Effect of Polysulfide and polyurathane on plastic ports
Polysulfides & Polyurethanes will adhere to metal, glass, fiberglass, wood, or any combination of these. Do not use either on PVC, Acrylic (Plexiglas, Lucite), ABS, or Polycarbonate (Lexan) plastics.
Although the modalities are (more or less) opposite, both “Poly” products are incompatible with the above “plastics” (excluding Nylon, Dehlrin, Marelon, or Epoxy):
The solvents in polysulfides can leach the plasticizer from these plastics and cause them to harden and crack.
Solvents, leaching from some plastics, can react with polyurethanes and cause a failure of the adhesive sealant compound.
For an adhesive seal of plastic components, select a silicone/polyurethane or epoxy/polyurethane hybrid.
Never use any caulk that is catalyzed by acetic acid (i.e., smells like vinegar) on acrylic; it will cause crazing.
Silcone has little if any adhesion. It is merely a gasket material, but an excellent gasket. It will not attack plastics, but may cause crazing on acrylics.