Causes of bubbles in LSR products

There are 7 reasons for bubble foam of LSR products. Here are the results of our analysis:

1. vulcanization temperature is too low

Vulcanization temperature is an important parameter in the process of silicone rubber molding. Common silica gel products are set at 160-200 ℃, but sometimes the mold cannot enter the machine in time due to long mold operation time or other reasons, so the low silica gel forming temperature will cause bubbles in the formed products. In this case, how to solve the bubble problem? We need to raise the forming temperature or heat the mold for a long time.

2. too high vulcanization temperature

If the vulcanization temperature is too low, bubbles will appear in the silicone parts. However, if the vulcanization temperature is too high, bubbles will also be generated. Why? Because if the molding temperature is too high, the surface of the silicone material has begun to form during the mold locking process. (the clamping process is not completed), the air is trapped in the mold, and it is difficult to release the air in the mold, which is easy to produce bubbles.

We can solve this problem by properly reducing the forming temperature.

3. too short vulcanization time

Similar to vulcanization temperature, vulcanization time is also one of the important parameters for silicone molding. The length of vulcanization time determines whether the silicone resin can be completely vulcanized. If the vulcanization time is too short, the silica gel product is not cooked, and there are bubbles in the product.

4. mold structure

If the mold structure is unreasonable and the design of silicone molding is unreasonable, bubbles will also be generated during silicone molding.

The design of exhaust structure is unreasonable. The exhaust position should be designed at the end of product forming. If necessary, vacuum pumping should be designed in the mold.

5. the mold is not clean

When cleaning the mold, pay attention to the method. Gently scrub it with a soft cloth to avoid mold deformation.

6. the design of glue injection port is unreasonable

For some large-scale liquid silica gel products, many engineers will design multiple injection ports in order to improve the filling of silica gel. Although the liquid silica gel material looks very viscous, it actually has good fluidity. Generally, there is no need to worry about filling. If multiple fuel injection ports need to be designed, the positions of fuel injection ports must be balanced and symmetrical, and the exhaust ports shall be designed at the corresponding positions. We do not recommend designing more than one injection port.

7. exhaust of feeding system

When installing new materials or replacing materials in the feeding system, if there is gas in the pump body, the pump shall be discharged. How to distinguish whether there is a gas pump: open the exhaust ball valve of the pump body and press the upward or downward rubber pump to check whether there is foam / sound in the exhaust ball valve of the material pump. If there is foam or sound, then we can ensure the gas.