Comprehensive Characterization of APTES Surface Modifications of Hydrous Boehmite Nanoparticles

Abstract

Hydrous boehmite (γ-AlOOH) nanoparticles (BNP) show great potential as nanoscale filler for the fabrication of fiber reinforced nanocomposite materials. Notably, the particle− matrix interaction has been demonstrated to be decisive for improving the matrix-dominant mechanical properties in the past years. Tailoring the surface properties of the nanofiller enables to selectively design the interaction and thus to exploit the benefits of the nanocomposite in an optimal way. Here, an extensive study is presented on the binding of (3-aminopropyl)triethoxysilane (APTES), a common silane surface modifier, on BNP in correlation to different process parameters (concentration, time, temperature, and pH). Furthermore, a comprehensive characterization of the modified BNP was performed by using elemental analysis (EA), thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA-MS), and Kaiser's test (KT). The results show an increasing monolayer formation up to a complete surface coverage with rising APTES concentration, time, and temperature, resulting in a maximal grafting density of 1.3 molecules/nm 2 . Unspecific multilayer formation was solely observed under acidic conditions. Comparison of TGA-MS results with data recorded from EA, TGA, and KT verified that TGA-MS is a convenient and highly suitable method to elucidate the ligand binding in detail.

Amorphization and modified release of ibuprofen by post-synthetic and solvent-free loading into tailored silica aerogels

“…Quantitative examinations of the degree of functionalization were performed by elemental analysis using a FlashEA 1112 from Thermo Fisher Scientific (Waltham, MA, USA). The molar concentration (c) of chemisorbed APTES ligand per g SA was determined from the ratio of the measured nitrogen weight content (x%) to the molar mass (Zarinwall et al., 2021c ): …”

The impact of water released from boehmite nanoparticles during curing in epoxy‐based nanocomposites

“…100:7 (AH:H 2 O). 8 Therefore, the hydrolysis of the AH by BNP is partial. A partial hydrolysis of the AH in a resin system alters the curing process and the properties of the cured epoxy polymer.…”

“…One promising additive are boehmite (γ‐AlOOH) nanoparticles (BNP) which has been shown to have a positive effect on many properties such as Young's modulus with an increase of up to 20%, 4 fracture toughness (61%) 4 and flame retardancy 5,6 . Furthermore, it is nontoxic, commercially available and offers possibilities to be surface modified with, for example, silanes according to its applications or surrounding matrix 7,8 …”

“…5,6 Furthermore, it is nontoxic, commercially available and offers possibilities to be surface modified with, for example, silanes according to its applications or surrounding matrix. 7,8 The enhancing effect of BNP in epoxy-based nanocomposites on the macroscopic scale encouraged recent research to investigation of the micro-and nanoscopic properties of the additive in epoxy-based nanocomposites. A detailed analysis by small-and wide-angle X-ray scattering determined that the crystalline structure of the BNP is unaffected by the incorporation into the epoxy polymer matrix, 9 although the BNP have a tremendous impact on their surrounding epoxy polymer matrix.…”

“…7,16 An additional aspect that has not been considered yet for epoxy-based nanocomposites is the possible influence of water present in the BNP. 8,17 Recent research on boehmite reinforced polyamide or polysiloxane pointed out that water released from the BNP during the curing process has an influence on the polymer structure and properties. 18,19 A systematic FTIR-spectroscopic approach is chosen in this work to investigate interactions and reactions of the BNP and its present water with components of an anhydride cured epoxy resin during the curing process.…”