Research progress in the application of modified silicone resins in functional coatings!

This article outlines the mechanism of action of silicone resins in high temperature resistant, abrasion resistant and antifouling coatings, reviews the application and modification research progress of modified silicone resins in these coatings fields, and discusses modified silicone resin coatings. The future direction of development is forecasted.


introduction


As a polymer material, silicone resin is widely used because of its excellent heat resistance, cold resistance, radiation resistance, water repellency, stain resistance, chemical corrosion resistance and other special properties.


However, pure silicone resin has shortcomings such as long curing time, low coating adhesion at high temperature, and low mechanical strength, which limit its application [1].


Since the molecular structure of silicone resin still retains active groups such as hydroxyl groups, this provides more possibilities for the modification of silicone resins [2].


As the main film-forming substance of silicone resin coatings, silicone resin has received extensive attention in its modification [3]. This article mainly reviews the research progress of modified silicone resins in the fields of high temperature resistant coatings, wear resistant coatings and antifouling coatings in several functional coatings [4-6].


1 High temperature resistant coating


The difference with organic polymers is that the bond energy of Si-O bonds in silicone resins is higher than that of CC bonds in ordinary organic polymers. Silicon atoms and oxygen atoms form d-pπ bonds. Therefore, silicone resins have very Good thermal stability [7-8].


1.1 Epoxy modified silicone resin


Epoxy modified silicone resin is through the graft condensation reaction of epoxy groups and hydroxyl groups and polysiloxane active groups, so the modified epoxy/silicone coating has good stability and compatibility. It has the advantages of epoxy resin and silicone resin [9].


For epoxy-modified silicone resin, Sun Zhenning et al. [10] prepared epoxy-modified silicone polymer and applied the modified resin to the anti-splash coating of engine blades.


Through Fourier Infrared Spectroscopy (FTIR) analysis, the hydroxyl group in the silicone resin successfully reacted with the epoxy group, indicating that the epoxy resin is a chemical way to modify the silicone resin.


Through thermal weight loss analysis (TG), it is known that with the increase of the hydroxy silicone oil content in the system, the better the thermal stability of the modified polymer, and the better it can be applied to the anti-splash coating of the blade.


1.2 Inorganic filler modified silicone resin


When the silicone resin branch contains phenyl, its content can affect the heat resistance of the coating. The reason is that the electron-rich cloud in the phenyl can interact with pigments and substrates to enhance the adhesion of the coating [ 11].


Therefore, the use of inorganic fillers to fill and modify the silicone resin film-forming material can give the coating better performance.


Ding Chao et al. [12] used silicone resin as the film-forming resin, added aluminum silver paste, mica powder and other temperature-resistant fillers, and developed a single-component high-temperature-resistant anti-corrosion coating that can be used for a long time at 500℃. .


The flake structure of mica powder itself helps to improve the temperature resistance of the coating. The experiment shows that the amount of aluminum silver paste in the formula should be controlled at 10%~15%, and the amount of mica powder should be controlled at 12%~15%. The silicone high temperature resistant coating with this content ratio can show excellent thermal stability. sex.


1.3 POSS (polyhedral oligomeric silsesquioxane) modified silicone resin


The addition of nano SiO2 [13], carbon nanotubes [14], clay [15] and other nanoparticles [16] can improve the thermal and mechanical properties of polymers [16-17].


However, due to the agglomeration of nanoparticles, it is difficult to achieve nano-dispersion through mechanical blending.


POSS is a unique organic/inorganic nanomaterial. Non-reactive groups can improve compatibility with silicone resins. Reactive groups can achieve chemical bonding with silicone resins, which can solve this problem well. problem.


LiuY R et al. [18] successfully synthesized a methyl silicone resin/POSS composite with a higher decomposition temperature by mixing functionalized trisiloxybutyl POSS with hydroxylated methyl silicone resin.


Yang Z [19] synthesized a series of silicone resins containing silicon benzene units into the POSS framework to improve the thermal stability of silicone resins.


Yao X et al. [20] synthesized 3 kinds of polyhedral oligomeric silsesquioxanes. By adding POSS to the silicone resin, the thermal stability was significantly improved, and the results of aminopropyl POSS modified silicone resin It is concluded that the thermal stability is improved most significantly, and the decomposition temperature is nearly 45°C higher than that of pure silicone resin.


In addition, Yao X et al. also studied the thermal decomposition mechanism of different POSS silicone resins. Chemical simulations show that hydrogen bonds are formed between POSS and silicone resins, which greatly improves the thermal stability of silicone resins. A unique mode to improve thermal stability is developed: hydrogen bonds are formed to prevent the movement of resin chains.


Kong Guoqiang et al. [21] used POSS containing silanol groups to modify to improve the thermal stability of silicone resins.


They studied the influence of different POSS addition levels and addition methods on the thermal properties of silicone resins. The results showed that as the addition of trisilanol phenyl (P-POSS) increased, the thermal properties of modified silicone resins increased first After lowering.


When the mass fraction of P-POSS is 5% and the heating reaction method is adopted, a modified silicone resin with good thermal performance can be obtained.


In addition, silicone-modified organic resins have also made new progress. Yang Fei et al. [22] prepared silicone resins from siloxane monomers and silica sols, which were used to modify polyesters to obtain silicone-silica sol/polyester composite resins.


According to TG analysis, the higher the content of silicone resin, the better the thermal stability of the composite resin.