Causes and treatment methods of unpalatable powder during mixing of silicone rubber
1. Preface
Mixed silicone rubber is an important elastomer material and is widely used in automobiles, medical, electronic appliances and other fields. In the production process of compounded silicone rubber, fillers (such as silica) are important additives that can improve the mechanical properties and heat resistance of the rubber. However, during the mixing process, the phenomenon of "unpalatable powder" sometimes occurs, that is, the filler is difficult to evenly disperse into the matrix rubber. This problem not only affects the quality of the product, but may also make the processing process more difficult.


2. Reasons why it is difficult to eat noodles
Silicone rubber has a lower surface energy
Silicone rubber has a low surface energy, resulting in poor compatibility with fillers. This low surface energy makes the filler particles prone to agglomeration when entering the silicone rubber matrix, forming larger agglomerates that are difficult to disperse evenly.


Particle size and distribution of filler particles
When the particle size of the filler particles is too small or unevenly distributed, it will aggravate the agglomeration phenomenon and increase the difficulty of mixing. Especially for nano-scale fillers, such as ultra-fine silica, it is easy to form strong agglomeration in silicone rubber, resulting in unpalatable powder.


Mixing process parameters are inappropriate
Process parameters such as mixing temperature, time and speed have a direct impact on the mixing effect of silicone rubber. If the mixing temperature is too low, the fluidity of the silicone rubber matrix is insufficient and the filler is difficult to fully disperse; if the mixing time is too short, the filler may not completely enter the rubber matrix.


Mixing equipment problems
The type, status and rotor design of the mixing equipment will all affect the dispersion effect of the filler. If the equipment is worn or poorly designed, it may not be able to provide sufficient shear force, making it difficult to disperse the filler evenly.


3. Treatment method
Increase mixing temperature
Appropriately increasing the mixing temperature can increase the fluidity of silicone rubber, thereby helping to disperse the filler. It is generally recommended to control the mixing temperature between 150-170°C to ensure the fluidity of the rubber and the uniform dispersion of the filler.


Optimize mixing time and speed
Extending the mixing time and appropriately adjusting the mixing speed can make the filler fully dispersed in the silicone rubber matrix. Normally, it is recommended to control the mixing time between 5-15 minutes and the mixing speed between 40-60 rpm.


Use surface treated fillers
Surface-treated fillers, such as silica treated with silane coupling agents, have better dispersion and compatibility with silicone rubber, which can effectively reduce the occurrence of unpalatable powder.


Add dispersant
Dispersants can reduce the surface tension of fillers and reduce their agglomeration. Commonly used dispersants include silicone compounds and organic acid ester compounds. Adding an appropriate amount of dispersant during the mixing process can significantly improve the dispersion of fillers.


Improve mixing equipment
Choosing appropriate mixing equipment or improving existing equipment are also effective ways to solve the problem of unpalatable powder. For example, you can choose an internal mixer with high shear force or replace the rotor with a new type to improve the mixing effect.


Add filler gradually
During the mixing process, adding fillers gradually instead of all at once can effectively reduce the agglomeration of fillers. This method ensures that each filler added has enough time to fully mix with the rubber matrix.


4. Conclusion
The unpalatable powder phenomenon that occurs when mixing silicone rubber is mainly caused by factors such as poor compatibility between silicone rubber and fillers and unreasonable mixing process parameters. By optimizing the mixing temperature, time and speed, selecting appropriate fillers and dispersants, and improving the mixing equipment, this problem can be effectively solved, thereby improving the quality and production efficiency of silicone rubber products. In the actual production process, these processing methods can be flexibly adjusted according to specific conditions to better cope with the challenge of unpalatable powder.