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Need smallish quantity of Solventless Polyester Resin for coil winding impregnation

Cismontguy

Cismontguy

Aluminum
Joined
Feb 28, 2007
Location
Earlysville, VA
Hello Forum,

I need to make some custom magneto coils for a job. I have been trying to find a source for solventless Polyester Resin that you use to impregnate the coils after winding. Dolph CC-1305 is often used because it does not require a catalyst and you can dip your coil in a container, pull a vacuum to get the trapped air out of the windings and then pressurize the container to get full resin impregnation. BUT Dolph says they only have 55 Gal drums of the stuff. I do not need that kind of quantity! 1 Gallon would be fine for me.

Does anyone on the forum know of another brand of Polyester Resign that does not use a Catalyst to cure? I am in the US so I would prefer a US supplier.

Thanks,

Cismontguy
 
What you refer to as solvent is most likely a catalyst. Instead of a catalyst, you can heat cure most if not all resins. Get a small container of resin and heat it to 200-250F. It should cure. Same goes for epoxies.

Tom
 
Hello Tom,

Thank you for that information. It is very helpful. I did not know that. I do know the Dolph resin is supper low viscosity, so it easily flows into the coil under pressure. I expect I would have to find an equally low viscosity resin for this to work. I did try calling 3M and the sales person hung up on me when I explained what I was trying to do?
 
I did this years ago. Then I used just a standard fiberglass resin. I first waxed the plug that was mounted in a lathe. Then wrapped the plug in wax paper, coated the wax paper with resin and wound the coil on top applying a coat of resin on every wire layer. I tied off the wire ends turned the lathe back on at 30 rpm and slowly poured more resin on the coil to level the surface. I left the lathe running until the resin cured. Worked great. No air bubbles. Clear as glass. The application was 3" diameter coils about 4 inches long running inside 150 lb permanent magnets and used as a read/write head beam driver. The head beam was about 5 foot long with 128 head assemblies and a driver coil on each end. The head beam travel was about 2 ". The head beam ran in between two 2 foot diameter iron mass memory drums. These coils operated under very large acceleration rates. Maximum end to end latency time was about 68 msec.
 
WHEn I had to pull a few leads out a bit and solder on new wires inside a motor I just brushed on regular furniture type varnish. Several coats. I was not needing to get it in deep.
Bill D
 
The Dolphon cc-1305 is nominally available in 1 gallon containers for about $165. I guess you could search around for a gallon can. It may be that in your search, you find a unicorn first. Note that there's a pretty involved preheat/cool/dip/vacuum exposure/pressure (6-8 atmospheres!) exposure, then a 4 hour bake at 150°C. May be required if this is an aerospace application, but a lot of work.

If this is not a product NASA is using in its SLS Block 2 heavy launch vehicle you could try a product like Q-dope. It's solvent based (about 75% MEK) but you could probably draw vacuum down to about 2 psi or so without it bubbling. But it doesn't form a solid matrix - the MEK evaporates. You'd need a trap for your vacuum oven though, or you'd toast your pump's oil.

The Dolphon product is a polyester resin catalyzed by a dibenzyl peroxide. You could look around and find a polyester resin and buy a peroxide catalyst if you are really set on polyester. If you are willing to use a two-part epoxy, Epoxyseal 9000 has low viscosity and is made for potting electronics. It has a pot life of 45 minutes so you could mix it, dip your coil in, put it in the vacuum chamber and draw the vacuum and release. It takes 7-10 days to cure fully. You'd avoid an oven cure though.
 
Thanks for all these details. They are great. This is not a Space-X part but it has to be reliable as possible including some heat exposure of the internal combustion engine it will be sitting on. I tried searching for a smaller quantity of CC-1305 with 0 results. I like your idea of Epoxyseal 9000. This is my best candidate right now.

Thank you and everyone who wrote in. If someone else has some other suggestions I am still open to them, too.

Cismontguy.
 
Wow, did not even think if McMaster Carr? I order from them daily. Do not know whether I could empty the can into a container and submerge the winding, pull a vacuum and then after all the bubbles are gone, apply pressure?

Cismontguy
 
There are many resins specifically designed for impregnating motor and transformer windings. Typically, they come as resin plus catalyst, to be mixed just before use, often with an 8-hour cure time at room temperature. One generally bakes these at 180 F or so.

To reliably achieve fully solid windings, needed for reliability under vibration, one impregnates and bakes the winding twice.

Nothing suitable comes in spraycans.

In small quantities, it may be best to hire the job out to a motor rewinding shop.
 
I would give them a call. They must have an enormous library of suppliers they can call on.



Cismontguy said:
Wow, did not even think if McMaster Carr? I order from them daily. Do not know whether I could empty the can into a container and submerge the winding, pull a vacuum and then after all the bubbles are gone, apply pressure?

Cismontguy
Click to expand...
 
out of curiosity, why is this not done with epoxy? cheap and readily available. (i dont even want to know what that locktite costs.)
 
We used to pot small coils with Stycast 1266 epoxy, about the viscosity of water. Mix, outgas with a roughing pump, pour into mold, and cure under 4-5 atm. I recall there were different catalysts for room and elevated temperature cure, but that might have been more for 2850.
 
I have wound new coils for alternators, and had enough occasional trouble with ignition magneto cols, that I am a very interested bystander on this thread.
I would love to soak up any info about his project that Cismont is willling to share

Single coil or primary/secondary combined/center-tapped? Wire gauges? Number of turns? Random or layered winding? Core? Application?
 
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