Well, the first thing I would do is try to determine if your heat press platens were coated with Teflon. Many of them are. Just look up your model on the internet to find out, or let us know what you've bought and we can tell you.
I figured that a heat press platen that is coated with Teflon is pretty much the same as a frying pan that is coated with Teflon as far as cleaning is concerned. So I went to Dupont's Teflon website and came across the following.....
"We recommend you use a non-abrasive cleaner such as Bon-Ami®, or a non-abrasive cleanser and a sponge, dobie pad, or other cleaning pad that indicates it is safe for use on non-stick pans. Check in your grocer's cleaning/detergent aisle."
More FAQs about Teflon can be seen at their
website.
It also seems that Teflon is very resistant to most chemicals, which I've learned from that site.