If the cover that goes on top of the coil in your picture is made of standard plastic, that is a terrible design, and could possibly melt unless it is made of some temperature resistant material.
All the ones I have seen were metal, because coils get hot, like 600f hot. Standard Plastic melts at 338f.
If your RDA is the one in the video below, the "plastic" your referring to is made of PEEK, the melting point for Peek is 343c which is like 650f. Can a coil reach 650f, well according to this scientific chart (2nd link) below, I would say dry firing a coil looks bright red, slightly orange to me. The chart says bright red, slightly orange is 730c. The only time that would happen is if you dry burn the coil, which would ignite your wick (FIRE). Also take into consideration the color of the coils when WET, they are nowhere nearly as hot wet as they get dry, as the liquid cools them substantially. The other thing to consider is the space between the coil and the Peek material itself. This gap (you aren't building your coils so they can TOUCH the peek insulator are you?) would also provide some cooling.
If I were you I would disassemble the RDA, and check the inner surface of that Peek insulator in the RDA and see for myself what they look like. If they look burnt, I would surprised, unless I had been dry burning it, in which case I would be vaping charred cotton long before the PEEK started to smolder.
Thermal radiation - Wikipedia, the free encyclopedia
