Liya Chen

Highly populated and nearly monodispersed nanosilica particles in an organic medium and their epoxy nanocomposites.

An organic aminopropyl-functionalized nanosilica sol was synthesized in the presence of ethyl silicate, γ-(aminopropyl)triethoxysilane (KH550), and N,N-dimethylformamide (DMF) via a sol-gel technique and then used to prepare epoxy nanocomposites. Structure and morphology analyses of the obtained aminopropyl-functionalized nanosilicas were observed by dynamic light scattering (DLS), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). TEM and DLS showed that modified nanosilicas with an average diameter of 30 nm dispersed homogeneously in DMF. The effects of the aminopropyl-functionalized nanosilica particles on the flexural modulus, impact strength, glass transition temperature (Tg), and bulk resistivity (ρv) of the epoxy nanocomposites were investigated. The toughening mechanisms and microstructures were determined in terms of the impact fracture surface morphology using scanning electron microscopy.

Effect of aminopropylisobutyl polyhedral oligomeric silsesquioxane functionalized graphene on the thermal conductivity and electrical insulation properties of epoxy composites

In order to obtain homogeneous dispersion and strong interfacial interaction in epoxy nanocomposites, an effective approach is proposed to prepare aminopropylisobutyl polyhedral oligomeric silsesquioxane (ApPOSS) covalently grafted graphene (ApPOSS–graphene) enhancement epoxy (EP) hybrids with high thermal conductivity and electrical insulating property. The chemically converted ApPOSS–graphene 2D sheet with amine groups and rigid Si–O–Si cages is a versatile starting platform to prepare nanohybrids, which conduce to uniform dispersion and well compatibility of graphene in polymer matrix. Compared to pristine GO/EP, the interfacial interactions between ApPOSS–graphene and epoxy matrix through non-covalent and covalent bonds promote well dispersibility, compatibility and interfacial quality in composites, which contribute to improving thermal conductivity through forming effective heat conduct networks and decreasing thermal interfacial resistance. With the incorporation of only 0.25 and 0.5 wt% ApPOSS–graphene, the thermal conductivities of the ApPOSS–graphene/EP composites increase by 37.6% and 57.9% compared with neat EP, while maintaining high electrical resistivity. We believe that using ApPOSS chemically reducing and functionalized modifying GO may open a novel interface design strategy for extending applications of POSS and GO to fabricate high performance composites with high thermally conductive and electrically insulating properties.