Making a reusable bladder for closed molding, need input

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#1

I have been working with various closed molds and a inflatable bladder. The bladders are currently being made of Stretchlon 800 fused with a iron. The mold is laid up by hand with epoxy resin, mold haves closed and then the bladder is inflated to around 8-10 psi. The parts are coming out fairly well and consistent, since this will be a production part I am wanting to make a more reusable bladder. The SL 800 is a 1-2 time use bladder before it fails or is damaged from removal. I have thought of using rubber sheet and rubber cement to make a reusable bladder, I am looking for input on a good material suited for repetitive use. The part has some detail and is not a straight walled part, so a rigid bladder will not work. The part can be post cured with or without the bladder, depending on how temp sensitive the bladder material is.

Thanks in advance

#2

Addition cure silicone? Need to account for carbon part thickness though. How big is your mould?

#3

The parts are approx 3’ long with some recesses and detail, nothing too sharp or aggressive. The molds I am using are two sided closed molds, the parts are laid up in two halves with one side overlapping, the mold is closed and the bladder inflated. The entire back end of the part is open which is the largest section, so the bladder has plenty of room to be extracted from the finished part. The biggest issue I have had with the SL 800 is that it wants to adhere to the interior of the part when cured, but I have not tried any release agent on the bladders yet. The last part I made, I tried to vacuum the bag to collapse it hopping it would release, it did not. I thought of using Chemlease 70-90 on the bladder, since it is currently used on the molds with great results. I am to the point were a higher quality bladder needs to be made, it will see repeditive molds cycles. The time it takes to make a quality bladder that can only be used once, and has the risk of no being removed rendering the part useless is the biggest hangup at this point.

I looked into uncured silicone, it looks like it may be a good alternative. I thought of purchasing rubber sheets and gluing them together, then flipping the bladder in side out placing the seam on the inside of the bladder and gluing on the inflation stem.

#4

I have tried all kinds to bladders: Silicone, latex, Stretchlon, and poly. I ended up doing single use poly bladders for production work. If the part is complex I weld them. I could do the welding of 3 foot long bladders in about 5 minutes. If it’s simple and relatively tubular I used poly tubing and sealed the ends with an impulse sealer.
http://www.uline.com/Product/Detail/S-3521/Poly-Tubing/2-Mil-Poly-Tubing-Roll-1-1-2-x-1500?pricode=WY747&gadtype=pla&id=S-3521&gclid=Cj0KEQjwxpipBRCap8PR2Om7vq4BEiQA6V7OVZDsQ_OwxagvfpKs0pvQ8OKR8PNqOeNVTLdEW_JKtooaAulO8P8HAQ&gclsrc=aw.ds