A novel reduced graphene oxide decorated with halloysite nanotubes (HNTs-d-rGO) hybrid composite and its flame-retardant application for polyamide 6

Abstract

Polyamide 6 (PA6), a commercially important semicrystalline polymer, is widely used in engineering plastics, film and fibers [1][2][3][4], which usually causes fires and consequently leads to huge loss of human lives and property, which, to a certain degree, limits the range of applications. We demonstrate a novel strategy to improve the flame-retardant properties of PA6 by using reduced graphene oxide decorated with halloysite nanotubes (HNTs-d-rGO) hybrid composite. Graphene, exhibiting outstanding electronic, mechanical [5][6][7][8] and thermal [9,10] properties, is emerging as a rising star in the field of flame-retardant applications due to its endothermic and stable structure [10][11][12][13]. For example, the peak heat release rate (PHRR) of polyvinyl alcohol (PVA) filled with graphene is reduced by 49% [11]. However, in order to achieve fire resistance, the content of graphene used as flame retardant in polymer should be relatively high. Besides, nanocomposites consisting of polymer and clay, such as montmorillonite and kaolinite, are widely used to improve the flame-retardant properties of polymers [14,15]. Halloysite nanotubes (HNTs), one kind of nanoclay, have attracted research attention as fillers for polymer nanocomposites due to their improvement of mechanical [16,17] Abstract. The improvement of flame-retardant properties of polyamide 6 (PA6) was achieved by using reduced graphene oxide decorated with halloysite nanotubes (HNTs-d-rGO) hybrid composite as the additive in PA6 matrix. The intimate integration of reduced graphene oxide (rGO) and halloysite nanotubes (HNTs) through a three-step chemical functionalization, enabled the combination of their unique physical and chemical characteristics together. The nanostructure of HNTs-drGO was determined by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). A morphological study revealed that HNTs-d-rGO was dispersed uniformly in PA6 matrix. From the results of cone calorimetry measurements, the fire retardant properties of PA6 were further improved with the addition of HNTs-d-rGO when compared with that of either HNTs, or GO, or a mixture of HNTs and GO (HNTsm-GO) used in PA6 matrix. The results indicate clearly that higher flame-retardant activity of the integrated HNTs-d-rGO nanostructures than that of the simple mixture verifies the importance of the intimate integration between HNTs and rGO, which ascribe to the combination of the stable silica layer created by HNT and the barrier effect of rGO.

A green method to prepare nanosilica modified graphene oxide to inhibit nanoparticles re-aggregation during melt processing

“…Even when compared to the techniques employed to prepare other types of PA6-GO-ceramics nanocomposites [14,15], the route herein presented requires less time, lower temperatures and remarkably lower amounts of water.…”

“…On the other hand, the possibility to use graphemic compounds decorated with several nanoparticles, such as metal (Au, Ni), metal oxides (especially Fe 3 O 4 and alumine) and ceramics, as nanohybrid fillers for polymeric materials is gaining an increasing interest during the last years owing to the possibility to tune certain characteristics, such as thermal, electrical, magnetic and mechanical performance, or even to equip the nanocomposites with additional properties, useful to develop multifunctional materials [9,[14][15][16][17][18][19].…”

Graphene-based flame retardants: a review

“…The resulting residual char layer acts as a strong physical barrier to protect the substrate from heat and oxygen effectively, thereby slowing down the escape of flammable volatiles generated during polymer degradation as well as ameliorating the thermal stability, mechanical performance and flame retardancy. Li et al [147], using rGO decorated with halloysite nanotubes (HNTs-d-rGO) as the flame retardant filler, prepared a novel PA6-based flame retardant, and they claimed that the reduced PHRR and THR of the nylon-based composite are attributed to barrier effect of the uniform dispersion and network structure of the filler in the polymeric matrices.…”

“…Silica-based materials, such as silica nanospheres [140], silica [141,142], silicon nanoparticle [143] and silica-containing mineral nanomaterials (such as sepiolite nanorods [144], montmorillonite [145,146], halloysite nanotubes [147], and tubular clay [148]), can be combined with silicates. Most of them exhibit a layer structure for the silica-containing mineral nanomaterials.…”

Quantification of the Effect of Shish-Kebab Structure on the Mechanical Properties of Polypropylene Samples by Controlling Shear Layer Thickness

“…6,7 Nevertheless, this method usually decreases both modulus and strength. 8 (2) Introducing β-crystal to iPP.…”