There are several temperatures at which Glue Sticks (the sticks used in the glue gun used to secure PCB components) will melt at.
It depends on the colour of the stick (glue) to say what temperature it will melt at.
It also depends for how long you will apply 80 deg C for (I assume you are doing a soak test).
I would suggest that (if possible) you could scrape some glue and then melt it on tissue paper (or some other type of paper) and note the melting temp.
If your PCB is a military PCB you should be ok but I would not take risk with a comercial board.