I've written several articles on the topic over the years and while I'm not going to post any of them I will post a couple of excerpt that cover what are IMO the largest misconceptions.
Quote:
100% silicone does not mean they are all the same. As an example you can buy 100% silicone that contains fungicides, you can buy a 100% silicone that feature a joint movement of 25% while another product has 12% and yet another might have 30%.
Doesn't that tell you that 100% silicone's are not all the same? The time to cure, the shear strength, elasticity, level of adhesiveness to any specific material and many other properties all vary substantially in 100% silicone products.
So what is Silicone? Well elemental silicon (as listed on the periodic table) and silicone ( polymerized siloxanes) are completely different.
The common 100% Silicone adhesives or sealants are compounds created by blending members from the family of polymerized siloxanes in various ratios and manners using a variety of solvents to achieve a broad range of 100% silicone products each expressing specific desired traits.
They can generally be broken into two categories, silicone sealants and silicone adhesives. They can usually do each others jobs with little difficulty as long as they are used well within their design limitations. Most of the product found in the hardware store are sealants, not adhesives. They are designed to seal out the weather or for doing minor repairs.
|
Quote:
|
Products can be legally labelled as 100% pure while they may actually be 99.8% pure and some solvents do not have to be considered in the equation at all even though some solvents do change traits of the final product. When it comes to chemically derived products 0.2% can sometimes make a substantial difference in its properties.
|
Back in the day I also used Door and Window type 1 ( a product that to my knowledge has been discontinued for years and is only found as aged stock) and it worked pretty good. Back then I ignored warnings by professionals that it was not suitable for anything over 30 gallons. It simply lacks the strength as it was never designed to be an adhesive, but rather a sealant.
I used it anyway and over the years I built, repaired, modified 100's of tanks. I got away with it until I tackled a 180 gallon and I experienced my first seam split.
The SCS1200 that Grizz mentioned is a 100% silicone construction adhesive designed for use by professional glaziers. Because of the level of damage a failed tank can do I've always taken the approach that if I need to explain it than you are not qualified to do it so I do not recommend any particular product. In house the only product we use is SCS1200. It retails for $10 a tube and flows like silk when a quality caulk gun is used. I've personally used it on over 50 salt water aquariums up to 240 gallons.