Silicone adheres to most plastics, but not all. It will not adhere to acrylic.
from the DAP 100% Silicone Technical Data Bulletin
(
http://www.dap.com/docs/tech/00000683.pdf ):
"· Not recommended for use on cementitious materials or surfaces that might bleed oils, plasticizers or solvents. Substrates made of *methylmethacrylate, polycarbonate, polypropylene, polyethylene and **polytetrafluoroethylene do not allow for best adhesion and compatibility with sealant. Try test area before
using.
· Not recommended for use on brass, copper, magnesium, zinc, iron, galvanized metals or other surfaces
prone to attack by weak acids."
*methylmethacrylate is Acrylic
**polytetrafluoroethylene is Teflon
Silicone adheres just to fine to PVC, which is of course not on their listof non-recommended materials.
The silicone will work alright on acrylic as a gasket, but not as glue or in situations where it will be under pressure.