The frequency of use of silicone products in life is very high, many things in our daily life may be made of silicone, sometimes when we usually use silicone products, we will find that the surface or inside of silicone products will produce bubbles, for the reasons of silicone products have bubbles, why silicone products will have bubbles and how to deal with the problem of silicone products.
1. How to solve the bubbles produced in the production process of silicone products
In the case of silicone has not been cured with a vacuum machine to bubble processing, can be a good solution to the problem, if there is no vacuum machine can also use defoamer, defoamer defoamer is not very thorough, if these two things are not available, you can adjust the curing time of silicone as long as possible, and then put there, silicone products will slowly discharge bubbles.
2. Causes and treatment of bubbles in thermal silicone sheet
(1) The vulcanization temperature is too low or the vulcanization temperature is too high is one of the main reasons for the foaming of thermal conductive silica gel sheet. Vulcanization temperature is an important parameter of silicone molding, usually silicone products are set at 160~200 degrees Celsius, but sometimes because the operation time outside the mold is too long or other reasons so that the mold has not opened the vulcanization machine for a long time, resulting in the temperature of the silicone molding mold is low and the vulcanization temperature of the silicone, at this time it will cause the product bubble after the molding of the thermal conductive silicone sheet. For this, we only need to increase the molding temperature, or open the empty mold into the machine to heat up for a period of time in operation to solve the problem. If the vulcanization temperature is too high, the molding temperature is too high, which will also cause thermal conductive silica gel sheet bubbles. Why is that? When the molding temperature is too high, the surface of the silicone material has begun to form in the process of clamping pressure, at this time the air has been trapped inside and it is difficult to discharge, so it will cause thermal conductive silicone sheet forming bubbles. For this reason, just reduce the molding temperature appropriately.
(2) The reason for the bubbles of silicone products is the lack of exhaust gas, silicone raw materials placed in the molding mold, at the moment of closing the mold will bring a lot of air, and the air is impossible to be integrated with silicone raw materials, if the air is not discharged, it will cause bubbles on the surface of silicone button molding.
(3) The structure of the mold is unreasonable, and the design of the silicone molding mold is not reasonable, which will also cause bubbles in the silicone molding, such as the arrangement of the product in the mold, the partition way, the mold parting way, the design of the mold size, etc., will cause poor bubbles, but the cost of opening a set of molds is high, and it is not easy to modify. If the silicone molding bubble is caused by the structure of the mold, then it is usually solved from the above mentioned points.
(4) The vulcanization time is too short, like the vulcanization temperature, the vulcanization time is also one of the important parameters of the molding of the thermal silicone sheet, and the length of the vulcanization time determines whether the thermal silicone sheet can be completely vulcanized. If the vulcanization time is too short, it will not only cause the thermal conductive silicone sheet to be soft after forming, but also cause bubbles on the surface of the thermal conductive silicone sheet. The occurrence of such defects can properly extend the vulcanization time of silica gel.
(5) The production process is also very important: Antioxidant RD is easy to produce bubbles in the mixing operation of the open mill, which is mainly the melting point of antioxidant RD is high and the operating temperature of the open mill is low. Special attention should be paid to the dispersion of zinc oxide when mixing rubber, and its dispersion uniformity will also cause the thermal conductive silicone sheet to bubble, so the rubber mixing process is also a very important link.
(6) The moisture content of raw materials used in the formula and whether the mixing operation and products are sufficiently dried after water cooling are mainly caused by the volatilization of water when sulfur is added.
3. Reasons and treatment methods for bubbles after curing of potting silica gel
First, the bubbles brought in during the mixing or filling process are not eliminated. During the mixing process, due to the large viscosity of the glue or the wrong mixing method, it is easy to bring air into the glue, and if the viscosity of the glue is large, the bubbles are more difficult to eliminate. If the viscosity of the glue is small and the glue cures slowly, the bubbles will slowly rise to the surface and automatically eliminate.
Second, the bubbles produced during the curing process. There are several reasons for bubbles in the curing process: the curing speed is too fast, the heat dissipation temperature is high, the shrinkage rate of glue curing is large, and the amount of solvent and plasticizer added in the glue is too easy to produce bubbles in the curing process. Another is that the formula of silica gel contains a small amount of volatile impurities, which are vaporized to form bubbles when heated and cured.
In view of the causes of silica gel bubbles, there are several methods to avoid or remove bubbles for reference.
For the first reason, vacuum or centrifugation can be used to solve the problem. You can also take the method of standing for a period of time (30 minutes -2 hours) and wait for the bubble to float up by itself. If there is no vacuum machine, stir in the clockwise direction for 2 to 3 minutes, and place the glue for 5 to 20 minutes after stirring, but this method is only for those glue with thinner viscosity, if the glue is very thick, the bubbles remaining in it are not easy to rise and discharge.
For the second reason, the bubbles caused by volatile impurities in the silicone formula can be baked at low temperature, so that these impurities evaporate first, and then increase the temperature curing, so that there are no bubbles. To solve those problems in the curing process, it is necessary to adjust the overall formula of the glue.
4. The reason why there are small bubbles on the surface of silicone products
In fact, we can find that after the rubber surface is dry, break the bulging rubber, and you can see that it is empty, indicating that this is a small bubble. If you start in just a few minutes, it should be too high water, but if your product bubbles are sporadic, it means that the water is not too high, and if the rubber water is too high, the application period of your product should be shortened! I still doubt whether the bubbles in the rubber material are because your A component is too thick and air is stored in it when you put it into the rubber material bucket or your material is mixed unevenly.
There are not many opportunities for users to really have this problem, which is occasional, and more than 90% of products have no complaints in this regard. We have also suspected that there is no problem with the user's glue machine caused by the foaming phenomenon. But the user insists that his glue machine is no problem, we can only find the reason on the glue.
The A component in the two-component silica gel is vacuumed, and it is also noted when packaging. But the problem of moisture was not taken into account. Do single-component products know that dehydration is very important, do two-component products A component is indeed not seriously dehydrated. I always feel that it is two-component anyway, and A little water in component A will not affect the storage period. Through the above analysis, it seems that component A should also be considered seriously dehydration.
