Research Progress in Silicone Modified Epoxy Resin

Epoxy resin is a type of thermosetting resin that is based on aliphatic, alicyclic, or aromatic organic structures, containing two or more reactive epoxy functional groups, and can be crosslinked and cured under appropriate conditions and curing agents.Epoxy resin has been widely used in the fields of heavy-duty anti-corrosion coatings, adhesives, electronic sealing materials, and composite materials due to its strong adhesion, low shrinkage, and low cost.

There are various types of epoxy resins, among which bisphenol A epoxy resin is the most widely used, accounting for over 80% of its application share in the epoxy resin market. Although epoxy resin has excellent performance, it also has defects such as hard and brittle texture, poor weather resistance, and poor fracture toughness, which greatly limit its application in cutting-edge fields.

Polyorganosiloxanes (referred to as organosilicon) are a type of polymer with low surface energy, based on Si-O-Si segments as the backbone and possessing both organic and inorganic material properties（ γ The minimum can reach 19 dyn/cm, the main chain Si-O bond energy is large (422.5 kJ/mol), and the glass transition temperature (Tg) can be as low as -123 ℃ (such as polydimethylsiloxane PDMS). It has good weather resistance and cold heat resistance, flexible and hydrophobic chain segments, and its modification of epoxy resin can significantly improve the flexibility, elasticity, weather resistance, and waterproof, dustproof, and flame retardant properties of epoxy resin coatings, making it a research hotspot in recent years.

At present, the modification of epoxy resin by organic silicon is mainly divided into two categories: physical blending modification and chemical copolymerization modification.

Physical blending modification
Physical blending modification involves physically mixing organic silicon with epoxy resin before curing. The physical modification method has the characteristics of low cost and simple process. However, due to the solubility parameters (SP) of polyorganosiloxane ranging from 7.3 to 7.5, and the SP of epoxy resin ranging from 10.09, there are significant differences in their molecular structure and solubility parameters, which can lead to poor compatibility between polyorganosiloxane and epoxy resin, easy phase separation and turbidity, or make the system unable to cure uniformly, resulting in poor modification effect.

Based on this, the compatibility can be improved by adding transition phases (solubilizers), small molecule organic silicon coupling agents, and interface modifiers, thereby improving the modification effect.

An epoxy polysiloxane network structure was prepared by reacting and blending poly (3-aminopropyl) methylsiloxane) (PAMS) with an epoxy resin system, separating PAMS from the epoxy resin phase into spheres. The blending and compatibilization effects were generated during the reaction and crosslinking processes, and the impact resistance of the composite material and adhesive was improved.The epoxy system was prepared using PAMS as a curing agent, and it was confirmed that the epoxy coating changed from hydrophilicity to hydrophobicity, significantly reducing the water absorption of the epoxy system.

Three types of amino branched polydimethylsiloxane (ABP) were blended with epoxy resin for modification, and the effect of surface modification on the corrosion resistance of epoxy resin coatings was investigated. The results showed that the anti-corrosion performance of carbon steel coated with epoxy coating was significantly improved, and the size and density of corrosion points decreased with the increase of ABP molecular weight or content. However, there was a tendency for phase separation between ABP and epoxy resin, and the larger the molecular weight and content of ABP modifier, the more obvious the phase separation trend between ABP and epoxy resin.

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