Try a few tests. If it has no metal on it then put it on a bolle in the micro w/water in it or in a bowl of water in the micro. Bring to boil remove and test integrity. Water go's beyand the boiling tem in the micro. Then acid test it. Like i said though I'm SURE it will work. It apears to be heavier than a punch ballon. BTW ever notice how a ziplock bag can hold up to chems for days! To bad they can't handle heat.