How to make silicone molds without air bubbles?

Air bubbles are also known as packet wind, gas mark in the silicone rubber industry. There are still white air bubbles or white dots as silicone molds are completed, and you can see a shape of a honeycomb (sponge-like) inside the bubble, and feel soft and sticky when the bubble is torn or cut. Air bubbles not only affect the appearance of silicone molds, but also shorten the service life of silicone molds and reduce its performance.

 

The main reason for the air bubbles remain in the silicone rubber mold surface is that the air bubbles are not be removed completely. For this situation, you can mix the silicone rubber and hardener evenly and take them to de-air if you have a vacuum machine. If you haven’t vacuum container or tank, you should deal with the problem by reducing the proportion of the curing agent, for example, the mixing ratio can be changed from 4% to 1% -2%. Then the time of reaction for silicone rubber will be slower in the earlier period, and he air will be out of silicone molds to release air bubbles.

Secondly, the factor for the air bubbles remain in the silicone molds surface may be that condensate or excessive release agent is present on the original model. So, you should dry the model with the air gun. If you choose a wooden model, air bubbles will be generated in the gap. You can make silicone molds without air bubbles by filling these gaps with putty.

 

Thirdly, why are there air bubbles in the silicone molds surfaces can be due to the reason of incomplete vulcanization. So you had better extend the curing time to ensure complete curing for silicone rubber. Otherwise, it is easy to become soft after molding; the surface of silicone molds will have air bubbles.

 

Of course, please don't underestimate the importance of the curing temperature. Too high or too low curing temperature will induce air bubbles remain in silicone molds. For example, when the molding temperature is too high, the surface of the silicone rubber material is forming during the process of pressurization, then air has been trapped inside it and it is very difficult to discharge, which will result in forming air bubbles.

2017-10-13