Introduction to Organic Silicone Adhesive

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In the last few blogs we have introduced many aspects of silicone resins and their application products. Today, we are going to introduce one of its main products- silicone resin adhesives.

The Basis of Organic Silicone Adhesive

Organic silicone resin adhesive could be categorized to two main types- the ones whose main component is silicone resin and the others who mainly consist of silicone rubbers. It is due to the silicone resins, especially the silicone resins which contain phenyl has very good heating resistance. They could be the main components of high temperature adhesive. The organic silicone adhesive that uses the pure silicone resins as the foundation is made by the silicone resins, some inorganic fillers and organic solvents which are applied to bond metals or FRPs. When it is under the solidification process, it is needed to be heated and compressed.

To use KH-505 high temperature silicone adhesive as the example, it is made by the base of polymethyl phenyl silicone resins with titanium oxide, zinc oxide, asbestos and mica powders which are inorganic fillers. Among the raw materials, asbestos could curb crazes caused by the shrinking of the adhesive layers. The mica powders could increase the wetting property of adhesive layers. The titanium oxide could increase the corresponding strength and oxidation resistance. The zinc oxide could neutralize the slight acid and resist the corrosion to the materials. The solidification condition to it is 270 Celsius Degrees / 3h with the pressure of 5MPa; then continues to go through solidification without pressure under the condition of 425 Celsius Degrees / 3h and the adhesive strength will be better. KH-505 silicone resin adhesive’s outstanding property is the heating resistance, it could avoid damages from being used under 400 Celsius Degrees. It could be used for non-structural parts of metals or ceramics’ bonding and sealing under high temperature. The shortage is that the strength is lower and the toughness is smaller thus it could not be the structural adhesive.

The organic silicone adhesive which is made from the base of modified silicone resins are usually the silicone resins that are modified from epoxy, polyester, phenolic aldehyde organic resins. These adhesives could make use of the curing agents of organic resins to cure to lower the curing temperature and maintain a higher adhesive strength. Epoxy resin is the one of the organic resins which has the best adhesion. This is due to the molecular chain of epoxy resin contains polar hydroxyl and ether bonds which allow it to have good adhesion to all kinds of matters. It is due to the low shrinking of the curing process of epoxy resins which leads to the internal stress, this helps to the enhancement of corresponding adhesion. The high temperature which is made mainly from epoxy resin modified organic silicone resins is to be heating resistance tested under 200 Celsius Degrees for 10 hours, the corresponding shear resistance strength could reach 93 MPa. When the silicone resin adhesive which is modified from epoxy, it is because the existence of a large amount of epoxy groups, there must be some curing agents to be added to lower the curing temperature to increase the crosslinking degree and heating resistance to maintain the corresponding heating resistance at a higher level.

Properties & Applications of Pressure Sensitive Adhesive

Pressure Sensitive Adhesive or PSA is one type of adhesive which has a strong adhesion with other matters by just press it slightly. In most time, it could be also be able to be released by just pulling it slightly. It is widely applied in manufacturing adhesive tapes, some special types of tags, tampons and other similar products. For the requirements of macromolecular materials in pressure-sensitive adhesives could be partly controversial, they should be required to be stick to the surface of base materials with high shear resistance and peel strength, and they must to be completely removed from the surface of base materials when required. Organic silicone PSA are made from the raw silicone rubber, silicone resins, vulcanizing agents to be mixed with other additives. The temporary mass-applied ones are still solvent-type organic PSAs, the examples are toluene, xylene, dichlorotoluene, petroleum ether and the mixtures of them. Silicone rubber is the basic component of organic silicone PSAs, it is in order to make the PSAs have better adhesion, it is required to allow the silicone rubber has a higher molecular quantity (the molecular quantity should be more than one hundred thousand). Only under this circumstance, the adhesive could only to have good flexibility, cohesive strength and low mobility. The PSAs who have a proposition of silicone rubber is dry in room temperature, it will have adhesion when increase the pressure and temperature while the PSAs which contain more raw silicone rubber will have better adhesion in room temperature.

Organic silicone PSA is a new type of adhesive which has a bright developing future. Not only it has the good bond strength and initial viscosity, but also it has a lot of unique properties.

1.      PSAs have good adhesions to surfaces of different materials that have different surface energies. Therefore, it has good adhesion on the unprocessed materials which are hard to be bound like Teflon, polyimide and polycarbonate.

2.      It has evident cold and heating resistance, it could be used for a long-term period under the temperature between -73 and 300 Celsius Degrees and maintain its bond strength and softness.

3.      PSAs have good chemical inertia; they have long product life and have evident wetting resistance and electrical properties. Therefore, it is capable to be the raw material to produce the electric machinery insulating tapes.

4.      PSAs have excellent biological inertia and some degree of liquid penetration; they could be used to bond the medicines and skins of humans.

Summary

Organic silicone resin adhesives have many types and as described in the paragraphs above, they could be applied in different products or industries according to their different chemical structures. As one of the most important application of organic silicone resins, the corresponding adhesives are also urgently required by the market and the relevant market is growing fast as well.