What's a good consumer brand thermal tape?

Question:I just installed a portable air conditioner into a window which slides open and closed vertically. The window slides back somewhat if I try to create a tight seal with the vent attachment in place, so I need an effective way to seal up the gap and prevent air flow around the window kit. Is there a thermal tape on the market and readibly available for a job like this, or should I try something different? I want to stick away from foams and permanent solutions since this is a rental apartment and not a privately owned house. Thanks!

Answers:
the shiny silver duct tape is a special quality / high temp tape for furnace & air conditioning applications
it the best tape for you.