Spray on coating to stop heat transfer?
Spray on coating to stop heat transfer?
(OP)
We use metal frames to hold the edges of plastic sheets while they are heating in large ovens prior to a vacuum forming process. The heat is absorbed into the plastic and the plastic gets heated faster near the frame and is thus thinner at the end of the heating cycle. This thickness variation is a problem. Is anyone aware of a spray on coating that will stop or slow the transfer? Or perhaps a material to make the frames out of? The max heat is 550 F. Thanks very much.





RE: Spray on coating to stop heat transfer?
corus
RE: Spray on coating to stop heat transfer?
Heat transfer from oven floor to metal frame via conduction, and then from frame into plastic via conduction is probably much higher than the convective heat transfer at the center of the plastic sheet.
Cheap and simple first thing to try is get the racks out of direct contact with the oven. Just some simple spacers from any suitable insulating material would do the trick.
If that doesn't work, then some sort of ceramic for a frame probably would. I found this with Google, but there are many others:
http://www.zircarceramics.com/index2.htm
RE: Spray on coating to stop heat transfer?
This problem is that the portion that is in contact with the frame has a much higher thermal transfer coefficient to the oven that the rest of the material.
You could also try to design the frame to minimize contact area with the material being processed, e.g., use needle-like projections to minimize the contact area and increase thermal resistance.
TTFN