There are two basic types of glue systems being used on foam pads (that I know about):
Polyurethane Reactive (PUR)
Heat Activated
The PUR glue process bonds the Velcro to an entire sheet of foam in the foam manufacturing process, whereas the heat activated glue backings are applied by a press (the glue is already on the Velcro disk, heated and pressed on).
In general, the PUR glue process is stronger that heat activated and holds up better to washing and is not effected by polish saturation. I'm not going to point out who uses what. You can look at a pad and figure it out... is it a disk, or does the Velcro cover the entire back of the pad?