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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
a thought occurs, i maybe wrong so everybody check my logic and reasoning on this one....
mylar film (BoPET, which is a form of highly organized polyester.) is chemically resistant to most chemistry, with the exception of Alkali's.
what if i were to take mylar films, soften the outer surface with sodium hydroxide then stack them for many kV's of thickness, with the layers saturated in polyester liquid resin/catalyst?
would they merely peel apart when fully cured?
if a 0.0045" thick sheet could hold off 3.8kV x 4.5 = 17.1 kV, then 7 layers would break down at 120 kV.
if true, then 0.038" would definatly hold 40kV form long a duration.
Is this a good idea? or am i just out-smarting my self again?
Registered Member #3883
Joined: Fri May 13 2011, 06:30PM
Location: Norway
Posts: 87
It can be done. I recently made a few credit card-style caps from aluminum foil and hot-laminating pouches. I used a combination of the hot-glue on the pouches and epoxy, and while they could be pulled apart with force they didn't peel apart by accident.
Most of them failed pretty fast, but a few seems to work quite well. I would recommend a vacuum pump and a press to get a tight air-free stack.
Registered Member #3883
Joined: Fri May 13 2011, 06:30PM
Location: Norway
Posts: 87
It shouldn't peel with normal handling, but if you try to pull the layers apart they will separate. Takes a bit of force though, they don't just fall apart.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I think you're outsmarting yourself because given the available space I'd expect surface tracking to be more of a problem than dielectric strength.
Afterthought; assuming that this is for >= 10's kHz very high voltage between winding layers at high frequency will require a low loss dielectric I think. I'd guess around (number of layers) x (inter-layer capacitance) x (Vrms per layer)squared x 2.pi.F x DF Watts would be dissipated in the dielectric. DF for Mylar is around 1% I think. (DF=0,01) (probably a better approximation should be available)
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615
hitting mylar (PET) with an alkali will depolymerise it into terephthalic acid and ethylene glycol. This is not the same as solvent softening of a plastic, where the intact polymer partly absorbs some solvent.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
2Spoons wrote ...
hitting mylar (PET) with an alkali will depolymerise it into terephthalic acid and ethylene glycol. This is not the same as solvent softening of a plastic, where the intact polymer partly absorbs some solvent.
yes i realise that, and thats what i wanted but it didtnt work with or without the NaOH.
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HV insulation thoughts... Mylar, Polyester resin and alkali's...
