Slide 10 of 24
- Currently, polyurethanes, and other thermaset plastics, are deposited manually
- The polymers were not designed to mix or to be graded throughout a part. The manufactures discourage mixing the urethanes in arbitrary ratios (although all samples that have been mixed have cured satisfactorily.
- Depositing two grades of polymers at the same time (Wet-Wet Bond) creates a very good bond as the polymers mix locally at the interface.
- Controlling where the interface will be is very difficult. Polymers are not of same density and therefore even if a straight interface is initially established, the denser urethane will tend to seep under the less dense, ruining the boundary.
- Depositing and curing one material and then depositing a second material (Wet-Dry Bonds) allows superior control of the interface.
- Increase the surface area of the interface as much as possible.
- Roughen surface of first material before casting second. Roughen surface by machining interface.
- Keep surface clean - if possible final step before deposition should be machining of surface.