[1] Liquid Silicone Rubber for PU Resin description and application:

Liquid Silicone Rubber are generally named as two-part room temperature sulfurated silicone rubber, which features an exceptional fluidity and good operability. silicon flexible molds are used for mold duplication and delicate mold making for poli crafts, resin crafts lighting and candle crafts.

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It depends on your practical situation. Firstly you can deal the mixture with a vacuumizer if you have one;

If no such machine, you can reduce the mixing ratio of the hardener from 4% to 1%-2%.Then in the prior period of the reaction of the mixture will be slower, then the air in the mixture will exhaust by itself for a longer curing time to release the bubble.

1. The reasons why the silicone pad has a short service life are listed as follows:
The problem caused by inappropriate filtration of silicone rubber, and impurities in the packaging process due to the uncleanness of barrels and bags.
The short service life of the silicone pad has a close relationship with the adding amount of silicone oil. The more the silicone oil added, the softer the silicone pad will be. The silicone oil will destroy the molecule of the silicone rubber, thereby bringing about the non-durable and easy ageing of the silicone pad.
All the users should know the properties of pad printing silicone rubber. The service life of the silicone pad has close relationship with the size of the printed patterns. For example, if a big pattern to be printed, a big silicone pad is required; If a small pattern to be printed, a small silicone pad (the silicone pad has to be adjusted according to the size of the patterns, and the proportion between the size of the silicone pad and the pattern is 3: 1.

2. Why the patterns printed out is unclear and incomplete during the pad printing process?
The too hard silicone pad may cause the incomplete printing of patterns, because the pattern is too complicated. The silicon pad does not absorb the printing ink onto the silicon pad itself, may causes the incomplete printing of patterns. If the pattern is small with fine details, a soft silicone pad will be required.
The water content in the ink is too high, it may cause the incomplete printing of patterns with spots. It is strongly recommended that we should clean the inkcup, or change the ink or the thinner.
How does the water content form in the printing ink? Generally, it is related much with humidity in the air. In days with high temperature and especially heavy rain, most of the pad printing workshops will clean the floor frequently, the moisture rising from the floor and meet with the steel plate of printing machines will form water drops, then flow into the ink.

3. Why does the silicone pad can’t pick up the ink well?
Any silicone pad can pick up the ink. Generally, if a big pattern with big words to be printed, a silicone pad with higher hardness is required. If the silicon pad can’t pick up ink well may because the patterns or letters are too complicated but with harder silicon pad which didn’t pick up the ink from the cliche plate....

1. Why does the silicone rubber mold have few molding times?
The silicone rubber mold has few molding times is due to follwoing reasons: Adding too much silicone oil which will destroy the molecular of silicone rubber; Making the mold for small and fine detailed products with higher hardness silicone rubber which is easy to break; Making the mold for large products with soft silicone rubber which will reduce the tensile and tear strength of the mold, and the mold will have deformation. Thus, we should take the proper silicone rubber to make the mold for suitable products.

2. Why does the mold made of silicone rubber have an unsmooth surface with tracks and strips on it?
It is due to product or model to be molded should hasn’t been sanded or polished. If the mold or product is not sanded or polished, the mold made of whatever quality silicone rubber will not be good and smooth enough since the mold or the product itself is not smooth or perfect. Another case is that uneven brushing of the release agent will also bring about unsmoothness of the mold.

3. Why does the addition cure molding silicone rubber cures after a long time?
In spite of the correct proportion of the curing agent and the silicone rubber, the mold silicone rubber needs a quite long period for curing at the room temperature, because it is can be completely cured by heating up the temperature and stressing.
The general proportion of silicone rubber and curing agent is 10: 1 and their reactions are as follows:...

1. What should we do when the air bubbles appeared in the process of mold making?
To handle this situation depends on different cases. Under the condition of an available vacuum pumping machine, mix the silicone rubber and curing agent evenly and then take it to vacuum chamber to deair. If without a vacuum pumping machine, reduce the amount of the curing agent properly. For example, change the mixing ratio of the silicone rubber and the curing agent from former 4% to 1%-2%. In this way, the pre-crosslinking time of silicone rubber will slow down, so, the air in the mold will be eliminated gradually to reduce the air bubbles.

2. What should we do when silicone rubber mold didn’t cure evenly? The reasons why the phenomenon arises are as follows:
Incorrect mixing proportion of the silicone rubber and the curing agent due to unqualified weighing;
Uneven mixing of the silicone rubber and the curing agent, which may cause material wasting, and we should avoid it.

3. What should we do when the silicone rubber stick with the mold?
It arises because we didn’t handle the model mold (product mold) properly. Before mold making, the model mold has to be sanded and polished, and cleaned carefully concerning the master mold with a coarse surface or to make complex molds. And then brushing a layer of release agent evenly. General release agents include Vaseline, detergent, liquid paraffin, etc. The release agents can be selected according to the different textures of various model molds....