Will this stick to ___? What glue/adhesive should I use?
Two separate questions hide in here, "will it bond where I want it to" and "will it bond where I don't." Quick guidance:
- Bonding cured silicone to silicone (or to other surfaces): use Sil-Poxy, a silicone adhesive. Ordinary glues and epoxies will not reliably hold cured silicone.
- Repairing urethane rubber molds: use Ure-Bond II to repair tears or cuts in urethane molds.
- Bonding rigid urethane/resin parts: a urethane or epoxy adhesive works, as may cyanoacrylate adhesive; abrade and clean the surfaces first.
- Will new silicone stick to cured silicone? Fresh platinum silicone bonds to freshly cured platinum silicone if the surface is clean, but tin and platinum silicones generally won't bond to each other, and inhibition may occur.
- Stopping it from sticking (to your mold, master, or work surface), that's a mold-release question, see below.
For a deep, narrow repair: Sil-Poxy can be worked into a tight tear with a thin spatula or by thinning slightly; a white residue at the seam is excess adhesive, wipe back the excess before it cures and tool the joint cleanly.
Learning Center:
Full guide: Sticking, Release and Bonding Failures · Preparation of Surfaces for Epoxy Adhesive Bonding