LDPE source and thickness

I would like to make rolled caps, and I'm looking for LDPE sheets. I checked
Mcmaster-dot-com, and they have 1/16'' and 1/8'' which is 62.5 MIL or 125 MIL. I
read somewhere that the best thickness is 90 MIL, which is impossible to
obtain with these thicknesses.
But I read somewhere that LDPE would resist 1200V/MIL, which means that a
62.5MIL sheet would resist a 75000 V tension. My xformer is rated 12KV/30ma.
Can I use the 1/16''-thick sheet for my caps??? And what do you use a vacuum
pump for in the building of a rolled cap???

Thank you for your help