Why is silk screen silicone translucent?
In terms of the characteristics of the raw materials
Silicone polymer structure characteristics:
The base polymer of silk screen silicone is usually polysiloxane, whose molecular chain is relatively regular, but there are certain gaps and interactions between the molecular chains, which will affect the propagation of light. When light passes through, part of it can pass smoothly, while the other part will refract and scatter between the molecular chains, resulting in a translucent appearance. For example, polysiloxanes with different polymerization degrees have different molecular chains and different effects on light. Silk screen silicone made of polysiloxane with moderate polymerization degree often appears translucent.
The influence of additives:
Some additives are often added to silk screen silicone, such as curing agents, catalysts, fillers, etc., to meet different performance requirements. Some additives themselves may not be completely transparent, or there are certain limitations in their compatibility with silicone polymers. After mixing, they will interfere with the transmission of light, making the whole appear translucent. For example, some inorganic fillers (such as calcium carbonate, titanium dioxide, etc.) are added to enhance the hardness and wear resistance of silicone, but these filler particles will change the light propagation path, resulting in the light not being able to penetrate completely and evenly, thus making the screen-printed silicone translucent.
Production process
Factors introduced in the mixing process:
When producing screen-printed silicone, the raw materials need to be mixed and mixed evenly. If the mixing speed is too fast, the time is too long, or the mixing equipment is not sophisticated enough, a large amount of air is easily mixed in to form bubbles. Even if degassing measures are taken later, some tiny bubbles may still remain. These bubbles are equivalent to tiny "obstacles" inside the silicone, which will scatter the light and cause the final screen-printed silicone products to present a translucent appearance. For example, if the mixing speed and time are not precisely controlled, the mixing speed exceeds 60 revolutions per minute and the mixing is continued for more than 10 minutes, it is easy to produce more bubbles that are difficult to completely remove.
Influence of the curing process:
Curing temperature and time: The conditions of the curing process have a significant impact on the transparency of screen-printed silicone. If the curing temperature is not appropriate, such as too high or too low, the internal structure of the silicone will change, affecting the light transmission. Too high a temperature may cause local overheating, resulting in local deformation of the silicone molecular chain, abnormal cross-linking, etc., causing irregular refraction and scattering of light; too low a temperature may lead to incomplete curing and uneven internal structure of the silicone, which will also hinder the propagation of light and eventually appear translucent. Similar problems will occur if the curing time is too long or too short. Too long will lead to over-curing and change the texture of the silicone, while too short will lead to incomplete curing, which will cause the light transmission effect to deteriorate and present a translucent effect.
Curing environment: The humidity and air circulation of the curing environment are also critical. In a high humidity environment, moisture is easily mixed into the silicone, participating in the curing reaction or condensing on the surface of the silicone, interfering with the normal transmission of light and making the silicone look translucent. When the air circulation is not smooth, some small molecular volatiles produced during the curing process are difficult to be discharged quickly, and accumulate inside or on the surface of the silicone, which will also affect the transparency and make it appear translucent.