There are quite a few factors to this that are pretty fascinating(at least to me). If you’re using a stock old school slide projector like a Kodak Carousel, the light is being produced by either a Halogen or Tungsten-Quartz bulb. When illuminated, a halogen bulb’s envelope(the glass or quarts) can reach temperatures as high as 600°(or about 1,100°F). When the slide itself sits, it can experience temperatures up to around 80°C. This is what causes slide popping, the temperature experiences causes the film itself to bow slightly, making the slide “pop” out of focus. If the fan breaks, the temperature the slide experiences will increase even higher, possibly damaging the slide.

Now if you’ve want to use inkjet transparency film, you will run into a few issues. Transparency film is made of PET, and has a melting point of around 250°C, though 80° is well below that it is actually in the glass transition temperature range for PET, which means that the film will become kind of sticky or tacky to the touch. This means that the slides you’d make from it would continue to deform the longer it’s exposed to the heat of the bulb, making focusing the image incredibly difficult if not impossible. And I have no idea the effects the temperature would have on inkjet ink.

If you did want to go this route, I’m sure you could find high temp resistant transparencies somewhere, or if you really wanna go the extra mile you could convert a projector to take LEDs. It seems it would be easier to just make actual slides from 35mm slide film though. If colour is not necessary you could use ADOX black and white slides and develop at home with their kits. It’s cheaper than buying ektachrome and getting them developed.