How to prevent air bubbles in silicone rubber molding process

①Insufficient exhaust gas causes foaming

    The silicone raw material is placed in the hot vulcanization mold, because there will be air residue at the moment of closing the mold, and the air cannot be integrated with the silicone raw material. If the air is not discharged, it will cause the silicone after molding. Air bubbles are generated on the surface of the product.

Solution: Increasing the exhaust port, exhaust time, and exhaust times during the vulcanization process can mostly get better results.

②Silicon vulcanization problem

   The vulcanization temperature is too low. The temperature of thermally vulcanized silicone rubber is an important factor affecting the molding. The solid silicone vulcanization is set at 170~200 °C, but due to the long operation time outside the mold or other reasons, the mold has not been opened for a long time. temperature, resulting in a low temperature of the silicone molding mold. Below the vulcanization temperature of normal silica gel, the silica gel is prone to bubbles after molding. Among them, the lagging substrate will also have an effect on the temperature, so it is recommended that the lagging material should also be heated before bonding.

Solution: increase the molding temperature, open the empty mold into the machine and heat it for a period of time before production.

②-2 The hot vulcanization temperature is too high, and the vulcanization temperature is too low, which will cause foaming; in real life, the silicone molding temperature is too high, which will also cause the foaming phenomenon. Experts tell us that when the molding temperature is too high, the silicone on the surface begins to form during the molding process, and once the vulcanization degree is complete. Air trapped inside is hard to get out.

Solution: Control the thermal vulcanization temperature of the silicone before closing the mold, rather low than high, and exhaust while heating up.

②-3 The thermal vulcanization time of silica gel is too short. Like the vulcanization temperature, the vulcanization time determines whether the silica gel is completely vulcanized (completely vulcanized). If the curing time is too short, it will not only cause the silicone to become soft after molding, but also more likely to cause surface bubbles.

Solution: Extend the curing time of the silicone.

③ Wrong choice of silicone glue

  For non-pure silicone products, the heat conduction of metals (stainless steel, copper, iron, aluminum alloy, metal parts) is faster than that of silicone. The silicone glue applied to its surface also has an effect on foaming. Mostly appear in local blistering or non-sticky.

 Therefore recommends the use of brand silicone glue. Generally, CL-24 is used for the high-temperature vulcanization encapsulation process of solid silica gel, and CL-26AB glue is used for liquid silica gel injection molding and metal-adhering plastic.

④The structure of the mold is unreasonable

  The design of the silicone molding mold is not very reasonable, including the setting of the vent hole, the selection of the position of the parting line, etc. There is a reason for the formation of bubbles in silicone molding. For example, the arrangement of products in the mold, the partition method, the mold parting method, and the design of the size of the mold will cause bad bubbles. Due to the high cost of the mold, it is not easy to modify;

Solution: If the silicone molding bubbles are caused by the structure of the mold, it is usually solved from the points mentioned above.