Synthesis Of Epoxy Oligosiloxane And Its Application In Epoxy Resin

POSS utilizes a unique Si-O-Si hexahedral inorganic framework structure,and the top-angle Si atoms can introduce reactive or in-reactive groups,which can be designed into functional POSS with different properties and used to modify polymers.It is preferred to use nano-scale POSS with good polymer compatibility to modify the epoxy resin,and the multifunctional POSS can provide cross-linking points by physical blending or chemical bonding.To some extent,the dense network structure generated makes the thermal and mechanical properties of the composite material improved.In this paper,two epoxy-based POSS were prepared for epoxy resin modification.A series of characterizations and examination of the cured materials were carried out to improve the performance of the coating.Based on this,the specific research contents are as follows:（1）The epoxy-based silsesquioxane（EP-POSS）is synthesized by hydrolyzed polycondensation usingγ-glycidoxypropyltrimethoxy-silane（KH560）as raw material and catalyzed by hydrochloric acid.Multiple analytical methods such as FT-IR,NMR,and GPC proved that the expected structure was achieved,and the TGA curve and AFM results showed that EP-POSS had wonderful thermal stability,but and surface morphology was slightly poor.A series of experiments were conducted to investigate the effects of reaction temperature,pH,water amount,solvent and reaction time on the performance of EP-POSS.The results showed that:The reaction at a reaction temperature of 30℃,pH=3⁴,methanol and ethanol were mixed 1:1 and the amount of solvent and monomer was M_S:M_R=4,n（Si-OR）:n（H₂O）=1:2 was continued for 20 hours,and the target product with good performance was obtained.（2）EP-POSS was used as an additive component to modify epoxy resin,Dicyandiamide（DCD）as curing agent.The thermal and dielectric properties of the series of coatings were tested.Effects of dosage of accelerator and EP-POSS,different functional POSS and curing process on the mechanical properties of modified epoxy coatings were investigated.The results showed that EP-POSS was introduced into the epoxy system at a dose of 3 wt%of epoxy resin,which improved the thermal stability and glass transition temperature（Tg）of the coating while reducing the relative dielectric constant.Excellent synergistic curing effect was obtained when the accelerator dose was 0.5%.The coating properties were improved when different functional POSS modified epoxy resins,but the performance of ph-POSS and MA-POSS was slightly worse than that of EP-POSS.And when cured at 100¹20℃for 30min,the overall performance of the coating was better.（3）The active hydrogen atom in the chlorosilane was successfully introduced into the POSS structure by using the semi-closed caged heptasil silsesquioxane ph-T₇（OH）₃ and the dimethylchlorosilane acid-binding agent trimethylamine to produce the intermediate T₇^3H.Then a double-bond addition reaction was carried out with Si-H bond and allyl-glycidylether（AGE）to obtain triglycidyl oligomeric silsesquioxane(T₇^3EP-POSS)to modify two-component resins.The structure and thermal stability of the preliminary synthesized products were tested by IR,NMR and TGA.The particle size,Zeta potential and internal structure of the modified emulsion were observed by laser particle size analyzer and transmission electron microscopy（TEM）.The infiltration ability of the film was tested.The effect of T₇^3EP-POSS on mechanical properties of the coating was considered.The results showed that T₇^3EP-POSS and modified coatings had excellent thermal stability,and when the addition amount of T₇^3EP-POSS was 3%,the thermal stability and mechanical properties of the paint film were perfect and had certain hydrophobic properties.