Preparation Of Polyhedral Oligomeric Silsesquioxane And The Effect On The Properties Of Epoxy Resins

Polyhedral oligomeric silsesquioxanes（POSS）is a new type of nano-organic/inorganic hybrid material with Si-O-Si as the inorganic cage skeleton,which can be designed with different POSS structures with different properties by connecting different organic functional groups.Epoxy resins are widely used due to their excellent overall performance,but are limited in certain high-tech applications due to their poor heat resistance and brittleness.In this study,aminopropylheptyl caged polysesquioxane（NH₂-POSS）was added to epoxy resins to improve their heat resistance and mechanical properties.Based on this,anotherγ-glycidyl ether oxypropyl trimethoxy caged polysesquioxane（EP-POSS）was designed and prepared by direct hydrolysis to investigate the best preparation process of EP-POSS to improve the epoxy resin properties,and finally,the performance mechanism of different reactive POSS modified epoxy resins was investigated.The structural properties of commercially available NH₂-POSS were characterized and the material was found to have a good crystal structure with an initial thermal decomposition temperature of 243.67°C and good heat resistance.NH₂-POSS was added to epoxy resin to prepare NH₂-POSS/EP resin.The experimental results showed that the addition of NH₂-POSS did not change the amorphous structure of the epoxy resin,but effectively improved the thermal stability of the epoxy resin,and the strength and toughness of the epoxy resin were greatly improved when NH₂-POSS was added at 5%.EP-POSS was synthesized by direct hydrolysis,and the effects of the hydrolysis process,condensation process and different factors in the reaction environment on the synthesis were investigated.The structures of the products were characterized by Fourier infrared spectroscopy and nuclear magnetic resonance spectroscopy.The experimental results showed that when the hydrolysis time was 2 d,the catalyst content was 4%,the condensation temperature was 80℃,the condensation time was 2 h and the solvent ratio was IPAl:Xylene=2:1,the product was mainly T8 structure.The epoxy value was basically unchanged after20 days of resting and the product had good room temperature stability.The EP-POSS/EP resin was prepared by adding EP-POSS to the epoxy resin.Similar to the NH2-POSS/EP resin,the experimental results show that the EP-POSS/EP system is still an amorphous structure of the epoxy resin and that the EP-POSS/EP resin has good heat resistance,with a significant increase in strength and toughness when EP-POSS is added at10%.Comparing the reaction mechanism between NH₂-POSS and EP-POSS/EP in epoxy resin,we found that NH₂-POSS mainly introduces rigid chain segments in epoxy resin,while EP-POSS forms a cross-linked network in epoxy resin,so a small amount of NH₂-POSS can modify the performance of epoxy resin,and when the cross-link density is large,the performance of EP-POSS/EP resin is better than that of NH₂-POSS/EP resin.On this basis,the effect of EP-POSS on the corrosion resistance of epoxy resins was investigated and it was found that the addition of EP-POSS effectively increased the interfacial bonding and corrosion resistance of epoxy resins,and the 10%EP-POSS/EP coating increased the low frequency impedance modulus by about one order of magnitude compared to that of pure epoxy resins.