Silicone is an amazing material. Without silicone’s properties, keypads would not have moving keys or be able to close electrical switches or have self positioning features. This page reveals many of silicone’s basic properties that allow it to be molded into a multi-functional keypad.
Silicone Raw Material
Before being molded, raw silicone has the consistency of clay. The raw silicone is first mixed together with a catalyst which helps in the molding processes. Here, different base raw silicones can be mixed together in specific ratios to achieve a very specific silicone hardness.
Silicone parts can be made with different hardness ranging from 30 shore A to 80 shore A Durometer. Rubber bands have Durometer of 20 shore A, plastic is about 95 Shore A or higher. Raw silicone comes in base hardness of 30, 50, 70 and 80 Shore A.
Two raw Silicones can be mixed together to achieve a specific hardness. (Example: a mixture with 50% silicone at 50 Shore A and 50% at 70 Shore A will result in a final material with a Durometer of 60 Shore A.)
Differently hardness should be used for different purposes. Click on the image at the left to see a chart of ideally silicone hardness based on sealing requirements, tactile force requirements, insert molded keytops and pull throughs.
Silicone without pigment is clear or a slightly milky white color. Pigments can be added to the raw silicone mixture to make parts in virtually any color.
Rollers are used to integrate the pigments into the raw silicone.
If a keypad has multiple silicone colors, each color must be prepared separately.
Matching Silicone Color
The color of the silicone part is controlled by the amount and type of pigments used. Abatek use the Pantone system to match silicone colors, but we can also color match parts to plastic samples or color chips.
Because of silicone’s unique texture, it is possible that the keypad will not color match in certain lighting conditions. This is called metamerism. In this case, the pigment formula can be slightly changed (example: made darker or more yellow). Once part color is approved, the pigment formula becomes locked in assuring consistent color throughout production.
Transparent & Tinted Silicone
Raw silicone without pigments will appear transparent (clear) or slightly milky white after molding. This is perfect for backlighting legends and light pipes.
Using a tiny amount (say 0.2 – 0.005%) of pigment, the silicone can be made mostly transparent with a slight color tint. By varying the pigment color and amount, the tint can also be varied from highly transparent to virtually solid.