Sorry for the Blues Brothers quote - I couldn't help myself.
Not these Blues Brothers.
Photo by jpenner/iStock / Getty Images
I couldn’t afford to license a Blues Brothers image, but if you are curious check out this YouTube video. And then if you haven’t seen it check out the whole movie.
For the past eight months I have been working on a cable feed through that uses Torr Seal epoxy. Torr Seal is a specifically formulated low vapor pressure epoxy that is meant to seal vacuum leaks at very low pressures. A key feature is it’s very low off-gassing. It is a great product but I am now wondering if it also has some downsides for my application. Torr Seal is a thick product with the data sheet listing the viscosity as “Thick non-flow paste”. Also it appears to be a very rigid epoxy although its elongation (amount it can stretch when cured) is not listed on the data sheet. Finally the data sheet says “Will not adhere to Teflon, Kel-F, nylon nor polypropylene”. While not specifically listed I wonder how well it adheres to acrylic plastic. Torr Seal may work well with the aluminum end plates at least most of the time but a source of leaks for the all acrylic enclosure. The vacuum preparation of the Torr Seal appears to improve the situation but it is still not satisfactory especially for the acrylic version of the enclosure.
The upshot of all this second guessing is I have started a test program for a few different adhesives/sealants. Here is a list of the products I will try:
| Product | Formulation | Viscosity [cP] | Elongation [%] |
| Torr Seal | Epoxy | Thick non-flow paste | Not in data sheet |
| 1C-LV | Epoxy | 66,750 | 3 |
| Plastic Welder II | Acrylic | 55,000 | 5 |
| H3000 | Acrylic | 45,000 | 20 |
| E-30CL | Epoxy | 10,000 | 8 |
| U-09FL | Urethane | 5,000 | 175 |
I plan to test each of these products on a 9 mm acrylic end plate with and without vacuum preparation to remove air pockets. I started with the 1C-LV epoxy and right away the benefits of the lower viscosity are apparent - the 1C-LV readily filled the cable feed through opening in the acrylic with no air pockets even without vacuum preparation. A key feature of three of the products (Plastic Welder II, E-30CL and U-09FL) is the data sheets specifically state they are for use on acrylic plastic.
I have started testing the 1C-LV and results look promising.