In-Out Surface Modification of Halloysite Nanotubes (HNTs) for Excellent Cure of Epoxy: Chemistry and Kinetics Modeling.

Shahab Moghari,Mohsen Khodadadi Yazdi,Payam Zarrintaj,Maryam Jouyandeh,Aleksander Hejna,Seyed Hassan Jafari,Mohammad Reza Saeb

doi:10.3390/nano11113078

Abstract

In-out surface modification of halloysite nanotubes (HNTs) has been successfully performed by taking advantage of 8-hydroxyquinolines in the lumen of HNTs and precisely synthesized aniline oligomers (AO) of different lengths (tri- and pentamer) anchored on the external surface of the HNTs. Several analyses, including FTIR, H-NMR, TGA, UV-visible spectroscopy, and SEM, were used to establish the nature of the HNTs’ surface engineering. Nanoparticles were incorporated into epoxy resin at 0.1 wt.% loading for investigation of the contribution of surface chemistry to epoxy cure behavior and kinetics. Nonisothermal differential scanning calorimetry (DSC) data were fed into home-written MATLAB codes, and isoconversional approaches were used to determine the apparent activation energy (Eα) as a function of the extent of cure reaction (α). Compared to pristine HNTs, AO-HNTs facilitated the densification of an epoxy network. Pentamer AO-HNTs with longer arms promoted an Excellent cure; with an Eα value that was 14% lower in the presence of this additive than for neat epoxy, demonstrating an enhanced cross-linking. The model also predicted a triplet of cure (m, n, and ln A) for autocatalytic reaction order, non-catalytic reaction order, and pre-exponential factor, respectively, by the Arrhenius equation. The enhanced autocatalytic reaction in AO-HNTs/epoxy was reflected in a significant rise in the value of m, from 0.11 to 0.28. Kinetic models reliably predict the cure footprint suggested by DSC measurements.

Highlights

In-out surface modification of halloysite nanotubes (HNTs) has been successfully performed by taking advantage of 8-hydroxyquinolines in the lumen of HNTs and precisely synthesized aniline oligomers (AO) of different lengths anchored on the external surface of the HNTs
Tg as an evaluator of final nanocomposite performance. This project successfully introduced novel nanocontainers possessing halloysite nanotubes acting as the core and oligoanilines with two different lengths (CAT and capped aniline pentamer (CAP)) acting as the shell of the nanomaterial
The synthesis and grafting processes used in this study were verified by Fourier transform infrared (FTIR), H-NMR, thermogravimetric analysis (TGA), and Scanning electron microscopy (SEM) analyses

Summary

Introduction

In-out surface modification of halloysite nanotubes (HNTs) has been successfully performed by taking advantage of 8-hydroxyquinolines in the lumen of HNTs and precisely synthesized aniline oligomers (AO) of different lengths (tri- and pentamer) anchored on the external surface of the HNTs. Nanoparticles were incorporated into epoxy resin at 0.1 wt.% loading for investigation of the contribution of surface chemistry to epoxy cure behavior and kinetics. A well-dispersed nanoparticle epoxy system displays good anti-corrosive resistance in its coating applications, surface-active nanoparticles can participate in the curing of the epoxy resin with amine curing agents, leading to higher mechanical and thermal properties [8,9,10]. Nanoparticles can participate in the cure reaction of epoxy resin, which supports barrier performance by providing a denser polymeric network [13,14]. Nanomaterials 2021, 11, 3078 enhanced cross-linking density of epoxy nanocomposites with respect to blank resin is key to determining the performance of nanoparticles [15]. Anti-corrosive epoxy nanocomposite coatings are a class of epoxy nanocomposites for which the surface chemistry of nanoparticles plays a key role in corrosion inhibition

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Results

Discussion

Conclusion