Thermoforming Rohacell RIMA51

Do any of you guys know what the rubber diaphram material might be made of in this video (see 1:07 – 1:12 in the video)?

I need to thermoform some ¼ inch Rohacell RIMA51 core material to the shape of my new landing gear doors and will be using the gear door molds as the form. Basically, I need to figure out what to use as the diaphragm material and as well as a quick vacuum source (shop vac??) that will evacuate the atmosphere and form the foam to the mold before it cools.

The molds (when finished) will have a fairly large flange so my plan is to build a rigid frame with a rubber diaphragm that can be quickly positioned on the mold (will seal against the flange). The shop vac (if sufficient) will be plumbed into the frame.

Step 1: Heat the Rohacell to 419 F (don’t know how critical this temp is… in other words, is this the minimum thermoforming temp? Will it damage the Rohacell if heated beyond 419F?
Step 2: Place the heated Rohacell in the mold and quickly suck down the bag material to form the foam and allow to cool.

Rohacell thermoforming document:
http://www.rohacell.com/sites/dc/Downloadcenter/Evonik/Product/ROHACELL/product-information/ROHACELL%20Thermoforming.pdf

Video:
[ame=“http://www.youtube.com/watch?v=j_9xr2aAjjw”]http://www.youtube.com/watch?v=j_9xr2aAjjw[/ame]

I take it RIMA is different than the Rohacel IG?