Clear rubber question?

[DrStein99]

For a newbie to rubber product making, I'm looking for advice - please.

I'm looking for a clear-rubber substance; that I can pour into my cast - and will transfer red light from an embedded LED.

I will make a cast using plastic or aluminum - on my cnc-machine, POUR the rubber fluid into the cast (or mold), and put the LED at the top; set to dry (or cool).

Either by way of heating rubber in a vat, and pouring in my cast w/ a latel, or mixing a/b solution, or squirting through a tube - I dont know what process would be the best for my application, I could use some newbie advice. I can not have any bubbles in the end-product.

The consistancy would be something like soft rubber on remote-control keypads, sturdy, and as close to transpararent as possible - I want it to light up when the LED is activated (in the final product).

Please help!

[mxtras]

Look into water clear urethanes.

To rid your part of bubbles, you will want a very low viscosity resin and a good mold design.

Scott

[JavaDog]

What about silicones?

[DrStein99]

I was going to go to the hardware store and buy some tubes of clear silicone / caulk; but have no exp with this and am looking for some research to reduce trial and error time.

I've been told to try silicones from some rubber suppliers I've contacted (that seem to only want to sell rubber that stands up to super high temp, or radiation or other extreme circumstance).

I know I can make a mold, and squirt hot-glue from a gun into it and use that - but it melts so easily is not workable (it will melt in a car during afternoon lunch!). A hot-glue gun w/ rods that activate HIGHER would be a nice thing; or something I can mix and squirt out of a caulk gun; it doesnt have to cure instantly I'm patient it can cure overnight.

[JavaDog]

Well, just so we all are clear. Do you want the end-result to be hard or soft/rubbery? Silicone will stay pretty soft. The stuff in the tubes would be good to test with, I would think...

[SteveD]

Depending on how thick your part is going to be, the problem with silicones from the hardware store is the thicker you get the cloudier it will get. It would not hurt to try this method because the expense to try is so low. If this does not work try these websites for some help.

http://www.smooth-on.com/default.htm
http://www.freemansupply.com/index.htm

The smooth on tech reps are very knowledgable & can probably steer you in the right direction. They are also very good fo get small quantities for the hobbiest or DIY'er

[DrStein99]

Smooth-on will sell me a gallon of their transparent castable rubber at the generously low price of $200....

Going to check freeman supply now, and would like to entertain any other suggestions for suppliers please.

[Genguy]

Encapsulating and Potting Epoxy for circuit boards might also work.
It has a rubbery feel when cured. It takes 24 hours to fully cure.
It's about $20 for a 12oz bottle or $120 for 8gal.
Allied linky

[DrStein99]

Is that potting epoxy good for casting something the size of a mustard-cap, for perminant use?

[cbass]

SmoothOn's main competitor:

http://www.polytek.com/

[DrStein99]

I was looking for that - i knew there were two BIG makers for castible products, and didnt know the other one. Thank you!

[Genguy]

Originally Posted by DrStein99 Is that potting epoxy good for casting something the size of a mustard-cap, for perminant use?

It should be plenty strong enough, but I don't know how much it will contract when cured. The circuit boards I work with are encapsulated in it to a thickness of about 3/8" of an inch. I have tried to remove it from boards before and had to resort to a hammer and chisel. It’s impossible to remove without destroying the board. It's very tough stuff. It's not perfectly clear, it has a very slight amber tinge to it. I would describe the texture and hardness as close to that of wire insulation. Much harder that cured silicone.