Grafting amount and structural characteristics of microcrystalline cellulose functionalized with different aminosilane contents

Microcrystalline cellulose (MCC) has unique properties and its use as reinforcement for polymer composites has been increasing. However, the intrinsic incompatibility with most polymers requires surface modification to improve chemical compatibility prior to its incorporation into a polymer. In this paper, a grafting amount and structural characteristics of MCC functionalized with 3-aminopropyltriethoxysilane (APTES) (MCC-Si) at different contents was performed. We reported a comparison of three different methods for quantifying the APTES grafting amount: from TGA curves, nitrogen content, and silicon content. Supplementary analyses were performed: solid-state ¹³ C and ²⁹Si nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy with energy dispersive X-ray (SEM-EDX). A deep study of structural properties by X-ray diffraction was also conducted. A better correlation for grafting amount of APTES onto MCC was observed for nitrogen content method than residual mass according to the Pearson’s correlation. ¹³ C NMR revealed all the carbon structures from cellulose and side bands for MCC-Si samples and from APTES molecules and ²⁹Si NMR revealed T structures. The silane treatment did not alter the shape of MCC and all treated samples showed Si characteristic peak at ~ 1.75 kEv. The exposure to APTES in an acidic medium caused several effects on the MCC, splitting larger I_β crystallites in half and along the more reactive hydrophilic sides. The diameter of the smaller IV_I crystallites was largely reduced by the treatment, especially when the silane concentration was 1:5 (m/v), above which the diameter increases again.