Controlling POSS dispersion in epoxy in nanocomposite by introducing multi-epoxy POSS groups

Excerpt

In recent years, polyhedral oligomeric silsesquioxanes derivatives, providing nano-reinforcement, have been extensively employed to reinforce polymers by forming a nanocomposite. Incorporating POSS particles into linear thermoplastics or thermosetting networks markedly improves the thermal [1], dimensional stability [1] and oxidative [2] properties of several polymer resins, extending their applications as high-performance engineering plastics. Numerous thermoplastics and some thermosetting systems have thus been enhanced. These include methacrylates, [3, 4] styrenes, [5] norbornenes, [6] siloxanes [7] and epoxies [1, 8‐11]. Multi-functional POSS derivatives such as epoxy resin, [1, 8‐11] polyurethane, [12] polyacrylate, [13] polyimide, [14, 15] and polybenzoxazine [16, 17] have been utilized as curing junctions, further increasing the crosslinking density of the polymer. Introducing “multi-functional” POSS derivatives results in interesting thermal and mechanical characteristics. Two of the factors that significantly affect the thermal and mechanical characteristics of the nanocomposite systems are the crosslinking density and the dispersion state of nanofillers in the nanocomposite matrix. According to the character of substituents, types of the aggregated POSS within matrix could behave either as nanofiller reinforcing the matrix or as the plasticizer. In particular, the dispersion of nanofillers in the nanocomposite matrix is an important issue that has been studied by many scientists, because the crosslinking density [18] of the nanocomposite is related to the dispersion of the nanofillers therein. In nanocomposites with multi-functional POSS derivatives, POSS derivatives can react with the monomer units of the polymer, increasing their crosslinking density [12, 16, 19]. In some cases [15, 20‐23], the POSS derivatives react with the monomers of the polymer. The POSS that is aggregated inside the nanocomposite matrix behaves as the plasticizer, as revealed by the less favorable thermal properties. …