The transparency control method of silicone rubber requires coordinated optimization from multiple dimensions such as silica properties, silica formula and processing technology. The following are specific control strategies:

1. Selection and treatment of silica

Particle size control

Select silica with narrow particle size distribution (such as 15-20nm) and moderate specific surface area. Too large particle size will increase light scattering and reduce transparency; too fine particle size will easily agglomerate and affect dispersibility. For example, imported silica has a more uniform particle size distribution, and the silicone rubber made is more transparent.

Surface modification

Silica is surface treated with silazane, alkoxysilane, etc. to change it from hydrophilic to hydrophobic. Hydrophobic silica has better compatibility with vinyl silicone oil, which can reduce interface defects and improve transparency. For example, silicone rubber products made from silica treated with silazane have higher transparency.

Purity improvement

Strictly control the impurity content in the production process of silica, as impurities will significantly reduce transparency. High-purity silica (if produced using advanced preparation technology) can effectively reduce light scattering and improve transparency.

2. Silicone formula optimization

Raw rubber selection

Choosing raw rubber with low vinyl content and uniform vinyl distribution can avoid the loss of transparency caused by insufficient vulcanization. For example, too low vinyl content in methyl vinyl silicone rubber will lead to insufficient vulcanization and affect transparency.

Filler dosage control

The amount of silica needs to be precisely controlled. Too much will increase light scattering, and too little will not achieve effective reinforcement. Generally, the optimal dosage needs to be determined through experiments to balance transparency and mechanical properties.

Additive matching

Select additives with high transparency, such as hydroxy silicone oil, hydrogen silicone oil, etc., and avoid using opaque additives such as carbon black and dark dyes. At the same time, the amount of plasticizer and structure control agent needs to be controlled to prevent the decrease in transparency due to excessive addition.

3. Processing technology improvement

Kneading process optimization

Extend the kneading time of silica and vinyl silicone oil (such as 2-3 hours) to promote full mixing of the two, reduce interface defects, and improve transparency.

Vacuum degassing

During the mixing process, extend the vacuuming time to remove moisture and volatiles in the rubber material to avoid the decrease in transparency caused by bubbles. However, it should be noted that too long vacuuming time may cause the material to dry out, and the process parameters need to be strictly controlled.

Vulcanization condition control

Use appropriate vulcanization temperature and time to ensure sufficient vulcanization and no over-vulcanization. Over-vulcanization will cause molecular chain breakage and reduce transparency; insufficient vulcanization will cause mechanical properties to decrease.

4. Transparency improvement case

Highly transparent silicone pipe

By selecting high-transparency silica, optimizing the raw rubber formula and extending the kneading time, silicone pipes with a transparency of more than 90% can be prepared, which are suitable for medical, food and other fields.

Optical key glue

Using imported high-purity silica, combined with surface treatment and formula optimization, optical key glue with moderate key force and long fatigue life can be prepared, and the transparency can reach more than 85%.

5. Precautions

Balance between transparency and performance

When improving transparency, mechanical properties, aging resistance, etc. must be taken into account to avoid excessive pursuit of transparency leading to a decrease in other properties.

Process stability

Parameters such as temperature, humidity, and time must be strictly controlled during the production process to ensure transparency consistency.

Application scenario adaptation

Choose a suitable transparency control solution based on specific application requirements (such as medical, electronics, optics, etc.).