Frequently Encountered Problems And Solutions For Mold Silicone

- Aug 18, 2020-

During the operation of mold silicone liquid silicone mold silicone, I believe that everyone has encountered different problems. The following editor will introduce to you the problems and solutions encountered during the operation of mold silicone!

One: The mold silicone is partially cured or not cured

When making silicone molds with liquid silicone, sometimes we waited 48 hours and found that the mold silicone was still not cured, or only partially cured and partially cured. What caused the non-curing?

Reason 1: Too much curing agent or too little curing agent will affect the curing of silicone;

Solution: Add according to the specified curing agent ratio, and see clearly whether the instructions are volume ratio or weight ratio.

Reason 2: Different types of curing agents cannot be mixed, and the additive mold glue will not react when it comes in contact with the tin component in the condensation silicone;

Solution: Use the corresponding type of curing agent. Operating tools are also classified and not mixed. If it is an addition molding silica gel, never come into contact with condensation products.

Reason 3: The mixing of silica gel and curing agent is not uniform;

Solution: When operating the silica gel and curing agent, stir well, pay attention to the bottom of the container.

Reason 4: Incomplete curing (not dry) only occurs on the contact surface of the master mold, and other parts are cured intact;

Solution: Be sure to put a layer of isolation film on the surface of the master mold to prevent the components in the master mold that are not conducive to the curing of silicone from contacting the mold silicone.

Reason 5: The temperature is too low to cause non-curing. When the operating temperature is below 0 degrees, the silicone and curing agent will not react;

Solution: When the temperature is 20-30 degrees Celsius is the ideal mold silicone curing temperature.

2: What is the reason for the poor tensile force of mold silicone?

Mold silica gel has the characteristics of high temperature resistance, good tensile force, many times of mold reversal, and high frequency of repeated use. It is loved by silica gel manufacturers! However, some manufacturers add a lot of silicone oil to the silicone in order to make the silicone easier to handle in the production of mold silicone! Everyone knows that silicone oil can destroy the molecular weight of silica gel, and the viscosity of silica gel is reduced, making the silica gel softer and easier to operate, which eventually leads to poor tension in the production of silicone molds! Fewer times of mold reversal!

What are the influencing factors of the low number of mold silicone reversals? In fact, we have already mentioned the first point above. Due to the excessive addition of silicone oil, the second point is the use of low-hardness silicone molds for building products. Because the silicone is too soft, the performance is not strong and insufficient, which eventually leads to tension and tension. The tearing strength is reduced, and the produced mold is easy to deform, and the number of mold turns is reduced! There are also some small products with more complicated patterns, because the silicone is too hard for too long, it will be very brittle! It is easy to break, and opening the mold with a hard silicone mold will also reduce the number of mold reversals! As for solving the problem of the low number of times of mold silicone reversal, we only need to focus on the concept of making molds with suitable hardness of silicone!

Three: The solution to silica gel thickening?

Generally speaking, liquid silica gel is good for half a year. If it exceeds one year, the viscosity of silica gel will thicken with time. The expired liquid silica gel will solidify into a ball with almost no fluidity. We are very difficult. The expired liquid silicone will have very poor fluidity and almost form a ball, which will cause the AB glue to be difficult to stir and the phenomenon of non-leveling during filling. If a large amount of silicone oil is added, the tear resistance and toughness of the silicone will decrease after curing. How to increase the fluidity of liquid silicone without affecting the performance of silicone?

There is something called an expansion bolt on the market. You can buy a suitable length according to the amount of silicone, as shown in the figure below. After buying it back, we use pliers to break the front opening of the expansion bolt cover into a cross shape, then tighten the nut, tighten it, and a simple mixing head is ready. Next, the stirring head was stuck on the electric drill and began to stir frantically, and the stirred silica gel resumed its fluidity again. The liquid silica gel that has just been stirred will be a little hot due to friction and molecular movement, and has a lot of bubbles. It is unwise to use it immediately. First, it will foam easily, and second, because the heat itself will speed up the reaction, it will still foam easily , Let's let it go for a while, let it cool before use.

Four: Why does the mold silica gel have fewer re-molding times?

① Too much silicone oil is added in the process of making the mold, and the silicone oil destroys the molecular weight of the silica gel, so the mold will be less durable and not durable.

② If it is said that a small product with a more complex pattern is used to open the mold with a harder silicone, there will be less re-molding, because the silicone will be brittle and easy to break when it is too hard. On the contrary, if you make large products and use low-hardness silicone to make molds, the result will also be unsatisfactory. Because silica gel is too soft, its tensile strength and tear strength will be reduced, and the resulting mold will be deformed, so the number of mold turns will be reduced. The quality of the mold glue itself is very good, and there is no difference between good and bad silicone, only suitable and unsuitable. If we use silica gel suitable for the hardness of the product to make the mold, this situation will not occur.

Five: Why does mold burn occur in mold glue?

Because unsaturated resins and resin products are added with peroxide curing agents, they will generate a lot of heat when they react with the resin. Generally, the curing time of the resin is 3 minutes, so the mold must be demolded as soon as possible after 3 minutes to prevent the silicone mold from becoming Produce burn-in phenomenon.

Six: Why does the mold glue appear to dry on the surface?

Condensation mold silica gel, it is cured by absorbing moisture in the air. In the process of making silica gel, the water is evaporated to dryness without adding proper amount of water. This phenomenon will occur.

Solution: This phenomenon is not a product quality problem, but because the water content is not controlled, the storage period of the silica gel is increased, and the shelf life is long, some phenomena will appear. As long as the silica gel is used, an appropriate amount of 0.05% water is added and mixed evenly. Some situations can be resolved.

Seven: How to solve the problem that the mold silicone does not cure?

When making silicone molds, due to some reasons, the mold silicone has not been cured for 24 hours. Today we will analyze how to control the ratio of silicone to curing agent to avoid non-curing.

Mold silicone curing will be affected by temperature, high temperature will cure faster, on the contrary, low temperature will cure slower, so when making silicone molds when the winter weather is about to enter, the ratio of silicone and curing agent should be changed appropriately To ensure the normal curing of silica gel.

The greater the amount of curing agent added, the faster the reaction speed of silica gel, and the ratio of curing agent to silica gel should not be less than 1.5%. If the amount of curing agent added is too small, it will not cure for a long time. Adding no more than 5% of the curing agent will generally not have much effect on the hardness, tensile force and tear strength of the silicone.

①The amount of curing agent is 1%, the colloid is still flowing in 2.5 hours, and it can be demoulded in 6-8 hours;

②The amount of curing agent added is 2%, the glue will still flow after 50 minutes to 1 hour, and it can be demoulded in 2-3 hours;

③The amount of curing agent is 3%, the colloid is still flowing in 28-30 minutes, and it can be demoulded in 1.5-2 hours.