Typically, many adhesives can be used to bond polycarbonate. If you wish to try a light-curable acrylated urethane adhesive, one of the 3000-series products from Dymax (Torrington, CT), such as the 3099 or 3025 adhesive, might be a good option.

The weakening of the adhesive after initial good results is a concern, and I would recommend talking with the polycarbonate supplier or molder. To improve molding using polycarbonate, the raw resin supplier can add material to the polycarbonate to facilitate the release of the part from the metal mold. Alternatively, the polycarbonate molder could perhaps apply a Teflon mold release spray every 200th shot. If a monomeric mold release material is used, it can sometimes migrate to the surface of the polycarbonate, pushing the adhesive away from the bond line and interfering with adhesion over time. If a polymeric mold release material is used, it will not migrate as easily.

I would also ask about the levels of stabilizers. While most stabilizers are present in the plastic at acceptable levels so that they do not interfere with bonding, additional stabilizers are sometimes added to render the plastic light resistant, heat resistant, and stable. Such stabilizers can also migrate to the surface of the plastic over time, destroying the bond line. It is possible to have an analytical laboratory extract solvent from the surface of a polycarbonate sample before and after heat aging to determine whether a contaminant is present on the surface or to identify it. I have also even seen finger oils on a plastic surface migrate along the bond line and eventually degrade it. Finger oils change based on the foods the person has digested over a 12–24-hour period.