need input on bladder material

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#1

I have been working with a closed mold design, using two split mold halves and a internal bladder. The part is going to full production shortly, but the bladder is the weak link. Currently, the part is hand laid followed by placing a bladder in one side of the mold, mold halves are bolted together, and the bladder then pressurized. Results have been improving, especially after placing intensifiers in some of the more detailed areas the bladder couldn’t apply sufficient pressure.

The bladders have been fused together using Strethelon 800 which seems to work fairly well, but it is time consuming. The bladders often fail or can be difficult to remove, or they get damaged during removal. The goal is to construct a bladder that will alleviate the need to use intensifiers, can be reused, so it needs to be tear resistant and hold up to the epoxy resin. I have been looking at the Dragon Skin line of silicone rubbers, which can be brushed on http://www.smooth-on.com/Silicone-Rubber-an/c2_1115_1129/index.html. Should I be looking at silicone, or urethane rubber? I have attempted to make a bladder using shore 60 urethane, but the tear strength just doesn’t seem to be there.

#2

here is the orriginal thread with details about the part http://www.compositescentral.com/showthread.php?t=10392

#3

Hi

I’ve played around with silicon bladders with not much success. I painted mould first , then pured a little mix in the mould , closed it and rolled it on the seam axis to get a strong seam from the inside.
I damaged mine almost every time is removed them ( tearing) that’s when I changed to qualatex balloons.

Did you give qualatex balloons a go ?? They are very quick and easy to use and don’t pop and can be used up to 60psi. So with you intensifiers you would get a perfect part every time. Don’t underestimate how good they are , many manufacturers use them for this reason. For your job you would need the 646 size.

Tim

#4

I will try the balloons out and see if they will work, just ordered some. It appears that when I use intensifiers, or when the bladder is close to the exact contours of the interior mold, the part turns out much better (less voids, less air bubbles). The second concern is that the entire bladder must be able to be removed, or the part is not usable. I have read that the balloons may have a hard time releasing from the cured epoxy.

#5

Tim, what do you do for releasing them? You build gliders, right? So, I am sure you don’t just leave them in…

Maybe one could inflate them to slightly bigger than they would be in the mold and then spray a release on them? Inflating them before releasing would make sure the balloon is fully covered in the agent.

#6

Never had any problems getting them out they don’t seen to stick to epoxy very well , so that’s a good thing.
Also putting them under vacuum before you try and get then out helps them pull away from the sides. And yes , Also if you inflate then slightly and cover then in some wax or other type of release will help get a better release. But really never had issues getting them out.

Tim

#7

Piercan USA and Transition composites could make you silicone bladders from your mould, they take it and then create a pattern from your mould.

Is there an industrial source (eg in the far east to support sporting goods manufacture) that anyone knows of for v.light bag-type bladders that are non-reusable?

#8

Just on another point, Qualatex balloons - I checked online and they’re nearly £10 (in England) a balloon, is that what you pay for them as that seems pretty pricey!

#9

Haha. Holy crap :eek: 10 quid for a ballon

They are all over ebay very cheap also plenty of party shops sell them.

Here is a link to a local shop , and I’m sure they will send them to you. If not I’ll buy some and sent then to you :slight_smile: no problem.

http://www.balloonguy.com.au/product-category/350s/qualatex-350q-single-colour-bag-of-10

Tim

#10

I just got a txt back from the balloon guy. They will ship to Ireland no problem. But he has to do the order off site as the shipping software won’t do it on line to Ireland.
Send him an email first and he will sort it out if you would like some. Shipping won’t be expensive. :slight_smile:

Tim

#11

Box of 100 for £4.99 on one of the websites.

#12

Ah cool, thanks guys

#13

Just received the balloons, as well as the Dragon Skin 20, which is a shore 20 silicone. The 20 looks to be the best fit, long work time, high tear strength, and very thin so it can be worked around in the mold.

I’ll post results shortly.

#14

Interested to see :slight_smile: