Water Rocket Construction Update: 06-27-2009

Hello again everyone!

It's been a long week of construction and testing here at U.S. Water Rockets. We have been working for some time to meet some deadlines on our Project 3000 design. However, we have made an amazing discovery that we would like to share with everyone out there. We are proud to be the first team to share publicly an amazing find we made while doing some research for X-17.

What we have discovered is not one but TWO commercially available adhesives which are designed to bond with low surface energy (LSE) plastics. "Surface Energy" is defined as the ability of an adhesive to "wet out" the surface of the plastic to allow adhesion. Wetting out refers to how well a liquid will flow and ultimately cover a surface because this increases the area of contact. In general terms, maximum adhesion develops when an adhesive thoroughly wets out the surface to be bonded because the greater the overage the more area for the attractive forces to hold the bond.

Surfaces with high surface energy (HSE) generally wet out readily with conventional adhesives and form strong bonds easily. LSE plastics do not wet out well and this can be observed by liquids "beading up" on them. They often posses a waxy feel and appearance.  A quick test for a LSE plastic is to pit water on it and see if the water beads up on the surface. If it does the plastic is usually LSE and hard to bond.

LSE plastics include Polyethylene and polypropylene, which are common in plastic containers and packing materials. Of particular interest to water rocket builders is the fact that most soft drink containers use a cap made from Polyethylene. Traditionally, these caps cannot be used easily because of the inability of existing adhesives to bond with them. The ability to bond to caps is considered one of the "Holy Grail"s of water rocketry.

We have recently discovered what promises to be a solution to this problem, making various types of nozzles and interconnects possible to create for the average builder with no special tools!

 First up is Super Glue Brand "Future Glue Plastic-Fuse", which is a fairly standard Cyanoacrylate glue that is supplied in a blister package with two small glass vials of a chemical primer that must be broken open and used immediately on the LSE plastic surfaces. After application of the primer chemicals the remaining primer evaporates and cannot be saved.

Once the primer is used, the provided CA glue can then be applied and the joint glued normally.
The drawback of this product  is that you only really get two chances to use the glue, even though they provide a generous amount of primer you can only use it one time. The only solution to this is to prepare all your items and glue many of them all in one session.

Our second product is the Loctite Corporation's "Plastic Bonder". This is also a two part glue with a standard CA adhesive and a preparation chemical they call an "activator". The difference is that this product supplies the "activator" chemical in a small pen like applicator which has a tip like a felt-tipped pen and a cap that can be replaced to retain the activator when not in use. The number of times this version of the adhesive can be used is much greater than the adhesive from Super Glue.

We are currently in the process of constructing some bottle couplers (often called "Tornado Tubes" using these glues and we will be performing a complete battery of tests to determine the best glue of the two.

Stay tuned for our full report coming up soon!