"Our research lab is looking for a medical-grade adhesive to bond:
1.) Dacron cloth to silver plate and
2.) Glass and PMMA optical cylinder in a silver tube.
It needs to be moisture resistant and should last for a long time (20 years).
Please suggest a product."
Dacron is a commercial name for PET, or polyethylene terephthalate. Bonding cloth to a rigid substrate like a silver plate can be done in a few different ways. Bonding to cloth is mostly a mechanical lock that forms by encapsulating strands of the cloth and then locking them to the rigid substrate. The viscosity of the adhesive will play a role, as the thinner the viscosity, the more it will wick into the cloth. A very high viscosity will not wick very far into a cloth. A 2-part epoxy, such as found from Loctite or 3M, or a 2-part urethane, such as found from Lord Corporation, are just two products that you might want to explore. A silicone adhesive may also do the trick, and would suggest contacting representatives of Dow Corning, Momentive Performance Materials, NuSil Technology, or any of the other silicone manufacturers.
To bond glass and PMMA you may be able to use the same adhesive, but the application might require a lower-viscosity material, depending on the gap between the parts and method of assembly. The epoxy and silicone systems will be moisture resistant and have good usage life, but most manufacturers will not warrantee a 20-year usage lifetime. A 1-part, light-curable urethane acrylate, like 203A-CTH or 209-CTH from DYMAX, are options if you can get light to the adhesive.