BarryK wrote:Orion wrote:I remember three adhesives in particular. One was McNett's Silnet (now GearAid SilNet). One was GE general purpose silicone glue. And one was DAP All Purpose Aquarium silicone. All three claimed to be "100%" silicone. The first two were some type of neutral cure. The DAP was an acetic acid cure.
The DAP product was far superior in peel tests as compared to those other two.
I also have tested GearAid SilNet. It has very poor "grip" and I decided that it is not suitable. It is a "thinned" silicone, very runny compared with the silicone sealants that you buy in hardware stores. It is designed to seep into threads, for seam-sealing a tent.
I have done some comparison tests with neutral-cure and acetic-cure sealant, and not found any difference, with regard to bonding to a silicone surface. I did some comparison tests years ago. Can't recall all the sealants that I tested. I think, Parfix and Selleys brands from Bunnings. I do recall one that I used a lot, years ago:
selleys-310g-401-rtv-engineering-grade-silicone:
https://www.bunnings.com.au/selleys-310 ... e_p1231042Not sure if I remember correctly, but I think the acetic cure was better at bonding to glass. Both neutral and acetic were poor at bonding to aluminium. Both were superb bonding to existing silicone sealant.
The silicone sealant that I now use, for tent construction, I do
not thin. Especially after I discovered how poor Silnet is for glueing.
Maybe a contentious point, perhaps a little bit of thinning is OK.
Hi BarryK and other silfabric-gluers, I don't think what you are saying is contentious for glueing silicone coated fabrics. The thick pure silicone rubber is needed. ( I prime fabrics that are not already factory silicone coated, but that is a separate matter and the subsequent glueing is with thick glue.)
1.Your (BarryKs) glued sample of silnylon (sent to me), was it glued with your neutral cure RTV silicone rubber? It has excellent peel strength, by my assessment. So that is a tick for thick and neutral cure????.
2.Smellypaddler has just sent me another glued sample of silpoly glued with Prosil 20 100% acetic RTV silicone rubber. It has an impressively thin layer of glue (He was 'not happy' with the seal, but I think it also has excellent peel strength. So there is a tick for the thick acetic cure.
3. Orion Found that DAP100% acetic cure silicone rubber was superior to other non-acetic cure silicone rubbers. His tent is holding together 10 years later,(even if it has an ugly side! Another tick for thick acetic cure RTV.
4. Lastly, I have only used acetic cure RTV silicones of many brands, but always insist on acetic cure. They have always been capable of forming strong peel resistant bonds with compatible fabrics. These silicone rubbers have always bonded well with aluminium, stainless steel. titanium and copper. This seems to be at odds with BarryK observation about his acetic cure RTV not sticking well to aluminium. Have I got this correct Barry?
I know an acetic cure is not recommended for galvanized or zinc alum plumbing for reasons of the corrosive nature of the solvent. I have never taken any notice of this and it has never been a problem. I think it evaporates and gets neuralized just so quickly that it only does good! However, from a chemistry point of view, I like the corrosive nature of the glue as it can easily clean organic contaminants on surfaces, including metals. I still sand metal surfaces to remove oxides and provide scratches for improved keying.
Lastly, as a chemist, of all the solvents for RTV silicone rubber, acetic acid is a bit nasty smelling, but by far the safest. Acetate is part of life and we have evolved with it, unlike the other recent nasty creations of chemists that are used as solvents. I think this is why it is used for making fish tanks?
The evidence in support of acetic cure seems to be stacking up, although some neutral cure silicones could be an exception).
Thanks for your ideas, samples and help. Tim