Controlling Parameters for Silicone Printing on Shoe Uppers
Squeegee Selection and Pressure:
Squeegee Material: For mesh, use a 65-75° polyurethane squeegee (soft squeegees easily fill the mesh), and for PU/PVC, use a 75-85° squeegee (hard squeegees ensure uniform coating).
Squeegee Pressure: The standard is to ensure that the silicone completely covers the substrate with no gaps. Excessive pressure will result in thinning of the silicone (inadequate coating), while too little pressure will cause bubbles to remain (impairing bonding). Generally, control the pressure between 0.2-0.4 MPa.
Coating Thickness:
The recommended single-print thickness is 50-150 μm (depending on the design requirements, this can be done in 2-3 passes, with semi-curing required after each pass). Too thick (>200 μm) will result in inconsistent internal and external shrinkage during curing, generating internal stress and facilitating peeling. Too thin (<30 μm) will result in insufficient adhesive support. Curing Conditions (The Most Easily Overlooked Step):
The temperature and time must be determined based on the silicone type to avoid under-curing or over-curing:
Addition-type silicone: Baking at 80-100°C for 15-20 minutes is recommended (high temperatures can cause silicone decomposition, while low temperatures can result in incomplete curing).
Condensation-type silicone: Baking at 60-80°C for 20-30 minutes is recommended (ventilation is required to prevent small molecule residues from curing).
Leather substrate: Avoid high temperatures; cure naturally for 24 hours or bake at 40-50°C for 30 minutes.