It's difficult to repair plastic canoes and kayaks made of polypropylene or polyethylene because these suraces are difficult to bond to. But you can use TotalBoat FlexEpox flexible epoxy adhesive to repair plastic canoes and kayaks by following the directions below.
1. Use mineral spirits to clean the damaged area. This will remove oil, wax, dirt, and other contaminants. Then use 60-80 grit sandpaper to scratch the surface adjacent to and a bit beyond the repair.
2. Flame-treat the plastic surface to improve adhesion and remove any remaining contaminants. to flame treat, hold the flame of a propane torch 4-6" above the plastic surface and move it across the surface, slightly overlapping the previous area. Keep the flame moving so you don't discolor or burn the surface.
3. Apply a coat of FlexEpox within 30 minutes of flame treating.
4. From lightweight fiberglass (4 oz. fiberglass is good), cut patches that are staggered in size so the largest patch extends beyond the damaged area, with successive patches cut increasingly smaller. Multiple layers are best. For a slight tear, three layers of 4 oz. fiberglass should be enough for the inside of the hull and two layers should be adequate for the outside of the hull.
5. Starting on the hull exterior, place the largest patch onto the wet epoxy adhesive. Apply more epoxy adhesive, as needed to thoroughly wet out the fiberglass layer. Add the second patch, and wet out completely. Allow the repair area to cure, then repeat the process on the inside of the hull.
6. Repeat steps 1-5 on the hull interior. Let the repair area cure, then sand the cured fiberglass to smooth out the edges.
7. If you want to paint the repair, fair the stepped layers on the interior and exterior of the hull by thickening the FlexEpox with a fairing filler such as TotalBoat Glass Microballoons. Once cured, sand the fairing material until smooth.
8. Apply two sealer coats of mixed epoxy to the repair area and let it cure completely.
9. Remove any amine blush. Allow the surface to dry completely, then apply primer/paint, as directed by the coating manufacturer.