Enhancing thermal and dynamic‐mechanical properties of epoxy reinforced by amino‐functionalized microcrystalline cellulose

Abstract

AbstractIn this study, microcrystalline cellulose (MCC) was chemically modified with 3‐(aminopropyl)triethoxysilane and added to epoxy to improve chemical, thermal and dynamic‐mechanical characteristics of the composites. The composites were manufactured aided by sonication with 1.0%, 2.5%, or 5.0% wt/wt of untreated MCC or amino‐functionalized MCC (MCC‐Si). The epoxy/MCC‐Si composites showed a decrease in the ─OH band by Fourier‐transform infrared spectroscopy, and X‐ray diffraction analysis indicated better dispersion. The incorporation of MCC‐Si in epoxy resin decreased the heat of reaction, increased activation energy values (Ea) and pre‐exponential factor (A), and did not affect thermal degradation. All conversion degree (α) versus temperature curves for the composites showed a sigmoidal shape. MCC‐Si composites showed better dynamic‐mechanical properties than the MCC counterparts, and the functionalization effect was evidenced in storage modulus (E') and loss modulus (E"). At 2.5% wt/wt of MCC‐Si content an increase of 119% in E' at the glassy region, 127% in E' at the rubbery region and 173% in E" was observed compared to the neat resin, whereas the Tg barely changed among samples. Good adhesion between the amino‐functionalized MCC and the epoxy matrix was observed at the fracture surface, evidencing that surface modification of MCC improves their chemical interaction.