Modification of Silicone Modified Epoxy Resin

A series of organosilicon modified epoxy resins were successfully prepared using polymethyltriethoxysilane (PTS) through two methods: physical mixing and chemical copolymerization. Research has shown that chemically modified epoxy resin products have better performance than physically blended modified epoxy resin products.Therefore, the next focus of this article is to elaborate on the study of organic silicon chemical copolymerization modified epoxy resin.

Chemical Copolymerization Modification

Chemical copolymerization modification refers to the chemical reaction between active groups such as amino, hydroxyl, and alkoxy groups in polyorganosiloxane molecules and hydroxyl and epoxy groups in epoxy resin, in order to achieve chemical copolymerization and achieve the purpose of modification. After chemical modification of epoxy resin with organic silicon, the main products are organic silicon block or grafted epoxy resin copolymers, which can improve the compatibility between the two. In addition, introducing soft and stable Si-O chains into the coating structure of the cured resin can also improve the heat resistance and fracture toughness of the epoxy resin.

Functional group polysiloxane modified epoxy resin/coating

By introducing flexible polysiloxane segments with high bond energy into the epoxy resin system, an interwoven network structure can be formed between the two materials, significantly improving their compatibility, reducing the size between the two phases, and improving the flexibility of the epoxy resin coating, thereby enhancing the thermal stability, flame retardancy, and hydrophobicity of the coating.These characteristics lay the foundation for their applications in structural bonding, packaging, and aerospace fields. At present, significant progress has been made in the research of silicone modified epoxy resin both domestically and internationally.

First γ- Aminopropyltriethoxysilane (AP-TES) reacts with 2,3-epoxypropyl terminated polydimethylsiloxane (GPPMS) to open the epoxy group at one end of the GPPMS using an amino group to synthesize a polysiloxane intermediate (AGPMS). AGPMS is then mixed with bisphenol A epoxy resin (DGEBA) and cured to obtain an organosilicon modified epoxy resin coating.

The results showed that the impact strength, fracture toughness, and thermal stability of the obtained silicone modified epoxy resin coating were improved to varying degrees; However, when the amount of AGPMS added is low, the tensile strength of epoxy resin slightly decreases.

Using a similar method, a class of fused phenyl oligosiloxane bridged epoxy resin was prepared by the condensation reaction of C-OH of bisphenol A epoxy resin with Si-OH of the intermediate of hexaphenyl fused cyclosiloxane disiloxane. Research has found that a transparent organic silicon modified epoxy coating can be obtained by curing the modified resin with polyamide at room temperature. When the content of polycyclic phenyl oligosiloxane is 44.2%, the hardness of the obtained modified epoxy resin coating can reach 6H and the initial decomposition temperature can reach 348.96 ℃. However, the glass transition temperature (Tg) of the modified coating decreases with the increase of organic silicon modifier content.By chemically modifying epoxy resin with phenyl silicone resin, the heat resistance and impact strength of the modified epoxy resin were significantly improved.

In addition, using phosphoric acid as a catalyst, small molecule hydroxyl terminated polydimethylsiloxane (HPDMS) was reacted with bisphenol A epoxy resin (DGEBA), and the ring opening reaction between the silicone hydroxyl group on HPDMS and the epoxy group on DGEBA was carried out under acid catalysis.

First, a single ended polydimethylsiloxane modified epoxy resin ESR was prepared, and then a high gloss organic silicon modified epoxy coating (ESR-PA) was prepared using polyamide (PA) as the curing agent. Research has shown that siloxane has good compatibility with epoxy resin, and the mechanical properties, heat resistance, and corrosion resistance of ESR-PA coating are superior to pure DGEBA coating.

By modifying epoxy resin with low molecular weight bis (glycidyl ether propyl) tetramethyldisiloxane or bis (3-aminopropyl) tetramethyldisiloxane with a mass fraction of 15%, it was found that both small molecule modifiers can significantly reduce the glass transition temperature of epoxy resin coatings, and the modified coatings have reduced flexural strength, storage modulus, flammability, and slightly increased impact strength, But the siloxane modifier has almost no effect on its Brinell hardness.

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