Why silicone rubber stays uncured?

Firstly, it can be due to the reason of adding too much or too little curing agent. Increasing  the  amount  of the  curing  agent  will accelerate curing,  while  decreasing  the  amount  will slow  it  down. However, there is a limit to how much the curing agent can be increased or decreased.  Since condensation-cure products are used at room temperature, results can be affected by atmospheric temperature and humidity. The curing speed is faster at higher temperatures and high humidity, while it is slower at lower temperatures and lower humidity. Generally, the ratio of silicone rubber and curing agent is 100:2 at room temperature 25℃; When the operating temperature rises to 38-45℃, the proportion of curing agent should be 1%; If the local temperature drops to 10℃, then the maximum mixing ratio should be 5%; once the temperature of local weather is -5℃, no reaction will happen between the silicone rubber and catalyst. So, you must add the specified amount of curing agent according to local weather and humidity. Otherwise, uncured silicone will occur.

The second reason may be that you did not mix the silicone and curing agent thoroughly. If you did not stir evenly, it will appear the phenomenon of partly cured and partly uncured silicone. You should avoid this kind of situation of inadequate mixing. Otherwise it will generate many problems, such as sticky of the silicone mold, decrease of service time of silicone mold and even the waste of silicone rubber.

The third factor of uncured silicone is that the curing agent is not suitable. We often say to choose the right silicone with suitable hardness, viscosity, and colors to make molds. In fact, the choice of curing agent should also be determined by your product to be produced. We advise you use the correct curing agent to make mold. Our company deployed different models and specifications of the curing agent according to the different mold you want to make.

Fourthly, curing inhibition for addition-cure products may lead to an uncured silicone. Specifically, there are two cases. One is the inhibition only where the RTV silicone rubber is in contact with the master. The situation is treat the surface of the master with Barrier Coat. Another is RTV silicone rubber fails to completely cure. For this situation, please use a special mixing spatula and container. Then, work in an environment free from any cure inhibiting substances.

In addition, uncured silicone has a great relationship with other several reasons. For example, the room temperature is too low for the RTV silicone rubber to cure. You should raise the room temperature to between 20℃ and 30℃ for this case. It is also because the RTV silicone rubber has been improperly stored and deteriorated over time. So, you have to keep RTV silicone rubber in a cold, dark location and avoid storage under high temperatures and high humidity or where it can be exposed to direct sunlight. The last reason may be that the RTV silicone rubber has been stored for too long or is from an old production lot. Normally, we advise you do not store RTV silicone rubber for periods of longer than 3 months and use the RTV silicone rubber within 1 month after opening.