How do I control the proportion of electroplated silver powder added to silicone screen printing?
Matching Particle Size to Mesh Size
The mesh size of the screen printing screen (e.g., 80-300 mesh) must be compatible with the silver powder particle size. For finer mesh sizes (e.g., 200-300 mesh), choose finer silver powder (typically 1-10μm) to prevent silver powder particles from clogging the mesh and causing "ink breakage." For coarser mesh sizes (e.g., 80-120 mesh), use slightly coarser silver powder (10-20μm), but avoid using excessively large particles, which can cause rough edges on the printed pattern.
If you're looking for a high-mirror finish, it's recommended to choose spherical or quasi-spherical electroplated silver powder (rather than flakes) for enhanced light reflectivity. If you're looking for a matte metallic finish, choose silver powder with an irregular morphology.
Preferably, choose silver powder with a "silicone-specific" surface treatment. Ordinary electroplated silver powder may contain oil or an oxide layer on its surface, and adding it directly to silicone can easily cause "agglomeration" (silver powder clumps and becomes difficult to disperse). It's recommended to choose silver powder treated with a silane coupling agent (such as KH-550 or KH-560) or fatty acid. The surface of this type of silver powder can form chemical bonds with the silicone molecules, improving dispersion and strengthening the bond between the silver powder and the silicone, reducing subsequent shedding.
Pretreatment before use: Impurity removal and activation
If silver powder has been stored for an extended period, it should be dried at 80-100°C for 1-2 hours to remove any surface moisture. This prevents moisture from causing bubbles during silicone vulcanization.
If the silver powder is slightly agglomerated, pre-disperse it in a high-speed disperser (1000-2000 rpm) for 5-10 minutes before adding it to the silicone system.