How to Choose a specialized silicone type for shoe upper silicone printing?

Choose a specialized silicone type for shoe upper silicone printing:
Avoid general-purpose industrial silicone. Prioritize silicone specifically designed for shoe upper printing (available in "addition-type" and "condensation-type" varieties):
For mesh/knitted fabrics: Choose a highly elastic addition-type silicone (hardness 30-50 Shore A) containing a coupling agent (such as KH-550/KH-560) to penetrate the substrate fibers and create an "anchoring effect."
For PU/PVC/genuine leather: Choose a polar-modified silicone (with added polyester or polyether modified segments) to improve compatibility with polar substrates (PU/PVC contains polar groups) and avoid "surface repulsion."
Adding a coupling agent (adhesion enhancer):
If the silicone itself lacks adhesion, add a silane coupling agent (such as KH-550 for non-polar substrates or KH-560 for polar substrates) to the curing agent at a ratio of 1%-3%. Mix thoroughly before use. (Excessive coupling agent can make the silicone brittle, so the amount should be strictly controlled.) Control the viscosity and solids content of the silicone:
A viscosity that is too high (>5000 cP) can easily cause residual bubbles during printing, while a viscosity that is too low (<2000 cP) can easily penetrate the substrate, resulting in a "showing" effect. We recommend adjusting the viscosity to 3000-4000 cP (a small amount of silicone-specific diluent can be added, but water or alcohol should not be added). The solids content must be ≥95%. A low solids content will result in significant shrinkage after curing and poor adhesion.