We were asked to print on some silicon belting two or three years ago. Tried a wide variety of inks and processes, all would flake off after a short time of playing with the samples. One company suggested chemically etching the silicone to create an anchor pattern for the ink to grab onto and then printing with a two part epoxy. We never perused this option because we found someone who was able to sonic weld the imprint on the belting. Ended up just passing the information on to the customer and letting them handle it.