Epoxy nanocomposites containing mercaptopropyl polyhedral oligomeric silsesquioxane: Morphology, thermal properties, and toughening mechanism

Abstract

A novel polyhedral oligomeric silsesquioxane (POSS) containing a mercaptopropyl group [mercaptopropyl polyhedral oligomeric silsesquioxane (MPOSS)] was synthesized via the hydrolytic condensation of g-mercaptopropyl triethoxysilane in an ethanol solution catalyzed by concentrated hydrochloric acid and was used to modify epoxyamine networks by a cocuring reaction with diglycidyl ether of bisphenol A (DGEBA). The structure, morphology, and thermal and mechanical properties of these MPOSS/DGEBA epoxy nanocomposites were studied and investigated with thermogravimetric analysis/differential thermal analysis (TGA-DTA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). From SEM analysis, we observed that the miscibility between epoxy and POSS occurred at a relatively high POSS content, which characterized this mixture as a polymer nanocomposite system. The impact test showed that MPOSS reinforced the epoxy effectively, and the SEM study of the impact fracture surface showed that the fibrous yielding phenomenon observed was an indication of the transition of the brittle stage to a ductile stage and correlated well with the large increases in the impact strength; this was in agreement with the in situ reinforcing and toughening mechanism. The TGA-DTA analysis indicated that the MPOSS/DGEBA epoxy hybrids exhibited lower thermostability at a lower temperature but higher thermostability and higher efficiency in char formation at an elevated temperature. Differential scanning calorimetry showed that the glass transition temperature (T g ) of the MPOSS/epoxy hybrids were lower than that of the neat epoxy.

Novel nanocomposites based on epoxy resin/epoxy-functionalized polydimethylsiloxane reinforced with POSS

“…As Fu et al previously reported [46], this behavior can be attributed to the yields of silicon-rich residues, which make the materials more stable at elevated temperatures. Therefore, the thermal degradation behavior of epoxy resins is strongly influenced by the presence of POSS compounds due to the self-decomposition and self-condensation processes which occur at relatively low temperatures and form protective layers that increase the thermostability at higher temperatures.…”

An investigation of the mechanism of graphene toughening epoxy

“…Epoxy resins, which are the most important thermosetting resins in industry for various applications [3], have been reported to be successfully toughened by nanoparticles including metallic oxide (aluminium oxide and titanium oxide) [4], nano-silica [5,6], polyhedral oligomeric silsesquioxane [7], clay [8], carbon nanotubes [9,10] and graphene based nanoparticles [11][12][13][14][15]. Among these nanoparticles, graphene is a new kind of carbon nanofillers with two-dimensional structure [16].…”

Relationships between nanostructure and dynamic-mechanical properties of epoxy network containing PMMA-modified silsesquioxane

“…Consequently an improvement of thermal, oxidative and dimensional stability as well as mechanical performance of many polymeric resins is usually achieved. Mono-and multi-functionalized silsesquioxanes containing epoxy [7,[19][20][21][22][23][24][25][26][27], amino [28][29][30][31][32], mercapto [33], maleimido [34,35], and isocyanate groups [36] have been successfully employed in the preparation of epoxy resin-based hybrid materials. Mono-functionalized silsesquioxanes are prepared by corner capping reaction of a trisilanol with a functionalized trialkoxy silane, and results in POSS molecules grafted onto the epoxy matrix [14].…”