Jiangxi Yanxun Silicon Materials Co., Ltd.

Application of Polysilazane in Photoelectric Coating

Polysilazane is a highly active polymer with Si-N bonds as the main chain, which can react strongly with water, oxygen and a variety of polar substances. This material has a wide range of applications in the ceramic, aviation, aerospace and coating industries. According to their structure, polysilazanes can be divided into organic and inorganic two categories. Organic polysilazanes carry organic groups on their side chains, while inorganic polysilazanes, also known as perhydropolysilazanes or PHPS, contain only three elements, silicon, nitrogen and hydrogen. Because of its simple structure and high market value, PHPS is mainly used to make ceramic precursors and thermal insulation materials. PHPS does not contain organic groups and therefore can be converted by a variety of methods at lower temperatures and has good adhesion to the substrate. The characteristics of the converted coating include corrosion resistance, high and low temperature resistance, gas isolation, long-term durability, transparency and scratch resistance, so it has been widely used in the preparation of coatings. In photoelectric technology, an important branch of modern science, the development of coating technology is a challenge, and PHPS coating technology plays a vital role in improving the performance of photoelectric equipment and solving key technical problems in the photoelectric field.

Water-based silicone resin

Water-based silicone resin is a silicone resin emulsion with water as the dispersion medium. At present, it is widely used in silicone modified coatings, such as silicon modified acrylic emulsion, silicon modified polyurethane emulsion, silicon modified polyester emulsion, etc. The introduction of silicone in traditional polymer emulsion can enhance its aging resistance, waterproof, high and low temperature resistance, hardening and other properties. In the process of emulsion polymerization, silicone chain segments are introduced into the molecular structure of high molecular polymers. Commonly used silicone precursors are silane coupling agents, such as silane coupling agent 171,560,570, etc. These silane coupling agents are all trifunctional alkoxy structures. In the aqueous system, the alkoxy groups are hydrolyzed into hydroxyl groups, and the hydroxyl groups are further dehydrated and condensed to form a crosslinked structure. When the crosslinking degree is too large, the stability of the emulsion will be affected, resulting in gelation and unusable, therefore, there are certain restrictions on the amount of silane coupling agent. Generally, the amount is 1 ~ 10%. If the amount is too small, the modification effect is not obvious. If the amount is too large, the stability of the emulsion will be affected. The effect of silicon modification is limited or even not obvious.

Fundamentals of Silane

Silanes contain two different chemical functional groups, one end can react with hydroxyl groups on the surface of inorganic materials (such as glass fibers, silicates, metals and their oxides) to generate covalent bonds; the other end can generate covalent bonds with resins, so that the two properties are very different. The material is combined to improve the performance of the composite material. The silanization treatment can be described as a four-step reaction model:(1) hydrolysis of the three Si-OR groups connected to silicon into Si-OH;(2) dehydration condensation between Si-OH to form Si-OH-containing oligomeric siloxane;(3) formation of hydrogen bonds between the Si-OH in the oligomer and OH on the surface of the substrate;(4) formation of covalent bonds with the substrate accompanied by dehydration reaction during heating and curing.

Synthesis of Silicone Resin

The monomers for the preparation of silicone resins are chlorosilanes, which can be alcoholysis to give the corresponding alkoxysilanes. Because they are not corrosive, and have greater hydrolytic stability than the corresponding chlorosilanes, easy to preserve, easy to separate, are widely used monomer components. Changing the number of functional groups in the monomer and selecting different substituents can produce polymers with different degrees of polymerization, branching and crosslinking, and obtain products with different properties to adapt to different uses. The number of functional groups in the monomer can be expressed by the ratio R/Si of R to Si of the monomer mixture (R is the number of substituents and Si is the number of silicon atoms). Take the hydrolysis condensation of methyl chlorosilane as an example: when R/Si>2, (CH3)2SiCl2 and (CH3)3SiCl are mixed and hydrolyzed to produce oily polymers with lower molecular weight, namely silicone oil. When R/Si = 2, pure (CH3)2SiCl2 is used for hydrolysis and condensation to generate high molecular weight linear polymer, which is the base material of silicone rubber adhesive, also known as silicone rubber. When R/Si<2, (CH3)2SiCl2 is used to CH3SiCl3 co-hydrolysis. Or CH3SiCl3,(CH3)2SiCl2 and SiCl4 co-hydrolysis polycondensation, the formation of the network structure of the polymer, that is, silicone resin, appropriate change the value of R/Si, you can get different properties of silicon-containing polymers. R/Si is small, that is, when the proportion of trifunctional or tetrafunctional silicon-oxygen units is high, after curing, the crosslinking degree is high, and the silicone resin is hard and brittle; while R/Si is large, that is, the proportion of bifunctional silicon-oxygen units is high, and the flexibility of silicone resin after curing is good, and the R/Si usually used is between 1.2 and 1.5.

Other applications of MQ resins

It can be used to prepare organic silicon defoaming agent with high temperature resistance and strong alkali, and the defoaming agent also has the advantages of non-toxic and environmental protection. By adding high-viscosity hydroxyl silicone oil and MQ silicone resin to synthesize a network polymer with a high degree of branching, in order to improve the high temperature resistance and strong alkali resistance of the defoamer. Using MQ silicone resin containing SiH group or aralkyl group as crosslinking agent, under the action of platinum catalyst and silicone resin containing vinyl group and high phenyl group, the packaging material containing phenyl silicone resin was synthesized. The material has good compatibility and transparency, high hardness and high refractive index, and can be used for LED packaging and lens production. MQ resin-modified carboxyl silicone oil was obtained by the hydrosilylation reaction of MQ-containing silicone oil and silyl enoic acid ester under Pt catalysis. Its combination with amino silicone oil emulsion can give the fabric a better soft, smooth, plump feel.