Sometimes scientific glass design requires choices between means of attachment, and glue trumps fusion. Adhesives are availble in a number of formulations for glass. Choosing the appropriate glue will depend on your expected temperatures, resistance to solvents, acids, and bases, and required flexibility.
The photo to the right shows an application in which a base is precision mounted to an electrochemical cell. These cells are for use in an automated set-up, and positioning is an important criterion. We are more able to control this parameter using a UV curing glass adhesive between the base and the body.
Silicone adhesives are also a good choice in certain circumstances; they adhere to clean glass well, and allow flexibility when required. The image to the right depicts the silicone seal of a large jacketed vessel where this flexiblity is an excellent property; the seal easily accommodates the different rate of expansion between the inner and outer walls of the vessel.
The downside of silicones is that they are hard to remove if a piece of glassware needs to be repaired or modified later. If they are not completely removed, the silicone burns into the glass, and can screw up the surface of other glass in its proximity. In our annealing ovens, burning out silicone can damage the oven irretrievably.
We also use epoxy glues. The currently preferred epoxy is Loctite Hysol E-30CL. Reports from the field indicate that it holds up well to acids and bases.
Below, see a sequence of photos that illustrate another good use of adhesives. We need to attach a quartz optical window to a borosilicate glass body to make a photoelectrochemical cell. To fuse these components together would be unwieldy and very expensive. With the use of UV curing glass adhesives, we can achieve excellent results for a fraction of the cost, though this solution is contingent on what the contents of the cell will be.
The seat for a window is prepared from appropriate sized tubing, which is sealed onto the cell, and then annealed.
This tubing is then cut to size, providing a uniform surface for the window mount.
which is done with an anaerobic curing adhesive that is easily cleaned from the optical surface of the window.
We now have an optical electrochemical cell. Or is it a photoelectric chemical cell? Electro-optical? Spectroelectric........