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About:
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Traditional solvent based or PU based inks are not reliable for printing on the silicone surface. The surface energy of silicone is very low which the reason why the inks can not adhere to the silicone surface which makes the intermolecular forces very low. The intermolecular forces that contract the surface are termed surface tension. Surface tension, a measurement of surface energy, is expressed in dynes/cm. The higher the surface energy of the solid substrate relative to the surface tension of a liquid (water, printing inks, adhesives/encapsulation, coatings, etc.), the better will be its "wettability" and the smaller will be the contact angle. These types of chemically inert materials like silicone are hydrophobic and not naturally wettable. Compatibility between ink and polymeric substrate are the application challenges to achieve.
Pretreatment methods for Silicone Printing
Some manufacturers chose using electrical corona discharge, flame treatment, cold gas plasma, and ultraviolet irradiation as pre-treatment methods to achieve bonding with a wider range of adhesives. Each of these methods are application-specific and possesses unique advantages and potential limitations. The basic mechanism that happens in this process is a combination of both chemical and physical reaction. Due to the breaking of surface bonds of polymeric substrate during plasma or other pre-treatment methods, free electrons, ions, metastable, radicals are generated that makes the surface hydrophilic for a short time, thus makes the inks compatible to be printed. This creates very reactive free radicals on the polymer surface, which in turn can form, crosslink to the bonds of the ink formulation. In short, the wettability of the substate gets increased for a short time.
There are many types of silicone used for silicone ink for different requirement of silicone printing, like heat transfer silicone, embossing silicone, hd silicone, natural drying silicone, matte glossy silicone, puff silicone, etc.
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