Application of Epoxy Silicone Resin

In order to achieve the product's heat resistance, thermal elasticity, certain adhesive strength, electrical insulation performance, and low-temperature drying performance, the following factors are required to be considered in the formula.

(1)The ratio of R/Si, which is the ratio of organic groups to silicon atoms, mainly determines the thermal elasticity and hardness of the product. To achieve a certain mechanical strength of the resin, it is necessary to consider in the formula that the macromolecules are not below a certain limit and have a certain amount of crosslinking degree. Polymers have both thermal elasticity and a certain degree of mechanical strength, and it is generally believed that R/Si=l 44 is better.

(2)The heat resistance of products with phenyl content is related to the phenyl content. Phenyl is not easily oxidized and cracked, but if the phenyl content is too high, not only does the condensation slow, but the resulting resin is also very brittle. Generally, the maximum content of phenyl is 35.4%.

(3)The selection and dosage of catalysts: The condensation reaction of polysiloxane with a burning oxygen group and epoxy resin can only be carried out at 230-240 ° C without the need for a catalyst. However, this thermal shrinkage reaction proceeds too quickly, and the reaction is completed within 3-4 hours. If the temperature does not drop rapidly to below 160 ° C after the reaction is completed. The resin will fully bond within 15 minutes, making the reaction difficult to control. According to reports, aromatic acids can open the epoxy group to generate light ethyl, which promotes its condensation with silanols. In addition to a small portion of the light groups between molecules that dehydrate to form rings, the majority of the products from the hydrolysis and alcoholysis of chlorosilanes are small molecular stars with light groups.

Therefore, a catalyst is needed to activate the tibial group for dehydration to achieve the goal of increasing molecular weight. Zinc mandalate is a good polycondensation catalyst. The polymerization method is better than the thermal shrinkage method because the endpoint is easy to control.

Benzoic acid has a ring opening effect on the epoxy group of epoxy resin, promoting the condensation of epoxy and silicone alcohol.

There are various ways to synthesize silicone epoxy copolymers, but commercial epoxy resins are commonly used as raw materials in industry. According to different usage requirements, modified epoxy resins generally use medium molecular weight epoxies such as E-35, E-20, and E-12, which have moderate OH and epoxy groups. Choose an appropriate variety of epoxy resin and low molecular weight silicone resin containing hydroxyl or tibial groups to undergo a co condensation reaction in a solvent to obtain a copolymer. Commonly used solvents include cyclohexanone, isophorone, methyl cyclohexanone, etc.

The reaction generates an epoxy silicone copolymer, in which the epoxy group is retained. Therefore, amine curing agents of epoxy resin can be used to cure at room temperature, such as diethylenetriamine, ethylenediamine, polyamide, etc. to form a film. If low molecular weight polyamide resin is used for curing, the adhesion and toughness of the coating can be further improved.

Three types of epoxy modified organosilicon resins can be prepared using the aforementioned silicon intermediates.

(1) Intermediate containing ethoxy silicon+epoxy E-20 HW2s, HW73 epoxy silicone resin.

(2) Epoxide E-20 HW65 epoxy silicone resin containing ethoxy and lithium based silicon intermediates.

(3) Containing silicone intermediate+epoxy E-zo -. HW766 epoxy silicone resin.