The reasons why the raw materials for silicone rubber mixing need to be parked for a period of time are as follows:
The temperature of the silicone rubber mixing raw material is as high as 100 degrees when it is just out of the pot. At this time, the silicone rubber mixing is called the blank rubber. After cutting, parking and cooling, we extrude the blank rubber to remove impurities and then use plastic oil paper to pack.
After packaging, it is sent to the warehouse for parking and cooling, and finally packed and packed out of the warehouse. So why should the silicone rubber compound raw materials be parked for a period of time?
The production process of silicone rubber mixing raw materials is continuously kneaded by the powerful mechanical force of the kneader, and the temperature is as high as more than 100 ℃ when it comes out of the pot
Once these external forces disappear, because most of the silicone rubber is mixed with sandalwood and flowing raw rubber, there will be strong elastic recovery (that is, shrinkage), which is an inherent characteristic of raw collagen materials.
The higher the temperature of the silicone rubber mixing surface, the lower the hardness. If the temperature is too high, it is unfavorable for product molding. During park cooling, shrinkage progresses slowly over time, and after a period of cooling, it provides shape and dimensional stability, which is necessary for molding operations.
In the process of filtration and extrusion, because the temperature of the raw material for extruding silicone rubber is too high, the elastomer inside is damaged. The silicone rubber compounding usually needs to be parked and cooled twice before it can restore its shape and size, which is very important for the subsequent rubber mixing. Also helpful.
If the mixing temperature of silicone rubber is too high, the following problems are likely to occur in the process of adding the vulcanizing agent: the water-based vulcanizing agent is easy to volatilize, and the paste-like vulcanizing agent is easy to catch fire.
Even if the vulcanizing agent is successfully added, the self-cooking phenomenon of silicone rubber products is prone to occur, which leads to the scrapping of materials, and the silicone rubber mixing with too high temperature is prone to mucous membrane phenomenon when the silicone products are formed.
When the silicone rubber is parked and cooled, all kinds of auxiliary materials in the silicone rubber mixing will be further dispersed evenly with the parking. Although the silicone rubber is mixed with the continuous high-intensity stirring of the kneader during the production process, various auxiliary materials have been mixed evenly.
However, the mixing of silicone rubber is limited by the mixing time, and the required uniformity of dispersion is often not achieved. During the parking process, although the mechanical external force of the kneader no longer exists.
However, these auxiliary materials can still continue to be dispersed by means of the movement of the macromolecular raw rubber segment in the silicone rubber mixing, and the dispersion process that is too late in the mixing can be completed.
Although these processes cannot be seen by the naked eye, they can be confirmed by high-magnification electron microscope observation before and after parking, and can also be explained by comparing the vulcanization performance of silicone rubber products.
