How long is it appropriate to vacuum the inverted silicone rubber used for making silicone rubber mold

Turn-over silicone rubber is the preferred material for making silicone rubber molds, but this viscous mold liquid silicone rubber has a disadvantage that it will produce bubbles during mixing and stirring, so it is necessary to use a vacuum machine to eliminate bubbles, and then someone will ask how long it will take to vacuum?

First of all, let's understand the parameter knowledge point of silicone rubber operation time. The operation time of RTV (room temperature vulcanization) silicone rubber raw material refers to the time period from the mixing of components A and B to the beginning of substantial thickening, that is, within this time period, the steps of silicone rubber mixing, stirring, vacuuming and pouring into the mold frame need to be completed.

The operation time of silicone rubber raw material is mainly related to the brand of silicone rubber manufacturer, silicone rubber type and temperature (humidity). Below, we make statistics on the operation time of various types of silicone rubber at 25 ° C for common mold silicone rubber raw materials in the market:

Addition semi-transparent inverted silicone rubber: This kind of food-grade silicone rubber has low viscosity, and the operation time is usually about 30-40 minutes. The operation time is greatly affected by temperature. It is recommended to vacuum within 20 minutes.

Condensation mold turnover silicone rubber: the operation time of this kind of silicone rubber is usually about 20 minutes, which can be adjusted by the ratio of curing agent between 100:1 and 100:4. It is recommended that the vacuum pumping be within 10 minutes.

Addition of fully transparent mold silicone rubber: This kind of silicone rubber has high viscosity, so the operation time is usually about 60 minutes, and the vacuum pumping time can be 30-40 minutes.

Summary: The vacuumizing time should be determined according to the operation time of the silicone rubber. If there are still many bubbles, the amount of glue to be mixed each time or the proportion of curing agent should be reduced. You can also contact the silicone rubber manufacturer to prepare the mold silicone rubber raw material with a longer operation time.