Introduction to Organic Silicon Coatings - Part 1

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As we mentioned in some past articles, silicone resins contain excellent properties like heat resistance, cold resistance, humidity resistance and weather resistance. It could be used as special coating and it takes an utmost important role in special coating industry. There are many types of organic silicon coatings and we will discuss some of them in this blog article.

Organic Silicon Heat Resistance Coating

There is no clear conception on the definition of heat resistance. Heat resistance coating usually refers to the coating that its small coating film’s color and glossy are changed little, the coating film is complete and has no breaches, and it could still maintain proper physical mechanical properties and provides some protections. Heat resistance coating is widely used in high-temperature places, like steel chimneys, high-temperature steam pipes, heat transformer, high-temperature furnaces, high-temperature reaction equipment, engine parts and some decorations for military industry devices, it prevents the metals like steel from thermal oxidation corrosion to ensure the device to be used for a long-time. As the developing of aerospace and universe navigation, the demand on this type of coating is getting stronger and the consuming amount is getting bigger. Now there are many types of heat resistance coating and they could be divided to organic heat resistance coating and inorganic heat resistance coating.

It is in order in improve its pros and avoid the cons, and to fill the blanks with each other, it is usually to use organic resin and inorganic coatings to match or chemical modifying inorganic organic heat resistance coating. As for the silicone resin that used as the base material for heat resistance coating, many organic resin modified silicone resins are also applied besides pure silicone resins. When silicone resin modified organic resin’s component has more than half of organic silicon, its heat resistance will be increased evidently. Therefore, both of them are widely applied in heat resistance coatings, and they are important in them. Generally speaking, the latter one has worse hear resistance than pure silicone resin, but its solvent resistance, chemical resistance and adhesion are all better than pure silicone resin. Also in some specific conditions, to use silicone resin that contains organic resin could get better using effect. However, the thing that is needed to be pay attention to is the ratio of methyl and phenyl in the organic silicone low polymers of modified resins. It is due to phenyl functional group is better than methyl functional group in heat resistance but worse in physical mechanical properties. Therefore, among the modified resins those contain the same amount of organic silicon, if the ratio increases, then its coating thermal plasticity, light retention and color retention will be lower, but its physical mechanical properties, heat and micro breaching time will increase. Therefore, the designs of modified resins and corresponding organic silicon low polymer should be according to the special requirements come from the actual usages.

When matching the organic silicon heat resistance coating, some filler like mica powder, talcum powder, calcium carbonate and pigment like aluminum powder, zinc powder and carbon black and catalyst like zinc, iron and some other salts into silicone resins. The types of filler and pigment will have big influences on heat resistance. The filler and pigment used in heat resistance coating design will have high-temperature stability besides the general properties. In other words, they will not be decomposed, and their colors will not be changed. Thus, inorganic filler and pigments are more applied in this field.

Weather Resistance Coating

The coatings that used in outdoors will need to endure sunscreens, oxidation, and corrosion from rains. It is because organic silicone resin molecules do not have unsaturated chemical keys, thus it has outstanding resistance on air corrosion, and UV is hard to make it to be breached or crosslinked. When it is under extreme sunshine, it will not be breached and it has excellent weather resistance. For example, the pure silicone resin coating film could be exposed to extreme sunshine for 12 years, but no breaches occur on it and its coating film is complete as well. This proves it has very excellent weather resistance. Therefore, it is applicable to use a large quantity of powdered coating to make non-powdered coating. But it is since the manufacturing cost of silicone resin is high, and its solidification and adhesion to base material are dissatisfied, therefore, they are fewer to be used as the weather coating base material directly. In coating industry, this property of organic silicone resin is used to improve other organic resins and they are mainly used as the base materials of weather resistance coating. Recently, the work progresses much on modifications; it is one of the main research directions in coating use organic silicone resins. This type of organic silicone modified resin painting is cheaper than organic silicon resin painting. It could also be dried in room temperature, and it is convenient to use. It also has many improvements in weather resistance, decorations, heat resistance, isolation and waterproof to compare with the unmodified silicone resin painting.

The weather resistance of modified resin has positive relationship with the quantity of silicone resin in the design. Also, it is related to the organic silicon low polymer that being used of modifying agent. The more Si-O-Si keys organic silicone low polymer has, the better weather resistance is. The quantity of Si-O-Si keys is the main determination of resins’ weather resistance. Therefore in the design stage, when to choose between the organic silicone weather resistance resins that contain the same amounts, it is better to choose the one that has a larger ratio of methyl and phenyl.

Summary

As another type of important applications of silicone resin, the organic silicon coating may have different type of properties that applied in different industries. Thus we have introduced some types of them today. In the next article, we will introduce some other types of them to let more people know why ty are widely applied in industries now.